高能暂现源 · 每日文献综述

We describe ongoing efforts of high-redshift transient searches using multi-epoch NIRCam imaging (F200W+F444W) and NIRSpec MSA/PRISM spectroscopy from the NEXUS JWST multi-cycle Treasury program targeting the north ecliptic pole region. The transient search area covers $\sim 61.5\,{\rm arcmin^2}$ between the reference epoch and each subsequent NEXUS-Deep epoch at a cadence of $\sim2$~months. In the first year of observations from NEXUS, we detect 68 robust transients, with the host photometric redshift distribution declining rapidly at $z>2$ but extending to $z_{\rm phot}\approx 6$. In addition, we obtained secure spectroscopic redshifts for 37 transients ($\sim54\%$) from NIRSpec/PRISM and NIRCam/WFSS, with seventeen at $1 < z < 2$, eight at $2 < z < 3$, two at $3 < z < 4$, and one tentative host association at z = 6.151. Overall, the NEXUS program recovers observed supernova (SN) rates broadly consistent with other SN search programs with JWST. While NEXUS achieves the highest transient detection efficiency, 6.6 SNe per imaging hr ($2.6\times$ COSMOS-SN and $26\times$ JADES-SN), the limited filter coverage (F200W+F444W only) limits robust identification and classification of high-$z$ SNe for deep spectroscopic follow-up. We describe the details of the data reduction and transient detection pipeline, and report the Year-1 transient sample along with their light curves, available MSA spectroscopy, host association, and the raw detection rate. We also describe and release a new PSF photometry package that properly accounts for correlated pixel noise from combining drizzled images.

The First LHAASO Catalogue lists 90 sources of very-high-energy gamma-ray emission, many without an established counterpart at other frequencies, reopening the question of which Galactic accelerators produce the highest-energy cosmic rays. We search for low-frequency radio counterparts to the 55 1LHAASO sources that fall within the Galactic fields of the LOFAR Two-metre Sky Survey Data Release Three (LoTSS-DR3), using 144~MHz continuum maps at $6''$ and $20''$ resolution, complemented with archival data from other radio surveys where available. We present an overview of the radio emission towards all 55 sources, and identify the structures potentially associated with the gamma-ray emission. We report 24 new supernova remnant (SNR) candidates, nine flat-spectrum radio shells with faint or no infrared counterpart, and six sources with no clear Galactic radio emission present in the LOFAR maps. A bootstrap analysis shows that 23 of the 50 sources in the Galactic plane footprint (46\%, for $|b| \leq 5$) overlap a catalogued SNR, whereas random placement yields only $10.0\pm2.8$ matches even if the underlying Galactic SNR population is ten times larger than currently catalogued; in the outer Galaxy, where chance alignment is rarest, 4 of 12 sources coincide with an SNR against a null expectation of $\lesssim2$. We estimate that at least a quarter, and up to half, of the 1LHAASO Galactic-plane sources genuinely reside in SNR environments, consistent with a population dominated by pulsar wind nebulae, SNR--PWN composites, and cosmic-ray-illuminated clouds. Individual results include a new SNR candidate inside the TeV shell HESS~J1912+101, a radio candidate for the SNR hypothesised to explain the GeV emission of 1LHAASO~J1945+2424, and the first proposed counterparts of 1LHAASO~JJ0056+6343u and 1LHAASO~J2200+5643u.

Relativistic flows are common in astrophysics and often form shocks when different parts of the flow collide at relativistic relative velocities. Such collisions are often oblique, forming two shocks whose shocked fluids are separated by a contact discontinuity, which is treated here as an ideal reflecting ``wall'' where the flow on either side is modeled separately. The latter is modeled in the lab frame $S$ as a uniform cold planar shell propagating into vacuum at velocity $v_1=β_1c$ normal to its vacuum interface, colliding with the wall at an incidence angle $α_1$. The collision point $P$ moves along the wall at a velocity $v_p=v_{1}/\sinα_1$, and a boost along the wall at $v_p$ leads to a steady-state frame $S'$ where this problem is highly simplified. However, a ``super-luminal'' regime exists where $v_p>c\Leftrightarrow\tanα_1<Γ_{1}β_{1}=(1-β_{1}^2)^{-1/2}β_1$ and no steady-state frame $S'$ exists. It corresponds to only very small $α_1$ in the Newtonian regime, but nearly all $α_1$ in the relativistic regime. We solve this problem \textit{\textbf{fully analytically}} using integral conservation laws, in the attachmrnt region where point $P$ is attached to the wall. This region of parameter space is bound at high $α_1$ by the detachment line, which coincides with the sonic line for a cold initial shell. A weak-shock solution exist in all this region, while a strong-shock solution exists only in the sub-luminal attachment region -- between the luminal line and the detachment/sonic line where the two solutions coincide and beyond which point $P$ detaches from the wall and shocked fluid spills into the vacuum.

We present a systematic search for intermediate-mass black hole (IMBH) active galactic nuclei (AGNs) at $0.5 < z \lesssim 1$ using DESI DR1 spectroscopy.We identify 98 broad-line IMBH AGNs with black hole masses $M_\mathrm{BH}<10^6$ $M_{\odot}$ through quantitative spectral decomposition and broad-H$β$ selection. This sample spans $M_\mathrm{BH}=10^{5.5}-10^{6.0}$ $M_{\odot}$ and Eddington ratios from 1.2 to 9.0 extending systematic IMBH AGN searches to intermediate redshift. Compared with a consistently selected $z<0.6$ IMBH sample, the $0.5<z<1$ sources reach higher broad-H$β$ luminosities and substantially higher Eddington ratios, indicating more extreme accretion states at earlier cosmic times. They also show broader [O III] profiles and stronger blueshifted wing components, with these kinematic differences persisting after matching in black hole mass and Eddington ratio. These results reveal two distinct signatures of evolution among IMBH AGNs at $z<1$: ability of IMBHs to reach increasingly extreme accretion states toward higher redshift, and systematic changes in their ionized-gas kinematics. The former demonstrates that rapid, including super-Eddington, growth of IMBHs can persist to relatively late cosmic times, while the latter may indicate evolution in the ionized-gas environment and associated outflow activity of actively growing IMBHs. Together, these findings provide new constraints on the evolutionary pathways of IMBHs at $z<1$, and show that seed-mass black holes can continue to undergo rapid growth well after the cosmic dawn.

In this work, we study the polar perturbations of static, spherically symmetric neutron stars with anisotropic pressure in full general relativity, including linear-order perturbations of both the metric and the fluid. We calculate the $f$-mode frequencies and the corresponding damping times using a consistent treatment of the perturbation of the radial vector $k^α$. In particular, its Lagrangian perturbation $Δk^α$ is determined by the metric perturbations and the fluid Lagrangian displacement and is constrained to the $(\tilde{u},\tilde{k})$ plane, where $\tilde{u}^α$ is the normalized fluid four-velocity. This constraint introduces an additional dynamical degree of freedom into the perturbation equations. Considering three equations of state and the Horvat and Bowers-Liang prescriptions for pressure anisotropy, we find that the $f$-mode frequency increases with stellar mass, ranging from $1$ to $3$~kHz, while the damping time decreases, ranging from $0.5$ to $1.25$~s. Increasing anisotropy, in the sense of tangential pressure exceeding radial pressure, generally lowers the oscillation frequency, while its effect on the damping time depends on the anisotropy prescription: the damping time decreases with increasing anisotropy for the Horvat model but increases with increasing anisotropy for the Bowers-Liang model. We further find quasi-universal relations between the real and imaginary parts of the $f$-mode frequency, $Mω_R$ and $Mω_I$, and the stellar compactness $\mathcal{C}=M/R$, which are largely insensitive to the equation of state. Polynomial fits to these relations achieve an accuracy better than $10\%$, providing a simple phenomenological framework for constraining neutron-star pressure anisotropy through future asteroseismology observations.

We report on the discovery of a nulling pulsar, PSR J0052$-$7551, in archival MeerKAT L-band observations of the Small Magellanic Cloud (SMC). The discovery was made using the image-plane transient detection pipeline, TRON, which creates a residual image for each time sample and uses a heuristic pruning strategy to identify promising candidates in the resulting temporal image cube. The TRON pipeline triggered on the approximately minute timescale variability associated with the nulling behaviour of a canonical pulsar. Follow-up MeerKAT UHF-band beamformer observations revealed a pulsar with a spin period of 0.55 s and a measured period derivative of 6.1(6)$\times$10$^{-17}$s$\cdot$s$^{-1}$. The source is seen in projection toward the periphery of the SMC, and has a dispersion measure value of 29.24(2) pc$\cdot$cm$^{-3}$, which is on the order of the expected Milky Way contribution along the line of sight. We use a Gaussian Mixture Model to fit the nulling behaviour which yielded a nulling fraction of $\sim 32$%. We find that the null lengths are consistent with an exponential distribution indicating a stochastic process. Additionally, power spectra of the UHF visibility data reveal an unexplained quasi-periodic feature at ~5$-$7 s that cannot be attributed to the source itself, RFI, or standard instrumental effects. Following on from previous image-plane detections of pulsars by the TRON approach, which relied on either scintillation or eclipsing behaviour, this is the first detection triggered by nulling. This discovery confirms TRON's sensitivity to a wide range of astrophysical phenomena of medium timescale duration.

S301 is the fastest known star in the Galaxy. It orbits Sgr A* every 8.68 yr on an e = 0.9832 orbit that carries it within 136 Schwarzschild radii at 25,600 km/s (GRAVITY Collaboration 2026). An orbit like that must precess, by the same Schwarzschild effect that turns Mercury's perihelion, whatever the spin of the black hole. We ask whether an astrometry-only GRAVITY+ campaign covering the 2031.8 and 2040.5 periapsis passages can catch it. We validate a relativistic light-curve model, design a 131-epoch Fisher-optimal cadence with a periapsis floor, fit a seven-parameter orbit including the light-travel-time delay, and build a systematic error budget. With white noise at the 207 microarcseconds achieved on S301, the fit recovers the injected rate, 0.2307 deg/yr, as 0.2324 +/- 0.0023 deg/yr (+/-0.0012 at the forecast 100 microarcseconds). Real astrometric noise is not white. We add per-run calibration offsets and a wandering Sgr A* photocentre at GRAVITY's published amplitudes, marginalize over the reference zero point, mass and distance, add the bounded systematics in quadrature, and inflate by the excess scatter of real GRAVITY orbit fits. What survives is 0.0074 deg/yr, a 31 sigma detection. The Sun hides the first periapsis for 153 d, at a cost to the period and periapsis epoch but not to the precession rate. Radial velocities are out of reach at S301's magnitude; photometry only validates the light-curve model. The spin of Sgr A* could shift the rate by 5.17-5.74 per cent and cannot be bounded, so the campaign is a spin-agnostic test of general relativity, and a forecast until the star comes round.

The recently discovered S301 star, with an orbital period of 8.7 years and eccentricity $e = 0.982$, reaches a pericenter of just $140\,R_{\mathrm{s}}$ --- approximately nine times closer than S2's $\sim 1200R_{\mathrm{s}}$ --- offering an unprecedented laboratory for testing strong-field gravity. We demonstrate that S301's stellar spin precession provides a novel probe of the PPN parameter $γ$, scaling as $(2γ_{\mathrm{PPN}} + 1)/3$ relative to general relativity (GR). For maximum projected velocity shifts of $46.1~\mathrm{km\,s^{-1}}$, next-generation spectrographs could constrain $γ_{\mathrm{PPN}}$ to $\sim 10\%$ precision. When combined with S301's orbital precession --- a substantial $\sim 1.95^\circ$ pericenter advance per orbit (GR prediction), approximately an order of magnitude larger than S2's $\sim 0.2^\circ$, constraining $(2β_{\mathrm{PPN}} + 2γ_{\mathrm{PPN}} - 1)/3$ --- the spin measurement breaks the $β$-$γ$ degeneracy. A MCMC analysis of projected S2 and S301 observations yields $σ_β\approx 2.3 \times 10^{-4}$, with the $γ$ precision limited by the spin precession measurement to $σ_γ\approx 0.1$. While the spin precession provides an independent consistency check, its true significance lies in probing gravity at $φ/c^2 \sim 10^{-4}$ and $v/c \sim 0.08$ --- four orders of magnitude stronger than Solar System tests and an order of magnitude stronger than current S-star constraints. This complementary approach opens a new window for testing the PPN framework in the strong-field regime and demonstrates the power of combining multiple stellar probes at the Galactic Center.

We measure how accurately the characteristic halo mass of a rare, massive population can be recovered from clustering alone, using dark matter haloes in the Millennium simulation, where the true masses are known. Massive samples of 25 to 10000 haloes are cross-correlated against field reference samples of 5000 to 50000 haloes at six redshifts over $0 \leq z \leq 5.29$. The bias is measured at $r = 8\,h^{-1}\,\mathrm{Mpc}$ and inverted to return a characteristic mass, which we compare with the mean logarithmic halo mass measured directly from the simulation. Across 192 configurations the characteristic mass is recovered with a median absolute offset of $0.103$ dex. We show that (i) accuracy depends only weakly on the number of rare objects while the uncertainty falls from $\pm 0.71$ dex at 25 objects to $\pm 0.08$ dex at 10000; (ii) enlarging the smallest samples gives the greatest return, with a doubling from 25 to 50 objects reducing the uncertainty by about a third, against a tenth from 5000 to 10000; and (iii) the reference population carries an error of its own, which propagates coherently into every cross-correlation measured against it and is not reduced by observing more rare objects. Working with haloes rather than galaxies isolates the clustering measurement from the galaxy--halo connection, providing a benchmark before population-specific complications are introduced. For the best configurations, the uncertainty contributed by the calibration of the bias--mass relation, at $\sim 0.07$ dex, already matches that of the measurement itself.

We study the formation of primordial black holes (PBHs) from large primordial perturbations that re-enter the horizon during an epoch with equation of state ${\rm w}\geq1/3$. We consider a log-normal curvature power spectrum of finite width $Δ$ and determine the collapse amplitude by numerical-relativity simulations of a self-gravitating perfect fluid. Threshold scans are performed for five values of $\rm w$ and five spectral widths, and the resulting numerical thresholds are used in the PBH abundance and scalar-induced gravitational-wave (SIGW) calculations. For comparison, we also evaluate the semi-analytical $q$-function prescription. It reproduces the numerical trend close to radiation domination and for nearly monochromatic profiles, but it is not a reliable threshold estimator for generic finite-width profiles in stiffer backgrounds. We show how collapse thresholds increase with both $Δ$ and $\rm w$, changing the curvature amplitude required for PBHs to constitute all of the dark matter and, consequently, the normalization of the accompanying SIGW signal.

We study geometrically thin equatorial disc images in the static, axisymmetric q-metric spacetime using backward ray tracing. The Schwarzschild solution is recovered at $q=0$; for the nonzero deformations considered here, $r=2M$ is a curvature singularity rather than an event horizon. For a distant nearly face-on observer, we construct the first three equatorial transfer functions $r_m(b;q)$. In the {Schwarzschild} limit, the resolved third-crossing interval contains the critical impact parameter $b=3\sqrt{3}M$. As $q$ increases from $-0.3$ to $0.3$, the branch center shifts from $b_{3,c}/M\simeq3.716$ to $6.702$. In units of the physical monopole mass $\mathcal M=(1+q)M$, it instead decreases from $b_{3,c}/\mathcal M\simeq5.309$ to $5.156$. Much of the displacement in metric-parameter units therefore reflects the changing monopole scale. At fixed $\mathcal M$, the inclined first-intersection maps show that the contour dimensions increase with $q$, with larger relative changes near the inner disc. A prescribed power-law emissivity and relativistic frequency-shift weighting yield direct images whose integrated flux differs from the Schwarzschild value by at most $2.4\%$. Between the endpoint models, the horizontal median-flux position increases by $8.8\%$ and the interquartile width by $14.5\%$. Within this emission prescription, the residual deformation dependence appears mainly as a displacement and broadening of the brightness distribution. Higher-order radiative contributions are not included.

Ringdown gravitational waves probe black hole spacetimes via quasinormal modes (QNMs). Recent studies have reported oscillatory features in QNM-filtered waveforms, and have led to conflicting interpretations as to whether they represent a near-horizon "direct wave". Reexamining a particle plunging into a Kerr black hole, we show that the saddle-point approximation underlying the proposed interpretation fails near the horizon. Our exact analysis reveals that every source-induced horizon-mode pole is canceled by an infinite tower of Matsubara zeros, independently of orbital and black-hole parameters. The first four stages of this sequential screening are also confirmed by time-domain numerical integration. Thus, within the near-horizon perturbative framework, source-induced horizon-mode signals do not survive at late times.

The detection of gravitational waves from compact binary coalescences provides a powerful opportunity to test general relativity in the strong-field regime and to search for signatures of alternative theories of gravity. In this work, we consider Einstein-Maxwell-Dilaton (EMd) theory, in which black holes can carry both electric and scalar (dilatonic) charges. We employ the effective field theory approach, together with a temporal Kaluza-Klein decomposition of the metric in terms of non-relativistic gravitational fields, to derive the conservative two-body Lagrangian for charged black-hole binaries in EMd theory through second post-Newtonian (PN) order. Our calculation extends the previously known conservative dynamics at 1PN order and includes the gravitational, electromagnetic, and dilaton interactions at 2PN order. We verify the result in the appropriate Einstein-Maxwell, scalar-tensor, and general relativistic limits, and perform an independent test-body-limit check of the static 2PN sector. These results provide the conservative dynamics needed for developing higher-accuracy waveform models and testing EMd theory with gravitational-wave observations.

The cosmic-ray database, CRDB, has provided data and meta-data to the community since 2013. We present a new release, CRDB v4.2, which includes data and time series published in the last three years (from AMS-02, CALET, DAMPE, LHAASO, etc.), datasets missed in previous releases, and all peer-reviewed ultra-high energy cosmic-ray data (both historical and recent datasets). These data and meta-data are available from the web interface or from the CRDB pip-installable Python library. This release includes results from more than 60 experiments and publications, corresponding to 4534 new data points and 131624 time-series data points.

The effect of active region parameters on the evolution of solar axial dipole is well understood. However, their effect on the solar equatorial dipole has not been studied in detail. Understanding the development of the equatorial dipole is important as it drives the interplanetary magnetic field on intracyclic timescales (~ 1yr). We study how the latitude, tilt angle, and the polarity separation affect the evolution of solar equatorial dipole. We use dipole flux transport (DFT), a matrix implementation of surface flux transport (SFT) model, to simulate the dipole evolution of synthetic bipolar magnetic regions (BMRs) with a wide range of tilt angles and latitudes. We also study the evolution of active regions in HMI SHARP database and their associated BMRs. We quantify the dipole evolution by means of the maximum and mean amplification and the growth and decay times of the equatorial dipole. Tilt angle controls the amplification of the equatorial dipole, with larger tilt angles leading to stronger equatorial dipole. Latitude controls the timescale at which the equatorial dipole grows and decays. Low-latitude regions produce the longest living equatorial dipole. We find that only 31% of anti-Joy regions experience amplification of equatorial dipole, compared with 96 of regularly tilted active regions. Latitudes and tilt angles of active regions can have considerable effect on the solar equatorial dipole. Systematic changes in their properties could increase/decrease the strength of the equatorial dipole relative to the solar activity, which could lead to similar relative change in geomagnetic activity. We suggest that large low-latitude coronal holes and relatively high geomagnetic activity in the declining phase of solar cycle 20, could be related to emergence of unusually low-latitude active regions that produced strong and persistent equatorial dipole.

The astrophysical origin of the gravitational wave background (GWB) reported by pulsar timing array (PTA) collaborations has yet to be confirmed. A GWB signal made of the sum of individual gravitational wave (GW) from the population of supermassive black hole binaries (SMBHB) would show the imprint of a discrete Poissonian statistics in its spectral properties. In this work, we propose a tool based on the saddlepoint approximation method to estimate the distribution of characteristic strain for any given population model. This tool can be used for Bayesian inference or for a quick visualization of the statistics of the GWB from the output of more realistic semi-analytical models. We introduce the general family of variance mixture Gaussian distributions that models heavy-tailed behavior distributions that is expected for a non-Gaussian GWB signal. We show that setting the correct hierarchical priors to a Gaussian free spectrum PTA likelihood is effectively equivalent to a non-Gaussian likelihood. Using ideal simulations, we compare the performance of the saddlepoint approximation with a log-Normal distribution to infer the parameters of the astrophysical model from the statistics of the GWB and show that correctly modeling higher order moments is essential. Future PTA analyses should include the statistics of the GWB in their pipelines.

We investigate the presence of a Yukawa-like correction ($\propto \, αe^{- r/λ}$) to Newtonian gravity at the Galactic Center, using a multi-star fitting code, including the newly discovered star S$301$, to improve the constraints obtained using S$2$ orbit alone. We perform a Markov Chain Monte Carlo analysis using the astrometric and spectroscopic data of stars S$2$, S$55$, S$29$, S$38$ and S$301$ collected by GRAVITY, GRAVITY$^+$, NACO and SINFONI instruments, covering the period from $1992$ to $2025$. Compared to GRAVITY Collaboration 2025 (Paper I), in which only S$2$ was fitted, the tightest bound on the Yukawa coupling is again reached at $λ= 3\cdot10^{13}\,\rm m\ (\sim 200\,AU)$, where we find $|α| < 6 \cdot10^{-4}$, an improvement of roughly a factor five. The addition of S$301$ extends the constraint to short ranges that were inaccessible to S$2$, yielding $|α| < 0.004$ at $λ=10^{12}\,\rm m$ and $|α| < 0.006$ at $λ=5\cdot 10^{11}\,\rm m$, while S$29$, with its larger apoapsis, gives $|α| < 0.1$ at $λ\sim 2\cdot10^{15}\,\rm m$. The latter two represent the tightest limits at these scale lengths on a Yukawa correction obtained to date around a supermassive black hole.

Pulsar Timing Arrays (PTAs) constrain population properties of supermassive binary black holes (SMBHBs) through the observation of the gravitational wave background (GWB). Unlike other approaches that interpolate population-synthesis libraries or only consider the mean of the strain spectrum, here we capture its full strain probability density directly from semi-analytic population models. We apply our new method to the semi-analytic SMBHB population model, independently reproducing the parameter estimation for this model performed by the NANOGrav Collaboration with their 15-yr data. We also show the extent to which discrete SMBHB contributions to the GWB resolve degeneracies in the population parameter space. Finally, using the source-count intensity as the intermediate product in our calculation, we map PTA observations, as a proof of principle, to the SMBHB model based on the galaxy merger prescriptions from numerical hydrodynamical simulations "Illustris". We find the effect of delay times $τ$ between kiloparsec and subparsec SMBHB separations following galaxy mergers, finding $h_{\rm c}$ spanning $(1$-$6)\times10^{-16}$ and $N_{\rm c}$ spanning $(0.3$-$7.1)\times10^{-3}$ for $τ$ up to 8 Gyr.

The evolution of the mass function of massive galaxy clusters is a well-established probe of cosmology. Using the eROSITA X-ray instrument on board the Spectrum Roentgen Gamma (SRG) mission, the western Galactic hemisphere of eROSITA's first All-Sky Survey (eRASS1) delivers a uniformly selected and securely confirmed sample of 5259 galaxy clusters spanning $0.1 < z < 0.8$. When combined with overlapping weak lensing data from DES Year 3, KiDS, and HSC for mass calibration, this dataset enables precise tests of the standard $Λ$CDM framework and beyond. In this work, we use the $0.1 < z < 0.45$ subsample of the eRASS1 cluster catalog to place constraints on an axion-like Early Dark Energy (EDE) scenario. Such models have been proposed as a possible mechanism to alleviate the tension between early- and late-Universe measurements of the Hubble constant. In this framework, a scalar field temporarily enhances the cosmic expansion rate around the epoch of recombination before rapidly diluting at later times, leaving distinct imprints on structure growth. We leverage these signatures to present the first constraints on EDE derived from galaxy cluster number counts. Using eRASS1 number counts alone, we obtain an upper limit on the maximum EDE fraction of $f_{\rm EDE} < 0.3$, consistent with primary CMB analyses. Combining our cluster analysis with primary CMB measurements, baryon acoustic oscillations, and CMB lensing, while notably excluding distance-ladder calibration data, yields results consistent with a nonzero EDE contribution and $H_0$ values compatible with late-Universe measurements. The most significant detection, at $\sim 3.2σ$, arises from the joint analysis of the eRASS1 sample with the full set of external datasets, yielding $f_{\rm EDE} = 0.10^{+0.04}_{-0.03}$ and $H_0 = 71.4 \pm 1.4$ km/s/Mpc. [ABRIDGED]

Numerical relativity simulations provide the most accurate waveforms for binary black hole coalescences, but are prohibitively expensive for direct use in gravitational-wave data analysis. Surrogate models overcome this cost, and NRSur7dq4 is commonly used in parameter estimation for this reason. However, there is evidence in the literature that NRSur7dq4's accuracy could be improved in the merger-ringdown portion of the waveform, which is particularly important for the analysis of high-mass binary black hole events. Motivated by these observations, we construct NRSur7dq4v2, a multi-domain extension of NRSur7dq4 in which overlapping temporal subdomains allow tighter, independent error control over the inspiral and merger-ringdown portions of the waveform before they are smoothly combined. To assess the new model's performance in the merger-ringdown regime, we infer the mass and spin of the remnant black hole from quasi-normal fits to the ringdown portion of the surrogate waveform. We find that NRSur7dq4v2 produces significantly improved remnant mass and spin estimates, with gains of roughly factors of $3$ to $10$ over NRSur7dq4. Compared to NRSur7dq4, NRSur7dq4v2 also includes modes up to $\ell=5$, includes more accurate modeling of certain subdominant modes, and introduces a runtime model-complexity feature that gives users direct control over the tradeoff between evaluation cost and accuracy. Finally, alongside the model development, we have optimized the gwsurrogate package to achieve a fourfold speedup for precessing surrogates. The resulting precessing surrogates called through gwsurrogate are now slightly faster than their LALSimulation counterparts.

Peculiar velocities trace gravitational dynamics directly, complementing density-based clustering as wide-field spectroscopic surveys (DESI, Euclid, PFS) and kinetic Sunyaev-Zel'dovich (kSZ) measurements enter the precision era. Observational analyses of pairwise velocities and the pairwise kSZ signal remain largely restricted to linear and quasi-linear scales ($\gtrsim20-30$ $h^{-1}Mpc$), despite substantial cosmological information available at smaller separations. We present a simulation-calibrated likelihood for $v_{12}(r,a)$, built on the exact pair conservation equation and PyCAMB HMcode-2020 non-linear clustering, and validate it against the QUIJOTE and TNG300-3 suites across resolution, particle sampling, box size, and redshift. Using QUIJOTE, we show that extending the fit to non-linear scales tightens the $1σ$ uncertainty on $Ω_\mathrm{m}$ and $σ_8$ by $74\%$ and $81\%$ at $z=0.5$ ($r_{\rm min}=4$ $h^{-1}Mpc$), and by $70\%$ and $74\%$ at $z=0$ ($r_{\rm min}=8$ $h^{-1}Mpc$), relative to the linear-regime baseline ($r_{\rm min}=50$ $h^{-1}Mpc$) (all at fixed $r_{max}=140$ $h^{-1}Mpc$); $σ(fσ_8)$ tightens by up to $86\%$, and the joint $Ω_\mathrm{m}$-$fσ_8$ Figure-of-Merit improves by up to $9.1\times$ relative to the same baseline. These constraints are conditional on $h$ fixed at its QUIJOTE fiducial value, due to a near-degenerate response with $σ_8$; jointly sampling $h$ shifts and widens them substantially. This framework provides a validated route to exploiting that information in upcoming direct peculiar-velocity, redshift-space, and kSZ analyses.

The discovery of Little Red Dots (LRDs) with JWST provides a new source population for cosmology in a largely unmapped period of cosmic history. LRDs are most numerous at $4\lesssim z\lesssim9$, thereby bridging existing low-redshift large-scale-structure measurements and the cosmic microwave background. In this epoch, the Universe is deep in the matter-dominated era, where dark energy is dynamically negligible and the expansion history is tightly predicted in $Λ$CDM, making these redshifts a clean test of the standard cosmological model. Recent measurements indicate that LRDs have number densities of $\bar n\sim10^{-4}$ $h^3$ Mpc$^{-3}$, a bias rising from $b\sim 3$ to $\sim8$ over this interval, and distinctive spectrophotometric signatures -- a remarkably favorable combination for baryon acoustic oscillation (BAO) measurements. Using a Fisher forecast with these fiducial inputs, we find that a wide-field spectroscopic survey of LRDs over a DESI-like (14,000 deg$^2$) footprint delivers a percent-level isotropic distance scale measurement of $D_V/r_d$ across four bins spanning $4\lesssim z\lesssim9$. LRDs are therefore a compelling target for future wide-field near- to mid-infrared spectroscopy aimed at mapping large-scale structure deep into the matter-dominated era.

We investigate the dynamical instability of rotating boson stars described by the Gross--Pitaevskii--Poisson equations with contact self-interactions. Through three-dimensional simulations, we confirm that the rotating boson star undergoes a quasiperiodic conversion between ring-like and twin-star-like density configurations in the early nonlinear stage. We develop a systematic linear stability analysis to identify the modes driving this instability and show that repulsive self-interactions could significantly increase the lifetime of the rotating boson stars. We further construct a three-mode Hamiltonian to describe the early nonlinear stage, which explains the quasiperiodic conversion. This analytical framework agrees reasonably well with the simulation results and provides a clear picture to understand the dynamics of rotating boson stars.

Total transmission modes (TTMs) are a class of reflectionless solutions to black hole perturbation equations, closely related to quasinormal modes (QNMs), and can exhibit significant sensitivity to weak environmental perturbations. In this work, we investigate the spectrum (in)stability of TTMs of Tangherlini black holes by introducing a localized Pöschl-Teller bump perturbation into the effective potential, and employ a modified Chebyshev-Lobatto grid to improve the numerical accuracy of the localized perturbation. For $d=14$, $\ell=2$, and $s=2$, the purely imaginary TTM exhibits relatively strong spectrum stability, whereas the genuine complex TTMs undergo significant migrations even for small perturbations, consistent with the spectrum stability revealed by previous pseudospectrum analyses.

Contact binary systems exhibit complex evolutionary behavior governed by mass transfer, angular momentum loss (AML), and Roche geometry. The fillout factor ($f$) is widely used as a descriptor of the degree of overcontact, yet its physical and statistical role remains nonuniformly defined across the literature. We used a compiled observational sample of W UMa-type contact binaries to construct a data-driven classification framework based on $f$ and its relation to fundamental system parameters. Unsupervised clustering applied to the one-dimensional $f$ distribution reveals a robust three-class structure corresponding to shallow-, medium-, and deep-contact configurations. The statistically determined boundaries are located at $f \simeq 0.257$ and $f \simeq 0.561$, with a stable silhouette score of $S \simeq 0.613$. The stability of this classification is confirmed through perturbation tests in $f$ and parameter-conditioned samples. A random forest regression model shows that 60.7\% of the variance in $f$ can be explained by the considered physical and geometric system parameters, with geometric parameters providing the largest predictive contribution. Among the considered parameters, the mass ratio emerges as the dominant predictor. The identified subclasses therefore appear to reflect a continuous geometric sequence rather than discrete physical states, governed by the progressive evolution of the Roche equipotential configuration under mass transfer and AML. Notably, the second boundary separating medium- and deep-contact systems shows lower stability than the first boundary, suggesting that the transition toward deep contact may be more sensitive to the physical composition of the analyzed sample.

A localized Gaussian or Pöschl-Teller bump is widely used to probe the sensitivity of Schwarzschild quasinormal modes, where it is typically added to both the Regge-Wheeler and Zerilli potentials. We show that such an additive prescription is generically incompatible with the Darboux transformation connecting the two parity sectors. The reason is that such a transformation restricts a parity-blind bump to a fixed family of bumps with an unavoidable $r^{-2}$ tail, excluding any Gaussian or Pöschl-Teller profile with arbitrary amplitude, center, or width in the additive prescription. We give the complete classification of Darboux-admissible axial and polar pairs of bumps and propose two consistent scenarios: Darboux generator prescription in which a Gaussian or Pöschl-Teller profile is retained as a generator of the bump pair rather than as the bump itself, and Riccati completion prescription in which a Gaussian or Pöschl-Teller profile is regarded as one of the bump pair and its partner will be solved from the Riccati equation. Our frequency-domain calculations confirm that a finite and spurious axial-polar splitting of quasinormal modes will be produced if the Darboux-consistent scenarios are absent, while the centroid shift of the fundamental mode is nearly unchanged.

The conformal interacting dark energy (CIDE) model is investigated by introducing a scalar field representing dark energy (DE) coupled to dark matter (DM) via a conformal transformation, thereby yielding a class of scalar-tensor theories. The interaction term ${Q}$, that indicts the flow of energy between the dark sectors is proportional to the trace of the energy momentum tensor of the DM fluid, $T^{\mathrm{DM}}_{μν}$, as ${Q}=\frac{C'(φ)}{2C(φ)}g^{μν}T^{\mathrm{DM}}_{μν}$, where $C(φ)$ is the conformal function of a scalar potential (coupling) field. We assume the power-law parametrization $C(φ)\propto (1+φ)^m$, with $m$ a coupling parameter, and determine the direction and magnitude of the energy flow between the DM and DE components. The dynamical nature of DE is modeled by the two conformal interacting scenarios, CIDE and $w$CIDE, with $w$ the DE equation of state parameter. To test the viability of each model, we constrain them using a combination of early- and late-time cosmological data, namely: CMB measurements from the South Pole Telescope, Planck 2018, and the Atacama Cosmology Telescope (DR6) (\texttt{CMB SPA}); BAO data from the Dark Energy Survey (\texttt{DESI DR2 BAO}); and Supernova Type Ia distance compilations (\texttt{PantheonPlus, PantheonPlus + SH0ES, Union3}, and \texttt{DES Dovekie}). Parameter inference is performed with Monte Carlo Markov Chain (\texttt{MCMC}) simulations using \texttt{COBAYA} and a modified \texttt{CLASS}. Further statistical analysis using the Akaike information criterion (AIC) and the Bayesian information criterion (BIC) is summarized to assess the viability of the model in comparison with the standard cosmological model, investigating the model's potential to alleviate the $H_0$ and $S_8$ tensions.

In this study, we explore the thermodynamic topology of black holes within the Sharma-Mittal entropy framework. Our study covers several black hole solutions, including charged and uncharged black holes in $d$-dimensional, as well as Schwarzschild and Reissner-Nordström black holes. By introducing the Sharma-Mittal entropy characterized by two parameters $δ$ and $R$, we explore how deviations from the standard Boltzmann-Gibbs statistics modify the thermodynamic structure and stability properties of these systems. Using Duan's $Φ$-mapping theory, we compute the corresponding topological numbers and classify black holes into distinct topological categories according to the winding number $W$. Moreover, our analysis shows that, within the Sharma-Mittal formalism, the topological classification is independent of spacetime dimension in the case $d>4$, although dimensions higher than four exhibit distinct features compared to the four-dimensional Schwarzschild and Reissner-Nordström black holes, reveal different behavior of thermodynamic topology under generalized statistics.

An ultra-slow-roll phase during inflation could potentially produce the right abundance of primordial black holes (PBHs) for them to form all of dark matter (DM). We consider such a scenario, carefully treating the transitions from slow to ultra slow roll inflation and back, using a parametrisation of the inflaton potential that can describe inflation from the time when CMB scales crossed out of the horizon until its end. A $δN$ analysis shows that this model can possess $O(1)$ non-Gaussianity. When computing the primordial black hole abundance, we keep the full non-linear relation between curvature perturbations and the density contrast and consider the non-Gaussianity to all orders. We find that $O(1)$ non-Gaussianity is sufficient to enhance the PBH abundance by orders of magnitude, leading to reduced gravitational wave (GW) signals for fixed PBH abundance. The signal to noise ratio is computed for future gravitational wave observatories. We find that, in spite of the reduced strength, the GW signal is well above the sensitivity of LISA if PBHs form a significant component of DM.

We study the possibility of explaining the recently reported high-energy nuclear recoil event by the LUX-ZEPLIN (LZ) collaboration within the framework of singlet-doublet scalar dark matter (DM). Considering DM to be the CP even mass eigenstate formed out of a scalar doublet and a real scalar singlet, both being odd under an unbroken $Z_2$ symmetry, we find the parameter space of the model consistent with correct relic abundance and direct-detection limits on elastic scattering rates. A large part of the parameter space can also lead to inelastic up-scattering of DM with a rate and recoil energy consistent with the recent LZ event. Depending upon the singlet-doublet mixing, the model allows a much wider range of currently allowed parameter space compared to the pure scalar doublet DM limit. Presence of $Z_2$-odd right-handed neutrinos also leads to other interesting phenomenology related to the origin of light neutrino masses and leptogenesis.

We compute the large overtone quasinormal frequencies $ω_n$ of asymptotically AdS black holes with interior near-singularity Kasner epochs. We show that the Kasner exponents can be extracted cleanly from the large $n$ behaviour of the dispersion $\partial ω_n/\partial k^2$ at $k=0$, where $k$ is a boundary momentum. We show that Kasner transitions, as occur in BKL near-singularity chaos, are audible in the quasinormal frequencies and reveal a map between overtone number $n$ and proper time to the singularity. Our results are obtained using a WKB analysis that isolates non-analytic exponents, determined by the near-singularity spacetime, from non-universal data such as the optical distance from the boundary to the singularity. We check our formulae in several numerical models.

We define Filament-Arm Node Systems (FANS), a new class of cosmic-web objects consisting of multiple filament arms connected to a common node, and use their geometry to construct an object-based test of cosmic chirality. With the cosmic-web node providing a natural reference point, FANS span characteristic scales of ~60Mpc/h, allowing the coherent winding of their arms around the node to be measured directly. We define cosmic spirality as the amplitude of this winding and handedness as its signed clockwise (CW) or counter-clockwise (CCW) sense. We further introduce an axis-conditioned extrinsic estimator that searches for the projected signature of a coherent three-dimensional axial pattern of the handedness field, corresponding to a preferred axis of winding. Applying these measurements to two distinct SDSS filament reconstructions, and assessing their significance with sign-flip nulls and 27 controlled variations of the FANS construction parameters, we find no significant preference for CW or CCW winding, either globally or around a preferred axis. The data are therefore consistent with parity symmetry, as expected in standard LCDM cosmology. We additionally find that cosmic spirality decreases with cosmic time, a trend that may reflect the gravitational straightening of filament arms. These first constraints establish FANS as a new probe of cosmic-web symmetry and large-scale morphology and provide a baseline for future parity tests with the much larger filament samples expected from upcoming surveys.

A supergravity solution in the literature is an artifact that cannot be verified without re-deriving it: conventions might not be clearly stated, papers have typos, algebra is tedious. SolutionsX is a Mathematica package that turns an xAct environment, whatever physics it may describe, into a stored, machine-verifiable record: code that replays in a fresh kernel, carries its own verification, and can later be fetched for re-use or extension. The shipped examples are supergravity theories and their solutions, but the scope is anything xAct reaches: abstract tensors, differential forms, spinors in any dimension. We follow one published solution through the entire workflow, benchmark the package's component engine against xAct's, and report on three blind runs of an agentic workflow in which an AI coding agent, given the package and a small toolkit, correctly codified a recent paper in under three hours. A database of such records is useful to researchers today and gives agents worked examples to learn from. The package acts as an internal verifier during the thought process of an agent: a claim is checked in the kernel before it is made.

Weak gravitational lensing shear and convergence trace the distribution of baryonic and dark matter across space, making them a powerful probe of cosmic structure. Inferring shear and convergence from images is a challenging inverse problem. The prevailing approach to this task estimates shear from weighted averages of galaxy ellipticities, calibrates these estimates to account for systematic biases, and transforms them to reconstruct convergence, a multistage procedure that requires substantial computational resources and meticulous handling of statistical uncertainties. As an alternative, we propose a probabilistic approach to field-level weak lensing inference in which we train a deep neural network to directly map a multiband image to a variational distribution over the underlying tomographic shear and convergence fields. This neural posterior estimation (NPE) procedure implicitly marginalizes over nuisance variables in the cosmological forward model and does not require evaluating the likelihood function. It is also amortized, so it enables rapid posterior inference for astronomical surveys once the neural network is trained. When evaluated on synthetic images from the LSST-DESC DC2 Simulated Sky Survey, NPE produces well-calibrated variational distributions for shear and convergence that are consistent with the ground truth. We describe how maps sampled from these variational distributions could be used in a subsequent simulation-based inference procedure to approximate the posterior distribution over cosmological parameters.

Galaxy clusters are the most powerful strong lenses: they greatly magnify the flux of distant and faint sources. Strong lensing also allows for the reconstruction of their mass distribution with-1% level accuracy and enables investigating cosmological parameters. The number of known systems of this type is bound to increase in the next years thanks to wide imaging surveys. Using simulations in this context is crucial to validate the analysis methods before they are applied to real data, and to train machine learning algorithms that can handle large volumes of images. In this work, we present a simulated set of one hundred images of galaxy clusters that we have produced with a novel code for simulating cluster-scale strong lenses. One of the main novelties of our approach, distinguishing it from other existing codes, is the use of empirical relations, derived from state-of-the-art observations, for modelling the characteristics, such as morphology, color, and spatial distribution of the cluster member population. This allows us to reliably reproduce the complexity of real observations. The simulations are partly carried out with the latest version of SkyLens, a code that creates mock observations of strong lensing events in different systems and observational setups. The main improvements we introduce are the use of the message passage interface (MPI) paradigm, a standard for parallel programming that leverages the use of several processors to perform some given task, and the implementation of score-based diffusion models to augment the images of the background sources. Together, they lead to more efficient and realistic image simulations. We also present the validation of the code and simulations by comparing the properties of the mock clusters to those of real ones. [Abridged]

The formation of massive stars serves an important field of study, requiring research into whether these stars need to form together within clusters of low-mass stars or if they are able to form independently. Currently, there has been an increase in the number of massive stars found far from clusters in the Milky Way (MW) and Small Magellanic Cloud (SMC). The existence of isolation and composition in binary systems is an uncommon phenomenon among massive stars, and their rare occurrence presents valuable insights that are regarded as evidence in this field. This research looks for ways to increase the catalogue of identified massive stars in eclipsing binaries, particularly those that show significant indications of isolation. For the definition of the first step, we are analysing the eight double-lined spectroscopic binaries in the SMC, as detailed in the OGLE variable star catalogues, with the goal of identifying their astrophysical properties. Later, we examine the expected locations and characteristics of binary stars thought to be part of a cluster, using absolute parameters and a cross-validation approach to determine the connection between kinematic analysis and these parameters. If the kinematic connection with the cluster and the physical parameters match precisely with the cluster's isochrone, such stars could act as reliable standard candles for determining the cluster's distance and age.

Metric-affine gravity provides a natural geometric framework in which spacetime curvature, torsion, and non-metricity are treated as independent degrees of freedom, leading to novel cosmological dynamics beyond General Relativity. A generic consequence of such theories is the emergence of effective interactions among the cosmological fluids, even in the absence of explicit phenomenological couplings. Interestingly, the above happens while the Standard Model of Particle physics remains unmodified. In this work, we investigate interacting cosmological models that arise from metric-affine gravity and analyze their implications for the background evolution of the Universe. We derive the modified continuity equations governing the matter, radiation, and dark-energy components, highlighting the geometric origin of energy exchange in the dark sector. We discuss how these interactions modify the expansion history and can effectively mimic evolving dark-energy behavior. The resulting cosmological scenarios are confronted with the most recent observational data from Type Ia Supernovae (Pantheon+), Cosmic Chronometers, and Baryon Acoustic Oscillations (DESI DR2). Moreover, using model selection criteria, e.g., Akaike Information Criterion, Bayesian Information Criterion and the Bayesian Evidence, we compare the aforementioned models against the standard $Λ$CDM model. We find that the proposed framework performs slightly better than $ΛCDM$, in the light of the data sets considered here. Our analysis demonstrates that metric-affine-induced interactions constitute a viable and theoretically motivated alternative for the description of the Universe.

Complex organic molecules (COMs) are typically observed in the warm inner envelopes of Class 0 protostars. In more evolved Class I sources, COM emission is confined to the compact inner disk and obscured by high dust opacity, but the FU Orionis-type binary L1551 IRS 5 offers a valuable opportunity to probe disk chemistry, as its outburst luminosity thermally sublimates ices out to large radii. We sought to spatially resolve the origins of COMs in this system to distinguish between central radiative heating and shock-induced chemistry driven by heterogeneous accretion pathways. We analyzed high-angular-resolution ALMA archival data, focusing on COMs (e.g., CH3OH, CH3OCHO) and the shock tracer SO, and compared their spatial morphologies and kinematics to diagnose the excitation conditions associated with different accretion flows. We find that the COM emission in L1551 IRS 5 arises from both radiative heating and localized accretion shocks. In the northern source, the widespread low-excitation COM emission is primarily consistent with thermal heating by the recent outburst. This source also exhibits dual-mode accretion with distinct chemical signatures, with COMs along the spiral arm tracing steady equatorial circumbinary disk-to-circumstellar disk accretion and high-excitation COMs with bright SO along the eastern disk surface tracing a vertical envelope-to-disk streamer impact. In the southern source, methanol is confined to the southeastern streamer impact site, whereas SO forms a ring-like structure at the tidal truncation radius. We attribute this difference to differential chemical survival timescales. L1551 IRS 5 thus serves as an ideal laboratory to investigate how shock chemistry and binary-regulated accretion shape the chemical structure of protostellar disks.

We explored potential associations between ongoing mass transfer and the pulsation properties of $δ$ Scuti primaries in a sample of 17 oscillating eclipsing Algol systems. For this purpose, we combined binary modelling, updated O-C analyses, and frequency characterization based on TESS photometry. To ensure homogeneity, the $T_{\rm eff}$ of the components were derived using a consistent SED fitting approach. From the binary solutions and O-C diagrams, we determined the mass transfer indicators (Q, dP/dt, and dM/dt) and examined their relations with the dominant pulsation period and amplitude. For the full sample, the results indicate weak to moderate positive trends, with the strongest relation found between logdP/dt and logPpuls, while the relations involving dM/dt and pulsation amplitudes are weaker and statistically insignificant. After excluding the two prominent outliers, R CMa and BW Del, the correlations between logPpuls and the mass transfer indicators become statistically more significant, including relations with dP/dt, Q, and dM/dt under both conservative and non-conservative assumptions. These relationships may reflect the indirect effects of mass transfer on the structure of the accreting primary and on the orbital configuration, potentially reducing tidal constraints and allowing shifts toward longer pulsation periods. However, the large dispersion and limited sample size indicate that these relationships remain poorly constrained. Our results suggest that pulsation properties are primarily governed by intrinsic stellar parameters and the well established Porb-Ppuls relation, while ongoing mass transfer may contribute as a secondary factor. Although the present sample does not allow firm conclusions regarding the role of mass transfer, this study provides a homogeneous observational framework for future investigations based on larger samples and improved constraints.

We obtain the singular ''mother'' black hole solution by solving the coupling between Einstein gravity with a cosmological constant and a nonlinear electromagnetic field. The thermodynamic quantities of the ''mother'' black hole are first derived in the unconstrained phase space $(S, q, α, P)$, after which the regularity condition $M = q^3/α$ is imposed to obtain the thermodynamic quantities of a class of spherically symmetric AdS regular black holes self-consistently. We distinguish two categories of thermodynamic quantities: fundamental conjugate variables defined by the first law, and thermodynamic response functions constructed from them. For response functions involving second-order derivatives -- in particular the heat capacity -- we show that the order of constraint imposition and derivative calculation cannot be interchanged, and the correct procedure is to first impose the constraint and then construct the response function. Within this framework, we find that when $P<P_c$, the $G$--$T$ diagram exhibits a behavior qualitatively different from the swallowtail behavior of the standard RN-AdS black hole. Instead, it exhibits an 8-shaped structure for $P<P_z$ and a C-shaped structure for $P_z<P<P_c$, corresponding to first-order and zeroth-order phase transitions between small and large black hole phases, respectively. Imposing the regularity condition thus leads to a richer phase structure for this class of black holes than the standard RN-AdS case.

The quantum mechanical problem of a particle in a infinite potential well with slanted walls is studied. The energy eigenvalues are determined by a transcendental equation involving the Airy function of the first kind. Two limiting cases are discussed. Next, the allowed energies are found by graphical and numerical methods. The graphical analysis hints that for large quantum numbers the consecutive energy levels get arbitrarily close together. This asymptotic behavior of the energy spectrum actually holds, as shown by means of an intuitive argument and confirmed by resorting to basic properties of Airy functions. In a sense, Bohr's correspondence principle is more accurately fulfilled than in the cases of the standard particle in a box or the harmonic oscillator. A state is regarded the more confined the less the probability of finding the particle in the classically forbidden region. For some stationary states the confinement degree is calculated and a comparison is made with the harmonic oscillator, for which the ground state is the least confined of all stationary states. In the symmetric case --- right and left walls of equal slope --- something unexpected happens: beyond a certain critical slope the ground state is no longer the least confined eigenstate. Over and above its interesting physical features, this problem provides students with the opportunity to get acquainted with Airy functions, which do not belong to the standard mathematical repertoire of physics undergraduates.

We construct exact static, spherically symmetric charged solutions in four-dimensional non-polynomial quasi-topological gravity coupled to Born-Infeld electrodynamics. We focus on the model $h(p)=p/(1+\ell^{2}p)$, whose vacuum branch develops a curvature singularity at a finite radius. We show that Born-Infeld nonlinearities can remove this singularity within a finite region of parameter space, yielding globally regular geometries with an asymptotically flat exterior and a finite-curvature AdS-type core. The regular sector contains both horizonless configurations and RBHs, separated by a degenerate-horizon boundary. We further identify a continuous branch of regular black holes with a triple-degenerate inner horizon and a simple outer event horizon, satisfying $κ_-=0$ and $κ_+\neq0$. This provides a converse example to cases in which introducing charge spoils the regularity of a vacuum regular black hole. In the present model, Born-Infeld electrodynamics instead removes the finite-radius singularity of a vacuum-singular gravitational branch while supporting globally regular charged geometries, including RBHs with nontrivial inner-horizon structure.

The surface $r=\infty$ of the Kerr-Bertotti-Robinson spacetime is not a genuine boundary. We construct its natural analytic extension and show that $r=+\infty$ of one KBR region is smoothly connected to $r=-\infty$ of a neighboring one. Repeated continuation produces an infinite chain of regions connected by wormhole-like bridges and exposes the neighboring ring singularity without an intervening horizon, which violates the weak cosmic censorship conjecture. We then study a test massless scalar field on a two-universe scattering segment to probe the stability of the spacetime. For axisymmetric perturbations, we analytically establish purely imaginary growing quasinormal modes for every $\ell$ and trace their origin to the chronology-violating region. In the $(\ell,m)=(2,2)$ sector, unstable branches occur for sufficiently large rotation and sufficiently small magnetic field. Their marginal real modes obey an exact horizon-flux balance, supporting a black-hole-bomb interpretation in which superradiant extraction is amplified by trapping within the double-barrier potential. The same cavity also supports families of weakly damped modes and may produce echo-like responses.

Recently, the LUX-ZEPLIN (LZ) collaboration reported the observation of a single dark matter (DM)-nucleus scattering event at a nuclear recoil energy of $248\pm23_{\rm stat}\pm23_{\rm sys}$ keV, corresponding to an exposure of 2.84 tonne-year. The absence of events at lower nuclear recoil energies in the predicted spectrum is naturally explained if the underlying process is inelastic DM-nucleus scattering. Motivated by this, we investigate the singlet-doublet fermion DM model, in which the DM consists of two pseudo-Dirac states: the Majorana nature of the lighter state forbids tree level $Z$-mediated elastic scattering identically, while the same states enable inelastic DM-nucleus scattering via $Z$ exchange, with any residual elastic scattering proceeding only through a suppressed Higgs-mediated channel. We further extend the model with a $Z_2$-even scalar triplet, which is responsible both for generating the pseudo-Dirac splitting and for realizing Majorana neutrino masses via the Type-II seesaw mechanism.

The spherically symmetric sector of broad classes of $D$-dimensional gravitational theories can be effectively described by general two-dimensional Horndeski theories. Exploiting this correspondence, we study the low-temperature dynamics of near-extremal black hole solutions of the parent theories by deriving a universal near-horizon effective description in terms of Jackiw--Teitelboim (JT) gravity. We explicitly show that the logarithmic quantum correction to the entropy, $S_{\rm JT}=\frac{3}{2}\log \left(T/T_{\rm breakdown} \right)$, previously derived for near-extremal black holes in Einstein gravity coupled to matter from the one-loop exact JT partition function, is universal across all models admitting an effective two-dimensional Horndeski description. We determine the general form of the scale at which this correction becomes dominant, $T_{\rm breakdown}$, in terms of the data of the $D$-dimensional theories. We illustrate our general results with charged black holes in Lovelock gravities and regular black holes in Quasitopological gravities.

We impose unitarity constraints on two-dimensional field theories whose symmetries form the quantum conformal Bondi-Metzner-Sachs algebra, which combines conformal symmetries with asymptotic symmetries of asymptotically flat spacetimes. Positivity constraints put bounds on the central charge, 0<c<2.053. Positivity of the associated vertex algebra allows only four central charges, c = 1, 3/2, 13/7, 2. Thus, only four candidates for unitary field theories remain. We calculate their spectra of primaries and show that they are compatible with BPS-like and holographic inequalities.

We provide a novel diffeomorphism-invariant approach to asymptotically safe metric quantum gravity. It is based on physics-informed renormalisation group flows with a renormalisation group kernel that guarantees diffeomorphism invariance at each renormalisation group step. Importantly, it also allows us to control and maintain the relevance counting of operators in metric quantum gravity. The resulting effective action is quantum diffeomorphism-invariant and background-independent. As a first non-trivial application, we compute the Reuter fixed point in a manifestly diffeomorphism-invariant way. This computation is augmented with a detailed discussion of regularisation dependence and a systematic estimate of the errors arising from approximations.

Understanding the internal dynamics of red giants is essential for studying angular momentum transport and magnetic field generation during stellar evolution. We present three-dimensional magnetohydrodynamic simulations of a $1M_{\odot}$ red giant at the bottom of the red giant branch using a star-in-a-box setup with the Pencil Code, together with ongoing efforts to refine the numerical model. By varying the rotation rate, we explore different Rossby numbers and identify systematic changes in the convective dynamics and large-scale flows. As the rotation increases, convective motions become more anisotropic, showing clear signatures of rotational constraint and a shift in the dominant convective scales. These changes are accompanied by variations in the differential rotation profile, reflecting the redistribution of angular momentum within the convective envelope. The impact of rotation is also evident in the growth rate and saturation level of the magnetic field, indicating a strong dependence of dynamo efficiency on the underlying flow structure. Together, these results highlight the interplay between convection, rotation, and large-scale flows in shaping magnetic activity in red giant stars.

A coherent wave component with extremely small initial self-energy can substantially change the first response of a contracting spacetime. We demonstrate this effect in Einstein--Maxwell--scalar theory with two commuting spacelike Killing fields. Along a critical family motivated by scalarized black-hole interiors, the estimated magnetic delay leaves time for longitudinal propagation to redistribute the incident field. Increasing a low-frequency component at fixed initial electromagnetic energy enhances the scalar response on one background and suppresses it on another. A calculation that propagates the field and its momentum, then their quadratic scalar and geometric sources, predicts this reversal before nonlinear evolution. At the first suppression comparison, the coherent profile error is $0.38\%$, against $46.9\%$ when cross terms are omitted. The selected response develops into a magnetic pulse with electric and scalar exchange. The critical geometry thus preserves incident coherence as information that predicts its first departure from a Kasner epoch.

We study a scalar field nonminimally coupled to metric-affine gravity within actions linear in the affine curvature and containing all independent parity-even and parity-odd terms quadratic in torsion and nonmetricity, including mixed contractions. We also include Nieh-Yan-like derivative couplings between the scalar-field derivative and the four torsion and nonmetricity vectors. We derive the connection, metric, and scalar-field equations and, since the connection equation is algebraic, eliminate the independent connection on the generic nondegenerate branch to obtain an equivalent metric scalar-tensor theory in which the non-Riemannian interactions are encoded in an effective kinetic function. We classify several sectors and find that the pure quadratic nonmetricity and pure quadratic torsion sectors separately leave the Einstein-frame kinetic function unchanged relative to the simplest metric-affine scalar-tensor model, whereas their simultaneous presence, the derivative couplings, and generic mixed torsion-nonmetricity interactions can modify it. In the derivative-coupling sector, projective consistency imposes a relation among the couplings. We then consider polynomial coupling functions and study the resulting canonical field redefinition and Einstein-frame potentials. In particular, we illustrate how derivative and mixed torsion--nonmetricity couplings reshape quadratic and quartic potentials in canonical-field space, and show that a quadratic Jordan-frame potential can be mapped, for a suitable choice of derivative and nonminimal couplings, into a natural-inflation potential after canonical normalization. Finally, we separately impose the cosmological principle, determine the reduced combinations of quadratic couplings and the scalar field hypermomentum, and obtain the corresponding modified cosmological equations in the simplest sectors.

Entanglement wedge reconstruction provides the sharpest formulation of bulk locality in AdS/CFT, identifying the entanglement wedge as the largest bulk region reconstructible from a boundary subregion. While this statement is well understood at leading order in the large N expansion through both modular flow and Petz map reconstruction, its extension beyond the semiclassical regime has remained unclear. In this work, we show that quantum error correction provides the natural framework for addressing this problem. At leading order, we reproduce the known leading-order reconstruction formulas, and by employing the twirled Petz map, we obtain a systematic and explicit method for incorporating subleading 1/N corrections. Beyond the leading approximation, we have obtained an explicit bi-local correction controlled by a subleading Petz kernel. Our results establish a controlled approach to bulk reconstruction beyond large N and sharpening the role of quantum error correction in holography. This framework provides a controlled path toward understanding bulk reconstruction in fully quantum gravitational settings.

We perform a pulsation analysis of OO Dra using Light Curve data from TESS and present the first identification of six dipole modes as doublets from the primary star in OO Dra. The phases and amplitudes of these pulsation modes were analytically reconstructed. Among the six identified doublets, four are pulsating in $Y_{10x}$ mode with pulsation axis along the tidal axis, and two in $Y_{10y}$ with a pulsation axis orthogonal to tidal axis and the angular momentum axis. Our findings suggest that the primary star in a non-synchronized, post mass-transfer OO Dra could be a tidally tilted $δ$ Scuti pulsator.