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We demonstrate that the properties of eccentric gravitational-wave (GW) signals enhance the detectability of GW phase shifts caused by environmental effects (EEs). The signal-to-noise ratio (SNR) of EEs can be boosted by up to <inline-formula> <mml:math><mml:msubsup><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow><mml:mrow><mml:mi>max</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>n</mml:mi></mml:mrow></mml:msubsup></mml:math> </inline-formula> with respect to corresponding circular signals, where <inline-formula> <mml:math><mml:msub><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow><mml:mrow><mml:mi>max</mml:mi></mml:mrow></mml:msub></mml:math> </inline-formula> is the highest modeled eccentric GW harmonic and n is the frequency scaling of the GW dephasing prescription associated to the EE. We investigate the impact on a population level, adopting plausible eccentricity distributions for binary sources observed by LIGO─Virgo─Kagra (A+ and A# sensitivities), as well as Cosmic Explorer (CE) and the Einstein Telescope (ET). For sources in the high-eccentricity tail of a distribution (e ≳ 0.2 at 10 Hz), phase shifts can systematically be up to <inline-formula> <mml:math><mml:msubsup><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow><mml:mrow><mml:mi>max</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>n</mml:mi></mml:mrow></mml:msubsup></mml:math> </inline-formula> times smaller than in a corresponding circular signal and still be detectable. For typical EEs, such as Roemer delays and gas drag, this effect amounts to SNR enhancements that range from 10<SUP>2</SUP> up to 10<SUP>5</SUP>. For CE and ET, our analysis shows that EEs will be an ubiquitous feature in the eccentric tail of merging binaries, regardless of the specific details of the formation channel. Additionally, we find that the joint analysis of eccentricity and phase shift is already plausible in current catalogs if a fraction of binaries merge in active galactic nucleus migration traps.

X-ray spectral variability in active galactic nuclei (AGNs) can be either intrinsic or caused by external processes, such as variable absorption. Several transient occultation events from individual clouds or X-ray eclipses have been identified in a number of AGNs in the past two decades. We report results from the analysis of two Swift monitoring campaigns of the Seyfert galaxy ESO 362-G18, a changing-look AGN that showed transitions between optical spectral types 1.5 and 1.9 in the past, most likely induced by variable absorption. We identified two X-ray eclipses during the first Swift campaign, one of which we were able to follow almost entirely from ingress to egress. We used time-resolved spectroscopy to follow the evolution of the X-ray spectrum with time in order to derive the properties of the absorbing cloud and the size of the main X-ray-emitting region. The cloud is located towards the innermost dust sublimation zone, intermediate between the dust-free broad-line region and the dusty torus. The X-ray-emitting region is confined within ∼35 gravitational radii (R<SUB>g</SUB>) from the centre. A deeper analysis indicated that the eclipsing cloud likely comprises a denser core and a more tenuous atmosphere. We were also able to estimate the size of the soft excess and hot corona X-ray-emitting regions separately. These are two of the most relevant continuum components in the X-ray spectra of unobscured AGNs. Our analysis suggests that the soft-excess-emitting region is ∼50% more extended than the hot corona one. However, it appears to co-exist with and is not replaced by the hot corona one in the innermost ∼30 R<SUB>g</SUB>. Our results highlight the potential of X-ray eclipse tomography for providing a clearer view of the innermost accretion flow geometry and of the AGN surroundings out to the torus scale.

The recent evidence for a nanohertz gravitational-wave background from pulsar timing arrays highlights the urgent need to identify electromagnetic counterparts to supermassive binary black holes. Here, we perform global 3D general relativistic magnetohydrodynamic (GRMHD) simulations of a secondary black hole (mass ratio q = 0.1) interacting with a magnetically arrested disk (MAD) around a primary black hole using a time-dependent superposed Kerr─Schild metric and postprocessed general relativistic radiation transfer calculations based on the thermal electron distribution function (eDF). We explore three orbital configurations: a vertical impact orbit, a coplanar embedded orbit, and a high-spin, eccentric, inclined scenario. Despite clear orbital periodicity and recurrent shock formation, the thermal synchrotron light curves frequently lack expected shock-induced flares. In vertical impacts, shock brightenings are typically subdominant to the stochastic MAD variability of the primary black hole, unless viewed at specific alignment phases. Conversely, coplanar orbits produce distinctive, rapid flares driven by gravitational self-lensing. We identify a frequency-dependent emission hierarchy: the primary black hole dominates submillimeter flux, while the secondary dominates near-infrared emission due to higher electron temperatures in thermal eDF. Finally, spin─orbit coupling drives Lense─Thirring precession, yielding twisted, wobbling jets that following the tilt and precession of the primary black hole. Crucially, we show that intrinsic MAD turbulence can easily mask shock-induced radio flares, making self-lensing flares a more reliable electromagnetic counterpart candidate for supermassive binary black holes.

We present the New Online Database of Symbiotic Variables (NODSV), a comprehensive and publicly accessible catalog of known and candidate symbiotic stars in the Milky Way and nearby galaxies. The database provides an up-to-date census of confirmed symbiotic binaries and systematically compiles information previously scattered across the literature, including photometric and spectroscopic properties, orbital parameters, and characteristics of both their cool and hot stellar components. It further records auxiliary diagnostics such as detected emission lines, flickering, X-ray emission, jets, or information about outburst activity. In its current release, NODSV contains nearly 1400 objects, classified into confirmed symbiotic stars, three categories of candidates, and misidentified sources. Based on the collected data, though originating from heterogeneous studies, we present a statistical overview of the confirmed symbiotic population, highlighting the distributions of orbital parameters and the properties of the cool giants and their hot companions. Designed as a dynamic and evolving resource, NODSV provides a foundation for future observational campaigns and theoretical investigations of symbiotic binaries.

Neutrino self-interactions beyond the Standard Model are well motivated by the nonzero masses of neutrinos, which are the only known particles guaranteed to have new physics. Meanwhile, cosmic messengers, especially neutrinos, play a central role in probing new physics, as they provide experimental conditions far beyond the reach of laboratories and serve as the link between laboratory fundamental-physics discoveries and their roles in the Universe, where many new physics motivations originate. In this work, we propose a novel probe of neutrino self-interactions through ultrahigh-energy neutrinos scattering off the cosmic neutrino background when the lightest neutrino species remains relativistic today. This allows us to "Widen the Resonance" of such scattering [1]. In addition, we also provide a semi-analytic framework for cosmogenic ultrahigh-energy neutrino production, avoiding computationally intensive simulations and yielding results precise enough for beyond-the-standard-model studies. The widened resonance enables future ultrahigh-energy neutrino telescopes, in particular GRAND, to probe mediator masses from MeV to GeV, reaching couplings down to g ∼ 10<SUP>-3</SUP> — up to two orders of magnitude beyond current bounds. Our results enhance the discovery potential of neutrino self-interactions in the high-mass regime, potentially offering crucial insights into the connections between the neutrino sector and dark sector.

The detection of the Stochastic Gravitational Wave Background (SGWB) is one of the most challenging tasks for both current and next-generation detectors. Successfully distinguishing the SGWB from instrumental noise and environmental effects requires accurate and flexible analysis tools capable of detecting the signal and determining its origin. In this paper, we introduce a unified framework and a user-friendly tool for SGWB characterization: GWBird (Gravitational Wave Background Inventory of Response functions for Detectors). This code enables the computation of overlap reduction functions (ORFs), power-law integrated sensitivity curves (PLS), angular response functions, and angular PLS (APLS). It supports the full range of gravitational wave polarization modes (tensor, scalar, and vector), allowing for the characterization of both isotropic and anisotropic SGWB components for all the polarizations. Additionally, the code includes functions for circular polarization characterization, which is particularly relevant for probing parity-violating signals. The framework integrates analyses for ground-based, space-based, and Pulsar Timing Array (PTA) detectors, offering a versatile framework for SGWB analysis. The GWBird code is publicly available at: https://github.com/ilariacaporali/GWBird.

We search for a population-level signature of gravitational-wave recoiling supermassive black holes: a positive correlation between dust obscuration and the magnitude of the line-of-sight velocity offset of broad emission lines relative to the host. Using the SDSS DR16 quasar catalogue, we estimate the velocity offset, ∆v, as the difference between the broad Hβ redshift and a noise-weighted redshift from narrow lines ([O III] 5007, [O II] 3728, and Ca II 3934). We adopt the redshift-relative colour excess ∆(g - i) as a proxy for dust column density. Analysing ~10<SUP>5</SUP> quasars that meet basic spectral quality requirements, we find a modest but highly significant positive correlation between |∆v| and ∆(g - i) (Spearman r ≃ 0.12 and Pearson r ≃ 0.13, with p ≪ 10<SUP>-10</SUP> in both cases). The fraction of highly obscured quasars increases with |∆v|, indicating that the correlation is driven by a dust-reddened subpopulation. The result is robust to the choice of minimum |∆v| threshold and to the line redshift estimator (peak vs. centroid). As expected, the correlation is largely absent when velocity offsets are computed between narrow emission lines. We find systematic differences between redshifted and blueshifted subsamples, which may point to residual velocity biases or additional physical effects (e.g. winds, inflows, orientation-dependent obscuration, or asymmetric broad-line regions). Recoiling massive black holes provide a natural explanation for the observed correlation, but alternative scenarios should be explored. If confirmed, this would enable population-level constraints on massive black hole merger rates, recoil dynamics, and active galactic nuclei disc properties.

Multi-wavelength observations of quadruply lensed quasars constitute a powerful probe of cosmology, dark matter substructure along the line of sight, and the structure of X-ray emitting regions in high-redshift quasars. These investigations are conditional on acquiring an accurate model for the surface mass density of matter lensing these quasars. We propose a simulation-based machine learning method to accelerate parameter inference in real quadruply lensed systems by several orders of magnitude. We simulate a grid of quadruply lensed sources with Singular Isothermal Ellipsoid (SIE) lenses and use the projected positions of the four lensed images to train two fully connected neural networks that predict the mass parameter and ellipticity. For a large fraction of simulated systems, the neural network-initialised mass models converge in time-scales of a few minutes and recover the source position at the <0.''005 level for a broad range of lens masses and ellipticities. We apply our neural networks to seven quadruply lensed quasars, lensed by isolated galaxies or a galaxy-perturber pair, which have archival Chandra observations. The final optimised mass models for each quasar predict the observed lensed image positions in Gaia Data Release 3. These mass models enable the caustic method, which locates the X-ray-to-optical emission regions to milliarcsecond precision in these otherwise unresolvable systems, improving the effective angular resolution of Chandra at high-z by up to two orders of magnitude. Our approach accelerates this mass modelling by supplying informed initial parameters, enabling application to the many new quadruply lensed systems expected from forthcoming surveys.

Most cataclysmic variables (CVs) are discovered when they have an outburst generating an inherent selection bias against CVs that rarely, or never, outburst. CVs discovered by virtue of their spectroscopic characteristics are particularly valuable to offset this bias and we have used an established machine-learning technique to assist in searching 98 966 000 spectra obtained by the Dark Energy Spectroscopic Survey (DESI) to find such CVs. DESI observations are much deeper than previous spectroscopic surveys and we have identified 1029 CVs, 221 of which are new including ten of the AM CVn subtype. We have spectroscopically confirmed 441 CV candidates and obtained 84 new or improved orbital periods. We present revised space density estimates based upon this new data. We have also added ten more to the eight known examples of an intriguing class of CVs which exhibit peculiar changes in accretion.

This work investigates the optical appearance of a rotating black hole (BH) in nonlinear electrodynamics (NED) using two illumination models, namely a celestial sphere and a thin accretion disk. The BH images are constructed using a backward ray-tracing method together with a fisheye camera model. We examine the effects of the electric charge $Q$ and the NED parameter $β$ on the event horizon, shadow, photon ring, and optical appearance for both prograde and retrograde accretion flows. The results indicate that an increase in $β$ leads to a larger shadow radius with reduced distortion, whereas increasing $Q$ decreases the shadow size and enhances its deformation. These features are further quantified through the shadow radius and distortion parameter. We also analyze the direct and lensed images of the thin accretion disk, together with their corresponding redshift distributions and emission bands. The redshifted emission is found to dominate the observed images, while the blueshifted region is confined to the vicinity of the photon ring. Our results demonstrate that both $Q$ and $β$ leave distinct signatures on the optical appearance of rotating NED BHs, providing useful insights for future high-resolution observations.

Very-high-energy $γ$ rays from active galactic nuclei are attenuated through pair production on the extragalactic background light (EBL), providing a probe of cosmic expansion. We develop a Bayesian inference analysis framework that uses an observationally driven, redshift-dependent EBL model and anchors intrinsic source spectra to the Fermi-LAT 3FHL catalogue while marginalising spectral-shape departures and dataset normalisations. The method is validated on realistic mock observations and applied to 241 archival H.E.S.S., MAGIC and VERITAS spectra of 50 AGN compiled in STeVECat. Because the leading opacity depends on the ratio of the EBL normalisation to the reduced Hubble constant, the gamma-ray data primarily constrain this ratio rather than $H_0$ alone. We measure $r=1.723^{+0.096}_{-0.095}$. For a fixed EBL scale, this gives $H_0=58.3^{+3.4}_{-3.0},\mathrm{km,s^{-1},Mpc^{-1}}$; allowing an 18\% EBL-scale uncertainty gives $H_0=60.5^{+10.8}_{-10.0},\mathrm{km,s^{-1},Mpc^{-1}}$. Matched injections recover the input opacity without appreciable bias, and the tested intrinsic-spectrum and EBL-shape perturbations are subdominant except for large infrared-background mismodelling. The predominantly low-redshift sample leaves $Ω\mathrm{M}$ weakly constrained. The measurement is therefore limited by the EBL normalisation rather than statistics; reducing its uncertainty to a few per cent would make gamma-ray opacity a competitive, distance-ladder-independent probe of $H_0$.

The LIGO-Virgo-KAGRA collaboration has reported the results for searches for sub-solar mass components in compact binary coalescence during observing run O4a. No detection candidates were identified, but the most significant seven triggers were reported. We present the results of Bayesian parameter inference on these triggers. Five of the triggers show agreement between the Bayesian parameter estimation and the search pipeline trigger. Our results show that three of the triggers may contain a possible sub-solar mass component. Parameter estimation indicates that the other two events, if real, would be neutron star - black hole binaries. The remaining two triggers do not provide informative parameter estimation. We also study three O4a compact binary coalescence triggers, and one O3 trigger, that have been noted by three other groups, and our parameter estimation indicates that three of these may contain a sub-solar mass component. We study the data quality associated with these triggers. Finally, we discuss the challenges for parameter estimation on compact binary coalescence events containing a sub-solar mass component: long signal duration, possible small chirp masses, possible small mass ratios, and data quality issues over potentially hundreds of seconds of data.

We explore the possibility of explaining hard X-ray data obtained from one of the Magnificent Seven (M7) neutron-stars (NSs) employing QCD axion-converted photons. The emission of thermal axions along with neutrinos from the core has been considered. We adopt the nucleon-nucleon bremsstrahlung process as the baseline axion production mechanism and Cooper-pair breaking and formation (PBF) as an additional process. We investigate here whether the selectively enhanced QCD axion coupling model can better explain the hard X-ray excess than the commonly used KSVZ axion model. Our results suggest that meV-mass QCD axions cannot explain the hard X-ray observation within the adopted framework. The enhanced selective model in the micro-eV scale provides closer agreement with the hard X-ray data. We thus conclude that the emission of hard X-rays in the $2-8$ keV range from isolated M7 stars could be explained by QCD axions under an enhanced coupling scenario.

The stacked kinetic Sunyaev-Zel'dovich (kSZ) signal probes the velocity-weighted projected gas momentum around galaxies, and is emerging as a powerful probe of gas fractions and baryonic feedback. Its interpretation, however, rests on several assumptions that we test in this pair of companion papers. Using the FLAMINGO hydrodynamical simulations and DESI-like galaxy mocks for luminous red galaxies (LRGs), the bright galaxy sample (BGS), and emission-line galaxies (ELGs), we identify the ingredients required to model the signal to better than $10\%$. This first paper focuses on velocities. We decompose the signal into a dominant bulk-flow term, proportional to the mean optical depth, plus non-linear terms arising from the small-scale gas momentum and its coupling to the stacking velocity. When the stacking velocities are reconstructed from linear information in real space alone -- an idealisation which is not possible in practice -- the non-linear terms cancel and the signal traces the mean optical depth to within a few per cent. When the stacking velocity instead retains non-linear information or is affected by redshift-space distortions, the non-linear terms suppress the signal by $10-20\%$: a $1-2σ$ effect for current data that is expected to be statistically significant for upcoming surveys, and one that depends only weakly on baryonic feedback. Our results reveal a trade-off: velocity estimators that retain small-scale information boost signal-to-noise but require simulation-based modelling, whereas conservative reconstructions simplify the interpretation at the cost of signal-to-noise.

Primordial black hole (PBH) binaries in the stellar mass range may still contribute a fraction of the detectable compact object binaries by LIGO and future GW observatories. PBH binaries at formation typically have very high eccentricities. In this paper, we study the eccentricity of stellar mass range PBH binaries from all formation channels and account for all evolutionary pathways. We simulate large samples of PBH binaries, tracking their full orbital evolution up to their merger or to the present day. For those that merge, we compute their GW strain, detectability, and eccentricity distributions for LISA, DECIGO, ET, CE, and aLIGO. We find that PBH binaries that evolve in isolation completely circularize by the time their GWs enter any GW band except for LISA's, where residual eccentricities of order $O(10^{-2})$ can exist. Binaries that become part of dark matter halos can have multiple binary-single interactions with other PBHs, especially if they reside in the more dense environments among them and can have higher eccentricities even at their late inspiral phase, probed by the GW observatories. Considering the current limits on the abundance of stellar mass range PBHs, we predict that LISA and DECIGO together would be able to probe $O(10^2)$ such binaries with $e>0.01$. If these future GW observatories in space can exclude such eccentric binaries, then limits on the PBH abundance can be improved by an order of magnitude.

We consider how a class of morphological descriptors, the Minkowski Tensors (MTs), can be used to test the statistical isotropy of random fields on the sphere. The definition of the MTs involves an integral of a tensor, which is an ambiguous operation on a curved manifold. We find that existing estimators in the literature, when applied to fields on the two-sphere, either explicitly break covariance or artificially isotropize the MT due to a geometric rotation of tangent spaces. To evade these issues, we construct the MTs of individual connected components and use them to build correlation functions $ξ_{\pm}(θ,ν)$ of their relative orientations. These correlation functions are built from scalars and are therefore covariant, and can be used to search for alignment of structures as a function of scale (angular separation). We generate four sets of random fields on $S^{2}$ -- isotropic, dipole modulated, globally-sheared and locally-sheared, and show how the connected component correlation functions can distinguish scale dependent alignments. For the sheared fields, the decay scale of $ξ_{+}$ measures the angular coherence of the alignment, and the amplitude of $ξ_{-}$ at large separations measures its globally coherent fraction, distinguishing the two shear models. In contrast, dipole modulation generates no significant signal in the orientation statistics. We show analytically that its effect on the traceless component of the Minkowski tensor is second order in the modulation amplitude $λ\ll 1$.

In this work, we study the gravitational lensing of gravitational waves (GWs) by extending the geometric-optics approximation to higher order. With the help of the Newman-Penrose formalism, we reexpress the GW propagation equations as a series of scalar equations and present explicit expressions for the Weyl scalars that describe the GW polarizations. By combining the approaches of solving geodesic deviation and transport equations, we construct a solvable system of equations that describes the evolution of GW polarization along null geodesics. This framework fills the gap left by the leading-order geometric optics and the Kirchhoff diffraction integral, neither of which captures the polarization characteristics of GWs during the lensing process. This work applies the above framework to a Schwarzschild lensing configuration. Through a rigorous theoretical formulation and detailed numerical analysis, our results reveal the emergence of apparent vector and scalar modes in lensed GW signals, which originate from the smearing of the polarization plane and distortion of the wavefront and do not represent genuine dynamical degrees of freedom but rather arise as the propagation effects imposed by gravitational lensing.

We study a Schwarzschild-like black hole embedded in an exponential-sphere (ESM) dark matter halo, characterized by a halo mass $M_0$ and a scale radius $r_0$. We first show that the halo's effect on the marginally bound orbit (MBO) and innermost stable circular orbit (ISCO) is richer than a simple shift: the characteristic radii and energies vary non-monotonically with $r_0$, dipping below their Schwarzschild values before recovering, while the angular momenta decrease monotonically; as a function of $M_0$, the response can even reverse sign depending on how extended the halo is, with only the ISCO energy remaining monotonic throughout. We classify periodic orbits by the rational frequency ratio $q=ω_φ/ω_r-1=w+v/z$ and find that $r_0$ and $M_0$ leave clearly distinguishable imprints on the orbit spectrum. Using the numerical kludge framework, we compute the corresponding extreme-mass-ratio-inspiral (EMRI) waveforms and show that varying $r_0$ produces a strong, monotonic effect enlarging the orbits, lengthening the radial period, and introducing a clear dephasing while comparable variations in $M_0$ leave the signal nearly unchanged unless $M_0$ becomes a sizable fraction of the black hole mass. Together, these results indicate that EMRI waveforms can, in principle, disentangle the total mass of a dark matter halo from its spatial extent, offering a strong-field probe of the dark matter distribution around supermassive black holes.

An intermediate-mass black hole (IMBH) hidden in our Galactic Center (GC) may explain the puzzling observations of the stellar distribution around Sagittarius A* (Sgr A*), the supermassive black hole (SMBH) in the GC. Future observations with the next-generation radio telescopes, such as the SKA, are promising to discover pulsars orbiting around Sgr A*, and thus provide the possibility of constraining the hidden IMBH with pulsar timing. We study the detectability of a third-body, the IMBH, in the pulsar-SMBH system based on radio timing observation. We find that the pulsar-SMBH system is very sensitive to such a third-body perturbation and can be used to put stringent constraints on the existence of the IMBH. Even under strong perturbations caused by the complex GC astrophysical environments, timing observation will still complement the existing observational constraints.

Plasma streaming instabilities excited by relativistic charged particle beams play a pivotal role in astrophysical and laboratory environments. Their numerical study, however, is challenged by the disparity in spatiotemporal scales between the background plasma and beam particles, which can differ by several orders of magnitude for tenuous, ultrarelativistic beams. Here, we exploit the quasistatic approximation (QSA) to develop a new theoretical framework capable of capturing the full unstable spectrum in the spatiotemporal regime relevant for beams that continuously encounter unperturbed plasma at their leading edge. Within this linear, fully electromagnetic model, we uncover a previously unreported spatiotemporal evolution of the current filamentation instability and elucidate its interplay with the oblique two-stream instability, predicting the dominance of filamentation in the vicinity of the beam front. The good agreement between theory, kinetic particle-in-cell (PIC) simulations, and QSA-based PIC simulations validates the robustness of the approach. By pushing QSA-based PIC simulations to extremely dilute electron-positron beams, such as those found in blazar jets, we demonstrate their unique ability to capture the rich nonlinear dynamics of streaming instabilities in parameter regimes previously inaccessible to kinetic simulations.

Young M-type stars exhibit frequent flares, which would seriously impact their habitable planets. Since stellar surfaces cannot be resolved, flare locations remain unknown. Here, by using the Mg I b emission line in LAMOST spectra, the location of a stellar flare from a young M dwarf is pinpointed at $ (-123.0^{+8.0}_{-5.8}, 80.5^{+2.9}_{-3.2})$ in degree in the polar region. Our method can be used to accurately locate stellar flares. This would enable us to assess the impact of stellar flares on planets more accurately and improve our understanding of stellar dynamo models.

The Magnusian is a phase-space function that generates finite-time evolution through nested Poisson brackets. It is related to several familiar generators of classical dynamics, including the radial action, the eikonal phase and related quantities. In this work, we extend the Magnusian framework to systems with dissipation and nonlocal-in-time interactions using the in-in formalism, also known as the Schwinger-Keldysh or Galley formalism. This framework is particularly natural for binary dynamics, where integrating out the mediating gravitational field can produce both dissipative radiation-reaction effects and hereditary, nonlocal-in-time interactions. We derive the generalized Magnusian and show that it continues to generate finite-time evolution. As an application, we construct the Magnusian for Newtonian bound motion subject to the leading 2.5PN radiation-reaction force. The resulting generator defines a discrete evolution map from one cycle to the next and describes the evolution of the system in agreement with numerical solutions.

The radio halo in the cool-core galaxy cluster A1795 has recently been proposed to be of hadronic origin, because it extends on a scale of the order of Mpc, where no turbulence is expected to be injected in a relaxed cluster. In this paper we aim to constrain the properties of the non-thermal protons and the cluster magnetic field strength under the hypothesis of a hadronic origin of the radio halo at the light of the available gamma ray upper limit in this cluster. We assume a radial profile and several values of the central intensity of the magnetic field, and derive the corresponding properties of the non-thermal protons necessary to reproduce the flux density and the surface brightness profile of the radio halo. For the obtained results, we calculate the corresponding gamma ray emission and compare it with the Fermi-LAT upper limit. We obtain that, for a magnetic field energy radial profile following the thermal one, magnetic field central intensities $B_0<5\,μ$G imply a gamma ray emission similar to or above the Fermi-LAT upper limit. Therefore larger values of the magnetic field are necessary in the hadronic scenario. For these values the radial profile of non-thermal protons needs to be slightly decreasing with radius, although more slowly than the thermal one. For smaller values of the magnetic field different mechanisms for producing or accelerating the non-thermal electrons are necessary.

We develop a new method for simulating pressureless fluids of neutral dust coupled to magnetohydrodynamic gas through dust-gas drag. It has been pointed out that, in the strong-coupling regime, dust-gas multifluid methods suffer from artificial variations in the dust-to-gas mass ratio when the dust and gas are evolved with independent numerical fluxes. This problem arises from inconsistencies between the dust and gas mass fluxes. In the strong-coupling limit, the dust-to-gas mass ratio is advected with the local gas velocity. Recently, a new method based on the Harten-Lax-van Leer (HLL) solver was proposed. This method constructs the dust mass flux so that it is consistent with the gas mass flux, and successfully reduces artificial variations in the dust-to-gas mass ratio. Here, we develop a Split-Flux method that can be coupled to an HLLD gas solver. Through various numerical experiments, we show that the Split-Flux method suppresses artificial variations in the dust-to-gas mass ratio, while preserving the low numerical diffusivity of the HLLD solver.

We perform three-dimensional, high-resolution, general-relativistic magnetohydrodynamics (GRMHD) simulations of the magnetorotational instability (MRI) in differentially rotating neutron stars. We consider both high-mass models which collapse either promptly, or due to the outward transport of angular momentum removing rotational support, and lower-mass models, which remain stable even after solid-body rotation has been achieved. We measure effective transport coefficients of the resulting turbulent flow, shear-viscosity $α_{\rm vis}$, mixing-length $\ell_{\rm mix}$, and mean-field dynamo $α_{\rm DYN}$-parameter, and their correlations with mean-flow parameters, such as rest-mass density $ρ$, characteristic wavelength of the MRI $λ_{\rm MRI}$, and vertical Alfvén velocity $v_A$. At saturation, $\ell_{\rm mix}$ and $α_{\rm DYN}$ correlate with $λ_{\rm MRI}$ and $v_A$ respectively, as expected from dimensional analysis. However, both quantities show deviations of roughly an order of magnitude from the values predicted on the basis of these correlations. They are also highly intermittent in space and time. The mixing length is found to be largely independent of density, calling into question the $\ell_{\rm mix}(ρ)$ ansatz used in many general-relativistic large-eddy simulations. Our results show that, while the effects of MRI-induced turbulence might be qualitatively reproduced by simulations that employ transport coefficients chosen using dimensional-analysis considerations, fully-resolved GRMHD simulations are needed to make quantitative predictions.

Recent observations have demonstrated the presence of cosmic rays (CRs) in cosmic-web filaments. Cold streams supply gas inflows from these filaments into massive galaxies during the cosmic noon. As these streams are expected to be magnetised, external cosmic-web CRs may become entrained with this inflowing gas. We aim to determine whether this externally-supplied CR population can deposit energy to alter or disrupt the supply of cold gas to galaxies. We couple a spectrally-resolved CR transport calculation to a redshift-dependent analytical model of magnetised cold streams in galaxy haloes and investigate whether externally-supplied CRs can modify gas supply through this channel. We find CR energy deposition can alter the thermal state of cold streams. Dense stream cores remain largely resilient and only experience weak heating. Their temperature is raised by less than a factor of 10, which is insufficient to overcome radiative cooling at the stream-CGM interface. In more diffuse streams, and in partially mixed interface gas of the most massive haloes near the virial radius, CR heating becomes strong enough that radiative cooling can no longer balance it, and the gas is heated toward or above the mixing-layer temperature. This weakens the stability of the stream, making it more susceptible to disruption. Complete evaporation is possible only in extreme cases. Cold streams are therefore more vulnerable to CR heating at larger galactocentric radii, higher halo masses, and in more diffuse or partially-mixed stream material. By preferentially heating diffuse gas, externally supplied CRs may introduce additional selectivity into cold-gas accretion that modifies the gas supply and growth of massive galaxies. These CRs weaken fragile streams and erode their cold envelope, and may cause surviving cold flow components to appear thinner and more sharply confined far into galaxy haloes.

Automated solar filament detection using deep learning faces several challenges. Semantic segmentation of solar filaments is a complicated multiscale feature extraction task with long-tail distribution. Furthermore, a large-scale, highly complete, and finely detailed dataset has become mandatory for providing abundant information. To address these challenges, we present a series of machine learning approaches to develop a solar filament detection workflow that performs superbly. First, we manually annotated a small-scale solar filament dataset based on H$α$ spectra called MHAS. Next, we developed the Multiscale ORiented DENdritic (MORDEN) model, a semantic segmentation model focusing on multiscale feature extraction. We also introduced the Dense Conditional Random Field (DenseCRF) and Density-Based Spatial Clustering of Applications with Noise (DBSCAN) methods for post-processing. Using the proposed workflow, we generated a large-scale, high-quality dataset called AHAS. Experimental results demonstrate that MORDEN outperforms several existing solar filament semantic segmentation models with open access. DenseCRF has been demonstrated to effectively capture fine edge details. We also evaluated the effects of data scaling and the reliability of DBSCAN and found that both approaches yield satisfactory performance. Multiple visualization results substantiate our quantitative findings. Our work provides a foundation for maximizing the potential of deep learning models for solar filament detection.

We investigate phenomenological effects induced by a noncommutative deformation of Einstein--Rosen gravitational-waves within the framework of the Riemannian geometry of noncommutative surfaces developed by Chaichian et al. Considering a noncommutative structure between the radial and axial coordinates, we study perturbatively the motion of nonrelativistic test particles in the corresponding deformed geometry. We show that the deformation generates a coupling between the radial and longitudinal sectors, while the radial dynamics remains unaffected by the noncommutative deformation at the perturbative order considered. The induced longitudinal response is governed by a spectrally weighted functional of the gravitational-wave profile, implying that longitudinal observables depend on higher-order spectral moments than their commutative radial counterparts. As a consequence, noncommutative effects exhibit enhanced sensitivity to the ultraviolet structure of the gravitational configuration. We analyze separately monochromatic Einstein--Rosen waves and the localized Weber--Wheeler pulse. In the monochromatic case, the noncommutative correction induces a quasi-periodic longitudinal motion, whereas for the Weber--Wheeler pulse it produces an impulsive longitudinal response analogous to a gravitational velocity memory effect. In addition, we derive an explicit analytical expression in commutative General Relativity for the residual radial velocity generated by the Weber--Wheeler pulse at large radial distances in the perturbative regime.

We consider a cosmological first-order phase transition in which bubbles of true vacuum nucleate during inflation but do not collide and percolate until the Universe has entered the radiation-dominated era. If the collisions take place soon after the end of inflation, the size of these bubbles can be significantly greater than the Hubble length. This has two important consequences for the gravitational waves produced by the bubble collisions: First, as the peak frequency is determined by the comoving bubble radius, it can be well below the MHz frequencies typical for bubble collisions at the end of inflation. Second, when comparing collisions beginning at the same time, the amplitude of the gravitational waves is greatly enhanced relative to Hubble-sized and smaller bubbles. Together, these two effects mean that gravitational waves produced by super-Hubble bubbles soon after the end of inflation can be within the observable frequency and amplitude ranges of LIGO and NANOGrav, as well as LISA and other future gravitational wave experiments. We demonstrate this with a simple illustrative model.

The origin of the cosmic neutrino background (CNB) and the cosmic gamma-ray background (CGB) remains uncertain. Accretion disk winds driven by active galactic nuclei (AGNs) have been proposed as possible contributors, but their predicted background levels depend sensitively on poorly constrained wind energetics and ambient densities. We revisit the AGN disk-wind scenario by constructing a lepto-hadronic wind model calibrated with radio and GeV gamma-ray data of nearby Fermi Large Area Telescope─detected Seyfert galaxies. In our framework, cosmic rays accelerated both at wind-driven forward and reverse shocks produce synchrotron, external-Compton, and hadronic emission. We also incorporate recent XRISM constraints on wind parameters. Applying our calibrated lepto-hadronic models to an AGN population synthesis model, we find that disk winds contribute at most ≲5% of the CGB above 10 GeV and ≲10% of the CNB around 100 TeV, suggesting that they are unlikely to dominate both backgrounds. Finally, we identify nearby Seyfert galaxies hosting ultrafast outflows as promising targets for future TeV gamma-ray and TeV─PeV neutrino observations, which would offer firm tests of the disk-wind scenario.

Sterile neutrinos offer a minimal and testable explanation for dark matter (DM), with their radiative decay actively searched for in X-ray observations. We show that cold sterile neutrino DM can be efficiently produced during reheating from inflaton decays with a small branching ratio, BR ≲ 10<SUP>-4</SUP>. This production mechanism opens regions of parameter space where the active-sterile mixing is small enough to evade current X-ray constraints while reproducing the observed DM abundance. We systematically map the viable parameter space in terms of the sterile neutrino mass, mixing angle, inflaton mass, reheating temperature, and branching ratio. We further demonstrate that sterile neutrino DM can serve as a probe of inflationary reheating, with future X-ray observations capable of yielding information on the inflaton mass and the reheating-temperature ratio m<SUB>ϕ</SUB> /T <SUB>rh</SUB>. For a given inflationary model in which the inflaton mass is known, this leads to a lower bound on the reheating temperature that is several orders of magnitude stronger than the existing bound from Big Bang Nucleosynthesis.

Ultraviolet (UV) observations provide a uniquely powerful window into the hot and evolved stellar populations that shape the structure, evolution and integrated light of star clusters. Because UV wavelengths are highly sensitive to massive main-sequence stars, blue straggler stars (BSS), extreme-horizontal-branch (extreme-HB) stars, post-AGB objects, interacting binaries and compact remnants, UV studies enable constraints on fundamental processes that are inaccessible at optical and infrared wavelengths. This review synthesises five decades of UV investigations of star clusters across the Milky Way, the Magellanic Clouds (MCs) and nearby galaxies, drawing on results from early space telescopes, wide-field surveys, high-resolution imagers and the recent capabilities of AstroSat/UVIT and Swift/UVOT. In Galactic open clusters, UV photometry has revealed diverse compact companions—including white dwarfs, hot subdwarfs and stripped stars—and has been essential for establishing the mass-transfer origins of BSS and related populations such as Blue Lurkers and yellow stragglers. In globular clusters, UV imaging is indispensable for identifying multiple stellar populations through UV-sensitive molecular bands, probing helium enrichment and mapping HB morphologies from cluster cores to tidal radii. Wide-field UVIT surveys have provided homogeneous catalogues of HB and post-HB stars, extending earlier Hubble Space Telescope results to full-cluster scales. In the MCs, UV observations have transformed our understanding of multiple populations in intermediate-age clusters, rotation-driven extended main-sequence turn-offs and the recently identified UV-dim phenomenon. UV spectroscopic surveys have advanced constraints on massive-star evolution, winds and binarity at low metallicity. Meanwhile, UV mapping of the Magellanic Bridge demonstrates ongoing massive-star formation in low-density tidal environments. Beyond the Local Group, UV studies of extragalactic clusters reveal star-formation histories, stellar feedback and population synthesis constraints in diverse galactic environments. Collectively, UV observations now form a cornerstone of star cluster astrophysics and will continue to do so with upcoming missions.

Colliding winds in massive-star binaries generate non-thermal radio emission and an increased X-ray emission. We study the radio emission of the non-thermal emitter 9 Sgr, which is a long-period and highly eccentric binary. We conducted a monitoring campaign of 9 Sgr around its 2013 - 2014 periastron passage, obtaining radio, X-ray and optical spectroscopy data. In this paper, we analyse the radio data. The radio data at 3.6, 6 and 20 cm show a maximum near periastron. Other non-thermal radio emitters among O-type binaries have a minimum flux near periastron, because the synchrotron emission is absorbed by the free-free absorption in the two stellar winds. This is not the case for 9 Sgr, because even at periastron the orbital separation is sufficient to maintain the wind-wind collision and its associated synchrotron emission outside the effective free-free radius of both stars. Our standard modelling with a local magnetic field that decreases inversely proportional to the distance from the stars (1/r) fails to explain the observed fluxes. Instead, we need to adopt a local magnetic field that decreases faster than 1/r. While our model provides an acceptably good fit to the data, there is clearly still room for improvement. More advanced modelling should include magnetohydrodynamics and more detailed physics of the injection, acceleration and cooling of the relativistic electrons. Radio observations at orbital phases away from periastron can put further constraints on the models.

Supergranulation is one of the dominant scales of near-surface solar convection and provides an important diagnostic for studying the interaction between convective flows, rotation, and magnetic activity. We develop an automated framework to identify and characterize supergranular structures using subsurface horizontal-velocity maps inferred from time-distance helioseismology. The method applies Laplacian-of-Gaussian detection to horizontal velocity divergence maps and combines this with magnetic-field masking, divergence-based filtering, and multi-peak rejection to isolate supergranular cells under both quiet-Sun and active conditions. Using this approach, we analyze 16 years of SDO/HMI observations spanning Solar Cycles 24 and 25 and investigate temporal and latitudinal variations of supergranular properties. The results reveal a clear solar-cycle dependence: the mean supergranular diameter decreases near solar maxima and increases around solar minima, with systematically larger supergranules in the weaker Solar Cycle 24 than in the stronger Solar Cycle 25. The width of the diameter distribution increases during high magnetic activity, whereas the number of detected supergranules shows only weak cycle dependence. The mean velocity divergence within detected supergranules is strongly anticorrelated with sunspot number, indicating magnetic suppression of divergent convective flows. Time-latitude distributions of supergranular diameter and divergence closely follow the migration of solar activity belts, while the curl of the horizontal velocity shows weak cycle dependence but pronounced hemispheric asymmetry. These results establish supergranulation as a sensitive tracer of solar-cycle-related changes in near-surface convection.

Aims. The mass-loss process of red supergiant (RSG) and asymptotic giant branch (AGB) stars and its relation to variability are poorly constrained. We aim to study the photosphere and near-surface atmospheric structure, where the mass-loss is initiated. For this purpose, we studied two oxygen-rich evolved stars: the Mira-type AGB star R Car and the RSG VX Sgr. Methods. We used the VLTI-GRAVITY instrument operating in the near-infrared K-band. Our sample comprises 54 VLTI-GRAVITY snapshots (18 R Car, 36 VX Sgr) taken over about 7 years, making it the largest VLTI time series dataset to date. We determined the angular diameter as a function of time for the continuum (photosphere) and selected atomic and molecular bands, i.e., lines of Ti I and Sc I as well as bands of H<SUB>2</SUB>O and CO. Furthermore, we compared the variability and atmospheric structure to state-of-the-art radiative-hydrodynamics CO5BOLD 3D simulations. Results. The radii of photosphere (R<SUB>⋆</SUB>) and extended atmospheric layers are variable and relate to the light curve with phase shifts. The near-photospheric layers show a maximum radius near visual brightness minima (φ<SUB>vis</SUB> ∼ 0.4─0.6). Inner atomic (Ti I, Sc I) and molecular (H<SUB>2</SUB>O) layers are further phase-shifted by ∆φ<SUB>vis</SUB> ~ 0.05. The more extended CO layers show longer, irregular periods and maximum extensions of ∼1.3─1.7 R<SUB>⋆</SUB> for R Car and of ∼1.5─2.2 R<SUB>⋆</SUB> for VX Sgr. Comparison with synthetic interferometric data of an AGB model based on several pulsation cycles in CO5BOLD simulations revealed a similar behavior. The photosphere shows regular pulsations, but with maximum diameters preceding minimum brightness (φ<SUB>vis</SUB> &lt; 0.5). The H<SUB>2</SUB>O layer showed a much weaker extension compared to our observations, while CO showed a good agreement. Furthermore, during the 2020─2021 season, VX Sgr exhibited an extreme mass-loss event similar to that of Betelgeuse, preceded by two strong shocks and culminating with the extreme expansion of H<SUB>2</SUB>O and CO layers, both up to ∼2.2 R<SUB>⋆</SUB>. Unexpectedly, during this event, we also detected Brackett γ in interferometric data as well as strong Balmer emission in optical spectra, both of which are also signatures of a shock propagating through the atmosphere. Conclusions. The Mira R Car showed an estimated photospheric radius of R<SUB>⋆</SUB> = 280 ± 25 R<SUB>⊙</SUB>, with a regular fundamental mode (FM) pulsation amplitude of ∼13% of R<SUB>⋆</SUB>. During its active cycle, the extreme RSG VX Sgr showed R<SUB>⋆</SUB> = 1556 ± 110 R<SUB>e</SUB>, with an FM pulsation amplitude of ∼13% of R<SUB>⋆</SUB>, the same as R Car. During its quiescent cycle, it showed a smaller value, R<SUB>⋆</SUB> = 1456 ± 108 R<SUB>⊙</SUB>, and low-amplitude pulsations near the first overtone (O1), only ∼4% of R<SUB>⋆</SUB>. This supports a steady mass-loss process for Mira stars related to stable large-amplitude FM pulsation, whereas the mass-loss process for RSGs may be dominated by extreme events connected to changes in the pulsation mode from low-amplitude O1 to large-amplitude FM pulsations.

Direct observation of the orbital motion of a sub-parsec supermassive black hole binary (SMBHB) would provide the first conclusive electromagnetic proof of such systems existing. Widely considered to be the source of gravitational waves, binaries are expected to form as a natural consequence of galactic mergers, and determining the processes that drive their evolution is essential to understanding cosmological evolution. In this work, we evaluate the prospects of using ground and spaceborne Very Long Baseline Interferometry (VLBI) to observe SMBHBs and estimate their orbital parameters. The Black Hole Explorer (BHEX) is considered the primary case study. Achieving unprecedented resolution, BHEX will provide access to a new volume of binary parameter space, potentially enabling the first confident detection of an SMBHB. We present an orbit-fitting approach that uses relative astrometry and Bayesian dynamic nested sampling, and demonstrate its efficacy on a set of example binary systems. For simulating observations, we use a binary image model based on post-Newtonian orbit propagation and find that for BHEX, binary detection requires a total flux density of 40 mJy and a minimum separation of ∼2 µas. With three annual observations, BHEX could constrain the semi-major axis and the eccentricity of binaries with orbital periods of ≤10 years to within 0.06 dex of the true values under specific noise assumptions. We have also evaluated the benefits provided by BHEX for binary detection compared to ground-only observations by arrays such as the next generation Event Horizon Telescope (ngEHT). Finally, we constrained the requirements of a future spaceborne VLBI system capable of performing a statistically significant survey of SMBHBs.

We present a homogeneous multiwavelength analysis of 35 blue straggler star (BSS) candidates in nine open clusters, combining Swift/UVOT near-ultraviolet data with Gaia DR3 astrometry and optical-to-infrared photometry. We construct spectral energy distributions (SEDs) to search for signatures of hot companions associated with past mass transfer. Among the sample, 15 BSSs (∼43%) show ultraviolet excesses that are better described by two-component SED fits. The inferred companions are consistent with hot white dwarfs and pre-extremely low-mass (pre-ELM) white dwarf candidates, suggesting systems observed at different stages following mass transfer. We examine the radial distribution of the BSSs and find evidence for mass segregation in dynamically evolved clusters, a result that is broadly consistent with the estimated half-mass relaxation timescales of the host systems. To place the clusters in a Galactic context, we compute their orbits using galpy, obtaining low eccentricities (e ≤ 0.1) and disk-like trajectories. We also find a positive relation between the half-number radius of the BSS population (r<SUB>50</SUB>) and the total number of BSSs. Overall, our results are consistent with a scenario in which the BSS population in these clusters is dominated by binary evolution. The systems identified here provide observational constraints on post-mass-transfer evolutionary phases. While the number of robust detections is limited and intrinsic degeneracies remain in SED-based decomposition, these results provide a useful foundation for future spectroscopic confirmation.

We study slow-down effects for bubbles formed in a cosmological first-order phase transition (PT) focusing on deflagrations and hybrids, where the bubble wall is preceded by a shockwave of heated plasma. Slow-down has been observed in multi-bubble simulations together with a suppression of gravitational wave (GW) emission, mostly for slow walls. We study the impact of the shock waves on the wall velocity around percolation, by considering steady-state single-bubble solutions and incorporating the possible heating effects by two different mechanisms. First, we investigate the slow-down experienced by a bubble expanding into an impeding shockwave, where the temperature is higher than at nucleation, and the fluid is no longer at rest. Taking into account such heating and kinematic effects, we find that the most significant slow-down occurs for the fastest walls, and thus cannot explain the suppression of the GWs observed in the simulations. However, these effects are stronger for PTs with a sizeable change in degrees of freedom unlike what is usually implemented in simulations, suggesting that the degrees of freedom can be an important additional parameter for characterizing the GW spectrum. For the second slow-down mechanism, we study heated droplets of false vacuum that shrink towards the end of the PT. By implementing a suitable boundary condition motivated by energy conservation, we show how the droplet velocity, interpreted here as the late-time velocity of the bubble walls, can be predicted from the properties of the initial deflagration/hybrid, in remarkable agreement with numerical simulations. Droplets are found to shrink more slowly for stronger PTs and slower deflagrations, with a mild dependence on the change of degrees of freedom. Such slow droplets naturally correlate with a suppression of GWs, while geometrical properties such as the shock width play an important role as well.

We show the emission of the Nambu-Goldstone (NG) bosons from the cosmological evolution of global monopoles. The NG bosons are non-thermally produced from the dynamics of global monopoles such as the pair annihilation of monopole and anti-monopole. Our numerical lattice simulations demonstrate that the spectrum of NG bosons emitted from the scaling evolution of global monopoles has a peak around the horizon scale, as in the case with the global string and the semilocal string. We also estimate the abundance of the pseudo-Nambu-Goldstone (pNG) dark matter when one (or both) of the NG modes has a soft mass.

We investigate how modified electron dispersion relations affect the structure of cold white dwarfs (WDs). The deformation is introduced only in the degenerate electron equation of state, through the energy of a single particle and the group velocity, while the stellar mass density remains dominated by ions through the relation $ρ\simeq μ_e m_u n_e$ imposed by charge neutrality. The resulting equations of state are coupled to the standard TOV equations, with no modification of the gravitational field equations. For a baseline composed of carbon and oxygen with $μ_e=2$, the undeformed limit recovers a maximum mass in the Chandrasekhar scale, validating the normalization of the calculation before the modified cases are considered. The first model of modified dispersion produces only a modest stiffening over the parameter range studied, whereas the logarithmic model depends strongly on the sign of the deformation parameter: negative values increase the pressure and the maximum mass, while positive values soften the sequence. These results show that WDs can isolate the impact of modified electron kinematics on compact star structure, but the logarithmic branch in particular requires further restrictions from its physical domain, stability conditions, and observational constraints on mass and radius.

Strong lensing changes the phase of a gravitational-wave signal as well as its amplitude and arrival time. We study whether this phase information can distinguish three dark-matter structures in the lens: a Navarro--Frenk--White halo (NFW), a self-interacting halo (SIDM), and a fuzzy-dark-matter field (FDM). We generate waveforms for the detectable lensed massive-black-hole-binary population of a four-year LISA mission and fit every signal with the same smooth singular-isothermal-ellipsoid lens with external shear. In 132 lens systems, 311 images are resolved as separate signals in time. NFW and SIDM produce real waveform changes, but their slowly varying part is largely degenerate with the constant, gradient, and curvature of a smooth lens. The coherent density fluctuations of FDM leave a larger frequency-dependent residual after this fit. The NFW--FDM and SIDM--FDM populations become distinguishable with about 60 and 110 resolved image waveforms, respectively. These results show that repeated lensed LISA signals can probe the spatial form of dark matter in lens galaxies, rather than only the total lensing mass.

We present an audio gate plugin that uses real gravitational wave strain data from the LIGO and Virgo detectors as low frequency oscillator (LFO) modulation sources. Conventional audio gates rely on synthetic waveforms, sine, triangle, sawtooth, whose fixed harmonic content produces predictable pumping effects. By contrast, gravitational wave chirps from compact binary coalescences sweep through frequency and amplitude on subsecond timescales; when time scaled to LFO rates (0.1 to 10)Hz, these chirps yield modulation signals with continuously evolving harmonic structure. The plugin demonstrates that astrophysical signals can serve as musically compelling modulation sources, bridging sonification and creative audio processing.

Persistent discrepancies between early- and late-Universe measurements have made cosmological tensions a major test of the standard $Λ$CDM model. We investigate whether an entropic generalized Chaplygin-gas cosmology, describing a unified dark sector, can modify the parameter degeneracies associated with these tensions. The model is constrained using Type Ia supernova data from PantheonPlus+SH0ES and DES--Dovekie, DESI BAO measurements, RSD growth data, compressed Planck 2018 distance priors, and a Planck lensing-amplitude prior. We find that the entropic gCg model closely reproduces the $Λ$CDM background expansion while introducing a controlled late-time deformation of the distance--redshift relation. This shifts the preferred $(H_0,Ω_m,S_8)$ region and partially reduces background-driven discrepancies, especially those involving $H_0$. Using \texttt{Tensiometer} to quantify posterior shifts in the common derived parameter space $(H_0,Ω_m,S_8)$, we show that the displacement relative to $Λ$CDM occurs mainly along background-sensitive directions. The model therefore modifies the late-time expansion sector more effectively than the growth sector, leaving residual $S_8$ discrepancies comparatively robust. These results support the possibility that the $H_0$ and $S_8$ tensions arise from distinct physical sectors.

We present a linear instability in magnetized plasmas with charge fluctuations. It is driven by an electric current proportional to the charge chemical potential $μ$ and the bulk velocity. This charge-flow (C-flow) instability has hitherto not been considered in standard magnetohydrodynamics or its chiral extensions. We derive its dispersion relation and maximum growth rate, and confirm them with direct numerical simulations. We also show that the C-flow instability persists even for zero-mean fluctuations of $μ$, vanishing resistivity, and a magnetic Prandtl number of unity.

We present a systematic derivation of the equations of relativistic chiral magnetohydrodynamics (MHD) for a plasma of charged fermions in an expanding universe. Through a combination of a coordinate transformation and a rescaling of the dynamical variables, we bring the full system to the same form as in the Minkowski metric, with the Hubble expansion surviving only in the chirality-flipping rate and the kinematic viscosity. Retaining all four contributions to both the electric and the axial current yields terms absent from standard chiral MHD: charge-density corrections to the evolution equations for the chemical potentials, and an electric current proportional to the charge chemical potential $μ$ and the bulk velocity. The latter is mandated by current conservation, requires no chirality imbalance, and drives the charge-flow instability studied in a companion paper. For the radiation-dominated era, we evaluate all the coefficients in physical units and use them to estimate the magnetic Reynolds number, the attainable magnetic field strength, and the minimum temperature at which the chiral dynamo can operate. The resulting equations are cast in a form ready for direct numerical implementation.

We introduce Solar Neutrinos for Direct Detection ($\texttt{SNuDD}$): an open-source Python package that enables the computation of the solar neutrino rate spectrum at direct detection experiments. $\texttt{SNuDD}$ can be used to determine the differential rate for both nuclear and electron recoils within the Standard Model and in the presence of beyond Standard Model physics effects, such as those arising from neutral-current non-standard interactions (NSI). The package accounts for matter effects during neutrino propagation through both the Sun and the Earth and for modifications to the scattering cross sections at the interaction site. We employ $\texttt{SNuDD}$ to place new limits on the effective NSI couplings using results from the xenon-based direct detection experiments LZ, XENONnT, and PandaX-4T, and we project the sensitivity of a future xenon detector based on the planned XLZD and PandaX-xT observatories. We find that current direct detection experiments are rapidly approaching sensitivities comparable to those of dedicated neutrino experiments and that future xenon detectors can provide leading constraints. We recommend that $\texttt{SNuDD}$ be used to combine incoming direct detection data with those from neutrino experiments in future global fits, placing direct detection within the broader landscape of neutrino physics.

Large spectroscopic surveys require robust pipelines capable of inferring stellar parameters over a wide range of the Hertzsprung-Russell (HR) diagram from data of varying quality. SDSS-V is one such survey, where the data from the lower-resolution, optical BOSS spectrograph will provide a large dataset covering a wide range of Galactic stellar populations. To better analyze these data, we present BOSS-CLAM, a generative, forward modeling pipeline for inferring effective temperature ($T_\mathrm{eff}$), surface gravity ($\log g$), metallicity ($[\mathrm{Fe/H}]$), and $α-$abundance ($[α/\mathrm{M}]$) from continuum-normalized BOSS spectra. BOSS-CLAM maps stellar labels to Non-negative Matrix Factorization (NMF) basis vector weights via a polynomial mapping jointly optimized with the spectral decomposition, which provides a more flexible framework for working with the lower-resolution BOSS data. Additionally, training labels are drawn from four complementary sources (ASPCAP, BOSS-MINESweeper, wide binaries, and a hot star validation sample), which enables coverage from cool M dwarfs through hot OB stars, and across a wide range of metallicity. We infer parameters for 1,708,214 BOSS spectra, with a recommended clean catalog of 915,514 sources. Validation against open and globular clusters demonstrates homogeneous, accurate abundances across a wide range of metallicity. Wide binary tests yield abundance uncertainties of $σ_{[\mathrm{Fe/H}]} \approx 0.15$ dex and $σ_{[α/\mathrm{M}]} \approx 0.06$ dex at SNR = 10. Finally, we demonstrate that the BOSS-CLAM catalog recovers known chemical structure of the Milky Way disk and is well-suited for Galactic archaeology, chemical tagging, and stellar population modeling. The pipeline, trained model, and catalog are publicly released as part of SDSS-V DR20.

We present the first chemical survey of Class I and Flat-Spectrum (I/FS) disks using JWST MIRI/MRS, targeting sixteen sources in the Ophiuchus star-forming region. Through empirical line luminosity measurements and multi-component slab modeling, we characterize the molecular reservoir of these young systems and compare them to twelve Class II disks of similar stellar mass. Water, HCN, C$_2$H$_2$, and CO$_2$ are frequently detected in I/FS sources with inclinations $i < 70^{\circ}$, whereas edge-on systems show significantly suppressed emission. Compared to Class II disks, I/FS sources show suggestive---though not yet statistically significant---evidence for elevated cold water ($\sim$200\,K) mass and lower CO$_2$ excitation temperatures. Statistical analyses identify accretion luminosity as the primary correlate of molecular mass across both evolutionary stages. Once this dependence is removed, cold water and CO$_2$ masses anti-correlate with mm-dust disk radius, while hot water remains insensitive to disk size. These patterns are qualitatively consistent with pebble drift models that predict early water enrichment followed by delayed CO$_2$ delivery, suggesting an evolutionary progression from molecular-poor Class 0 sources, through water-rich Class I/FS disks, to Class II disks with reduced cold water excess. This work provides an initial evolutionary framework for disk chemistry that requires larger, multi-region samples to confirm.

In this work, we study Casimir wormhole solutions and investigate satisfaction of energy conditions in the framework of Einstein-Gauss-Bonnet (EGB) gravity. We firstly find traversable wormhole solutions supported by a general form for the Casimir energy density. Applying a specific redshift function, we choose suitable parameters that respect the energy conditions in the vicinity of the throat due to the presence of higher order curvature terms. Then, we check the energy conditions considering non-constant redshift function and for suitable choice of model parameters, we find that these conditions are satisfied at infinity as well as in the vicinity of the throat. The stability of the Casimir traversable wormhole solutions are investigated using the Tolman-Oppenheimer-Volkoff (TOV) equation. Finally, we study trajectory of null as well as timelike particles in the wormhole spacetime.

We study a modification of the model of axion inflation coupled to a $U(1)$ gauge field where the vector field is massive. In the conventional scenario with a massless gauge field, the onset of the regime where the gauge field strongly backreacts on the inflaton displays an instability whose nonlinear evolution and endpoint remain poorly understood. We argue that, if the gauge field is massive enough, the transition to the strong backreaction regime instead occurs smoothly, avoiding this instability. This observation suggests that axion inflation with massive gauge fields admits a controllable strong backreaction regime, so that a phenomenologically viable realization of inflation might be possible in this class of models.

In this article we describe a scheme for sensing both the mode mismatch and alignment of a cavity which does not require custom sensors and uses only Quadrant Photo-Detectors (QPDs). The technique is simple relying upon cylindrical lenses and thoughtful Gouy phase telescope design, and is trivial to implement alongside a Pound-Drever-Hall (PDH) locking scheme. The Gouy phase telescope design utilizes all three of the QPDs to sense each degree of freedom which also increases sensitivity and provides redundancy. The technique we show also works without RF modulation, which is useful for providing other general diagnostic information in complex optical experiments. An analytical overview of the technique as well as generic design equations for the Gouy phase telescope is provided. Finally, a detailed optical simulation is presented to verify the technique.

We study the scalar and Dirac perturbations of quantum-corrected black holes with cosmological constant. Using two different methods (WKB and double-null characteristic integration) we compute the quasinormal modes (QNMs) of de Sitter and Anti-de Sitter solutions considering linear field perturbations in the background geometry. In the limit of general relativity black holes our methods demonstrate good convergence with the available results in literature. In the presence of an extra quantum parameter we verify that all perturbations are stable evolving in towers of quasinormal oscillations. We scrutinize the spectra of both dS and AdS solutions studying the influence of that extra parameter in the frequencies.

We construct two exact nonlinear-electrodynamic generalizations of the Kerr-Newman-NUT-$Λ$ spacetime. Imposing alignment between the principal directions of the electromagnetic field and the metric tetrad reduces the Maxwell-Faraday sector to a pair of potentials constrained by a single integrability condition, the key equation. Within the polynomial aligned ansatz considered here, the key equation selects two admissible families, corresponding to electromagnetic potentials that are cubic and quartic polynomials. For each family the Einstein equations reduce to a single radial ordinary differential equation that gives a deformation of the Kerr-like radial metric function which is exactly solved. We derive the corresponding metrics, electromagnetic fields, stress tensors, horizon structure, and we analyze the associated energy conditions. The nonlinear sector breaks conformal invariance and, in the cubic family, can mimic an effective cosmological contribution. The explicit Lagrangians as functions of the electromagnetic invariants are obtained in selected static subsectors. The curvature invariants show that the nonlinear contribution does not remove the Kerr-like curvature singularity, while the solutions present the NUT axial conical singularity.

The Polarimeter to UNify the Corona and Heliosphere (PUNCH) mission will remotely observe solar wind transients with high signal-to-noise ratio, high-cadence, high-resolution polarized white-light images. Using different polarization states, an important PUNCH data product will be polarization ratio images. In the small-Sun limit, and using two simple line-of-sight density distributions with a finite angular width that can approximate a stream or corotating interaction region (SIR/CIR), we analytically investigate how the polarization ratio will provide three-dimensional location information and what the uncertainty in this estimated location is.

Axion inflation, characterized by a Chern-Simons interaction between the inflaton and a gauge field, provides a powerful mechanism for generating primordial gravitational waves (GWs) through tachyonic enhancement of the gauge field. While recent literature has predominantly focused on the Strong Backreaction (SB) regime to maximize GW signals for future interferometers, this regime suffers from computational complexities as well as the risk of overproducing scalar perturbations. In this work, we investigate gauge field amplification and GW production strictly within the theoretically safer Weak Backreaction (WB) regime, with a particular focus on the largely unexplored non-instantaneous reheating phase. Because the tachyonic enhancement during slow-roll typically increases as inflation approaches its end, it is crucial to investigate how the production of GWs behaves at the very end of inflation and thereafter. By continuously tracking the evolution from slow-roll through reheating to radiation domination, we present a complete picture of inflationary and post-inflationary GW production in this framework. A particularly interesting feature of the post-inflationary phase is that the oscillatory behavior of the inflaton during reheating leads to frequent sign-flips of the instability parameter $ξ$, exciting both helical modes of the gauge field. Our analysis reveals that axion inflation can naturally generate one of the strongest known primordial GW signals at high-frequency bands. The yield is relevant for future precision measurements of the effective number of neutrino species, $N_{\rm eff}$, and also strongly motivates the development of novel high-frequency GW detectors.

I study a particular exact solution for static stars in four-dimensional non-projectable Horava gravity, which has been proposed as a renormalizable gravity model without the ghost problem by abandoning Einstein's equal-footing treatment of space and time through anisotropic scaling with z > 1. Considering the spherically symmetric static black-hole solutions in z = 3 Horava gravity as the exterior spacetimes of stars, I obtain an exact solution for incompressible (i.e., uniform-density) static stars with an arbitrary cosmological constant and isotropic pressure, and lambda=1, in which Birkhoff's theorem holds. For a vanishing cosmological constant, I obtain a modified Buchdahl bound on the maximum compactness for uniform-density stars, which ranges from 4/9 to 1. By contrast, I find that Ultra-Compact Objects (UCOs) with compactness C > 1 also exist with negative pressure while, surprisingly, satisfying all four standard energy conditions. UCOs include the regular (non-singular) black-hole solutions with masses above the extremal black-hole mass. In these solutions, the matter is localized at the timelike core region bounded by the inner horizon, while their exterior metrics are unaffected by the core matter and identical to the corresponding vacuum Horava black-hole solutions. These long-sought regular black-hole solutions are essential manifestations of Birkhoff's theorem in Horava gravity. I also find negative-mass stars with positive pressure that violate all standard energy conditions. Finally, I prove Buchdahl's theorem in non-projectable Horava gravity. The proof uses a weight-monotonicity condition on the average density and Birkhoff's theorem, together with the usual assumption that average density is non-increasing.

We investigate the viability of the light inflaton scenario in light of the latest inflationary constraints from the Atacama Cosmology Telescope (ACT), together with bounds from collider and intensity-frontier experiments searching for a feebly coupled light scalar with a sub-GeV mass. Assuming a quartic inflaton potential, we identify the region of parameter space consistent with the ACT observations and derive constraints on the inflaton mass and inflaton-Higgs mixing using results from NA62, KOTO, BaBar, Belle, LHCb, MATHUSLA, FASER2, SHiP, and neutral meson oscillations. We also explore the prospects for dark matter production during reheating within this framework, while remaining consistent with the inflationary observables.

In this paper, we investigate the almost $η$-Ricci-Yamabe soliton as a fundamental geometric regulator for a static, spherically symmetric black hole coupled to an imperfect fluid. We have shown that the scaling parameter $ω(r)$ is governed by thermodynamic friction along the radial vector field, and the geometric coupling with the Hawking temperature: $α(r_H) S_{tt} = 2πT_H$ at the horizon. We also derive the Poisson equation along the gradient vector field of the soliton and prove that the flow's kinematic expansion is explicitly dependent on the fluid's equation of state $ρ= γσ$. Diverging from traditional methodologies that assume a geometric shape function apriori, we analytically proved the geometric flow endogenously transitions the black hole geometry into a traversable wormhole throat by regularizing of temporal coordinate and satisfying spatial flare-out condition. This transition occurs when fluid enters the dark energy era at $γ= -1$ and violates the Null Energy Condition $ρ+ σ< 0$, with the soliton strictly dominating the local curvature gradient $ω^{\prime}(r_H) > f^{\prime\prime}(r_H)$, to keep the throat open. Moreover, by smoothly attenuating at spatial infinity, the soliton preserves the exact cosmological spacetime. Finally, through tensorial perturbation analysis, we demonstrate that the geometric flow introduces a localized dissipative mechanism, that the perturbation evolution reduces to damped wave equation, imposing geometric drag on the manifold.

We ask whether a cored dark matter (DM) correction can leave a resolved caustic trace after a spinning vacuum binary is allowed to imitate it. The vacuum comparison varies lens scale, common spin, separation, mass ratio, projected spin angle, and one phase offset fitted over the full orbit. Nearby unequal component spins and projected directions are also tested. The best high-resolution fit remains the equal-mass, common-spin model. In the selected encounter, the local root mean square residual is $1.34\times10^{-2}$, the maximum residual is $4.02\times10^{-2}$, and the aligned crossing shift is $1.51\times10^{-3}$. A nearby resolution gives $1.50\times10^{-2}$, $4.02\times10^{-2}$, and $1.82\times10^{-3}$. All three rising half-response crossings are checked, and the selected event is not the largest. This is a numerical demonstration within a tested effective family, not an observational claim or an exact binary-spacetime calculation.

MANAS is a single antenna, ground-based platform built to measure the sky averaged ('global') redshifted 21-cm signal from Cosmic Dawn. The cosmological signal is expected as a ~ 100-200 mK absorption trough against a foreground of 3-4 orders of magnitude brighter. The current crop of 21-cm experiments are limited by systematics namely the sky, ionosphere, beam, and signal path effects. MANAS combines an achromatic monopole antenna, an absolutely-calibrated receiver, and in-situ beam mapping with the OVRO-LWA, and develops an end-to-end error budget that quantifies each systematic.

(abridged) In order for the universe to develop astrophysical structures and support life, the fundamental constants that determine the laws of physics and the cosmological parameters that specify cosmic properties must fall within a range of values. The goal of this review is to delineate these ranges. We start with the premise that multiple universes can exist and can sample different realizations of the laws of physics. This treatment focuses on the coupling constants that determine the strength of the fundamental forces $(α,α_G,α_{\rm s},α_{\rm w})$ and the masses of the particles $(m_u,m_d,m_e)$ that make up atomic matter. We also consider cosmological parameters, including the energy density parameter $Ω$, the dark energy density $ρ_v$, the baryon-to-photon ratio $η$, the dark matter contribution $δ$, the amplitude $Q$ of primordial density fluctuations, and the number ${\cal D}$ of spatial dimensions. These quantities are constrained by the need for the universe to emerge from its epoch of nucleosynthesis with an acceptable chemical composition, live for a long time, and ultimately produce galaxies, stars, and planets. Stellar lifetimes must be long enough and surface temperatures must be high enough to support life. These requirements place constraints on the fundamental constants and cosmological parameters. This overview discusses several classic instances of possible fine-tuning in stars, including the triple alpha reaction, stable diprotons, and unstable deuterium. Finally, we note that for universes with significantly different parameters, a variety of astrophysical processes can generate energy, drive nucleosynthesis, and potentially support habitability.

Here we discuss the effect of gravitational repulsion on geodesic deviation in the Schwarzschild-de Sitter spacetime. In particular, the geodesic deviation shows different behaviour inside or outside a critical surface, which is the divider between attractive and repulsive regions of gravity. This in turn makes it possible to locate the critical surface and regions of gravitational repulsion and attraction from the behaviour of geodesic deviation.

The discovery of the accelerated expansion of the cosmos has sparked great interest in studying the nature of the mysterious force behind this effect, often called dark energy. Several theories were proposed to study the nature of dark energy, and holographic dark energy stands out among them due to the relation between dark energy density and the principles of quantum gravity and holography. Recent progress made in fractional cosmology has led to the addition of fractional correction terms to the definition of holographic dark energy. Based on such progress, in this study, we investigate the behavior of fractional holographic dark energy in forming exotic spacetimes, especially traversable wormholes, which represent intriguing solutions of Einstein's field equations connecting distinct regions of spacetime. In the present article, a new class of Morris--Thorne wormhole solutions is obtained under the consideration of fractional holographic dark energy as the source of the gravitational field with a varying redshift function in the context of Einstein gravity. To study the nature of wormholes, their geometry, viability, and thermodynamic behavior, a shape function is obtained, and the wormholes are analyzed in detail via embedding diagrams, throat geometry, active gravitational mass, compactness, exoticity factor, energy conditions, conservation law, volume integral quantifier, Kretschmann invariant, and complexity factor. Moreover, thermodynamic properties of the wormholes are studied via the examination of several parameters, including Hawking temperature, wormhole temperature, entropy, energy, work density, and heat flux, aiming to understand the influence of fractional holographic corrections on the stability and evolution of traversable wormhole structures.

We present a directional dark matter search using the MIMAC (Micro-tpc Matrix of Chambers) detector at the Modane Underground Laboratory. Operating a low-pressure gas mixture of i-C4H10 and 50% CHF3 at 30 mbar, without any shielding, the detector allows the reconstruction of the 3D tracks of nuclear recoils produced in the 6-liter active volume. Directionality is a crucial tool to discriminate true WIMP signals from those of background producing identical recoils, such as neutrons. We analyze data from two independent chambers with effective exposures of 495.1 and 354.2 days, respectively. To estimate the background directly from the data, we apply a standard ON/OFF spatial analysis. By projecting the reconstructed tracks onto the galactic map and applying a moving kinematic energy cut depending on the WIMP mass, we compare the event rate in the signal direction with multiple OFF-source regions. Finding no significant excess of events in the direction of the Cygnus constellation, we set an upper limit on the spin-dependent WIMP-protoncross section.

The temperature-redshift relation, $T(z)=T_0(1+z)$, is a cornerstone of the standard cosmological model, but it is violated in many physically motivated extensions thereof, e.g. when photon number is not conserved. We apply the methodology of cosmography, a model-independent approach to cosmology, to this observable, and use astrophysical Sunyaev-Zeldovich and high-resolution spectroscopic measurements spanning the redshift range $0\le z\le6.34$, to constrain violations of the standard relation. We explore the impact of different cosmographic approaches and expansion variable choices and also compare the cosmographic constraints with those obtained, with the same data, in the canonical adiabatic extension model of Lima. While these choices have some impact, overall we find that such violations are constrained to percent level, and that a single non-standard parameter suffices to describe them. We also show that the directly fitted slope of the temperature-redshift relation is compatible with (but slightly smaller than) the one inferred from FIRAS, and that standard cosmography lore, based on scale factor expansions, does not apply to this observable, e.g. Padé approximants have no meaningful advantage over plain Taylor series.

DESI DR2 BAO combined with CMB and Type~Ia supernovae in the Chevallier--Polarski--Linder (CPL) parameterisation prefers evolving dark energy over $Λ$CDM at roughly $2.8$--$4.2σ$. We reconstruct the same late-time expansion history with a hierarchical Gaussian process (GP) that co-samples the kernel hyperparameters $(σ_f,l)$ together with $(H_0, Ω_m, Ω_k, ω_b h^2)$, coupling BAO, compressed Planck distance priors, and Pantheon+ through a Monte-Carlo effective likelihood conditioned on 37 cosmic-chronometer $H(z)$ points. The baseline posterior gives $w(z\simeq 0)=-0.80^{+0.26}_{-0.23}$ (68\%~C.L.), about $0.8σ$ from $w=-1$, with $l=3.79^{+0.81}_{-1.12}$. A CPL fit on the identical compressed Planck pipeline improves nested $Λ$CDM by only $Δχ^2\sim 1$ ($\sim 1σ$). Ablations that fix $(σ_f,l)$, drop SN or LRG1/2 BAO, replace the radial-basis kernel by Matérn-$5/2$, or tighten the prior on $l$ leave the median $w(0)$ within $\lesssim 1σ$ of $-1$. The mild preference reported here is therefore specific to this compressed-CMB analysis and does not address DESI's full Planck-likelihood result.

We investigate scalar-induced gravitational waves (SIGWs) in an inflationary model with symmetry breaking, in which charged scalar fields are coupled to an isotropic triplet of Abelian gauge fields through a kinetic function. Such SIGWs can be enhanced to a detectable level when the mixing between the inflaton and gauge-field perturbations is sufficiently large. We find that the longitudinal mode and the charge-dependent mixing between perturbations become relevant only when the gauge-field excitation occurs sufficiently late during inflation. In this regime, the corresponding SIGWs are shifted to ultra-high frequencies, typically can around the GHz band. We show that the parameters characterizing the effects of the longitudinal mode and charge-dependent mixing affect the signal in qualitatively different ways. This provides characteristic signatures for distinguishing the neutral case from the charged one through the frequency profile of the stochastic gravitational-wave background.

We use the non-linearly coupled Einstein-matter field equations to prove four theorems that bound from above the dimensionless force function ${\cal F}=4πr^2\cdot p(r)$ in spatially regular curved spacetimes of spherically symmetric self-gravitating matter configurations [here $p(r)$ is the radially-dependent pressure inside the spatially regular matter configurations]. In particular, for generic (not necessarily isotropic) matter configurations it is proved that: (i) ${\cal F}\leq 2$ for matter fields that satisfy the dominant energy condition, and (ii) ${\cal F}\leq 1$ for matter fields with a non-positive energy-momentum trace. In addition, for self-gravitating isotropic matter configurations we derive the stronger upper bounds: (iii) ${\cal F}\leq 1$ for matter fields that satisfy the dominant energy condition, and (iv) ${\cal F}\leq 1/2$ for matter fields with a non-positive energy-momentum trace. Our analytically derived results are in accord with the spirit of the maximum force conjecture in general relativity.

Magnetic fields in interplanetary coronal mass ejections (ICMEs) often display a flux rope structure at large scales and a turbulent cascade of fluctuations at smaller scales. However, the nature of fluctuations at transition scales between the flux rope and turbulence - i.e., at mesoscales - has not been previously examined in detail. Mesoscale fluctuations of the magnetic field in 142 ICME intervals with clear flux rope signatures at 1 au have been examined using wavelet power spectra, with "mesoscale" defined here as spacecraft-frame frequencies $10^{-4}\ \text{Hz}<f_\mathrm{sc}< 10^{-3}\ \text{Hz}$, equivalent to timescales $2.8\ \text{hr}\gtrsim τ\gtrsim 17\ \text{min}$. The spectra were found to be significantly less steep at mesoscales than at larger and smaller scales, with an average spectral slope close to $-1$ at these intermediate scales. The mesoscale fluctuations had relatively high cross helicity magnitudes and low compressibility, suggesting a significant degree of Alfvénicity, while also having more negative residual energy than the turbulent fluctuations found at smaller scales. Uncertainties in the spectral slope values at mesoscales were used to distinguish between spectra showing a relatively smooth power-law behavior or (less commonly) a more bumpy trend; the smoother power-law intervals had a balanced cross helicity distribution while the more bumpy spectra had a predominantly antisunward cross helicity. Slow wind intervals were similarly analyzed, and showed similar properties to the ICMEs. These results indicate that a spectrally narrow $1/f$ range is typically present in ICMEs at mesoscales.

The formation, extension, and morphology of extra-tidal stars around globular clusters depend on the internal kinematics of the host cluster and the Galactic potential. Tracing the kinematics of faint tidal tails sheds light on their formation and contribution to the Milky Way halo. NGC 7492 is an outer halo globular cluster with conflicting evidence regarding the presence of tidal tails. If present, the tails are expected to be faint and overlap on the sky with the Sagittarius stream, located at a similar heliocentric distance but with distinct kinematics. We carried out a GIRAFFE spectroscopic follow-up of ten fields covering the expected tidal tails of NGC 7492. Gaia parallaxes were used to remove foreground contaminants, while only loose proper-motion constraints were applied in the target selection. Radial velocities and metallicities were derived for more than 700 stars, from the red giant branch to the upper main sequence. Cluster and extra-tidal stars were identified from their proper motions, radial velocities, and metallicities. This population extends at least 1.8 deg from the cluster center, confirming the tidal tails previously detected only photometrically, with positions consistent with particle-spray models of the cluster disruption. The Sagittarius stream is clearly identified through its distinct proper motions, radial velocities, and more metal-rich population. Despite the low spatial density of the extra-tidal stars, their kinematic signature is clearly detected, demonstrating that the tidal tails overlap on the sky with the Sagittarius stream but are physically unrelated. This spectroscopic dataset provides a robust basis for future studies of the tails at larger angular extents and fainter magnitudes.

We investigate the equivalence of the Jordan and Einstein frames of the Brans--Dicke theory before and after relational deparametrization of the constrained Hamiltonian system. Although the two conformal formulations are equivalent at the covariant level and related by a canonical transformation on the standard ADM phase space, their equivalence after reduction with respect to an internal clock is nontrivial. Using the Brans--Dicke scalar as a relational clock, we show that the apparent discrepancy between the reduced Hamiltonians does not indicate a physical inequivalence of the two frames. Instead, it arises from a mismatch in the canonical embedding of the clock sector prior to reduction. While the scalar configuration variable is preserved under the conformal transformation, its conjugate momentum is shifted by a contribution involving the gravitational momentum trace. Consequently, relational dynamics are determined not by the clock variable $T$ alone, but by the complete canonical clock pair $(T,P_T)$. We construct a frame-adapted canonical chart in which the clock sector is consistently transformed prior to deparameterization. The resulting reduced Hamiltonian coincides with that of the Einstein frame, restoring the equivalence of the reduced relational dynamics. Our results identify the canonical clock sector as the fundamental structure governing relational evolution in Brans--Dicke theory and provide a general framework for understanding frame dependence in scalar--tensor gravity and reduced phase-space quantization.

We obtain explicit formulas for the expected number and height distribution of critical points of smooth isotropic Gaussian random fields on $\mathbb{R}^d$. The expected number density formula is expressed in terms of at most one-dimensional integrals, regardless of the dimension $d$. To obtain the formulas, we provide a variant of de Bruijn's theorem, as well as Weierstrass' convolution formula with a Gaussian random variable and its inversion.

Cosmological stasis, a surprising phenomenon in which the abundances of different energy components in the universe with different equations of state remain constant despite cosmological expansion, has been a focus of recent attention. This behavior emerges as the consequence of an attractor that governs the dynamics of the corresponding cosmological system and pulls it towards stasis even if the system is not initially in this state. However, while some systems actually reach stasis in finite time, it is also possible for such systems to spend considerable time under the influence of this attractor, continually heading towards stasis without ever quite reaching it. This too represents behavior that is entirely unexpected within standard cosmological scenarios. In this paper, we present an explicit model which realizes both of these behaviors in a thermal context while satisfying all relevant phenomenological and cosmological constraints. Within this model, we then examine how the attractor influences the cosmological dynamics and explore the potential consequences for the early universe.

As the nearest protoplanetary disk to Earth ($d = 60.14$ pc), TW Hya is one of the most studied protoplanetary disks and a critical benchmark for testing planet formation theories. We present high-contrast coronagraphic imaging of the TW Hya disk from JWST/NIRCam across four filters (F187N, F200W, F356W, and F444W). We detect the disk's scattered-light emission in F200W, F356W, and F444W. An elliptical fit to the disk image yields an average inclination of $i = 8.74^{+1.03}_{-0.94}$ degrees and a position angle of $\mathrm{PA} = 75.62^{+7.86}_{-6.56}$ degrees. We find tentative evidence for radial variations in these parameters, a trend consistent with a disk warp. Our companion search yields no new detections, placing the lowest mass limits yet on companions that might be responsible for carving out the dust gap. Assuming no local extinction and a system age of 10 Myr, the F444W data are sensitive to masses down to $\sim 0.4\,M_{\rm Jup}$ at separations of $1$ arcsec ($\sim 60$ AU). Accounting for local disk extinction analogous to the AS 209 system, our limits reach sub-Jupiter masses beyond $2$ arcsec. Furthermore, our analysis provides a detailed view of a previously detected feature in the outer disk at $\sim 120$ AU, confirming its morphology as a distinct bifurcation structure. This feature may indicate the presence of complex substructures arising from dynamical planet-disk interactions. These results demonstrate JWST's ability to characterize the architecture of protoplanetary disks and constrain the properties of forming worlds.

We investigate the quasinormal modes (QNMs) of scalar perturbations and strong cosmic censorship (SCC) in regular Ayón-Beato-García-Bronnikov-de Sitter (ABGB-dS) black hole spacetime. The main motivation of this work is to clarify whether the regularization of black hole core, which removes the central singularity, can also change the fate of SCC connected to the Cauchy horizon. We first study the dependence of the scalar QNM frequency (QNF) on the scalar mass and black hole parameters. For angular number $l=0$, a small scalar mass can give rise to a slowly decaying mode which is purely imaginary. We also find that the black hole charge and cosmological constant affect the QNM spectrum in qualitatively opposite ways. We then examine SCC under massless and massive scalar perturbations. For massless perturbations, the QNMs spectrum can be organized into photon sphere (PS), de Sitter (dS) and near-extremal (NE) families. Compared with the SCC in the Reissner-Nordström-de Sitter (RN-dS) case, SCC is generally more easily violated in the ABGB-dS spacetime, although this tendency is reversed for sufficiently large cosmological constant. For massive scalar perturbations, we find that the scalar mass does not restore SCC. Instead, it can enhance the violation by driving the system into the regime $β>1$. At last, we discuss what we may expect from the violation of SCC in a regular black hole spacetime.

Modern stellar surveys measure millions of spectra, yet one self-consistent atmosphere and spectrum can require tens of minutes. This cost has motivated grids, spectral emulators, and data-driven models. We present Payne Zero, which reorganizes one-dimensional LTE Kurucz calculations for GPU-native synthesis and multicore atmosphere iteration, and validate it against the original Fortran programs. A 300--1000 nm solar spectrum sampled at $R_{\rm grid}=300{,}000$ takes about 14 s on an NVIDIA H100 GPU, while the APOGEE 1500--1700 nm interval takes about 1 s. Physical atmosphere iterations take 2--5 s on 16 AMD CPU threads, and learned initializers reduce the iterations required for convergence. Final spectra remain in practical parity across the tested dwarf and giant regimes. These speeds place direct synthesis inside an optimizer without a label-to-flux spectral emulator. We demonstrate direct many-element fitting of reduced APOGEE spectra and recover multi-element abundance trends broadly consistent with the survey catalog. GPU-resident velocity shifts, broadening, line-spread-function convolution, and detector sampling add negligible cost relative to synthesis. The direct-synthesis search takes less than one minute per star on an H100, while atmosphere verification runs independently on multicore CPUs. The same computational graph calibrates more than $10^5$ oscillator-strength and damping corrections jointly against the Sun and Arcturus in about one minute on an H100. Payne Zero therefore brings direct physical fitting and atomic-data calibration to survey scale. The code is available at https://github.com/tingyuansen/payne-zero.

We investigate gravitational wave (GW) emission from periodic timelike orbits of a test particle around a magnetized Ernst black hole and the gravitational waveforms generated by their orbital dynamics. The bound geodesics are systematically classified using the zoom-whirl representation labeled with three integers $(z,w,v)$. Gravitational waveforms are computed within a numerical framework that combines exact geodesic motion with the quadrupole approximation, which is well-suited to extreme mass-ratio inspirals (EMRIs). This analysis is particularly relevant for assessing the capability of future gravitational-wave observations to detect the effects of magnetic fields. Our results show that an intrinsic magnetic field imprints characteristic features on the GW signal, highlighting GW astronomy as a promising avenue for probing magnetized black hole spacetimes.

Relativistic particle beams propagating through dense ambient plasmas are susceptible to streaming instabilities that can govern the system dynamics in various astrophysical and laboratory settings. For an unmagnetized, collisionless plasma pervaded by a dilute, cold relativistic beam, the dominant instabilities are the quasielectrostatic, oblique two-stream (OTSI) and the essentially magnetic, current filamentation instability (CFI). While their linear and nonlinear properties have been researched for decades, most treatments assume unbounded, uniform systems and thus predict purely temporal instability growth. This assumption, however, is questionable for realistic configurations where a bounded beam continuously encounters fresh plasma. This feature causes instabilities to grow in a spatiotemporal manner. Whereas spatiotemporal perturbative treatments of streaming instabilities were derived as early as the 1960s, only recently have the spatiotemporal regimes of OTSI and CFI been addressed theoretically. Yet these models are restricted to a specific instability class, and hence cannot describe the competition between spatiotemporal OTSI and CFI. In this work, we present a unified, fully electromagnetic quasi-static model of all unstable modes arising throughout the beam. By not adopting the slowly varying envelope approximation (SVEA), we find that a previously unreported spatiotemporal CFI actually prevails near the front, precisely where the SVEA fails, and is only superseded by OTSI further back in the beam. Furthermore, we demonstrate that our model also captures the growth of the self-modulation and hosing instabilities excited by long, narrow beams. Comparisons with particle-in-cell simulations confirm the validity of the quasistatic approach for modeling streaming plasma instabilities triggered by relativistic dilute beams.

We show that retarded correlators in conformal field theories of scalar primary operators evaluated at finite temperature using $AdS/CFT$ scale anomalously at large light like momenta. The anomalous scaling depends on the curvature of the horizon. Setting the momenta equal to the frequency $ω$, the retarded correlator for black holes with planar horizons scales as $ω^{\frac{2}{d+2} (2Δ- d) }$ as opposed to the scaling behaviour of $ω^{2Δ- d}$ expected by dimensional analysis at generic fixed momenta and large frequencies. $Δ$ is the dimension of the primary and $d$, the number of space-time dimensions. For black holes with spherical and hyperbolic horizons when the frequency squared equals the Casimir along the horizon, the retarded correlator scales as $ω^{\frac{2Δ-d}{2} }$. We establish this using exact results in $d=2$, and a numerical analysis of the Heun equation for the $AdS_5$ planar black hole and finally using the WKB approximation in general $d$. The exact result for black holes with hyperbolic horizon as well as the analysis at large $d$ provides additional checks for the anomalous scaling behaviour. Finally we evaluate the anomalous scaling exponent for the stress tensor correlator in all its 3 channels.

We establish exact analytical thresholds and present a unified thermodynamic state-space representation for the regular Hayward black hole, resolving the full phase structure without reliance on numerical approximations. By evaluating the Hawking temperature, Helmholtz free energy, and heat capacity against the classical Schwarzschild baseline, we derive the exact geometric watershed for the zero-temperature extremal remnant at $r_h = \sqrt3l$, along with the exact Davies critical transition at $r_h = 3l$. Within the intermediate regime $\sqrt{3}l < r_h < 3l$, we uncover a distinct horizon bistability where two distinct horizon radii share identical free energy and temperature profiles. We demonstrate that the Davies singularity acts as a precise thermodynamic divide, separating a locally stable ($C_V > 0$) quantum Small Black Hole branch from an unstable ($C_V < 0$) Large Black Hole branch. Furthermore, we evaluate the exact integrated non-area law entropy at the critical turning point, yielding $S_{turn} = πl^2 \left[ \frac{63}{8} + 2\ln(8l^2) \right]$. Finally, we introduce a compact, 3-parameter thermodynamic state-space diagnostic that tracks the continuous evolution of regular black holes from classical thermal evaporation to cold remnant lock, offering a quantitative framework for quantum-gravity phenomenology.

We study the inflationary primordial perturbations in $κ$-Minkowski non-commutative space-time, a Lie-algebraic type deformation of canonical space-time motivated by quantum gravity scenarios. Employing the $κ$-deformed star product formalism, we construct the bilinear action for curvature perturbations and derive the $κ$-deformed Mukhanov-Sasaki equation and obtain the perturbative solutions. Further, we compute the primordial power spectrum and spectral index, showing that the leading order corrections to the power spectrum induces scale-dependent term proportional to $(\ln k)^2$. The spectral index also exhibits an explicit $\ln k$ dependence, which persists even when the slow-roll parameters are constant. We also perform a Bayesian MCMC analysis using ACT DR6 data and constrain the $κ$-deformation length scale to $λ=6.32^{+6.00}_{-4.30}\times10^{-30}m$ at $1σ$ CL, approximately four orders of magnitude larger than the Planck scale, demonstrating that the $κ$-deformed space-time offers a potential window into quantum gravity phenomenology through precision cosmology.

The Planck all-sky surveys at (sub)millimeter wavelengths enable us to accurately determine the corresponding local luminosity functions up to the highest luminosities. The detected galaxies are strictly local, so evolutionary effects, which are known to be particularly strong at these wavelengths, are not a problem. However, previous studies have so far relied only on the Planck Early Release Compact Source Catalog (ERCSC) for this purpose. Another important improvement over earlier estimates is the availability of complete all-sky catalogs of galaxies within hundreds of megaparsecs, with redshift-independent distances for nearby objects, for which redshifts are not reliable distance estimators. In this paper we re-estimate the (sub)millimeter local luminosity functions using data from the Second Planck Catalog of Compact Sources, which supersedes the previously used ERCSC and contains far more sources and more accurate photometry. We computed the luminosity functions using both the classical $1/V_{\rm max}$ and the nonparametric kernel density estimation (KDE) method, which overcomes limitations of binning techniques. Our implementation of the KDE uses the $1/V_{\max}$ weighting to account for survey selection effects. We obtain Planck-based local luminosity functions at 857, 545, 353, and 217 GHz, as well as the total IR luminosity function and the dust mass function. We find significant differences from earlier estimates and discuss their possible origins.

The origin of black hole entropy remains one of the deepest mysteries in modern physics. Two recent developments offer complementary perspectives on this puzzle: the entropy release from regular Schwarzschild black holes with a de Sitter core (the OCK construction), and the local thermodynamics of the de Sitter vacuum (Volovik). In the OCK framework, the inner horizon carries positive Bekenstein-Hawking entropy $S_{\rm inner}=πh_c^2$ that is gradually released as the core shrinks, until a classical Minkowski breaking obstructs the evolution at $n=0$. In Volovik's framework, the total entropy of a homogeneous de Sitter region is $S_{\rm dS}= \operatorname{sgn}(H)\,π/H^{2} = \operatorname{sgn}(H)\,A/4$: expanding de Sitter ($H>0$) carries positive entropy, while contracting de Sitter ($H<0$) carries negative entropy. We show that the sign of the Hubble parameter is the unifying element linking the two pictures. The OCK core is de~Sitter only for $n>2$; the Minkowski breaking is a classical kinematic obstruction, not a dynamical transition to a contracting de Sitter phase. Any connection between the expanding and contracting regimes would require a quantum mechanism that remains speculative. Nevertheless, both frameworks embody the same thermodynamic principle, the shrinking of the interior drives the system toward increased total entropy, and together they provide a consistent picture of entropy flow during gravitational collapse. The integer nature of the OCK parameter suggests a quantized entropy spectrum and a statistical interpretation of black hole entropy, while the generalized second law is satisfied in both frameworks, and in the speculated quantum connection provided the environmental entropy is properly accounted for.

Massive stars have a major impact on their environment in their host galaxy. Observational determinations of their physical parameters are required to better constrain evolutionary models. In this context, the binary system WR 25 whose dominant spectral type is that of a nitrogen sequence Wolf-Rayet star, is of particular interest. It exhibits the highest known hydrogen content among the Milky Way Wolf-Rayet stars, as well as additional absorption lines. It is most probably an object still on the main-sequence or close to leaving it. We acquired new high-resolution spectra of this extremely interesting object. We present an improved version of the SB1 orbital solution for the motion of the WN component. We confirm the detection of the previously reported probable O companion and definitively prove that it is indeed gravitationally bound to the WN star. A first SB2 solution is presented, and a mass-ratio WN/O of 2.02 +/- 0.36 is derived. Following a spectral disentangling procedure, we identify the companion as an O5(f^+) star belonging to either the main-sequence (V) or giant (III) luminosity classes. The spectral type of the companion, together with the above-mentioned mass ratio, points to a very massive primary WN star of at least 55 solar masses. This confirms that WR 25 belongs to the family of very massive WNLh objects, a very poorly populated class in the Milky Way. We demonstrate that the absorption component in the P-Cygni profile of the He II lambda 4859 line of WR 25 is mainly due to the O-type companion, and we propose to adopt a WN6ha spectral type for the WN component of the system. On the basis of the extracted disentangled spectra, we derive approximate physical parameters through a detailed CMFGEN analysis, given the difficulty in constraining both the extinction towards WR 25 and the definitive brightness ratio between the components.

We present a compact and unified framework for quantum-information diagnostics of time-dependent two-mode bosonic systems based on the Bogoliubov ratio $λ_k(η) \equiv β_k(η)/α_k(η)$. For a general time-dependent quadratic two-mode Hamiltonian, the state dynamics is exactly reduced to a single complex Riccati equation for $λ_k$. Upon tracing out one partner mode, the spectrum of the one-mode reduced density matrix is determined entirely by the squared magnitude $q_k(η) = \vert{}λ_k(η)\vert{}^2$. Consequently, we could construct the explicit, model-independent formula for the for the reduced-state purity, linear entropy, Rényi-2 entropy, and von Neumann entropy without reconstructing and diagonalizing the reduced density matrix on a model-by-model basis using coupled squeezing parameters ($r_k, φ_k$). We demonstrate the utility of this framework in two distinct non-stationary setups: primordial cosmological perturbations and a chirped-pulse nondegenerate optical parametric amplifier. In the cosmological context, our formulation clarifies how background-induced phase rotation and frequency softening regulate squeezing growth and state mixedness; in the optical domain, it captures the delayed onset, suppression of squeezing accumulation, and late-time entropy saturation induced by finite pump duration and frequency chirp. By cleanly factorizing model-dependent driving protocols from universal information-theoretic metrics, this framework offers an efficient, standardized diagnostic tool for a broad class of parametrically driven quadratic bosonic systems.

We update the Hubble constant measurement with corrected Pantheon+ and DES-DOVEKIE supernovae. The use of DES-DOVEKIE here is the first application of DES-DOVEKIE to a distance-ladder $H_0$ determination. Recent reanalyses of supernova datasets have put Pantheon+, DES-DOVEKIE, and Union3.1 samples on the same footing with regard to the evidence of dynamical dark energy ($3.2$--$3.4σ$), and thus an update on the Hubble constant is the next logical step. The $H_0$ Distance Network (H0DN) baseline is $73.499\pm0.809$ km s$^{-1}$ Mpc$^{-1}$, a $7.1σ$ tension with the cosmic microwave background (CMB) determination in a $Λ$ cold-dark-matter ($Λ$CDM) cosmology, $H_0^{\rm CMB,ΛCDM}=67.24\pm0.35$ km s$^{-1}$ Mpc$^{-1}$. A revised host-mass correction applied to the older Pantheon+ changes 114 of the total 1701 apparent-magnitude rows. The calibrator supernovae are not affected, but 52 of the 277 Hubble-flow rows are. Applying only these magnitude corrections, with the H0DN covariance, redshifts, and velocities unchanged, gives $H_0=73.264\pm0.806$ km s$^{-1}$ Mpc$^{-1}$ and a $6.85σ$ Hubble tension. This is our main baseline result and the update for the astrophysics community. Alternatively, replacing the complete Hubble-flow treatment with the corrected Pantheon+ data gives $73.139\pm0.791$ km s$^{-1}$ Mpc$^{-1}$ and $6.82σ$. For DES-DOVEKIE, 220 supernovae span $0.025\le z_{\rm HD}\le0.151$ in Hubble-diagram redshift, and 196 of them overlap with corrected Pantheon+. These overlaps determine the offset used to place the public DES-DOVEKIE distance moduli on the H0DN apparent-magnitude scale. Holding this offset fixed gives $H_0=73.267\pm0.828$ km s$^{-1}$ Mpc$^{-1}$ and a $6.70σ$ tension. Extending to $z_{\rm HD}\simeq0.3$ raises $H_0$. However, both rises are smaller than the H0DN uncertainty. Neither update resolves the Hubble tension. (abridged)

We investigate the influence of nonlinear longitudinal disturbances, triggered by an initial field-aligned velocity flow, on the damping of standing kink oscillations in fine-structured, cool coronal loop strands under isobaric conditions. Using two-dimensional ideal MHD simulations, we model different realistic flow geometries, bounded, unbounded, and external, and quantify their impact on wave excitation, damping, and energy leakage. Our modelled loop strand incorporates strong density contrasts ($d = 5$ and $d = 20$), providing a configuration consistent with cool-loop observations from Hinode/SOT and SDO/AIA. Our results show that while the nonlinear disturbances exert mild influence on the oscillation period, they substantially modify the damping time. Unbounded flows yield the strongest damping, reducing the damping time by up to $\sim 25\%$ compared to bounded flows, caused by enhanced wave-flow coupling and scattering. Longitudinally inhomogeneous flows further intensify the damping, with high-density strands exhibiting faster convergence toward the uniform-flow limit. In cases with supersonic internal flow, slow sausage-mode harmonics and weak slow shocks are additionally excited, indicating the generation of mixed-mode wave responses in flow-dominated loops. These findings demonstrate that realistic, spatially extended nonlinear disturbances play a significant role in the damping of kink oscillations and should be incorporated into forward modeling and coronal seismology diagnostics.

We present a homogeneous analysis of rotational variability and spot properties in young stellar objects across multiple star-forming regions observed by the Hunting Outbursting Young Stars (HOYS) project. From over 2000 candidate members, we identify 144 YSOs with robust periodic signals and well-constrained multi-band amplitudes. The sample has a median age of $\sim$1~Myr, effective temperatures of 3500--6500~K (masses $\sim$0.6--2~M$_\odot$), and is dominated by Class~2 objects, one third of which exhibit inner disc dust emission. The rotation period distribution is strongly bimodal, with 55 percent fast rotators ($P<5.5$~d) and 45 percent slow rotators. Fast rotators are predominantly inner disc-less, whereas slow rotators include both disc-bearing and disc-free systems, indicating that disc braking alone cannot explain the observed rotational states. We derive spot properties from multi-band amplitudes and find that, after correcting for observational biases, the intrinsic cold-spot coverage distribution of fast rotators is well described by an exponential function. This implies that small spot coverages are intrinsically much more common than large ones, consistent with stochastic magnetic flux emergence governing spot formation. In contrast, slow rotators show a pronounced deficit of small cold spots. After considering observational biases and alternative physical explanations, we conclude that small spots on slowly rotating YSOs have significantly shorter lifetimes. These results provide new evidence that magnetic surface structure and its evolution depend on stellar rotation, placing new empirical constraints on models of magnetic activity and angular momentum evolution in young stars.

Stellar binaries and multiples are common objects. Their identification and characterization are primarily limited by the angular resolution of current instrumentation, survey depth and dynamic range. Towards the Galactic plane, stellar crowding further complicates these studies. We aim to identify unresolved binaries with good astrometric solutions and M dwarf primaries in the b294 field from the Vista Variables in the Vía Láctea (VVV) survey using publicly available data. We examine the catalogue of M dwarfs within 500 pc in the b294 tile, employing binarity tracers based on statistical parameters from Gaia Data Release 3, multi-band photometry, and information in the literature. We reassess the astrometric and photometric parameters typically used for binary detection, establishing new boundaries and validating existing ones in the dense stellar field examined. We compare these results with those obtained in the solar vicinity. We present 990 unresolved binary candidates and 43 previously known binaries, including five possible triple systems. These represent the 13\% of the catalogue, rising to 14.9\% in well-covered regions. Binary-model SED fitting yields effective temperatures for 98 primary stars, with the properties of their secondary candidates indicating that nearly half may be substellar objects. We select 120 of the most promising binary candidates. Tangential velocities, where calculated, place 95\% of the studied binary candidates within the young disc population (tau <= 1 Ga). We demonstrate that the influence of nearby Gaia detections on the statistical parameters is small, allowing constraints similar to those that are applied in less crowded regions.

We present a refined astrometric and photometric analysis of the well-studied intermediate-age open clusters NGC 2266 and NGC 2324 using high-precision Gaia DR3 data, complemented by 2MASS and LAMOST DR7 catalogs. Probable cluster members are identified using unsupervised machine learning techniques. We apply both Gaussian Mixture Models (GMMs) and \texttt{pyUPMASK}. We find that the GMM-based membership sample yields a cleaner, more coherent cluster sequence in the Gaia CMDs than pyUPMASK. We identified 719 and 852 high-probability members ($P \geq 0.7$) for NGC 2266 and NGC 2324, respectively. Using the parallax method, we determine distances of 3.55 $\pm$ 0.23~kpc for NGC 2266 and 4.18 $\pm$ 0.24~kpc for NGC 2324. The radius estimates for both clusters are 7.23 $\pm$ 0.47 pc and 10.94 $\pm$ 0.63 pc. Isochrone fitting estimated ages of $1.1 \pm 0.1$~Gyr for NGC 2266 and $790 \pm 150$~Myr for NGC 2324. These age estimates were derived assuming metallicities of $Z = 0.0084$ and $Z = 0.0038$, respectively. The King profile fitting indicates that both clusters exhibit compact, well-defined radial structures. Their tidal radii are $8.84'$ (9.13 pc) for NGC 2266 and $10.97'$ (13.34 pc) for NGC 2324. The slopes of the present-day mass functions are $1.13\pm0.18$ for NGC 2266 and $1.24\pm0.19$ for NGC 2324, indicating a deficiency of low-mass stars. The derived mass-function slopes are consistent with dynamical evolution in both clusters. The clusters exhibit short relaxation times, while only NGC 2324 shows a mild indication of mass segregation. This study highlights the power of Gaia astrometry to resolve internal structures within open clusters and refine their dynamical parameters.

We revisit the derivation of the diffraction integral, which is an approximate evaluation of the Kirchhoff integral, widely used in the literature for phenomenological applications in gravitational lensing. We propose a systematic approach to evaluate the Kirchhoff integral within a beyond-eikonal expansion, carefully tracking all approximations involved in its standard derivation. In this framework, we recover the usual diffraction integral as the leading contribution, together with a correction term that is typically small in realistic lensing scenarios. We further show that our evaluation of the Kirchhoff integral is equivalent to a beyond-eikonal expansion of wave propagation, after summing over all geometric-optics images. This result clarifies the physical origin of diffraction in gravitational lensing and demonstrates that diffraction effects and beyond-eikonal corrections are not distinct phenomena, but rather different but equivalent descriptions of the same underlying physics.

Neutrino oscillations establish that neutrinos are massive, providing the only laboratory detection of physics beyond the Standard Model. Direct kinematic experiments bound the electron-neutrino mass to $m_{ν_e} < 0.45$ eV (KATRIN, 90% CL), implying $\sum m_ν\lesssim 1.3$ eV. Conversely, cosmology within $Λ$CDM is highly constraining: Planck CMB, CMB lensing, and DESI DR2 BAO yield $\sum m_ν< 0.056$ eV (95% CL), in 2-3$σ$ tension with the inverted-ordering floor (0.10 eV). However, this bound relies on $Λ$CDM, while data hint at an evolving dark energy. To determine the model dependence of cosmic neutrino mass bounds, we deconstruct each probe's sensitivity to late-time physics and pursue two robust routes to a $\sum m_ν$ bound: (i) The existing dark-energy-marginalized route, retaining all data and marginalizing over $(w_0, w_a)$, is shown to also be immune to flexible binned and cubic $w(a)$ histories, yielding $\sum m_ν< 0.152$ eV, sharpening to $σ(\sum m_ν) \approx 0.043$ eV with Simons Observatory lensing and Spec-S5 BAO. (ii) A new late-Universe-free route combines primary CMB, marginalizing over acoustic-peak smoothing via $A_{\rm lens}$, with the reconstructed lensing spectrum $C_L^{κκ}$, removing late-time expansion dependence by construction. This yields $\sum m_ν< 0.41$ eV today, tightening to 0.31 eV (Simons Observatory) and 0.28 eV (cosmic-variance limit) across all tested dark-energy models. These relaxed bounds trade statistical power for model independence. Interestingly, they land in the sensitivity range targeted by next-generation laboratory experiments like Project 8 ($m_{ν_e} \sim 0.1$ eV), motivating vital synergies between future cosmological and terrestrial neutrino measurements.

To identify globular clusters (GCs) belonging to Sagittarius, we conducted verification from multiple aspects and carried out a detailed analysis of member GCs and the associated objectives. From the cluster catalog of E. L. Hunt &amp; S. Reffert, we obtain the candidates of Sagittarius through the geometric space with proper motion (μ<SUB>α</SUB>, μ<SUB>δ</SUB>). We conduct further verification to make sure they are genuine members of Sagittarius using parameters such as proper motion, V<SUB>gsr</SUB>, and direction of motion. After three steps of verification, we confirm that 10 GCs belong to Sagittarius. Among them, nine have been reported in previous studies, and our verification further confirms their membership in the Sagittarius system. The remaining one, HSC 61, is a newly identified member. Combining these with 21 credible Sagittarius-associated GCs from D. Minniti et al., our final sample includes 31 Sagittarius-associated GCs. Twenty-six are located in the core, and five are located in the stellar stream. We constructed the metallicity distribution in all of Sagittarius; there is one rich peak in the core, and there is one poor peak in the stream. The reason may be that the outer and poorer GCs of the core were first pulled into the stream. Additionally, we analyze the Sagittarius merger event through energy and angular momentum. Elqui is the most distant stream discovered in the Dark Energy Survey at a distance of 50 kpc, and Malhan thought Elqui belongs to the Sagittarius merger. We present new evidence that Sagittarius and Elqui belong to the same accretion event. Through verification, we have added two new star clusters to this large accretion event of Sagittarius. We found that the Large Magellanic Cloud has a certain influence on the orbits of Elqui and Sagittarius.

We present a sample of 88,959 K giants from Dark Energy Spectroscopic Instrument Milky Way Survey Year 3 data, which we use to characterize the chemo-dynamical properties of the stellar halo at Galactocentric distances of 12 to ∼100 kpc. Using HDBSCAN, we identify five prominent stellar halo substructures: Aleph, the Sagittarius stream, Gaia-Sausage-Enceladus (GSE), Cetus-Palca, and the Orphan─Chenab stream. We present the properties of each of these structures as they appear in our catalog, and examine how uncertainties on distance affect the characterization of substructure with this approach. We also examine regions associated with previously reported overdensities (such as the Virgo Overdensities and the Sagittarius spur) that we do not recover with HDBSCAN. The size and distance range of our catalog allows us to explore in detail the residual stellar halo, comprising stars that we do not associate with any substructure. We find that samples of ∼2000 outer halo stars with both highly prograde and highly retrograde angular momenta have similar metallicity distribution functions (MDFs), which do not resemble the MDFs of either GSE or Sagittarius. Both the prograde and retrograde residual halo MDFs are bimodal, with a metal-poor peak at [Fe/H] ∼ −2 and a metal-rich peak at [Fe/H] ∼ −1.3 (prograde) or −1.5 (retrograde). The MDF for lower-angular-momentum residual halo K giants does not show clear evidence for a metal-poor peak, and broadly resembles the MDF of GSE, even at much lower binding energies than GSE itself. We discuss possible interpretations of these findings for GSE accretion scenarios.

With regard to the observed dark matter density profiles in galaxies and clusters, the scalar dark matter scenario has been previously studied for its potential detectability through gravitational wave observations at measurable signal-to-noise ratios. In the present study, we consider dark matter described by a massive vector field, also referred to as a Proca field. The density profile in the vicinity of the black hole is explicitly constructed for a broad range of dark matter masses, μ ∼ 10<SUP>-10</SUP>-10<SUP>-15</SUP> eV, allowing the dark matter to exhibit both particle and wave-like characteristics. While the computation of the DM density distribution is analytically tractable in the particle regime, we find it convenient to compute the same numerically in the wave regime. Nevertheless, in the outer region, the surrounding dark matter is assumed to follow a broken power-law distribution, represented by a Navarro-Frenk-White (NFW) profile with a central spike. To investigate the detectability of the vector dark matter in the gravitational wave spectrum, we have modelled a stellar-mass black hole (1M <SUB>⊙</SUB>) inspiralling into a Schwarzschild black hole of mass 10<SUP>4</SUP> M <SUB>⊙</SUB> within such a vector dark matter environment. Using this setup, we have analyzed the dephasing in the gravitational wave strain induced by vector dark matter and performed a Fisher forecast for upcoming LISA observations, with particular emphasis on the distinctive features arising in both the particle and wave regimes of the dark matter. Additionally, most of the important results have been compared with the scalar dark matter case.

We investigate a radiative seesaw model under a non-holomorphic modular S <SUB>3</SUB> flavor symmetry, addressing neutrino masses, dark matter candidates, and lepton flavor violations. Neutrino masses arise at the one-loop level, and we confront the model with neutrino oscillation data, lepton flavor violation bounds, and relic density requirements through a chi-square analysis. By incorporating the latest JUNO results, we find that the allowed parameter space is strongly constrained: For the normal hierarchy, both fermionic and bosonic dark matter scenarios remain viable but highly localized, whereas for the inverted hierarchy with fermionic dark matter no allowed region survives. These findings demonstrate that JUNO provides decisive constraints and that our framework is highly predictive.

This paper presents the construction of the supersymmetric (SUSY) deformed version of the time dependent metric that describes the interior of the Schwarzschild BH. First, the noncommutative bosonic model is constructed by inducing the deformation in the minisuperspace coordinates and the associated canonical momentum. Following the methods of SUSY quantum mechanics, the supercharges of the deformed models are constructed and the deformed SUSY Wheeler-DeWitt equation is obtained. The classical dynamics are also obtained using the WKB approximation, we find the classical solutions and the conditions to satisfy the Hamiltonian constraint for both the SUSY and bosonic cases. Finally, the effects of the deformation in the context of deformed phase space cosmology and black holes are discussed.

We construct Vaidya-type solutions of quasitopological gravity coupled to nonlinear electrodynamics in arbitrary spacetime dimensions. Starting from the corresponding static spherically symmetric charged solutions, we obtain their dynamical counterparts by promoting the integration constants, in particular the mass and electric charge, to arbitrary functions of the advanced or retarded null coordinate. We show that the resulting field equations are satisfied provided suitable charge-carrying null currents and null fluid fluxes are included. The formalism applies to a broad class of nonlinear electromagnetic theories and provides a simple and systematic method for generating exact radiating charged solutions in quasitopological gravity.

Classical delay, chorus, and reverb effects model multiple pro- pagation paths using discrete delays or statistical distributions. This work proposes a model inspired by gravitational lensing, where an audio signal is treated as a wave packet traversing a temporally distorted potential rather than physical spacetime. The distortion generates multiple effective propa- gation paths with different delays, phases, and gains, producing controlled constructive and destructive interference.

White dwarf (WD) atmospheric metal pollution provides strong evidence for the presence of remnant planetary material and it can be used as an indirect tracer of outer planetary systems. We analyze whether the presence of a wide stellar companion affects the occurrence of outer planetary systems by comparing the incidence of calcium (Ca) pollution in hydrogen-atmosphere WDs in wide binaries and in apparently single stars. We construct two sample pairs: a large homogeneous SDSS low-resolution spectroscopic set and a smaller high-resolution sample. For each WD, we measure Ca abundances or upper limits and compute detectability-corrected cumulative pollution fractions that account for variations in effective temperature, signal-to-noise ratio, and spectral resolution. In the SDSS-based samples, we find pollution fractions <1%, defined as the fraction of WDs with detected Ca, for both single WDs and WDs in wide binaries. After correcting for detectability, the cumulative abundance distributions of the two populations are statistically consistent. The same conclusion is obtained for the higher-resolution samples, despite their different raw detection fractions. Our results indicate no statistically significant difference in the occurrence rate of remnant outer planetary systems between single stars and stars with wide (~200 au) companions, within the current uncertainties. These uncertainties are significant because the samples contain only a small number of polluted WDs. The corrected detectability cumulative fraction approach used here provides a framework for comparing samples with different detection sensitivities and can be extended to larger spectroscopic datasets. Such samples will be required to determine whether wide stellar companions affect the survival and delivery of planetary material and to search for more subtle trends, for example, as a function of companion separation.

In general relativity and its metric-formalism extensions, the innermost stable circular orbit and the photon ring of a charged black hole contract as the charge increases. In this paper, we discover a qualitative anomaly that violates this universal behavior, serving as a smoking-gun signature of geometric nonmetricity. By considering a minimal coupling between the bosonic field and the independent affine metric, we demonstrate that nonmetricity induces an effective geometric force that triggers a trajectory expansion of both massless and massive bosons with increasing black hole charge. This qualitative inversion directly imprints onto the black hole shadow, lifting the degeneracy between metric-affine gravity and general relativity. Using Eddington-inspired Born-Infeld gravity as a concrete implementation, we show that next-generation horizon-scale imaging can resolve this signature, probing a complementary high-energy window up to the $10^{5}_{~}\,\text{TeV}$ scale.

A detailed analysis of high-resolution spectra in the optical and near-infrared range of the central zone of the proto-planetary nebula Hen 3-1475, obtained in 2006 and 2024, is conducted. The spectrum primarily revealed stellar emission of H Balmer and Paschen series, lines of iron (Fe I, Fe II, and [Fe II]), and other significant lines of He I, Ca II, [Ca II], and O I. Several multiplets of Fe II, the H Balmer series, Ca II H and K, Na I D and He I lines exhibit P-Cygni profiles and bump-like features, which are clear indicators of strong stellar winds. The terminal velocity of the winds was calculated, reaching values up to ~ 800 km/s. [Fe II] and Fe I lines were used as gas density indicators. In these observations, no photoionized nebular lines of planetary nebulae were identified, suggesting that the central star has not reached the temperature required to photoionize the nebula. A comparison between the observations from 2006 and 2024 reveals some few significant differences, being the most important the probably ejection of a new jet emerging from the central zone and the detection of a broad component adjacent to H α, probably originating from emission associated with a jet at 700 km/s. High-spectral resolution observations of the knot NW1 obtained on August 2024, are also presented. This knot shows a typical spectrum of shocked gas. The emission of this knot has changed, presently not showing [O III] 5007 and other ionized lines that were reported in 2006.

An additional term of the form $λ\mathbf{T} \cdot \mathbf{C} \cdot \mathbf{T}$ in the Einstein-Hilbert Lagrangian was introduced to explain the interaction between matter and pure gravitational field [H. W. Lee and A. Qadir, Motion of test particle for Weyl-interaction gravity, {\it Int. Jour. Mod. Phys. D} {\bf 28}(16) (2019) 2040014], the modified relativistic dynamics (MORD). In this paper, we estimate the shadow parameters of black hole in a spherically symmetric static spacetime within the MORD framework. As a first approximation, we assume that the black hole is surrounded by a constant-density baryonic matter halo. The analysis is then extended by introducing a homogeneous plasma background. We compute the shadow radii for various black hole masses and analyze their dependence on the WIG coupling parameter $λ$. In addition, we compute the fundamental quasi-normal mode (QNM) frequencies under test-field approximation, and perform a time-domain integration analysis.

We investigate ghost dark energy (GDE) in a cosmological framework derived from Kaniadakis entropy. By applying the first law of thermodynamics to the FRW apparent horizon, we obtain modified Friedmann equations that include a correction term characterized by the Kaniadakis parameter $λ$. We then study the evolution of a flat universe containing pressureless matter and interacting GDE within this modified gravity setup. Our numerical analysis reveals that the Kaniadakis correction mildly affects the dark energy equation of state and shifts the transition to cosmic acceleration. Stability analysis via the squared sound speed shows the model remains generally unstable, though the instability is moderated for larger $λ$. Statefinder diagnostics indicate that the model approaches the $Λ$CDM fixed point in the future, with deviations decreasing as $λ$ increases.

Planck-scale signatures of quantum gravity may emerge semiclassically not only through modifications of spacetime geometry but also through the geometry of momentum space. In this work, we develop a $(2+1)$-dimensional framework in which a noncommutative algebra of spacetime localization operators reconstructs a locally anti-de Sitter momentum-space geometry in the classical limit. The resulting momentum-space curvature deforms the phase-space structure, modifies particle kinematics, and leads to a finite renormalization of the particle mass. Using an effective configuration-space action, we derive the corresponding stress-energy tensor that consistently sources the classical Einstein equations without modifying the gravitational dynamics. The resulting spacetime is a deformed BTZ black hole whose conserved mass, horizon radius, Hawking temperature, and Bekenstein-Hawking entropy acquire finite Planck-scale corrections. We further investigate Hawking radiation using the Hamilton-Jacobi tunneling formalism and show that the return time of an emitted massless particle receives two distinct contributions: a geometric correction induced by curved momentum space and a dynamical correction arising from Hawking backreaction. Remarkably, the null geodesic equations remain unchanged, indicating that the observable effects originate entirely from the deformation of the effective spacetime geometry rather than from modifications of particle trajectories. These results provide a concrete semiclassical mechanism through which quantum kinematics encoded in curved momentum space can generate observable gravitational phenomena without requiring a quantization of spacetime itself, thereby offering a phenomenological bridge between quantum geometry and black-hole physics.

We combine the axiverse with a negative cosmological constant $Λ$, both originating from the string landscape, and apply an observation-time-weighted anthropic argument. Adopting a uniform prior on $Λ$ and a typical string-motivated axion decay constant comparable to the reduced Planck scale, this framework predicts a $\sim 40\%$ probability of observing $0.1 < Ω_m < 0.9$, thereby naturally resolving the long-standing fine-tuning and coincidence problems of dark energy. Unlike many scalar-field dark energy models, the anthropic Lambda-axion universe (ALAverse) statistically disfavors slow-roll dynamics, as slow-roll requires fine-tuning of the initial field displacement. Moreover, the negative cosmological constant renders fast-roll scenarios anthropically unfavorable, since they typically yield only a very brief observational window with positive dark energy density. Having ruled out both extremes, the ALAverse characteristically predicts a moderate-roll dynamics. We derive a two-parameter parametrization in terms of $δ_Ω$ and $|\varepsilon_s|$ that covers ALAverse solutions as well as a broad class of canonical and phantom field models. Current observational data yield $δ_Ω= -0.0498 \pm 0.0186$, corresponding to a $2.7σ$ rejection of $Λ$CDM ($δ_Ω= 0$) and phantom models ($δ_Ω> 0$). The data also show a mild preference for the ALAverse over slow-roll quintessence, a trend that can be conclusively tested with future high-precision measurements of the Hubble diagram.

Under the assumption that black hole horizon area is quantized, each Hawking evaporation step, during which the black hole loses mass and transitions to a lower area level, is interpreted as the erasure of one bit of information. In this paper, by employing Landauer's principle, we test the consistency of various black hole entropy relations with this information-theoretic framework. For the Bekenstein-Hawking entropy, the energy emitted per step saturates the Landauer bound. We extend this analysis to a broad class of generalized entropy models, yielding three distinct outcomes. In the first category, Landauer's principle imposes constraints on the Hawking temperature and, consequently, on the black hole mass. In the second, it restricts the free parameters of the entropy model. The third category, exemplified by Kaniadakis entropy, proves incompatible with Landauer's principle. For all compatible models, we derive the area quantization parameter and the corresponding area spectrum. While this parameter is constant for Bekenstein-Hawking entropy, it becomes level-number-dependent for many generalized models. Nonetheless, the relative spacing between successive area levels vanishes in the classical limit. Our findings point to a deep link between information theory and black hole thermodynamics.

The Arches cluster, located in the Galactic Centre (GC) is one of the best astrophysical laboratories to study the properties of massive stars and young massive clusters (YMCs). However, several fundamental parameters of the Arches cluster remain uncertain. Our goal is to constrain key cluster parameters (cluster age, mass, and initial mass function, IMF) by comparing the observed stellar radio flux density distribution of the Arches cluster to those derived from a set of synthetic clusters. We use the deep X-band (10 GHz) Very Large Array data from our previous radio continuum study of the Arches cluster. We model each simulated cluster with three parameters: age, mass, and IMF slope. We use three different stellar evolutionary models: GENEC, PARSEC, and MIST at two different metallicities, solar ($Z=0.014$) and super-solar ($Z=0.020$). We run Markov-chain Monte-Carlo simulations for each model/metallicity combination in order to explore parameter space. All models and metallicities return preferred ages in the $2\lesssim t_{\rm age}/{\rm Myr}\lesssim 3$ range. We obtain an IMF slope of $α_{\rm IMF}=-1.85^{+0.28}_{-0.20}$, averaged over all models, where uncertainties are dominated by the degeneracy between cluster mass and IMF slope. If we use the IMF slope from previous infrared studies as prior, the cluster mass distributions peak at $\sim2.7\times10^4\, M_\odot$ and we can establish a lower limit at $\gtrsim2\times10^4 M_\odot$ for the Arches cluster mass. Radio continuum observations of their most massive stars can be used to constrain YMC parameters. In the case of the Arches cluster, age can be determined regardless of prior spectroscopic information, which can be useful to characterise newly discovered YMCs in the GC. Our results support the idea that a top-heavy IMF may be preferred in the GC or in YMCs in general.

We study the structure and evolution of the Galactic bar's resonant phase space in self-consistent N-body simulations of the Milky Way, with and without perturbations from the Sagittarius dwarf galaxy. In an idealized disk evolution model in which stars are perturbed solely by a bar that spins down due to dynamical friction against the dark matter halo, it is predicted that stars trapped in the bar's corotation resonance form a characteristic "tree-ring" structure in phase space: as the resonance expands in volume while sweeping outwards, it sequentially captures surrounding stars at its surface, such that stars captured earlier in the inner disk are found preferentially near the core of the resonance. However, it has not been clear whether such a structure persists in a more realistic galactic disk subject to a variety of time-dependent perturbations, in particular those by spiral arms and passing satellite galaxies. This paper demonstrates that the predicted tree-ring structure indeed emerges in a realistic noisy environment using self-consistent N-body simulations. Despite the presence of spiral arms, encounters with the Sagittarius dwarf galaxy, as well as fluctuations in the bar's pattern speed, and not least numerical noise—all of which drive stellar diffusion in phase space—, the tree-ring structure remains well-preserved in the slow angle-action space. Our results demonstrate that the tree-ring structure of the bar's resonance is a robust signal of the bar's spin down, and hence its discovery in the Milky Way implies the existence of a dark matter halo that removed angular momentum from the bar.

The transmission of three-dimensional anelastic internal gravity wave packets incident upon a retrograde background jet flow are examined through fully nonlinear numerical simulations. The background winds are chosen to be representative of the eastward and westward flows of the Quasi-Biennial Oscillation (QBO) in the equatorial stratosphere. Transmission, which is quantified by the relative pseudomomentum of waves passing above the jet, is found to be smaller for incident waves with larger initial frequency. Due to anelastic effects, the amplitude of the transmitted wave packets tends to grow exponentially, ultimately inducing a local mean flow that acts to drive the waves to overturn and break turbulently. The results are compared with previous studies that predicted transmission of small amplitude wave packets, and implications are discussed for the influence of wave transmission across the QBO.

We define doubling conditions for measured Lorentzian length spaces in terms of chronological diamonds, and prove that such conditions are implied by suitable timelike curvature bounds. In particular, for the first time, we relate doubling to curvature bounds in Lorentzian geometry. As a consequence, we obtain compactness results for Lorentzian generalized cones with respect to the Lorentzian Gromov--Hausdorff convergence introduced by Mondino--Sämann.

The pre-inflationary QCD axion is often said to require low-scale inflation. We derive a general isocurvature bound for a light axion with a scale-invariant spectrum, treating its inflationary normalization $f_I$ independently of the late-time decay constant $f_a$ and allowing for an arbitrary axion dark matter fraction, nontrivial perturbation transfer, and the full anharmonic abundance response. In the minimal benchmark, where axions constitute all of the dark matter, $f_I=f_a\leq M_{\rm Pl}$, and the angular perturbation is conserved, the least restrictive CMB limit considered gives the 95% C.L. upper bound $H_I<1.25\times10^{10}\,\mathrm{GeV}$ on the inflationary Hubble scale. For an initial misalignment angle $θ_i=1$, the bound strengthens to $H_I<2.2\times10^7\,\mathrm{GeV}$, with still stronger constraints near the hilltop. Combining the isocurvature and tensor spectra yields axion-tensor and axion-conditioned Lyth bounds. If the observed curvature perturbation is generated by a canonical cold single-field slow-roll inflaton and the tensor amplitude varies slowly across the observable CMB window, these relations limit the inflaton excursion to $Δφ_{\rm CMB}/M_{\rm Pl}\lesssim10^{-7}\text{-}10^{-4}$ and require $|M_{\rm Pl}V'/V|\sim10^{-8}\text{-}10^{-5}$ while $M_{\rm Pl}^2V''/V\sim-10^{-2}$. This hierarchy favors models with independent control of the inflationary scale, potential derivatives, exit, and reheating, including hybrid, running-mass, and inflection-point models. Reheating and the requirement of Peccei-Quinn non-restoration sharpen these conditions, while nonminimal scenarios can relax them by modifying the primordial fluctuation, its transfer, or the relic abundance.

We revisit Kerr-NUT metrics and related spin-$s$ fields in $D\geq4$, and study their associated scattering amplitudes. Starting in position space, we highlight the interpretation of mass and (multiple) NUT charges as being associated to distinct solutions of the rotation-deformed radial equation, which is made explicit in Cartesian multi-Kerr-Schild coordinates. This interpretation extends to electromagnetism with magnetic-type charges, and also extends to higher-spin counterparts, in accordance with the classical double or multi copy. We then establish a notion of ``electric-magnetic" duality in higher dimensions, relating mass/electric to NUT/magnetic charges, which generalises the $D=4$ case in a novel manner. For $D\geq6$, this involves the choice where the multiple magnetic charges are equal. The duality is revealed in momentum space, by the 3-point scattering amplitudes that generate the solutions. For all spins, these amplitudes are constructed from a spin-raising operator $\mathcal S_μ$ and take the form $\varepsilon^{μ_1\cdotsμ_s}{\mathcal S}_{μ_1}\cdots {\mathcal S}_{μ_s}$ acting on a scalar seed. The scalar seed of the electric sector is dual to that of the magnetic sector: where the former's rotation dependence resums to a Bessel function $J_{\frac{D-5}{2}}$, the latter resums to a Bessel function $J_{-\frac{D-5}{2}}$. Finally, we explore the notion of self-duality that arises from this picture. Studying the classical $2\!\mapsto\!2$ amplitudes that determine leading-order scattering, we find no evidence of a higher-dimensional analogue of the integrability of $D=4$ self-dual gravity.

The goal of this paper is to provide an exhaustive study of the K 4p-5s doublet at 1.243/1.252~$μ$m perturbed by He and H$_2$ in physical conditions of brown dwarfs. This work is applicable to analysis of the ESO SupJup Survey's J-band spectra such as for Luhman~16. Line profiles of this doublet computed within a unified line-shape theory exhibit a blue asymmetrical behavior. This effect is of increasing importance with He and H2 density, and as a result, the full treatment of the infrared K doublet reveals strong effects on its opacity outside the impact approximation. For a He and H2 perturber density larger than $10^{19}$~cm$^{-3}$ (0.4 bar) the impact approximation breaks down and is not applicable to calculate the shape of the line profiles and their line core parameters.

We investigate the cosmological signatures of two-field dark energy with curved field-space geometry. We numerically solve the background and linear perturbation equations and assess the validity of the effective single-field description. We examine three distinct dark-energy clustering mechanisms: effective sound-speed suppression, dynamical excitation of the heavy mode, and tachyonic instabilities induced by field-space curvature, and explore their possible imprints on the matter power spectrum and cosmic microwave background anisotropies. Our analysis establishes multifield dark energy as a rich and testable extension of quintessence, with observable clustering signatures relevant to current and future cosmological surveys.

We study static, spherically symmetric self-gravitating non-Abelian 't Hooft-Polyakov monopoles in Einstein-scalar-Gauss-Bonnet gravity for two classes of scalar-Gauss-Bonnet coupling functions. We demonstrate that the branch structure of the monopole solutions depends sensitively on the choice of the coupling function. For the polynomial coupling, we show that, for sufficiently large values of the coupling parameter, the principal part of the field equations becomes locally degenerate at a critical radius, leading to a critical solution that signals a geometric phase transition. By contrast, the exponential coupling acts as a natural regulator, preventing the degeneration of the principal part and preserving smooth field profiles. Finally, we discuss a possible physical interpretation of the critical solution, in which spacetime separates into an inner region where quantum-gravitational effects may become important and an outer region that remains well described by classical general relativity.

We present Hermes, an in situ multiresolution framework for efficient and flexible measurements of cosmic large-scale-structure statistics from discrete catalogues. Hermes reconstructs a catalogue as a continuous density field in a compact scaling-function basis and replaces explicit counting of particle tuples with algebraic operations among window-filtered fields. Standard binning schemes for counts-in-cells, two-point and higher-order correlation functions are thereby expressed through choices of window functions, while new statistics can be constructed by modifying the kernels without redesigning the estimator. We introduce PyHermes, an open-source Python implementation combining multiresolution reconstruction, FFT-based convolution, MPI/thread parallelism, and GPU acceleration. It supports isotropic and anisotropic two-point statistics, marked correlations, standard and multipole three-point functions, filtered statistics, and differential operators for derived physical fields. Tests with cosmological N-body halo catalogues demonstrate a range of clustering measurements and quantify the computational efficiency and scalability of the approach. By separating field representation from statistical windows, a single reconstructed field can be reused for many standard and customised measurements, making Hermes well suited to large data sets from current and future galaxy surveys.

Several inequivalent thermodynamic formulations of spacetimes with NUT charge obey their own first laws and Smarr relations, so macroscopic consistency alone does not fix the black hole state space. We introduce a two-horizon sector diagnostic whose temperatures are fixed by harmonic-mean relations rather than adjusted as potentials. For uncharged Taub-NUT, the sum sector closes with the mass and NUT charge, whereas the difference sector closes, within a restricted homogeneous diagnostic class tested here, only after including the rotation-like thermodynamic secondary hair $J_n=mn$. Thus, within this sector diagnostic, the NUT parameter enters through both $N=n$ and the homogeneous combination $J_n=mn$. The secondary hair is defined off shell in the homogeneous mass representation, not as a new metric parameter or asymptotic charge. Hidden conformal symmetry of the rotating Kerr-NUT parent gives a consistency check, without assuming a holographic dual.

In this study, we study static and spherically-symmetric wormhole configurations within the recently proposed class of extended symmetric teleparallel gravities characterised by the functional form $f(Q,T)=αQ+βT+γT^{2}$, where $Q$ is the non-metricity scalar, $T$ is the trace of the energy-momentum tensor, and ($α,β,γ$) are constant coupling parameters. By varying the action with respect to the metric, we derive the modified field equations and cast them in an effective Einstein-like form containing additional geometric contributions that depend on $Q$ and $T$. We conclude that the $f(Q,T)=αQ+βT+γT^{2}$ framework offers a viable arena for constructing physically realistic wormholes without invoking severe energy condition violations, opening new pathways for connecting modified gravity phenomenology with astrophysical signatures of non-trivial spacetime topologies.

Context. A significant fraction (>30%) of planet-forming disks and planetary are misaligned with respect to the rotational axis of their host stars, yet the dominant mechanism responsible for these misalignments remains unclear. Aims. We aim to observationally constrain the angular momentum of Class II protoplanetary disks and assess whether late-stage infall of material can bring sufficient angular momentum to tilt them. Methods. We first computed the angular momenta of 15 disks with surface density profiles inferred from dynamical modeling of high angular resolution ALMA observations. Based on this sample, we derived a relation linking disk angular momentum to stellar mass, disk mass, and the radius enclosing 90% of the 13CO flux and used it to estimate angular momenta of 18 more disks. We then compared disk values with theoretical predictions for late-stage accretion from clouds and observed streamers. Results. Angular momentum for most disks is lower than what theoretical models predict for late infall. This is also in qualitative agreement with comparison with streamer observations, however, characterization of mass of reservoirs feeding the streamers is needed to confirm this picture. Conclusions. Interactions with nearby clouds, resulting in late-stage infall of material onto Class II disks, can potentially explain the observed misalignments within disks and planetary systems.

We develop the cosmological framework for Hassan--Schmidt-May multi-gravity, a ghost-free extension of bimetric theory with genuinely non-pairwise interactions of multiple spin-2 fields. For metrics that are simultaneously homogeneous and isotropic, the background dynamics reduce to a modified Friedmann equation supplemented by a system of coupled quartic polynomial equations for the scale-factor ratios. The spin-2 interaction contributes to the Friedmann equation as an additional effective fluid. We identify a regular high-density branch that approaches the standard radiation- or matter-dominated Universe, while regular low-density branches approach proportional vacuum solutions, where the interaction acts as a cosmological constant and the leading correction to the effective spin-2 energy density provides an additional matter contribution. We also determine the relative null-cone structure: on the regular high-density branch, the additional null cones approach wider opening angles than the matter-coupled null cone, while all null cones coincide in the vacuum limit. At linear order, we solve the algebraic equations determining the non-metric vielbein perturbations, derive the first-order consistency equations and their scalar and vector projections, and obtain the complete system of coupled tensor perturbation equations. These results establish a framework for studying cosmological solutions and perturbations in ghost-free multi-gravity beyond bimetric theory and its pairwise-interacting extensions.

We constrain the $z \approx 1$ HI distribution by jointly modeling two independent, existing observations of the 21-cm signal, the HI density parameter $Ω_{\rm HI}$ measured using uGMRT by stacking the 21-cm emission from blue, star-forming galaxies, and the 21-cm autocorrelation power spectrum (PS) measured using CHIME. We assign HI to the dark matter halos in a cosmological simulation using an HI mass-halo mass (HIHM) relation with three free parameters whose values we estimate by performing a joint Bayesian inference comparing the simulated $Ω_{\rm HI}$ and 21-cm PS with the measurements. We use the inferred HIHM posterior to simulate the HI distribution and predict the $z \approx 1$ HI mass function (HIMF). We find that the HIMF remains nearly constant at low HI masses $( \lesssim 3.6 \times 10^9 M_\odot)$, and it declines rapidly for larger HI masses. Around $\sim 90$ percent of the total HI gas is contained in the mass range $M_{\rm HI} \in [2 \times 10^9, \, 4 \times 10^{11}] \, M_\odot$. Our estimates predict a larger abundance of high mass HI galaxies than predicted by earlier observations and hydrodynamical simulations. We expect these results to be useful in understanding galaxy evolution and star formation.

Solar neutrinos have been studied for over half a century to test both the Standard Solar Model and the electroweak sector of the Standard Model of particle physics. Contemporary experiments are now entering an era of high-precision measurements, demanding corresponding theoretical predictions with sub-percent accuracy to enable meaningful comparison. In this paper, we identify and analyze the essential physical and computational components required to compute solar neutrino fluxes with high fidelity, and present a unified, computationally efficient framework. This framework incorporates: (i) the time-varying Earth-Sun distance; (ii) Earth matter effects modeled using both one-dimensional (1D) and three-dimensional (3D) Earth electron-density profiles; and (iii) a fast, Strang-splitting-based implementation of the Mikheyev-Smirnov-Wolfenstein (MSW) neutrino propagation formalism, enabling rapid, large-scale scans over neutrino trajectories and energy grids. We deliver site-specific predictions for the China Jinping Underground Laboratory (CJPL) and other underground laboratories actively engaged in solar neutrino programs.

I investigate the behaviour of the Higgs field in Schwarzschild spacetime by introducing a Planck-suppressed coupling between the Higgs field and the Kretschmann scalar, the leading curvature invariant in Ricci-flat geometries. I show that spacetime curvature modifies the Higgs effective potential, causing the vacuum expectation value to decrease continuously with increasing curvature. A critical curvature is derived at which the Higgs vacuum expectation value vanishes, signalling a curvature-induced restoration of electroweak symmetry. For Schwarzschild black holes, we obtain analytical expressions for the critical curvature, the corresponding phase-transition radius, and the Planck-curvature radius that marks the onset of quantum-gravity effects. These results identify a self-consistent region inside the event horizon in which electroweak symmetry is restored while the effective description remains applicable. The model provides a simple analytical framework linking strong gravitational fields to the Higgs vacuum through a single dimensionless curvature-Higgs coupling.

Bow shocks (BSs) around massive stars are commonly identified in mid-infrared (MIR) surveys. In contrast, systematic optical investigations of these structures remain scarce with only a few possible detections reported so far. We performed a targeted Halpha imaging survey of 78 IR BS candidates compiled from literature catalogues. Observations were obtained with multiple ground-based facilities and complemented with archival MIR images from Spitzer and WISE. For the detected bow structures, geometrical parameters were measured, and the bows were classified based on the parameters of their central stars, the measured stand-off distances and adopted plausible ISM conditions Clear arc-shaped Halpha nebulae are detected in 15 objects, with one additional BS discovered serendipitously. A further 35 objects exhibit diffuse Halpha emission associated with complex background structures, while 28 show no detectable Halpha emission. The Halpha and IR morphologies generally trace the same large-scale structures, although most of the IR arcs lie slightly closer to the star and appear broader than their optical counterparts. We find that several systems are consistent with radiation-supported BSs, bow waves or dust waves, while others remain compatible with classical wind-supported BSs. This survey demonstrates that a fraction of IR BS candidates around OB stars also exhibit detectable ionised gas structures in Halpha, and both stellar wind momentum and radiation pressure can contribute to shaping these structures. No correlation is found between the detection of an Halpha BS and the stellar parameters, and the overlap in objects observed in Halpha and in the radio regime was too small for firm conclusions. Future spectroscopic observations will be required to determine the physical conditions and kinematics of the ionised gas and to further constrain the nature of these BS systems.

Hydrodynamics provides a universal description of many-body systems at long wavelengths. Its long-lived collective excitations, known as hydrodynamic modes, admit long-wavelength expansions whose convergence is encoded in the analytic structure of retarded correlators of conserved quantities in thermal equilibrium. We show that a boost can change which nonhydrodynamic singularity limits such an expansion. At large boost, the relevant singularity originates in the large-momentum, near-light-cone region of the rest-frame spectrum. After removing the Lorentz-factor growth, the rescaled convergence scale is controlled by the microscopic spectral structure of the theory. We explicitly demonstrate this in two examples: relaxation-time kinetic theory and holography.

We propose a geometric cosmological probe: the nodal line of the anisotropic galaxy correlation function --- the locus in the plane where the function changes sign. Because the nodal line depends only on this sign, it is invariant under any amplitude rescaling, and its information is mostly independent of and complementary to BAO. In a proof-of-concept analysis of DESI DR1 galaxies, the nodal line constrains $Ω_m h^{3/2}$ to 3\% at fixed galaxy bias, degrading to 4.8\% under a 10\% prior. Combined with BAO, it yields a 4.45\% sound-horizon-free constraint on $H_0$.