高能暂现源 · 每日文献综述

Sagittarius A* exhibits frequent flaring activity across the electromagnetic spectrum that is often associated with a localized region of strong emission known as a hot spot. We aim to train a deep learning model to provide a link between key parameters of this phenomenon - hot-spot emission radius, and black hole inclination and spin - to the observed angle difference between the primary and secondary image ($ΔPA$) that present and future interferometric arrays could resolve. Using the general relativistic radiative transfer code IPOLE, we generated a library of $\sim100.000$ models with varying system parameters and computed the position angle difference on the image plane between the primary and secondary images of the hot spot. We explore equatorial and non-equatorial circular orbits and evaluate our models against approximate observational constraints, including partial-orbit visibility and observational errors. Our algorithm STIHOS shows remarkable accuracy in calculating spin and inclination from the majority of the observational tests we perform ($σ_{a_*}=0.04,\,σ_i=2^{\circ}$), even in extreme conditions where only half of the orbit is visible. The off-equatorial estimation provides softer constraints in the absence of prior information. Our results demonstrate the importance of hot-spot observations for spacetime estimations. Given the increasing efforts to detect the photon-ring, our framework could prove valuable in interpreting the first observations of lensed emission.

Type Ia supernovae (SNe Ia) are major contributors to cosmic chemical enrichment, and their elemental abundances provide a probe of progenitor properties and explosion physics across cosmic time. We employ an artificial intelligence-assisted inversion technique to analyze spectra of high-redshift SNe Ia from the Supernova Legacy Survey and of gravitationally lensed SNe Ia observed by the James Webb Space Telescope, extending the sample to redshift 2.05. We find a positive correlation between SN Ia calcium abundance and redshift. The redshift-dependent variation in calcium abundance exceeds that predicted by SN Ia nucleosynthesis simulations with varying progenitor metallicities, suggesting that high-redshift SNe Ia may undergo different explosion mechanisms from nearby SNe Ia.

Neutron-star cores hold the only known matter in the universe that is simultaneously cold and strongly interacting, compressed beyond nuclear density into a state of unknown composition. The equation of state links stellar masses, radii and tidal deformabilities to this regime, but recovering this key quantity from sparse observations is an ill-posed inverse problem. Existing analyses bury a prior in a fixed functional form, unevenly weighting admissible solutions and biasing the result. We reconstruct the equation of state with a denoising diffusion model that keeps prior, physics and data separate: it learns an inspectable, physically motivated prior anchored to first-principles nuclear theory, while perturbative-QCD and astrophysical constraints are imposed exactly. Future measurements therefore will update the posterior by reweighting alone, without retraining or resampling. The inferred radius of 12.6 km and tidal deformability of 469 at 1.4 solar masses reproduce Gaussian-process and heavy-ion-informed inferences despite a far broader prior. We find near-conformal but still stiff matter in the heaviest stars, consistent with a gradual hadron-quark crossover and disfavouring a strong first-order phase transition. More broadly, coupling a learned prior to exactly enforced physics establishes a template for ill-posed inverse problems where theory and data constrain different regions.

The Galactic Center is a crowded region containing powerful particle accelerators and objects producing non-thermal radiation, including the diffuse very-high-energy (VHE) gamma-ray component known as the `Ridge', whose hard spectrum suggests particle acceleration up to PeV energies. The relevant processes can be tested, and the source parameters can be constrained via Cherenkov telescope observations. Two Single-Mirror Small-Size Cherenkov Telescopes (SST-1M) are currently operated in stereoscopic mode at the Ondřejov Observatory. Their future relocation is being considered, including a site with excellent visibility of the Galactic Center. We present recent observations demonstrating SST-1M capabilities for detecting extended emission and discuss prospects for probing the Galactic Center region, including searches for a spectral cut-off above 10 TeV. We show that the large field-of-view and good VHE sensitivity make SST-1M an ideal instrument for the search for PeVatrons.

Modern machine learning is leading to substantial gains in precision, flexibility, and computational efficiency in fundamental physics. Statistical validation, uncertainty quantification, and robustness assessment are less systematically addressed. The VERaiPHY initiative (Validation & Evaluation for Robust AI in PHYsics) is a series of articles developed within the PHYSTAT programme, aimed at establishing statistical standards for the development, evaluation, and deployment of ML techniques. Each article focuses on a specific methodological domain from a statistics perspective and clarifies statistical questions, tests, and the interpretation of results. This opening article establishes the probabilistic, statistical, and machine learning foundations that the later contributions assume, together with the notation used throughout.

We present an empirical study of a disrupted CME, parts of which fall back to the Sun, using observations from SOHO, STEREO-A, and SDO. At UT 18:00 on 2024 August 16, a slow CME is overtaken by a faster CME. A leg of the second CME carries part of the slower CME out with it, resulting in an unusually well-defined flux rope leg for this CME. This second CME is observed in radio by the VLA, with Faraday rotation measurements showing a clear magnetic flux rope signature. A strong response is also later seen when the radio-observed line of sight enters the CME leg enriched by material from the disrupted CME. Outside this leg, the rest of the disrupted CME simply disappears and is replaced by a large number of small jet-like downflows. We see clear evidence of this plasma falling back to the low corona in EUV images from SDO, roughly 6-17 hours after the CME is disrupted, with an inferred downward velocity of V=-30 km/s. There is a clear temperature dependence, with the downflows seen first in the 211 bandpass, followed successively by responses at 193, 171, and 304. The downflows are much slower than would be expected for a ballistic descent, so we model the downflows using a kinematic drag model. In the 304 bandpass, coronal rain activity is triggered by the downflowing CME material, suggesting that downflows from the upper corona could be contributing to coronal rain more generally.

We describe the upgraded Polarimeter using Imaging CMOS Sensor and Rotating Retarder 2 (PICSARR-2), describe its applications, and characterize its performance for stellar polarimetry on a 36-inch and 14-inch telescope. On the larger telescope in the SDSS $g^\prime$, $r^\prime$ and $i^\prime$ filters a precision of $σ_p=$ 5.7 ppm on bright stars is recorded using a fast modulation rate corresponding to frame exposures of 12 ms; accounting for the internal errors in the individual observations gives a limiting precision of $e_p=$ 1.3 ppm. Longer frame rates are required for stars with $m > 5$, but the recorded errors only underperform a photon shot noise derived extrapolation for $m > 8$, when even longer frame exposures are required. Stars as faint as $m = 11$ were observed. The position angle precision is measured as 0.0845 degrees, and there is very good agreement between observations made by both the PICSARR-2 and HIPPI-2 polarimeters. On the smaller telescope the instrument's performance approaches similar levels, and there is good cross-platform stability in the observation of standard stars. PICSARR-2 is therefore an excellent instrument to explore stellar variability due to a range of phenomena; examples from our ongoing pulsating star campaign and other variable star programs are presented.

I critically examine claims in the paper arXiv:2608.11978 that the double-detonation (DDet) scenario explains the type Ia supernova (SN Ia) remnant (SNR Ia) SNR 0509-67.5, and find the arguments supporting the DDet scenario weak; hence, I reiterate my claim that the core-degenerate (CD) scenario, where a lonely white dwarf (WD), which is the merger product of a lower-mass WD and the core of an asymptotic giant branch star, exploded inside an old planetary nebula, i.e., an SNIP, best explains SNR 0509-67.5. I find that the flat edge of the SNR in the north-northeast, which in the DDet scenario is due to a shadow by the companion to the WD that exploded, is not unique in this SNR, and that the circumstellar matter, i.e., an old planetary nebula, shaped this edge, as well as other structures on the edge of this SNR. I emphasize that analyses of SNRs Ia and SNe Ia at late stages must consider the claim that most normal SNe Ia are SNIPs, implying that old planetary nebulae can heavily shape their morphologies. The bulk velocity inferred from an iron emission line in SNR 0509-67.5, which the DDet explosion attributes to the orbital motion of the exploding WD around its companion, can be an outcome of the explosion of a near-Chandrasekhar lonely WD; an off-center delayed-detonation transition explosion can form asymmetrical nucleosynthesis, while leading to a bulk motion of nickel that decays to iron. I repeat my claim that the CD scenario of a SNIP is the most likely scenario for SNR 0509-67.5.

We investigate black holes (BHs) in momentum-dependent spacetime geometry and assess its quantum Reissner-Nordström (RN) consistency with the weak gravity conjecture (WGC). Quantum corrections are introduced through the non-commutative momentum space algebra as the quantization process, and spacetime renormalization approach as a map between momentum and spacetime spaces. For the Schwarzschild case, thermodynamic analysis indicates the existence of a hot (non-zero temperature) BH remnant when evaporation stops (the entropy becomes zero), obeying a complementary third law for black hole thermodynamics. We extend this framework to the RN solution and examine its extremal limit. For large BHs with $M \gg M_P$ ($M_P$ for Planck mass), the quantum-improved RN geometry exhibits a non-zero Hawking temperature in the extremal case, consistent with the WGC, which stipulates that extremal states should not be exactly stable or cold. The resulting momentum-dependent metric and thermodynamic properties are shown to reproduce the results derived from the Poincaré algebra (classical model) in the infrared (IR) regime.

The five-dimensional Einstein--Yang--Mills black hole obtained from the higher-dimensional Wu--Yang ansatz carries a logarithmic non-Abelian contribution to the metric function, making it an analytically tractable setting for studying how gauge charge reshapes horizon thermodynamics beyond four dimensions. We derive expressions for the mass--radius relation, the Hawking temperature, the entropy, the Yang--Mills potential and the first law, and record the curvature invariants, which show that the logarithm sharpens the central singularity rather than smoothing it. A non-perturbative exponential entropy correction is then added, and the corrected heat capacity and free energies are obtained analytically. The geometry is extremal at $r_h=|Q|$ and the heat capacity diverges at $r_h=\sqrt{3}\,|Q|$, a Davies-type point. The correction moves that point inward, $r_{\rm tr}/|Q|\simeq\sqrt{3}-9λαη\,e^{-3\sqrt{3}λ}$. Using the generalized off-shell free energy we find a conserved topological charge $W=0$ carried by a stable--unstable defect pair whose inner member alone responds to the correction. We then solve the spherically symmetric magnetic Yang--Mills perturbation sector, which probes the gauge field itself rather than a test scalar. Two independent numerical schemes agree to better than $1.2\times10^{-7}$ and give a purely imaginary unstable mode whose growth rate falls monotonically from $Γ_{0}r_h=0.414753$ at $Q/r_h\to0$ to $0.317520$ at $Q/r_h=0.99$, passing through the Davies scale without any feature. Because the effective potential decays as $-9/(4r_{*}^{2})$, with a coefficient above the critical value $1/4$, the sector supports an infinite geometric tower of unstable modes accumulating at $Γ\to0$ with the charge-independent ratio $Γ_{n+1}/Γ_{n}\to e^{-π/\sqrt{2}}\simeq0.108453$, which we confirm numerically.

We introduce a bilingual domain-specific language (DSL) for modelling compute kernels within a generic solver for hyperbolic partial differential equations (PDEs). Users express PDE terms, i.e.~the underlying physics, in a familiar native language such as C or C++, while the numerical scheme is specified in a Python-embedded DSL, DSLHyPE. DSLHyPE's compiler lowers the Python description to MLIR and introduces a translation pass that integrates it with native code likewise mapped to MLIR. Our approach keeps the numerical representation and the physics implementation separate for as long as possible, while delegating optimization to the compiler through existing MLIR optimization passes. This separation of concerns benefits researchers developing numerical schemes on top of existing PDE implementations or with applications involving nonlinear systems whose PDE terms must solve PDEs themselves. We demonstrate the feasibility of the approach using a gravitational-wave solver and a matter-evolution solver on x86 processors and H200 GPUs.

The evolution of protoplanetary disks, and consequently the outcomes of planet formation, are thought to be significantly altered in regions containing massive stars. Extreme cases in the Orion Nebula Cluster (ONC) demonstrate the impact of external irradiation (FUV$\gtrsim10^{4}$ G$_{0}$) on disk evolution, but intermediate environments remain less observationally constrained. We present JWST/MIRI Medium Resolution Spectroscopy (MRS) observations of seven proplyds in NGC 1977 exposed to an external FUV field of $10^{3}-10^{5}$ G$_{0}$ from the B1V star 42 Orionis (42 Ori). We characterize emission from molecular (H$_{2}$) and atomic (e.g., [Ne II], [Ar II], HI) species, and in some cases, MIRI reveals extended emission tracing the proplyd ionization front and wind. The closest disk to 42 Ori, KCFF#1, is undergoing extreme mass loss, traced by a 1000s-of-au-long dusty tail, and lacks clear H$_{2}$ or HI emission, indicating an advanced stage of dispersal. The remaining six disks exhibit two-temperature components of H$_{2}$ emission (500--700 K and 1000--1500 K), likely tracing the disk molecular layer and a photoevaporative wind, alongside HI lines which are used to estimate mass accretion rates. When comparing KCFF#2 and #6, which have similar host stars, KCFF#2 (closer to 42 Ori) is dominated by externally driven mass loss, with extended molecular and atomic emission, whereas KCFF#6 only shows extended H$_{2}$ emission, with roughly equal contributions from accretion and external mass loss. While the sample is small, this work demonstrates how JWST/MIRI can assess environmental impacts on disk evolution, with NGC 1977 bridging strongly irradiated disks in the ONC and the more local population.

The Facility for Laboratory Reconnection Experiments (FLARE) has been constructed to study magnetic reconnection in multiple X-line regimes relevant to space, astrophysical, and fusion plasmas. Building upon the successful design of the Magnetic Reconnection Experiment (MRX), FLARE features a larger physical volume, stronger magnetic fields, and an independent ohmic heating drive to significantly extend the accessible parameter space, targeting Lundquist numbers up to S ~ 10^5 and normalized system sizes up to λ~ 10^3. This paper details the facility's core engineering components, including the primary vacuum vessel, internal flux cores, highly segmented external coil systems, modular capacitor banks, and the safety interlock and control architecture. An initial diagnostic suite is presented, comprising high-resolution 2D magnetic probe arrays, triple Langmuir probes, a fully fiber-coupled interferometer, ion Doppler spectroscopy, and fast camera imaging. Initial operations demonstrate the device's experimental flexibility and reliability, successfully executing symmetric push-pull reconnection, spheromak merging, and asymmetric downstream configurations. Currently operating within "Stage 2.5" with S ~ 2,500 and λ~ 60 for anti-parallel reconnection, FLARE provides immediate access to the multiple X-line regimes. Planned hardware upgrades, advanced diagnostic additions, and integration with fully kinetic simulations will further expand its capabilities as it transitions into a collaborative user facility for the broader plasma science community.

The bright-end cutoff of the planetary nebula luminosity function (PNLF) serves as an extragalactic standard candle. However, the physical properties of planetary nebulae (PNe) at the PNLF cutoff have been studied only in nearby galaxies, where the PNe appear mostly as point sources. Galactic PNLF is further poorly constrained, primarily due to uncertainties in Galactic PN distances. Following a recent Galactic PNLF survey based on Gaia distances, we aim to characterise PN candidates at the Galactic PNLF cutoff. We observed three PN candidates at the Galactic PNLF cutoff using the Potsdam Multi-Aperture Spectrophotometer (PMAS). We determined their chemical abundances and constructed photoionisation models to derive the central star luminosity (L) and effective temperature (Teff). We constrained the central star masses and most likely distances consistent with the prediction of stellar evolution models. Using these distances, we determined the absolute magnitude M5007. PNe of our sample are located within the top 1 mag of the Galactic PNLF (-4.20 < M5007 <-3.60), with similar nebular properties and a narrow progenitor mass range (1.30-1.75 Msolar). The measured extinction is mostly dominated by the foreground Galactic extinction. The trend between the circum-nebular extinction and central star mass of our PNe is in agreement with those derived in the Large Magellanic Cloud (LMC) and M31. All PNe in our sample exhibit weak-emission line star (wels) features in their spectra, but we confirmed that some of these lines originate from the nebula. The PNe are similar in terms of their nebular properties and evolutionary stage. Their characteristics are also consistent with the most [OIII]5007-luminous PNe in the LMC and M31. We demonstrate the importance of circum-nebular extinction and the initial-final mass relation (IFMR) to understand the universality of PNLF as a standard candle.

It has been proposed that primordial quark pellets or PQPs --ultra-dense quark-matter mini- stars-- formed at $T\sim 1$ GeV maybe a good candidate accounting for the dark matter of the universe. If correct, dark matter would consist of very compact objects with a maximum mass of $10^{-2} \ M_\odot$ and radii of approximately 100 m, although smaller objects would be much more abundant and encompass the bulk of the dark matter content. Here we describe a viable formation mechanism based on the enhancement of the local baryon density when supra-horizon Peccei-Quinn domain walls formed at an earlier epoch sweep and accumulate quarks and gluons before entering the horizon. Assuming an efficient baryon concentration by contracting Peccei-Quinn domain walls, we derive the resulting primordial quark pellet mass spectrum, minimum mass and cosmological abundance The results confirm that PQPs potentially constitute a conservative, Standard-Model-based, and observationally viable solution to the dark-matter puzzle.

We investigate density-induced conversion of neutrons into a neutral dark baryon $χ$ in cold, charge-neutral, $β$-equilibrated neutron-star matter containing hyperons and all $Δ(1232)$ quartet. The hadronic sector is modeled within a density-dependent covariant density-functional framework using the DDME2 parametrization. A scalar Higgs portal is included as a possible interaction channel between the visible and dark sectors, although its mean-field contribution is negligible for the couplings adopted here. Unlike fixed dark-matter admixture models or scenarios in which nucleon-to-DM conversion is driven by Higgs exchange, the $χ$ abundance is determined self-consistently from chemical equilibrium and baryon-number conservation. We find that hyperons and $Δ$ resonances alter the neutron chemical potential, delay the onset of $χ$, and suppress its abundance relative to nucleonic matter. This competition induces characteristic changes in the equation of state, particle fractions, sound speed, and adiabatic index. For $m_χ=1250$, $1300$, and $1400$ MeV, the maximum masses of the complete $N+Y+Δ+χ$ configurations are $1.806$, $1.899$, and $2.024,M_\odot$, respectively, indicating that the massive-pulsar constraint disfavors the lighter dark-baryon benchmarks. The radial profiles further show that for $m_χ=1400$ MeV, $χ$ is confined to the inner core of the most massive stars, while canonical configurations remain essentially unaffected. Thus, the stellar modifications arise primarily from conversion-induced rearrangement of the equilibrium composition rather than from Higgs-mediated interactions. These results highlight the importance of treating conventional non-nucleonic degrees of freedom and density-generated dark baryons on an equal footing when assessing the astrophysical viability of dark-sector extensions of dense matter.

We report the discovery of a spatially resolved clumpy ejecta structure in the reverse-shocked ejecta of SNR 0509-67.5, revealed through multiple faint and broad forbidden coronal emission lines in deep MUSE observations. We also identify two new broad coronal emission lines not reported before in this remnant, [Fe xi] 7894 A and [Fe x] 6374.5 A , which extend the set of previously reported [Fe xv] 7059.59 A, [Fe xiv] 5302.86 A , [Fe ix] 8236.55 A , [Ca xv] 5695 A, and [S xii] 7611.0 A. Near-continuous ionisation states of Fe allow us to follow the ionisation progression behind the reverse shock. We use a 1D analytical model to evolve Fe charge states following reverse shock interaction to compare with observations, indicating the need for preshock clumping or over-density in order to reproduce the observed surface brightness of the [Fe xiv] line. Additionally, we report the spatially resolved distribution of ejecta clumps and show that reverse-shock interaction drives their compression and fragmentation. We also find a clear trend of decreasing velocity width with increasing Fe ionisation state, from the broadest [Fe ix] emission to the narrowest [Fe xv], with intermediate-ionisation species ([Fe x], [Fe xi], [Fe xiv]) showing intermediate widths. Finally, we compare our observations to a dynamically driven double-degenerate double detonation (D6) 3D remnant model at similar Fe and S ionisation states and conclude that the observed clumps are predominantly due to Rayleigh-Taylor instabilities.

We introduce the Dianoga set of cosmological simulations of galaxy clusters and groups, specifically aimed at studying the impact of the implementation of AGN feedback and star formation. Using the OpenGadget3 code, we carry out simulations of 28 regions centred on massive galaxy clusters, and of a cosmological box. This generates a sample of 293 halos with M_{200}> 1.5 x 10^{13} M_{\odot}. Parameters of AGN feedback in the reference implementation were minimally calibrated exclusively to match the local relation between SMBH masses and stellar masses of host galaxies. Simulations are compared to observed galaxy stellar mass function (GSMF), stellar mass fraction in clusters and groups, BCG masses, scaling relations between ICM/IGM properties and profiles of their thermodynamical properties. In the appendix, we show how results vary as we modify the reference feedback model in six alternative configurations. Our reference model predicts a GSMF in general agreement with observations, albeit overestimated in the high end. BCG stellar masses and mass fractions are higher than observed in massive clusters, while being closer to observations for groups. Predicted properties of the ICM/IGM are in general agreement with observations, with the core regions of simulated clusters having entropy and temperature profiles that are slightly less "cool-cored" than observed. A comparison with other implementations of AGN feedback highlights that models including thermal evaporation of the sub-resolution interstellar medium succeed to bring BCG masses and stellar mass fractions closer to observation, and to increase the cool-coreness of simulated clusters. Our results demonstrate that the details of the interface between AGN energy injection and the sub-resolution interstellar medium model are at least as critical as the total feedback efficiency itself.

The formation of the majority of brown dwarfs (BDs) remains uncertain. They may form in molecular cloud cores in a process akin to low mass star formation, or via fragmentation in circumstellar discs. Studying the youngest, most embedded sources is crucial for distinguishing these scenarios. We investigate molecular gas morphology and kinematics around one young & embedded very low luminosity object (VeLLO), IRAM 04191+1522, utilising archival ALMA observations of 13CO, C18O, and SO. We trace gas on scales of a few 10s to 100s of au around the source to search for outflowing and/or infalling structures. The red and blueshifted 13CO (3-2) emission show distinct morphologies and kinematics. The blueshifted emission to the north-west may trace shocked material oriented differently from the previously reported approx. 0.1 pc CO outflow. Redshifted emission mainly to the south-east and south-west may trace the base of an outflow cavity. The position angle of this cavity suggests the presence of a second outflow, which supports the possible binary nature of this VeLLO. The C18O (2-1) emission is highly complex, comprising structures at different spatial scales and distances from the source. These may trace a mix of molecular outflow, outflow cavity, and disc emission. SO 65-54 reveals evidence for anticlockwise rotation around the central source, together with a northern structure of uncertain origin. We have identified a complex set of 13CO (3-2) and C18O (2-1) structures alongside evidence of a new outflow cavity at a distinct position angle from previously detected outflows. This supports the scenario that IRAM 04191+1522 is a binary system. The northern SO gas structure remains unexplained. Higher spectral resolution observations at intermediate scales are needed to characterise these substructures, their connection to larger scale structures, and to determine this system's final fate.

We investigate infrared line signatures from radiatively decaying sterile-neutrino dark matter using publicly available JWST/NIRSpec IFU blank-sky observations. The main signal considered is the sterile-to-sterile transition $N_1\to N_2γ$, induced by the transition magnetic dipole coefficient $d_{NNγ}$, with $m_1>m_2$. In contrast to ordinary two-photon decays of axion-like or Majoron-like particles, the observed photon energy is not fixed by the full dark matter mass, but by the small mass splitting $Δm=m_1-m_2$. Thus, a keV-scale sterile-neutrino dark matter state can generate an eV-scale infrared photon line in the JWST band. We construct a $χ^2$-based line-search analysis using the NIRSpec IFU $\rm F170LP$-$\rm G235M$ blank-sky data toward $\rm GN\text{-}z11$, modelling the smooth continuum with a cubic spline and including the Milky Way halo decay flux. In the absence of a significant excess, we derive projected limits on $d_{NNγ}$ and on the decay width $Γ_{N_1\to N_2γ}$ for $0.1~{\rm eV}\lesssimΔm\lesssim1~{\rm eV}$. For a sterile component saturating the dark matter abundance, the strongest sensitivity reaches $d_{NNγ}\lesssim7\times10^{-14}~{\rm GeV}^{-1}$ and $Γ_{N_1\to N_2γ}\lesssim10^{-25}~{\rm s}^{-1}$. We also include a minimal anomalous-Majoron benchmark, $ω\toγγ$, obtaining JWST sensitivity to $λ_{ωγγ}\sim10^{-11}$-$10^{-9}~{\rm GeV}^{-1}$ for $m_ω\sim0.6$-$1~{\rm eV}$.

We aim to exploit the large area coverage, good sensitivity, and low instrumental background of eROSITA to detect the faint surface brightness emission of galaxy groups from the Two Micron All Sky Survey Redshift Survey (2MRS). Using the data from eROSITA-DE Data Release 1, including images, exposure maps, and local background maps, we performed a wavelet decomposition of image mosaics in the 0.6--2.3 keV band at angular scales of 1/8-16'. We adopted 8-16' scales for source detection and 2-4' scales to improve catalog purity. A novel identification method based on the ranked partial Hausdorff distance fully exploits the X-ray image and group membership information. Random catalogs were used to control match purity, and the identification threshold was chosen to maximize the catalog size at a fixed purity. {We present a catalog of 619 X-ray galaxy groups with 80% purity, and define subsamples with 90% and 97% purity. Bright sources closely match the AXES-2MRS catalog (which is based on ROSAT All Sky Survey data analysis on spatial scales of 12-24'). The X-ray luminosity function of our groups agrees with previous studies down to 5.e41 erg/s. Using dynamical mass estimates, we find that the X-ray counterpart completeness for groups with >=4 members exceeds 60% for masses >2e13 Msun. We modeled the 2MRS group catalog and justify the inclusion of two-member groups in the identification. This study demonstrates that large X-ray sources on spatial scales relevant for cosmological studies of baryonic distributions can be reliably detected and identified using nearby galaxy group catalogs.

We analyze the constraints on the composition of ultra-high-energy cosmic rays (UHECRs), and on the density and distribution of their sources, that may be inferred from their arrival-direction distribution, using a novel semi-analytical description of the propagation energy loss of atomic nuclei ($A>4$) with energy $>2\times10^{19}~\text{eV}$, that allows generating UHECR arrival maps faster than by using detailed propagation simulations and yields insights to the impact of propagation energy loss. We show that the anisotropy of the UHECR arrival direction distribution due to the large-scale structure (LSS) of matter distribution is larger for heavy nuclei composition compared to protons, despite their larger deflections by magnetic fields, due to their shorter propagation distance and weaker dependence of rigidity on observed energy. Identifying the LSS anisotropy signal is hampered for heavy nuclei due to their large deflections by the uncertain Galactic magnetic field (GMF). We introduce a new measure of anisotropy, an "entropy" of the arrival-direction distribution, that is largely independent of the GMF configuration and has strong discriminating power between heavy- and light-composition models. Analyzing the public $>3.2\times10^{19}$~eV Auger data, we show that the correlation with the LSS on large angular scales is weak and requires a low source density, $s_0\le10^{-4}{\rm Mpc}^{-3}$, to allow masking the LSS signature by "cosmic-variance" ($s_0=10^{-2}{\rm Mpc}^{-3}$ is ruled out at $>99\%$ confidence level (CL)). The high entropy of the distribution is consistent with proton models and inconsistent with heavy nuclei models at $>96\%$ CL for $s_0\ge10^{-5}{\rm Mpc}^{-3}$. Reducing the absolute energy calibration uncertainty may allow detection of the LSS correlation for proton models (increased exposure alone will not suffice due to the dominance of cosmic variance).

Young stars accrete material from their circumstellar disk through their magnetosphere while still contracting, two processes that impact their rotational evolution. We investigate stable and unstable accretion regimes (due to the interchange instability) and examine the associated stellar torques to assess the spin evolution of young stars. We perform 3D MHD simulations of disk accretion onto an inclined stellar dipole. We run 21 simulations with varying stellar stellar rotation rates, dipole field strengths and obliquities, and mass accretion rates. We find that stars with a ratio of truncation to corotation radius $R_t/R_{co} \gtrsim 0.80-0.85$ accrete via a stable regime, while accretion becomes unstable otherwise. Besides, our $R_t/R_{\ast}$ parametrization weakly depends on the mass accretion rate and the dipolar intensity, while strongly on the stellar rotation rate. We derive torque formulae for each flow component affecting the stellar rotation, i.e. accretion, magnetospheric ejections and stellar winds. Finally, we apply our results to a sample of young stars with measured magnetic fields, mass accretion rates, and rotational periods and find that most of them should currently accrete in an unstable regime and undergo spin-up torques. Our study comforts and expands upon previous results. Unstable accretion should lead to a net spin-up torque on the central star, while stable accretion can lead to stellar spin-down. When applying our truncation radius and torque prescriptions to observational data, we find that most young stars in our sample should be in a spin-up state. Thus, the angular momentum problem for young stars remains.

Aims. We investigated the properties of the water snow line during the early stages of disk evolution, paying particular attention to the effects of gravitational instability and dust growth on the snow line's shape and position. Methods. We used the FEOSAD numerical hydrodynamics code to simulate the disk formation and evolution in the thin-disk limit. The simulations incorporate the coevolution of gas, dust, and volatiles, including dust growth, volatile phase transitions, and dust-size-dependent opacities. Results. The position of the water snow line is highly nonsteady during the considered disk evolution period, first moving outward during the disk build-up and then retreating back as the disk cools. Its form in the disk midplane deviates strongly from a circular shape in the early gravitationally unstable phase of disk evolution. An increase in the amounts of grown dust and water ice as well as in the maximum dust size just beyond the snow line, as is readily observed in one-dimensional viscous disk evolution models, in our hydrodynamic models occurs only after gravitational instability diminishes. Dust-growth-induced opacity changes have a profound effect on the position of the water snow line, shifting it closer to the star by almost a factor of two compared to models that do not take this effect into account. Conclusions. The shape, position, and properties of the water snow line in young, gravitationally unstable disks differ from those of older, axisymmetric disks. Our results highlight the importance of taking into account the dependence of opacity on dust size when studying disk evolution.

Context. In the context of Milky Way studies, the Vera C. Rubin Observatory's Legacy Survey of Space and Time is often described as a deep extension of the Gaia survey. In the future, joint analysis of the Gaia and LSST data promises to bring new insights into our understanding of the Galaxy's structure and formation history. However, the relatively small overlap in the magnitude ranges of the two surveys raises the question of how to perform a joint calibration of these datasets. Aims. In this paper, we produce high-quality synthetic LSST photometry from Gaia XP low-resolution spectra, using SDSS and DES observed photometry to calibrate the spectra. Methods. We develop a method of empirical correction of Gaia XP spectra using SDSS Stripe 82 photometry. We project sources for which Gaia XP data are available onto a magnitude-magnitude grid and calculate residuals between uncorrected synthetic and observed SDSS magnitudes, which are then used to derive correction coefficients across spectral regions corresponding to each photometric band. Results. The correction significantly reduces systematic trends and scatter in the synthetic magnitudes: the median residuals decrease by an order of magnitude (e.g., for the u band the improvement is from 0.038 to 0.002 mag), and the standard deviation of residuals typically becomes up to factor of two smaller (e.g., for the u band from 0.2 to 0.07 mag). Conclusions. Our correction approach improves the reliability of synthetic photometry derived from Gaia XP spectra and enables joint analysis of Gaia and LSST data for studies of Galactic structure and stellar populations.

We present a decomposition of the Kerr Green's function in the time domain, motivated by the frequency-domain split previously studied in the Schwarzschild limit. We show that the identification of a quasinormal-mode contribution, a direct part, and a late-time tail is still available, where the split times are determined by the black hole spin and positions of the emitter and receiver. We have checked this Green's function with time-domain Teukolsky numerical simulations and find excellent agreement. We also apply this decomposed Green's function in the time domain to a model problem with a test particle plunging into a Kerr black hole. The dynamically excited direct wave and quasinormal modes are obtained by convoluting the Green's function with the particle's source term, which may be viewed as the first order in mass ratio of a spinning black hole ringdown.

Working in the Worldline Quantum Field Theory framework, we obtain the classical gravitational Compton amplitude through the fifth post-Minkowskian order, $\mathcal{O}(G^5)$. At this order, the point-particle description must be supplemented by the leading static tidal operators. After removing lower-order iterations, we extract the corresponding $N$-matrix element and match it to black-hole perturbation theory. The matching fixes the static tidal Wilson coefficients to zero, providing confirmation of the vanishing static Love numbers of a Schwarzschild black hole.

The dimensionless spin angular momentum, dimensionless spin function, and blackhole mass components of Sagittarius A* (Sgr A*) were obtained by Daly et al. (2024) by applying the outflow method to six independent sets of simultaneously or contemporaneously obtained X-ray and radio data. Here, results obtained for Sgr A* with the outflow method are reviewed. Consistent results were obtained with each data set. Set I (the preferred data set) indicates that Sgr A* has a dimensionless spin angular momentum $a_* = (0.90 ~\pm~ 0.06)$ and a dimensionless spin function $F = (0.62 ~\pm~ 0.10)$. The results are consistent with the value of $a_* = (0.93~\pm~ 0.15)$ obtained with the outflow method applied to an independent data set (Daly 2019). The application of the outflow method to a weak compact radio source such as Sgr A* in its current state is most accurately determined with simultaneous or contemporaneous radio and X-ray measurements.

Variations in dynamical states of galaxy clusters can introduce biases and scatter in observable-mass relations. The dynamical state of a cluster is an emergent feature of its mass accretion history (MAH), it is therefore useful to constrain the MAH of the cluster. In this work, we characterize 305 massive clusters from The300 project by connecting features from their projected stellar distributions to their mass accretion histories (MAH). As a baseline, we first correlate host dark matter halo dynamical state indicators at $z=0$ with their MAH via the Spearman rank correlation coefficient $ρ_{\mathrm{sp}}$. Both substructure mass fraction and center-of-mass offset measurements correlate strongly with the MAH measured between $0.1\lesssim z\lesssim 1$. We repeat this exercise with morphological measurements of projected stellar density maps, many of which exhibit moderate correlation strength with different times in the MAH. Broadly, core morphological measurements ($r \leq 30\,\mathrm{kpc}$) correlate better with early-time MAH. Core-excised ($50\,\mathrm{kpc} \leq r \leq 1\,\mathrm{Mpc}$) morphological measurements correlate better with late-time MAH. We further quantify the MAH prediction power of both traditional dynamical state indicators and morphological parameters using Multivariable Conditional Abundance Matching (MultiCAM). MultiCAM employs simple rank-ordering operations, making it straightforward to translate to observed datasets. We find reasonable ($ρ_{\mathrm{sp}} \geq 0.6$) performance for predictions of the mass fraction between $1\lesssim z\lesssim 0.1$, though with notable information loss when using projected quantities. In one example application of our methodology, we use the coefficients of the MultiCAM models to select subsamples of galaxy clusters that have accreted more (or less) of their $z = 0$ mass budget over a given time frame.

In this study, we use the Bayesian methods in the Enterprise package to examine the fully general parameterization of pulsar timing models in tandem with noise. We investigate four pulsars, PSR J1600$-$3053, PSR J2043+1711, PSR J0740+6620, and PSR J1640+2224, through the lens of Bayesian timing. These four are selected as they are well-studied, but exhibit interesting characteristics under the lens of Bayesian timing. Our new pulsar mass constraints (medians and 68\% confidence intervals) for our fully general non-linear Bayesian timing models are $m_{\mathrm{p}}=1.6(1)~\mathrm{M}_{\odot}$ for PSR J2043+1711 and $m_{\mathrm{p}}=2.3^{+0.9}_{-0.7}~\mathrm{M}_{\odot}$ for PSR J1600$-$3053 both using the NANOGrav 12.5-yr data release, and $m_{\mathrm{p}}=2.06(6)~\mathrm{M}_{\odot}$ for PSR J0740+6620 using the data from Fonseca, et al., 2021. We investigate the effects on placing physical priors on timing model parameters, including restricting the upper limit on the pulsar mass for PSR J1640+2224, which has a mass often estimated to be greater than $3~\mathrm{M}_{\odot}$. We find \ark{that restricting the allowed sampling space of the pulsar mass for PSR J1640+2224 to} $m_{\mathrm{p}}<3~\mathrm{M}_{\odot}$ results in a pulsar mass of $m_{\mathrm{p}}=2.2(5)~\mathrm{M}_{\odot}$ for PSR J1640+2224 using the NANOGrav 12.5-yr data release. For the first time, we find evidence for intrinsic red noise in PSR J2043+1711. We show how fully general Bayesian timing can better model the interplay of the intrinsic noise and the timing parameters.

Quantum dots are tunable semiconductor nanocrystals that can be produced at industrial scales. We present the first ab initio calculation of the scattering of dark matter on electrons bound in quantum dots. The momentum-dependence of a quantum dot's electronic response depends on its morphology and on the dark matter mass, interaction operator, mediator coupling, and mediator mass. Therefore, the relative rates across an array of distinct quantum dot targets form a ``barcode'' that carries information about the nature of the dark matter interaction. We project the sensitivity of a detector concept in which a collection of independent target subunits, each loaded with silicon quantum dots of a particular morphology, are read out by Skipper CCDs. Given a future signal, this barcode could discriminate between interaction operators and mediator types. We quantify the discrimination power for a benchmark pair of models as a function of readout noise and exposure.

The extreme bright end of the galaxy UV luminosity function during reionisation remains poorly constrained, particularly where the galaxy and quasar luminosity functions overlap and source classification becomes ambiguous. We present JWST/NIRSpec and ALMA Band-6 observations of J1450-0144 ($z=6.627$) and J1429-0104 ($z=6.796$), two $M_{\rm UV}\simeq-23.5$ sources originally classified as faint quasars by SHELLQs. NIRSpec reveals blue UV continua, strong P Cygni profiles in N V, Si IV, and C IV, broad He II $\lambda1640$ emission with rest-frame equivalent widths of $8.8\pm1.2$ and $3.7\pm1.1$ Å, respectively, and narrow nebular lines, reclassifying both as extremely UV-luminous galaxies. Standard population-synthesis models cannot simultaneously reproduce the strong He II and wind features, whereas models incorporating very massive stars (VMS; $M\gtrsim100\,M_\odot$) with dedicated wind prescriptions can. These models favor a star-formation duration of 2-4 Myr for J1450-0144, with a broader allowed range for J1429-0104, stellar masses of $\log(M_\star/M_\odot)\approx9.2$-$9.9$, and star-formation rates of $\simeq300$-$540\,M_\odot\,{\rm yr}^{-1}$. Under the same VMS wind models, equivalent-width diagnostics imply $M_{\rm up}\gtrsim225\,M_\odot$ for J1429-0104, while J1450-0144 lies beyond even the $M_{\rm up}=475\,M_\odot$ grid. ALMA detects luminous [C II] 158 $μ$m emission in both systems, with $L_{\rm [CII]}\approx0.8$ and $4.1\times10^{9}\,L_\odot$, respectively. J1429-0104 additionally shows bright dust continuum, with both [C II] and dust offset by $\sim5.4$ kpc from its UV emission. These sources demonstrate that VMS can power some of the most UV-luminous galaxies at cosmic dawn and show that source classifications, and hence the inferred demographics of both galaxies and quasars in the crossover regime, need revisiting.

We begin by introducing a new parameterization for the Ovcharenko-Podolský family of exact solutions of the Einstein-Maxwell equations describing uncharged and non-accelerating static black holes immersed in an external Bertotti-Robinson electromagnetic field. The new spacetime is, in general, different from the original Ovcharenko-Podolský one, in particular on the branches solving the field equations, for which the original parameterization can lead to black holes with a negative mass, whereas the new one always leads to black holes with a positive mass. Moreover, by introducing additional gauge constants, we remove the various pathologies and ensure consistency with the laws of black hole thermodynamics. We then obtain a new family of Einstein-Maxwell solutions by generalizing this new parameterization, through Harrison transformation within the Ernst method, to also include an external electromagnetic field of the Bonnor-Melvin type. We again identify the appropriate gauge constants required to remove the possible pathologies and ensure that the resulting solutions satisfy the laws of black hole thermodynamics. Finally, we investigate the vacuum subcase of the new family and establish its relation to previously known metrics.

As well as obtaining beautiful images of the Universe, the Hubble Space Telescope's CCD detectors are sensitive radiation dosimeters that have been monitored in Low Earth Orbit for more than 24 years. The rate of radiation damage they received has varied over each Solar cycle, but several years out of phase with the appearance of sunspots or coronal mass ejections. We investigate functional forms that successfully fit the time series of damage to telescopes elsewhere in the Solar system. We obtain remarkably accurate fits to Hubble data but with physically absurd parameter values. During image post-processing, such fits can be used empirically, to correct more than 99.5% of the radiation damage's effect on image quality. However, fits to the time series with physically reasonable parameters produce worse performance. Our results highlight the diversity of radiation environments in different parts of our Solar system, and the complexity of Low Earth Orbit in particular. Our results also motivate continued monitoring of radiation damage to currently operational spacecraft, to more reliably predict the rate of degradation in (and useful lifespan of) future missions.

Strong gravitational lensing is a unique probe of the matter power spectrum on small scales, where the abundance of dark matter subhalos in galaxies could be used to distinguish the predictions of the concordance cold dark matter model from alternatives such as warm dark matter. Extracting this signal poses major computational challenges, since perturbations of the lensing potential induced by substructure can be degenerate with both the macro-model of the lens and highly flexible models of the background source. Here, we introduce a framework to quantify these degeneracies using a differentiable strong-lensing simulator. Substructure is represented in a spectral basis confined to an annular domain surrounding the lensed image, allowing signals from a population of NFW subhalos to be encoded in a finite vector space. We then use the Fisher matrix to determine how much information about substructure is absorbed by nuisance components of the model. We find that macro-model degeneracies are largely confined to low-order perturbations of the lensing potential, while degeneracies with the source model can strongly suppress sensitivity across a broad range of scales as the expressivity of the source model is increased. Finally, we introduce the Fisher Graph Laplacian prior as a diagnostic tool to study how the internal degeneracies of the source model can be used to regulate the sensitivity of the data to an unresolved population of dark matter subhalos.

We develop a perturbative framework for structure formation in a broad class of MOND-like theories characterized by a generalized nonlinear Poisson equation. We derive the modified evolution equations governing matter perturbations and obtain the corresponding linear growth equation, extending the analysis into the mildly nonlinear regime through one-loop corrections to the matter power spectrum. Beyond the theoretical framework, we perform a cosmological analysis based on two phenomenological scenarios: one parametrized by a quantity controlling the degree of nonlinearity in the generalized Poisson equation, and another describing the interplay between the MOND acceleration scale and the cosmological acceleration associated with the background expansion. We constrain these scenarios using recent measurements of the growth rate of structure, $fσ_8$, DESI-DR2 baryon acoustic oscillation data, and Type Ia supernova compilations. We find no statistically significant evidence for departures from the standard $Λ$CDM cosmology. The inferred constraints are fully consistent with the GR + $Λ$CDM scenario within the current observational uncertainties. At nonlinear scales, we note that MOND-like modifications can alter $P_{\rm NL}(k)$ and leave signatures that current and future high-precision large-scale-structure observations may probe. Our results establish a systematic connection between MOND-like gravitational dynamics and large-scale structure observations, providing a consistent framework to assess the phenomenological viability of MOND-inspired modifications of gravity in a cosmological context.

Accretion onto massive stars embedded in Active Galactic Nuclei (AGN) disks around supermassive black holes (SMBHs) is regulated to the stellar Eddington rate in the fast-diffusion or radiatively-efficient limit, $c/τ> c_s$, where $τ$ is the optical depth of the accretion flow and $c_s$ the sound speed. However, when the ambient density is sufficiently high, the opposite slow-diffusion limit applies. In this regime, accretion proceeds quasi-adiabatically and forms a hydrostatic circumstellar envelope (CSE) that stalls further mass inflow in the absence of self-gravity. We perform 3D hydrodynamic simulations in the adiabatic limit to investigate the structure and evolution of such envelopes. For low thermal mass ratios, $q_{\rm th} \equiv M_\star/M_{\rm th}$ where $M_{\rm th}=c_s^3/(GΩ)$ is the thermal mass, the CSE boundary smoothly matches the ambient disk entropy and density without forming a shock. In contrast, when $q_{\rm th} \gg 1$, a strong shock develops at the envelope boundary, substantially increasing the entropy of the envelope and thereby regulating its structure and mass, $M_{\rm env}$. In marginally self-gravitating disks with Toomre parameter $Q \sim 1$, we find that at sufficiently large $q_{\rm th}$ the envelope mass satisfies $M_{\rm env}/M_\star \gtrsim 1$. This condition is equivalent to stating that the post-shock material entering the envelope possesses lower radiation entropy than the characteristic stellar value, which triggers dynamical runaway growth on a dynamical timescale once envelope self-gravity is included in our simulations. In realistic AGN disk environments with SMBH mass $\sim 10^8M_\odot$, runaway may occur close to the minimum self-gravitating radii and produce supermassive stars of $\sim 10^5M_\odot$.

We show that a spatially closed universe can exhibit effective phantom dynamics ($q<-1$) and reach a finite-time cosmological event without violating the Dominant Energy Condition (DEC). Whereas the standard Big Rip is driven by a phantom fluid that breaks the energy conditions, here non-null spatial curvature acts as an active geometric contributor: for matter that strictly obeys the DEC ($ω\ge-1$), positive spatial curvature by itself drives the deceleration parameter to values below $-1$ and brings the expansion to a stop at a finite value of the scale factor, where the Hubble parameter vanishes while the energy density stays finite. Since the curvature also keeps the Hubble radius regular at this point, the event is naturally interpreted as a cosmological bounce rather than a disruptive singularity. We contrast this DEC-preserving mechanism with the genuine phantom case ($ω<-1$), for which the same closed geometry produces an early bounce followed by a late Big Rip, and we comment on the observational status of the curvature contribution.

We study weak gravitational lensing and steady spherical test--fluid accretion by a static charged black hole in a Lorentz--violating Kalb--Ramond background with two nonminimal curvature couplings, assuming minimally coupled probe radiation. Using the Gauss--Bonnet theorem with the correct boundary term and perturbed ray boundary, we obtain the complete local deflection angle through second post--Minkowskian order. In a homogeneous cold plasma, the mass and charge sectors acquire different frequency dependences, producing distinct chromatic signatures. The two Lorentz--violating couplings are also separated: one controls the conical geometry and mass normalization, while the other first enters through the effective charge. For neutral adiabatic accretion, we derive the conserved fluxes, Bernoulli relation, Hamiltonian flow, and sonic--point conditions. These results disentangle local, global, dispersive, and accretion effects and establish the calibrations required for phenomenological constraints.

It is known that in vacuum, two infinitesimally separated timelike observers under free fall notice a relative acceleration due to the tidal field (or the `electric' part of the Weyl tensor), and if they are carrying inertial guidance gyroscopes, they notice relative precession between these gyroscopes due to the frame-drag field (or the `magnetic' part of the Weyl tensor). The frame-drag field thus has no Newtonian analog. In this paper, for a family of timelike observers carrying inertial gyroscopes and forming a congruence, we define these fields as constraint equations in the presence of matter using (1+3) covariant splitting of spacetime. Unlike Newtonian gravity, the relative velocities of the observers around a closed contour formed by their spatial separations (and a temporal vector that closes this contour if the congruence is not hypersurface orthogonal) do not add up to zero due to the frame-drag field and momentum density of the fluid. Moreover, the relative orientations of the gyroscope spins around the same contour do not generally cancel out due to the tidal field, the fluid variables (anisotropic pressure and energy density), and the spatial cross-product of relative velocities associated with the separation vectors that form the contour. Additionally, it is shown that even in the absence of the frame-drag field, neighboring observers see relative precession between their gyroscopes when their relative velocity and acceleration are non-parallel due to differential Thomas precession.

A closed Friedmann-Lemaitre-Robertson-Walker Wheeler-DeWitt model is formulated as an exact reflection problem. The derivative of its reflection phase defines a relational crossing duration whose first two clock moments follow from a covariant scalar-clock observable. An analytic expression is obtained for this duration, its classical recollapse limit, and the leading quantum correction. A finite spectral packet also gives an operational, equal-prior minimum error probability for distinguishing the two orientations of recollapse with a geometric reading. The construction is extended to a bounded finite quantum detector. Its multichannel reflection matrix yields probe transitions, spectral-probe correlations, and a matrix duration. A direct weak-coupling calculation verifies the predicted transition and duration scalings. Scalar-clock conditioning and oriented geometric sections are shown to be local representations of the same positive-frequency Dirac sector. These results define duration and transition observables entirely through correlations and scattering records of a stationary constrained state, without introducing a background clock.

Ostrogradsky's theorem shows that higher-derivative dynamical systems inevitably yields a Hamiltonian featuring a ghost mode that is unbounded from below. However, we argue that this theorem is inapplicable to gravitational systems, as the Hamiltonian constraint, which encodes background independence by dictating that the total Hamiltonian vanishes, holds strictly. The ghost mode obeying this constraint constitutes an indispensable component in the construction of space and time. Nevertheless, it should be underscored that the use of the weak-field (graviton) approximation, being a background-dependent scheme presupposing the existence of absolute time, invokes this theorem; consequently, it is allowed only in the domain below the Planck scale, where second derivative terms dominate.

We present Galactic chemical evolution (GCE) models for the chemical clocks [Zr/Ti] and [Ce/Ti], tracing first- and second-peak s-process nucleosynthesis, and compare them with a high-precision sample of 68 Kepler red giant stars with asteroseismic ages from individual-mode frequencies and high-resolution spectroscopy. Using a multi-zone GCE framework, we explore variations in metallicity-dependent asymptotic giant branch (AGB) nucleosynthetic yields, including proposed enhancements to high-metallicity Ce production. Our baseline model reproduces [Zr/Ti] and the high-$α$ sequence in both age and metallicity space, but systematically underestimates [Ce/Ti] at young ages and intermediate metallicities, indicating a persistent deficit in second-peak s-process enrichment over the last $\sim6$ Gyr of Galactic disc evolution. Increasing second-peak yields from high-metallicity AGB stars only partially reduces this discrepancy, suggesting that simple yield rescaling is insufficient and more fundamental revisions to s-process nucleosynthesis at high metallicity, alongside a self-consistent treatment of stellar dynamics, may be required. In fact, models reproduce abundance trends more tightly in metallicity than in age space, with additional age scatter partly attributed to radial migration. This Letter highlights the diagnostic power of precise asteroseismic ages for GCE studies and the limitations of current models in capturing the complex interplay between s-process nucleosynthesis and stellar dynamics.

We compute the renormalized scalar vacuum polarization $\langle φ^2 \rangle$ of a massive, non-minimally coupled quantum field in the Hartle--Hawking state exterior to a family of static, spherically symmetric quantum-corrected, effective and regular black holes: the Kazakov--Solodukhin quantum-deformed black hole, the two effective loop-quantum-gravity geometries of Zhang--Lewandowski--Ma--Yang, the renormalization-group improved Schwarzschild black hole of Bonanno--Reuter, and the Bardeen regular black hole. We adapt the extended point-splitting mode-sum formalism, implemented as a high-performance code, and present the exterior profile of the vacuum polarization over a grid of the quantum-deformation parameter, the field mass $μ=mM$ and the curvature coupling $ξ$. The five geometries display qualitatively distinct horizon responses. In all five geometries the deformation imprint is governed by the sign of the background Ricci scalar through the DeWitt--Schwinger curvature term linear in $(ξ-1/6)\mathcal{R}$, and is strongly suppressed at conformal coupling. We verify this both in magnitude and in the $ξ$-dependence. In the near-extremal regime of the two geometries with inner horizons we find a sign change of the horizon polarization at light field mass -- absent for Reissner--Nordström at matched temperature and removed by conformal coupling -- identifying a genuinely quantum-geometric, de-Sitter-core-driven regime. Every result reduces to the Schwarzschild value in the classical limit, validating the calculation.

We develop a thermomechanical framework for viable Horndeski scalar hair with spacelike scalar-field gradients. Adapting the $(1{+}1{+}2)$ formalism to the scalar configuration, we apply the effective imperfect-fluid decomposition to the model and derive general results governing its thermomechanical properties. Specifically, we infer the constitutive relations for the effective medium, in both observer-dependent and observer-independent approaches, thereby identifying the conditions under which the scalar hair admits thermomechanical interpretations. The observer-dependent approach leads to an analogy with anisotropic media characterized by a preferred spatial direction, whereas the observer-independent view shows similarities with layered media. The general results are then specialized to static, spherically symmetric configurations with scalar hair depending solely on the areal radius. Interestingly, this scenario allows us to connect the thermomechanical framework with the Tolman--Ehrenfest criterion for thermal equilibrium.

Non-gravitational processes that expel hot gas beyond the virial regions of groups and clusters of galaxies, known collectively as baryonic feedback, play a key role in reshaping the matter distribution of the Universe on Mpc scales. We use eROSITA observations of a complete sample of 25 galaxy groups selected from the first public release of the eROSITA-DE data (eRASS1) and identified with the Two Micron Redshift Survey optical group catalogue (2MRS). We extract and fit surface brightness (SBx) profiles and present hot gas mass and hot gas fraction profiles out to $R_{200}$. We perform a Bayesian analysis of $M_{\mathrm{gas}}-M_{\mathrm{tot}}$, $L_{\mathrm{X}}-M_{\mathrm{tot}}$, and $L_{\mathrm{X}}-M_{\mathrm{gas}}$ relations, taking into account the aperture covariance effects. At $R_{500}$, we report uniformly flat SBx profiles with a mean $β$ parameter of $0.38 \pm0.04$, steepening to $β= 0.76\pm0.19$ beyond $R_{500}$. We measure a sub-cosmic hot gas fraction at the median mass of our sample $M_{500} = 2.54\times10^{13}M_{\odot}$ of $ f_{\mathrm{gas,500}} = 4.32\pm0.42\%$. Similarly, at $R_{200}$ and the median mass $M_{\mathrm{ 200}} = 3.69\times10^{13}M_{\odot}$, we obtain $f_{\mathrm{gas,200}}=5.78\pm0.69\%$. Our $f_{\mathrm{gas}}-M_{\mathrm{tot}}$ and $L_{\mathrm{X}}-M_{\mathrm{tot}}$ relations show significant deviations from the predictions of the strong feedback variants of the FLAMINGO simulation ($2.5σ$ to $8.0σ$ tension), while fiducial FLAMINGO and BAHAMAS provide the closest match to our measurements. Using our measured baryon fractions and the \texttt{SP(k)} model, we infer a $10\%-15\%$ reduction in the matter power spectrum at $k = 5\ h\ \mathrm{Mpc}^{-1}$ relative to a dark matter-only universe, in agreement with fiducial FLAMINGO and BAHAMAS, while revealing a growing tension on smaller scales with the strong feedback variants.

We study the existence of Einstein scales and compatible metrics in Grassmannian geometry. As a special case, this includes the conformal-to-Einstein problem for anti-self-dual (ASD) conformal structures. In the ASD setting, given a genericity condition algebraic in the Weyl curvature, we obtain necessary and sufficient conditions for the existence of a local Einstein scale that refine those previously appearing in the literature. We also prove that in Riemannian signature, a non-Ricci-flat ASD-Kähler metric is locally conformally Einstein if and only if it has a holomorphic Killing vector field with anti-self-dual derivative proportional to the Ricci spinor. Next, we consider some generalisations of the ASD conformal-to-Einstein problem for $(2n,2)$-Grassmannian structures. When $n > 1$, given an analogous genericity condition, we obtain necessary and sufficient conditions for the existence of a local Einstein scale. Using tractor calculus, we obtain algebraic obstructions to the existence of compatible metrics and show that the unique submaximally symmetric model of the geometry has the submaximal number of linearly independent compatible metrics.

We derive a compact analytic formula for the one-loop triangle correlator of conformally coupled scalars in de Sitter space. The result is organised as six leading-singularity prefactors multiplying pure weight-two functions of the six energy variables. It contains forty-two dilogarithms, compared with approximately one hundred and twenty in the previously known closed-form representation, and requires no auxiliary regulator. The dilogarithms occur in Galois-conjugate pairs, making each contribution separately real throughout the physical region. We validate the result numerically. Moreover, we show that its symbol can be derived directly from the dressed integral representation or, independently, bootstrapped from Landau singularities and general consistency conditions. Finally, we show that the correlator (in a suitable normalization) is a Stieltjes function of each squared energy separately and is jointly completely monotone in all six squared energies. These structures suggest a route towards higher-point one-loop cosmological correlators.

We present a reformulation of four-dimensional chiral gravity in terms of a chiral gauge connection and a Clifford-valued coframe. The exterior algebra generated by $e^a γ_a$, together with the gauge curvature $F$, provides a natural and systematic construction of gauge-covariant differential forms. We show that suitable combinations of the chiral actions reproduce Einstein--Cartan--Holst gravity with a cosmological term. The original superconnection invariants yield only algebraic fermionic equations, so the fermionic one-forms do not propagate but instead generate a mass-like mixing between the two chiralities. Spinor propagation is supplied by a spinorial BF-type term, which under the matter ansatz reduces to the standard first-order Weyl kinetic action, including the torsion coupling. We also review the symmetry and variational properties of the matter ansatz, including its Lorentz equivariance, its relation to residual supersymmetry and twistor spinors, and the connection between the reduced and unrestricted field equations.

The definition of a Lorentzian gravitational path integral requires specifying which causal struc- tures are admitted off shell. Of particular importance are light-conical singularities, codimension- two irregularities of the light cone structure that render the gravitational action complex and can therefore lead to exponential enhancement or suppression of configurations. We investigate the prevalence and structure of such singularities in Lorentzian Regge gravity. We develop an efficient algorithm for randomly generating realizable Regge geometries satisfying the generalized triangle inequalities, and use it to sample the configuration space of four-dimensional triangulations. We find that light-conical singularities are generic: for bones shared by many four-simplices, configurations with irregular light cone structure overwhelmingly dominate, with trouser-type singularities gen- erally entropically favored. Restrictions on the causal character of subsimplices, such as requiring all tetrahedra to be spacelike, can substantially alter these statistics. We further show that both yarmulke- and, in four dimensions, trouser-type singularities can occur on unbounded regions of configuration space associated with simple refinement moves. Beyond light-conical singularities, we analyze the causal structure of Lorentzian triangulations more generally, for example by introducing the notion of pairwise embeddable chrono-topologies and a set of discrete causality data. Our re- sults demonstrate that causal irregularities are an intrinsic and abundant feature of the unrestricted Lorentzian Regge configuration space, sharpening the question of which causality conditions should be imposed in Regge gravity, spin-foam models, and ultimately the continuum gravitational path integral.

We calculate the five-point tree-level Compton amplitudes for minimally coupled spinning matter in gauge theory and gravity in the massive spinor-helicity formalism, using BCFW recursion and KLT relations. The results are written in terms of symmetrized spinor products and are simultaneously valid for a range of matter spins, which directly generalizes the amplitudes of Arkani-Hamed, Huang, and Huang to the five-point case. Unlike the three- and four-point cases, each amplitude can be a sum of two or more distinct spin structures. Spurious poles are manifestly canceled through a mechanism that holds for all massive spins $s\leq 1$ in gauge theory and $s\leq 2$ in gravity. While we keep the amplitudes exact, their classical limits are expected to be relevant for binary systems of Kerr black holes in the post-Minkowskian expansion.

Current and forthcoming wide-field galaxy surveys, such as SPHEREx and Euclid, provide a unique opportunity to probe the ultra-large scales of structure formation, where primordial non-Gaussianity, often parameterized by $f_\text{NL}$, is expected to leave its most detectable imprint. At the same time, these surveys inevitably enter regimes where relativistic and wide-angle effects become significant, requiring careful modeling to extract unbiased cosmological information. We address these challenges by applying the total-angular-momentum (TAM) formalism to describe redshift-space clustering beyond the flat-sky approximation. The standard Fourier-mode description, which characterizes distortions by the angle between a mode and a line of sight, becomes ill-defined over wide fields, whereas the TAM basis naturally separates radial and angular contributions and incorporates the relevant relativistic effects. Within this framework, we provide a new parameterization of wide-angle predictions that can be compared directly with survey data. We then introduce PowerFull, a modification of the Julia-based 2-FAST package, which enables efficient computation of the full relativistic angular power spectrum. Finally, using Fisher information matrix-based analyses, we show that a survey like SPHEREx reaches $σ(f_\text{NL}) \sim 1$, but that neglecting the relativistic and wide-angle contributions shifts the recovered $f_\text{NL}$ by an amount of order its own uncertainty: at this precision the inferred value is biased unless the clustering is modeled consistently.