高能暂现源 · 每日文献综述

We explore the multimessenger signatures from ultracompact minihalos (UCMHs) seeded by stellar-mass primordial black holes (PBHs) and composed of QCD-axion dark matter. Using the secondary-infall framework, with relic-abundance and isocurvature conditions from a pre-inflationary Peccei-Quinn scenario, we numerically recover the characteristic halo profile and adopt a conservative constant-density core for the innermost region. We study the gravitational wave and electromagnetic signatures from neutron-star-PBH inspirals inside these dense structures. Dynamical friction produces a gravitational-wave dephasing relative to the vacuum binary, observable with LISA for primordial black holes with masses $\lesssim\! 10M_\odot$. Simultaneously, gravitationally focused axions can resonantly convert into photons in the neutron-star magnetosphere, producing a narrow-band radio signature. For nearby galactic neutron stars, the projected sensitivity of the Green Bank radio telescope GBT captures the QCD-axion band in the $μ{\rm eV}$ mass range. Gravitational waves therefore probe the presence and structure of the UCMH, while the radio signal probes the particle nature of its dark matter, making their joint observation a distinctive test of a mixed dark sector.

Mergers of black holes (BHs) have been shown to be a ubiquitous phenomenon in the Universe. However, uncertainties remain in our theoretical understanding of the evolution of the BHs prior to their merger. Black hole progenitors are seemingly born primarily in triples or higher-order multiples, and the presence of a tertiary object can perturb a black hole binary (BHB) enough to precipitate a merger. We used population synthesis coupled with orbit-averaged descriptions of triple dynamics to evolve a population of triples with initially wide orbits and massive progenitors. Wide orbits were chosen to avoid stellar interaction prior to BH formation. Systems that remain bound and form an inner BHB were evolved using a direct n-body code with post-Newtonian terms up to an order of 2.5. We also simulated the precession of the BH spin vectors by coupling the n-body solver with the differential equations for the spins. For the dynamically stable triples with inner BHBs, mergers occur with an estimated rate density of $\sim 5$ Gpc$^{-3}$ yr$^{-1}$. Mergers also occur in triples that become dynamically unstable at a rate of $\sim 1.4$ Gpc$^{-3}$ yr$^{-1}$. At the point of entering the 10 Hz gravitational wave frequency band, the merging inner binaries exhibit eccentricities between $10^{-4}$ and $10^{-2}$. The final effective spin of a BHB that merges through this channel can display a wide range of values between $-1$ and $1$, with a slight tendency towards $χ_\text{eff} \approx 0$. This is a result of the strong three-body dynamics experienced by the merging triples before the inner binary begins to shrink due to GW emission. The inner angular momentum can explore the full phase space before the binary rapidly shrinks and decouples from the tertiary, effectively freezing out the effective spin to its value at the time of the highest inner eccentricity.

Jets launched by accreting supermassive black holes represent a major mode of active galactic nucleus (AGN) feedback. However, how their energy is divided among bulk kinetic motion, thermal gas, magnetic fields, cosmic rays (CRs), and radiation - and how this distribution changes with spatial scale - remains poorly constrained. NGC 4438 provides a unique laboratory for probing this evolution, hosting two 200-pc-scale nuclear bubbles and a lopsided ~10 kpc galaxy-scale outflow plausibly associated with the same AGN. We present a multi-wavelength analysis to investigate the morphology, radiation mechanisms, and energetics of these structures. Joint radio-X-ray modeling shows that the non-thermal emission in the nuclear bubbles may require two distinct populations of cosmic-ray electrons, suggesting that in addition to shock acceleration at the bubble rim, the highest-energy particles may be linked to acceleration processes closer to the unresolved central engine. A spatially resolved energy inventory reveals that bulk kinetic energy dominates the current energy budget of the nuclear bubbles, while roughly half of the injected energy has already been transformed into thermal, CR, and magnetic energy, as well as radiative losses. Across all bubble sizes, the thermal and magnetic pressures are consistent within the uncertainties, implying that magnetic fields remain dynamically significant on all examined spatial scales. Furthermore, the empirical correlation between radio luminosity and jet power, established for kiloparsec-scale jet bubbles (MerloniHeinz2007), matches the energetics of the galaxy-scale outflow but substantially overestimates the power of the 200-pc-scale nuclear bubbles, underscoring the scale dependence of jet energy dissipation.

Several pulsar timing arrays have reported evidence for a nanohertz gravitational-wave background. This background is thought to arise from the superposition of signals from a population of inspiraling supermassive black hole binaries. A key test of this interpretation is the search for individually resolvable binaries whose signals emerge above this background. Here we investigate this possibility by addressing two related questions: (1) what are the most probable properties of the first resolvable binary; and (2) how can pulsar timing observations be optimized to maximize its prospects for electromagnetic identification? By simulating populations of supermassive black hole binaries constrained by evidence for the gravitational-wave background and studying the loudest binary in each simulation, we infer the expected properties of the first individually resolvable systems. If MeerKAT continues its current observing strategy for a total of 9 years, the probability of detecting an individual binary is $\approx10-27\%$. Improving the timing precision by a factor of two changes this probability to $\approx11-28\%$, whereas increasing the cadence by a factor of four gives $\approx12-30\%$. Combining both improvements yields a detection probability of $\approx12-33\%$. Furthermore, implementing a high-cadence observing campaign preferentially resolves higher-frequency systems ($\gtrsim\unit[10]{nHz}$), whose shorter orbital periods make them considerably easier to identify through electromagnetic observations than lower-frequency binaries that repeat infrequently. We discuss prospects of electromagnetic follow-up of gravitational-wave resolved binaries with current high-cadence all-sky optical surveys.

We study mesoscopic configurations of a neutron superfluid coupled to a proton superconductor in the outer core of a neutron star. The condensates are described by a two-component Ginzburg-Landau free energy with local couplings, neglecting genuine phase-gradient entrainment. In two spatial dimensions, we minimize the free energy using quasi-periodic boundary conditions and constrained phase-imprinting calculations to study vortex-fluxtube and fluxtube-fluxtube interactions. We find that, for locally attractive couplings in the free energy, vortex-fluxtube overlap is energetically favoured and several pre-existing proton fluxtubes can bind around a neutron vortex, forming finite vortex-centred aggregates that we call fluxtube bouquets. These bouquet configurations may become so dense that a vortex can effectively accommodate several quanta of magnetic flux. We also confirm the possible presence of a type-1.5-like regime and find that it survives in the zero-entrainment regime considered here. In this type-1.5 regime, the fluxtube-fluxtube interaction is repulsive at short distances and attractive at intermediate distances, leading to self-assembled clusters while the individual fluxtubes remain topologically distinct. Possible implications for dissipative coupling and transport in neutron stars are discussed.

The observed deficit of bright late-type giants in the central parsec of the Milky Way remains an open problem. We investigate whether repeated passages of red giants (RGs) through a past jet from Sgr$~$A$^*$ can modify their envelopes and apparent spectral types. Three-dimensional hydrodynamical simulations follow a $1\,M_\odot$, $100\,R_\odot$ RG through up to ten jet crossings at $10^{-3}\,\text{pc}$, using jet kinetic luminosities of $10^{42}$, $10^{44}$, and $10^{48}\,\text{erg}\,\text{s}^{-1}$. Each passage produces shocks, envelope ablation, and an asymmetric downstream tail. For jet luminosities up to $10^{44}\,\text{erg}\,\text{s}^{-1}$, the cumulative ablated mass evolves approximately as $ΔM\propto t^{1/2}$ and reaches about $10^{-4}\,M_\odot$ over a $10^5\,\text{yr}$ active phase. Repeated heating also raises the surface temperature from about $3600$ to $8500\,\text{K}$ during the first ten passages, potentially making an M-type giant appear as an A-type source. Jet feedback may therefore contribute to the apparent depletion of cool giants and the excess of hot stars in galactic nuclei (GN).

We present sequential 12-18 and 18-26 GHz radio-band ($Ku$, $K$) VLA observations of the 22 Myr dM1e star AU Mic. We detect two flares and two marginal events over a total of 3 contiguous hours on source, resulting in a radio flare rate of $\sim$1 flare hour$^{-1}$. While this rate is consistent with previous $Ku$-band observations, both flaring ($<$1 mJy) and quiescent ($\sim$0.4 mJy) flux densities are significantly lower. Furthermore, the quiescent spectral shape here is distinct, allowing for unique constraints on the radio-emitting sources of AU Mic. The time-averaged quiescent spectrum is best described by gyrosynchrotron radiation with a peak around 17 GHz and an optically thin spectral index of $α\approx -0.6$. We estimate that the source regions have magnetic field strengths of $\sim$1 kG and cover a fraction of $<$0.5% of the stellar surface, yet the instantaneous total electron kinetic energies are $\sim$10$^{28}$ erg. The power-law index describing the distribution of electrons with energy derived from the spectral index, $δ\approx 2$, implies a near-continuous injection of electrons. This could arise from micro-flares that occur over the surface of AU Mic that sustain the radio radiation. One clear flare per band occurs, with decay-to-rise $e$-folding time ratios of $3 - 4$, indicating magnetic trapping of the electrons. The $Ku$-band flare is optically thick during the rise and peak times, indicating a peak frequency above 18 GHz. Together, these quiescent and flaring characteristics suggest that continuous, unresolved micro-flaring and magnetic trapping dominate the non-thermal radio emission of active M-dwarf coronae.

A recent study has discovered a highly polarized millimeter continuum source called {\it Punctum} located at the central region of NGC 4945 which doesn't fit any known category. Apart from the radio detection at $\approx 100$ GHz, there is no identified counterpart to {\it Punctum} in other radio, infra-red, optical, and X-ray bands. All available potential models, including magnetar, supernova remnant and microquasar, cannot provide satisfactory explanation for the exceptionally high polarization of $\sim 50$\% and large luminosity in mm band $L_{\rm mm} \approx 2\times 10^{35}$ erg/s within a small size $<2$ pc shown in {\it Punctum}. In this article, we discuss the possibility that {\it Punctum} is indeed a primordial black hole (PBH) with a dark matter density spike. We show that the synchrotron radiation due to the electrons and positrons produced from dark matter annihilation can satisfactorily explain the observed properties of {\it Punctum} and we can effectively obtain the annihilation cross section $\langle σv \rangle \sim 10^{-33}$ cm$^3$/s using our developed analytic framework. Furthermore, if the {\it Punctum} PBH mass is $\sim 10-100M_{\odot}$, the preferred dark matter mass range is $m_{\rm DM} \sim 10-1000$ MeV.

The origin of white dwarf magnetic fields is an open question. Furthermore, such fields play a vital role in the evolution of interacting binary stars. Here we present a study of white dwarf fields in so called pre-polars (or low accretion rate polars, LARPs , i.e. magnetic cataclysmic variables, where the mass losing secondary star is not in Roche lobe contact, but the systems experience accretion via stellar wind. Such systems play a crucial role in understanding the magnetic braking and the angular momentum evolution of close binaries. We aim to identify a set of wind-accreting pre-polars amongst our sample of nine candidate systems. We also attempt to measure the white dwarf magnetic fields and study the accretion geometry associated with wind-accreting pre-polars. We have obtained optical circular imaging photopolarimetry and circular spectropolarimetry of the targets. These are used to model the cyclotron emission and to estimate the white dwarf magnetic field strengths. We find that at least in four out of our nine candidate systems, we can confirm the magnetic nature of the white dwarf. Out of these, One system, ZTF J1737+4013, appears to be an eclipsing polar. Furthermore, ZTF J2220+0721 and ZTF J2353+4153 appear to be very strong candidates for wind-accreting pre-polars (or LARPs), with the fourth, ZTF J0056+4926, showing strong variable $H_α$ emission, atypical of pre-polars. However, the emission could be related to the strong activity of the donor star, dominating the optical spectrum. One system, ZTF J0504+2145, is likely a novalike CV. The exact nature of the other systems remains unclear.

We performed B- and V-band photometry of the probable dwarf nova LY UMa. We find that it has apparent magnitude V=15.26+/-0.03 on 2024-04-14, V=15.43+/-0.02 on 2025-04-28, and V = 15.57+/-0.02 on 2025-06-02. Using the GAIA distance d=310pc, we find that the lower values correspond to absolute V band magnitude M_V=7.94-8.10 and indicate that the mass donor of LY UMa is a K7-K8V star with M_V=8.0-8.5. Our B-band measurements show slightly bluer B-V index of LY UMa than that of its donor, consistent with its nature as a cataclysmic variable. Close to LY UMa is the Active Galaxy Nucleus Mrk 153, for which we estimate V=14.81+/-0.03.

We compute the weak gravitational deflection of light by a neutron star that carries a self-consistent dark-matter component, in the regime in which the dark matter forms an "extended halo" reaching beyond the baryonic surface. Two observations motivate this configuration. First, a dark-matter core confined within the baryonic radius leaves no distinctive lensing signature, since by Birkhoff's theorem the exterior is Schwarzschild with the total mass, so a ray passing outside the star feels only that mass and the compactness it implies. Second, the signature we seek resides in the complementary case, in which the ray genuinely traverses the halo, so that the surrounding density enters the optical geometry directly. We model the star by integrating the coupled two-fluid Tolman--Oppenheimer--Volkoff equations, with the baryonic and dark components interacting solely through gravity, and we obtain the deflection angle from the resulting external profile through the Gibbons--Werner construction of the Gauss--Bonnet theorem. The defining feature of the approach is that the deflection is tied to a "self-consistent" two-fluid profile rather than to a medium inserted by hand. We show that, for impact parameters smaller than the halo radius, the deflection departs measurably from the point-mass prediction, the deficit being governed by the dark-matter fraction and the halo extent, and we argue that the "shape" of this deficit furnishes a geometric, lensing-based handle on the degeneracy between dark matter and the nuclear equation of state. The framework thereby unites the structural modelling of compact stars with their gravitational-lensing phenomenology.

Post-RGB and post-AGB binaries, collectively shell-burning stripped giant (SBSG) binaries, contain a primary star recently stripped of its envelope, alongside a main-sequence companion. These systems are characterised by a stable circumbinary disc (CBD), thought to have formed from envelope material stripped via mass transfer. Their eccentricities range between $0-0.63$, contradicting canonical binary evolution that predicts such post-mass-transfer systems should have circularised. We investigate whether CBD-binary interaction can explain the observed eccentricities of SBSG binaries using a new formalism based on hydrodynamic simulations. To compare with observations, we generated model populations for which post-mass-transfer eccentricity and amount of mass accreted from the CBD were free parameters. We found that CBD-binary interaction can reproduce the observed eccentricity distribution of SBSG binaries, provided that: (1) their post-mass-transfer eccentricities range up to at least 0.05, (2) their CBDs have initial masses of at least $0.1$ $M_\odot$, and (3) accretion onto the SBSG star is highly inefficient to prevent refilling of its Roche lobe. Our model requires higher post-mass-transfer eccentricities than canonically predicted and more massive CBDs than currently observed. We speculate that there is a population of post-mass-transfer progenitor systems with CBDs massive enough to facilitate significant eccentricity pumping. Mass loss via the $L_2$ point during mass transfer needs investigation, as this could form the CBD and shorten the orbital period, necessary for many SBSG binaries assuming they formed stably. We hypothesise that the observed eccentricities are related to the amount of mass lost via $L_2$. Since many other post-interaction systems exhibit similar orbital properties, we speculate that they may all have interacted with CBDs shortly after mass transfer.

Constraining primordial non-Gaussianity (PNG) provides key insights into the physics of cosmic inflation and the initial conditions of the Universe, which remain central topics in cosmology. In this study, we use the cross-correlation between the integrated Sachs-Wolfe (ISW) effect and the thermal Sunyaev-Zeldovich (tSZ) effect derived from Ibitoye et al. (2024) to jointly constrain PNG and early-Universe energy injection, including the standard intergalactic medium contribution. For scale-independent PNG we obtain $f_{\rm NL} = -358^{+140}_{-114}$ ($68\%$~C.L.). For a scale-dependent model ($f_{\rm NL}=f_{\rm NL}^{0}(\ell/\ell_{0})^{n_{\rm NL}}$, with $\ell_{0}=200$), we find $f^{0}_{\rm NL} = -296^{+173}_{-157}$ and $n_{\rm NL} = 0.62^{+1.02}_{-0.64}$, both consistent with Gaussian initial conditions. We also constrain the early-Universe energy injection amplitude to be $α_{\rm inj} = -3.93^{+1.34}_{-0.99}$, with uncertainty reduced by a factor of $\sim\!2.6$ if Planck 2018 $f_{\rm NL}$ constraint is applied as a prior. Future surveys such as Simons Observatory and Euclid will tighten these constraints further. Complementary to conventional probes, this work provides the first ISW-tSZ constraint on exotic energy injection and enables precision tests of early-Universe physics while probing late-time gravitational potential and thermal energy perturbations.

Very-high-energy (VHE) $γ$-ray emission detected from the central molecular zone (CMZ) hints at diffusive propagation of cosmic rays (CRs) injected continuously near the Galactic center (GC). Using H.E.S.S. VHE $γ$-ray observations, we aim to construct a multi-component description of the region in order to derive the spatial and spectral distributions of CRs and discuss their potential origin. We rely on a spectro-morphological analysis, in which spectral and spatial parameters of different components are fit simultaneously, and on a three-dimensional description of the CMZ and CR distributions. The GC ridge emission is well reproduced with the assumed gas distribution model weighted by a $1/r^α$ CR density profile with $α= 1.10 \pm 0.05_{\rm{stat}} \pm 0.10_{\rm{syst}}$. We detect no significant spectral variations across the CMZ, which supports a continuous injection from the GC. We report a significant (> 3 $σ$) curvature in the GC ridge $γ$-ray spectrum, implying a parent proton break (or cutoff energy) of $E_b \sim 15-50$ TeV ($E_{\rm{cut}} \sim 60-160$ TeV). We also derive the best-fit spectral parameters of the other sources in the region and report a significant cutoff at $E \sim 5$ TeV in the spectrum of the pulsar wind nebula G0.9+0.1. Finally we constrain the position of the injection site to be close to the GC (ruling out the Arches and Quintuplet clusters as major contributors to the emission). We discuss possible origins for the GC ridge emission, potential mechanisms for causing the observed curvature, a possible contribution of the gas content to the emission of HESS J1745-290 and derive qualitative constraints on the line-of-sight positions of the clouds shaping the CMZ.

The rapid growth of large-scale astronomical surveys and advances in data-driven analysis techniques have transformed the study of late-stage stellar evolution. Modern facilities are producing large volumes of photometric, spectroscopic, and astrometric data, enabling systematic investigations of compact stellar populations across the Milky Way. Among the most important tracers of these advanced evolutionary phases are hot subdwarfs and white dwarfs: hot subdwarfs are core-helium-burning tracers of late, binary-driven stellar evolution, while white dwarfs represent the final evolutionary endpoint of low- and intermediate-mass stars. These compact objects provide important laboratories for studying stellar interiors, binary evolution, and the long-term fate of planetary systems. This paper explores how recent advances in machine learning are being applied to the detection, characterization, and, when combined with follow-up spectroscopy and modeling, the physical interpretation of hot subdwarfs and white dwarfs. By combining photometric, spectroscopic, and time-domain observations with these computational tools, it is now possible to efficiently discover rare objects, detect stellar variability, and probe the internal structure and evolutionary pathways of compact stars. Ultimately, these developments highlight the growing role of advanced algorithms in supporting the study of the final stages of stellar evolution, provided their outputs are validated against physical observables.

The interaction between massive black hole (MBH) binaries and circumbinary discs (CBDs) affects the spin orientations of merging binaries - a key observable for the future LISA mission. While gas accretion is known to align BH spins with the orbital angular momentum via the Bardeen-Petterson effect, the impact of AGN feedback on this process has remained largely unexplored. We present hydrodynamical simulations of an equal-mass MBH binary embedded in a CBD, using the GIZMO code with a subgrid model that self-consistently evolves BH mass, spin, and anisotropic AGN feedback. We explore different BH spin magnitudes and orientations to identify the configurations producing the strongest feedback effect on the disc structure and binary evolution. AGN winds substantially modify the CBD and minidisc structure, enlarging the central cavity and, after 20-25 binary orbits, destroying the minidiscs in all feedback simulations. Feedback-driven cavity excavation suppresses the gravitational torques driving orbital evolution, causing the binary to stall. AGN feedback dramatically affects MBH accretion, reducing the Eddington ratio by one to two orders of magnitude before ultimately suppressing it entirely. This strongly inhibits Bardeen-Petterson spin alignment, delaying it well beyond the feedback-free timescale. Extending one simulation to 70 binary orbits reveals a feedback-regulated duty cycle of alternating active and quiescent phases, with the binary spending most of its time in low-density, quiescent conditions that further suppress alignment. These results indicate that AGN feedback is an important, previously overlooked channel for preserving spin misalignment in MBH binaries prior to coalescence, with direct implications for interpreting LISA gravitational-wave observations.

Magnetically dominated Alfvénic turbulence creates an effective environment for particle acceleration. However, when a strong mean field is present, traditional mechanisms like mirror and curvature acceleration become inefficient at explaining non-thermal particle energy distributions. Based on numerical and phenomenological study, we propose that in such turbulence, particles are accelerated in charge-starved current sheets, corresponding to current velocities approaching the speed of light. The distributions of the electric currents, plasma density, fluctuations of electric charge, as well as the energy distributions of accelerated particles, approximately follow log-normal statistics. Non-thermal particle distributions thus arise from particle acceleration in these charge-starved current sheets rather than from conventional Fermi-type particle acceleration by turbulent eddies.

We present a first application of sparse-autoencoder-based mechanistic interpretability to particle physics. Studying a neutrino foundation model pretrained on IceCube data and fine-tuned for direction reconstruction, we identify a validated atlas of physical concepts in the model representation, using a strict validation protocol consisting of held-out tests, matched nuisance controls, and replication across independent dictionary trainings. Causal interventions show that the direction head barely draws on this atlas. Motivated by this underused information, we train an uncertainty head on the same event-level representation to predict the model's angular reconstruction error. Unlike the direction head, it depends causally on quality and brightness features from the atlas. At $20\%$ selection efficiency, this interpretable estimator improves the median angular resolution from $20.2^\circ$ to $3.2^\circ$. These results suggest that mechanistic interpretability can reveal learned latent physics encoded within a model's internal representation and help design downstream tasks that exploit it.

Calibrated torsion-balance spectra constrain deterministic and stochastic deviations from standard Newtonian gravity. Using one-sided spectra, we derive a calibrated angle-equivalent noise budget and finite-time matched-filter/Cramér-Rao bounds for known torque templates. For stochastic models, subtracting the calibrated standard noise budget (thermal, Newtonian, environmental, imprecision, backaction) from the observed angle spectrum yields a residual spectrum, convertible to an equivalent residual torque spectrum via calibrated torsional susceptibility. This bounds additional stationary stochastic torque noise. This frequency-resolved bound compresses to a single torque-diffusion coefficient, $D_τ$, only in the Markovian white-noise limit; non-Markovian or colored models require the full residual spectrum. Page--Geilker branch discrimination and Fedida-Kent mixture-equivalence tests address distinct physical questions, but upon projection onto torque templates, both reduce to the same statistical matched-filter discrimination problem. For a room-temperature Cavendish benchmark, resonant thermal angle ASD is $1.36\times10^{-4}\,\mathrm{rad}/\sqrt{\mathrm{Hz}}$, while measurement-added SQL is $3.25\times10^{-12}\,\mathrm{rad}/\sqrt{\mathrm{Hz}}$. For the Yan \emph{et al.} search, the reported $0.3\,μ\mathrm{rad}/\sqrt{\mathrm{Hz}}$ sensitivity at $2.5\,\mathrm{mHz}$ yields a conservative bound $D_τ\lesssim 2.4\times10^{-23}\,\mathrm{N^2\,m^2\,s}$, assuming white torque noise. These formulations provide an interface linking calibrated torsion-balance data, deterministic tests, and stochastic semiclassical-gravity searches, without asserting a direct test of the full relativistic semiclassical Einstein equation.

Recent results from DESI and other cosmological datasets have indicated a preference for dynamical dark energy, with a time-evolving equation of state (EOS), $w(z)$. Furthermore, analyses using the CPL parameterization give an EOS with a phantom crossing of the $w(z)=-1$ line. In a companion paper-I, we assumed the CPL parameterization and its generalization, and introduced the formalism of the optimal scale factor (or redshift), a quantity designed to simultaneously maximize the distance from the cosmological constant value of $-1$ and to minimize the uncertainty on the EOS, thereby maximizing the tension with the cosmological constant at that specific redshift for a given dataset combination. In this paper-II, we apply the optimal-redshift formalism to available baryon acoustic oscillation, Cosmic Microwave Background, and supernova dataset combinations, with a particular focus on the phantom-line crossing within CPL. Motivated by the relatively low significance of previous constraints on the EOS in the region below the phantom line, we calculate the optimal redshift for a variety of dataset combinations to identify those that best constrain departures from $w(z)=-1$ before and after the crossing. We find combinations and corresponding optimal redshifts for which $w(z)$ lies below the ``$-1$'' line with new significance levels reaching $3.01$--$3.22σ$ before the crossing point, and $3.30$--$3.55σ$ above ``$-1$" after the crossing. Our focus in this work is the application of a new framework that maximizes the significance of the phantom-crossing signal within CPL using currently available datasets. Determining whether this crossing is effective or intrinsic, and identifying the underlying microphysical models, constitute separate questions from the aim of the present work and remain important directions for future investigation, further motivated by our findings. Abridged.

We study the Laplace surface of eccentric orbits around a Kerr black hole with a companion star. The two relativistic effects (periapsis apsidal precession and Lense-Thirring precession) balance companion's tidal effect. By solving the secular equations, we find that the two branches of equilibrium solutions exist only in a narrow range of orbital inclinations of test particle, and that the stability exists when companion's obliquity approaches 90 degree. We then study the black-hole effects on Lidov-Kozai cycles. In addition to the black-hole suppression on cycle amplitude, we find that the cycle frequency is non-monotonic about distance from black hole and reaches its minimum in the transition between GR apsidal precession and companions's tidal precession. Finally we use this mechanism to well interpret the nearly isotropic orientation of S-cluster in the Galactic center.

This paper summarises our previous work on a fully $3$D Summation-by-Parts scheme, derived for a class of linear wave equations on hyperboloidal slices on a fixed Minkowski background. The scheme is derived in spherical polar coordinates, and allows having grid points at the origin and on the $z$-axis, despite coordinate singularities, and at infinity, by introducing compactification followed by rescaling, and is proved to be stable. Reducing it to the standard Cauchy problem, or to finite spacelike slices with an outer boundary, will follow a similarly. Second-order accurate finite-difference methods are used to implement this scheme numerically, but higher-order finite-difference or spectral methods could also be used. Kreiss-Oliger dissipation operators are generalized to curvilinear coordinates and are defined everywhere in the domain, including at the boundary points, such that they satisfy the dissipative property in the energy norms. We also propose new norm convergence tests that include all the grid points at all resolutions and produce more accurate results. Promising results are obtained, giving hope for application to fully nonlinear systems, like the Einstein Field Equations, and extracting the resulting gravitational waves free of systematic errors or gauge ambiguities.

Ultralight bosonic fields can form macroscopic clouds around rotating black holes, whereas the existence of analogous stationary fermionic condensates is strictly constrained by their intrinsic spin. Here we establish a complete geometric and kinematic framework to resolve the stationary bound states of massive Dirac fields on Kerr and Kerr-Newman backgrounds. By mapping the Kerr-Dirac system to a globally integrated sourced radial problem, we strictly isolate the boundary constraints dictated by horizon causality. The angular sector reveals a fundamental topological distinction: because the azimuthal quantum number is strictly half-integer, the regular boundary branches prevent the local field density from vanishing on the rotation axis. Consequently, rotating fermionic clouds inherently form globally filled, oblate geometries, in stark contrast to the hollow toroidal structures characteristic of scalar condensates. Crucially, our radial indicial analysis unveils the exact mathematical origin of the absence of synchronized Dirac hair. Precisely at the kinematic synchronization locus, the Frobenius matrix of the Dirac operator is non-defective and entirely devoid of logarithmic divergences. Without these singular branches to be selectively excised by boundary regularity, the physical burden of existence falls entirely onto the causal flux barrier, which strictly trivializes the zero-source amplitude. This synchronization veto demonstrates that a black hole's capacity to support macroscopic stationary fields is governed not merely by superradiant kinematics, but by the profound interplay between local horizon causality and quantum spin statistics.

We study pair creation for quantum fields of spin $0$, $1/2$, and $1$ in the presence of weak gravitational and gauge backgrounds. Using resummed heat-kernel techniques, we obtain closed expressions for the pair creation probability up to quadratic order in the ``generalized curvatures''. In addition, for gravitational backgrounds, we recast the pair production probability in terms of the matter distribution required for consistency with the Einstein equation. Finally, to illustrate the powerfulness of our methods, we analyze the effect of pair creation in a binary star system.

We study a localized spin-$1/2$ detector falling into a Schwarzschild--MOG black hole. The detector interacts with a neutral massless scalar field through a charge-preserving two-level transition, while its translational wave packet obeys the MOG-charged Dirac equation. Near the outer horizon, the separated radial system reduces to an inverse-square equation with index $Θ_{\rm D}=E_{\rm H}/(2\hbarκ_α)$. The gauge-invariant horizon energy satisfies $E_{\rm H}=m_ψU_{\rm H}>0$ for every future-directed crossing trajectory. We quantize the scalar field in a globally normalized Boulware scattering basis and retain both radial-flux branches of a mode that is outgoing at infinity. This treatment does not identify a local outgoing ansatz with a complete mode. A finite radial gate $χ_p(x)=(x/L_χ)^p e^{-x/L_χ}$ gives closed-form excitation and absorption probability densities that include the ingoing contribution and scattering-phase interference. Within the controlled near-horizon approximation, the full detailed-balance ratio factorizes into a branch-resolved outgoing ratio and a two-branch factor. Only the outgoing ratio approaches $\exp(-2πν/κ_α)$ when the near-horizon, adiabatic, high-gap, and branch-isolation conditions all hold. The leading switching correction is controlled by $(ν/κ_α)/(S_\pm L_χ)$, not by $(S_\pm L_χ)^{-1}$ alone. In a weak-MOG expansion, the local correction separates into surface-gravity, trajectory-prefactor, and finite-gate terms. The full response also contains a contribution from global scattering. This separation shows which terms follow from the local horizon geometry and which depend on the detector protocol and scalar propagation outside the horizon region.

Integrating realistic active galactic nucleus (AGN) feedback into cosmological hydrodynamical simulations remains a major challenge as resolving the spatial coupling of jet energy over cosmic timescales is computationally prohibitive. We present an analytic framework that predicts the radial and polar-angle dependence of feedback energy from lobed AGNs, enabling a physically motivated, computationally efficient prescription for jet feedback. Built upon the Radio AGN in Semi-analytic Environments (RAiSE) dynamical model, our approach tracks the post-AGN jet phase evolution of radio sources through two distinct mechanisms: buoyantly rising bubbles subject to ablation, and the gravitational collapse of swept-up gas in the shocked shell. We find that these two feedback mechanisms produce strongly contrasting spatial distributions across ten representative cluster environments. Buoyant bubbles preferentially deposit energy in steep density gradients near the core radius, while the collapsing shocked gas shell drives heating within flatter cluster cores. Weak, short-lived AGN outbursts ($Q<10^{37}$ W and $t_{\rm on}<10$ Myr) confine their energy deposition to the inner 10 kpc of the cluster; longer-lived events ($t_{\rm on} \geqslant 100$ Myr) deposit less than 1% of their injected energy within 30 kpc. We find that time-averaged heating rates across multiple outbursts are sufficient to offset radiative cooling in all but the highest density cluster cores (within 100 kpc) for duty cycles of $0.08< δ\leqslant 1$. This framework provides a scalable basis for modelling anisotropic, physically motivated jet feedback that can be incorporated into next-generation cosmological simulations.

Separating Galactic dust emission from cosmic infrared background (CIB) anisotropies is challenging because both the emission components have similar spectral properties. The primary objective of this work is to develop a component-separation algorithm to extract the Galactic dust emission from CIB anisotropies dominated sky regions using Wavelet Phase Harmonics statistics (WPH). We apply our algorithm to the \textit{Planck} $353\,\mathrm{GHz}$ frequency band over three sky regions spanning a range of neutral hydrogen ($\text{HI}$) column densities at high Galactic latitudes. In all three regions, we successfully recover the dust signal without significant leakage between the dust and CIB anisotropy components. We use the low signal-to-noise ($\mathrm{S/N}$) region to validate the component-separation algorithm and compare its performance with the standard template-fit approach that uses the linear dust-$\text{HI}$ correlation relation. For intermediate and high $\mathrm{S/N}$ regions, we separate the dust signal map from the contamination while preserving the statistical correlation with $\text{HI}$ column density map. Dust maps are used to analyze the relationship between dust and $\text{HI}$ emissions. We characterize the spatial variations in dust emission relative to the hydrogen column density as a function of the angular scale.

Alternative dark matter (DM) models have emerged to solve the challenges faced by the predictions of collisionless cold dark matter (CDM) on galactic scales ($\lesssim 1\Mpc$). However, disentangling alternative models from CDM is difficult on such small scales because of the degeneracy with baryonic physics. It is therefore necessary to use DM probes that are not affected by baryons, e.g.\ that stand on intermediate scales, larger than galactic while remaining smaller than the scale at which the models converge to CDM. For the first time, we distinguish self-interacting DM (SIDM) from CDM using the genus statistic, a metric that characterises the topology of the density field. We carried out the analysis on the Darkium DM-only cosmological simulations, using one CDM model and four SIDM models with cross-sections of various amplitudes and velocity dependencies. We computed the genus on selected 3-virial radius wide regions centred around halos, for few hundred halos with masses ranging from $10^{12}$ to $10^{14}$ M$_\odot/h$ over redshifts $z=0$ to $z=2$. We also explored a more observation-like configuration, where the DM density field is traced only from the halo distribution in thick 2D projection since in principle redshift errors hinder a 3D reconstruction of the density field. We find that the density field is systematically clumpier in CDM than in SIDM models up to $0.05~\mathrm{Mpc}/h$, for halos of masses larger than $10^{12}\Msol/h$ at $z=0$. These predictions show that the genus of the density field is sensitive to DM self-interactions, suggesting that topological analysis could provide a valuable probe for distinguishing SIDM from CDM in observed halo distributions.

Generalized horizon entropies are widely used as theoretical modifications of the Bekenstein-Hawking area law, but through the Wald construction they may also encode modifications of the underlying gravitational dynamics. We reconstruct metric $f(R)$ gravity from prescribed entropy-area relations and show that the procedure is intrinsically branch dependent through the required area-curvature map. On the maximally symmetric branch, where $A=48π/R$ exactly, the reconstruction reduces to a single quadrature and can be performed non-perturbatively. We obtain closed-form Lagrangians for several generalized entropies and show that an entropy term $a~S_{BH}^{q}$ generates a curvature term proportional to $R^{2-q}$. In particular, Kaniadakis entropy produces a $1/R$ correction, while logarithmic entropy generates an $R^2\ln R$ term. We further derive a branch-independent criterion, $\partial_{R}^{2} f=(ds/dR)d(S/s)/ds$, relating Dolgov-Kawasaki stability directly to the entropy functional, together with $m_{\rm sc}^2=S'(s)/(3f_{RR})$ on the maximally symmetric branch. Comparison with the fixed-mass Schwarzschild-de Sitter branch reveals different reconstructed Lagrangians and reversed stability properties. Finally, the weak-isolated-horizon boost charge reproduces the original generalized entropy. These results establish a direct non-perturbative link between generalized horizon thermodynamics and modified gravitational dynamics.

Cosmic filaments are the most striking feature of the hierarchical cosmic web. Yet, their own sub-structure remains unexplored, unlike the well-known, universal halo/sub-halo hierarchy. We use a hierarchical reconstruction scheme to identify sub-filaments within larger filaments. Examining differences in the radial phase-space profiles of parent and sub-filaments, we argue that the latter constitute a statistically distinct class of structures. Establishing the existence of a universal filament hierarchy must then account for these differences, with implications for cosmology and dark matter.

We investigate the cosmological evolution of a universe with an initially large negative vacuum energy, corresponding to an anti-de Sitter (AdS) space-time. Such a universe inevitably contracts and collapses into a singularity. To prevent this collapse, we propose a dynamical mechanism of vacuum energy compensation based on a scalar field non-minimally coupled to the curvature scalar. Numerical and analytical calculations demonstrate that the suggested mechanism completely compensates the gravitational impact of the vacuum energy, successfully driving the curvature to zero. As a result, the universe avoids the singularity and evolves into a power-law expansion, typical for a radiation-dominated cosmology.

We present a spatially resolved, multi-wavelength study of the massive, star-forming galaxy REBELS-25 at a redshift of $z=7.31$. We combine new high-resolution ALMA [O III]88$μ$m observations with resolution-matched [C II], dust continuum, and JWST/NIRSpec IFU spectroscopy, providing a $\lesssim1$ kpc view of the morphology, interstellar medium (ISM) conditions, and multi-tracer gas kinematics of one of the most mature galaxies known in the reionisation era. We find differing morphologies from the rest-frame UV to far-infrared (FIR) emission, with the UV and optical emission appearing clumpy and irregular, whereas the FIR emission is well-described by near-exponential disc profiles, with [C II] being the most extended. Comparing the resolved UV and FIR emission, we find that obscured star formation contributes $\sim55$-$98$% of the total star formation rate across the galaxy, demonstrating that dust obscuration strongly shapes the observed UV and optical morphology. Resolved ionisation-line diagnostics show no significant variation across the source at $\sim1$ kpc resolution, consistent with broadly similar ISM conditions among the identified regions. Kinematic modelling reveals that both the warm ionised gas, traced by [O III]88$μ$m, and the colder neutral gas, traced by [C II], share the same large-scale rotating structure and are dynamically cold, with ratios of ordered-to-random motion, $V/σ$, of $\sim11$ and 4.5, respectively, although we find evidence for non-circular motions that are not well-described by a simple rotating disc. Overall, these results further support a picture in which REBELS-25 hosts a dusty, chemically enriched, and dynamically cold ISM already in place at $z=7.31$.

Color-magnitude diagrams (CMDs) have been foundational across astrophysics, from galaxies and stars to brown dwarfs, and JWST now extends them to transiting exoplanets and self-luminous substellar objects at overlapping temperatures. We compile JWST dayside emission spectra for 13 transiting giant planets, 57 self-luminous objects, and the irradiated brown dwarf ZTF J0038+2030 B, spanning ~350-2600 K and log g = 2.5-5.5, plus ~2150 SPHEREx ultracool dwarfs, converted to synthetic photometry in 2MASS J/Ks and five NIRCam medium bands isolating H2O, CH4, CO2, and CO. Low gravity and inflated radii make transiting planets resemble young substellar objects, with shallower features and redder colors from high-altitude clouds that raise the photosphere. Transiting planets follow the L-dwarf sequence on the J versus J-K CMD, with WASP-80 b (T_eq~800 K) showing no T-dwarf-like blueward turn, suggesting a delayed or suppressed L/T transition in irradiated, low-gravity atmospheres. Methane onset is delayed from substellar to transiting-planet atmospheres, and cloudy radiative-convective models indicate that lower gravity and cloud back-warming shift atmospheres toward CO-dominated chemistry, suppressing photospheric CH4. The irradiated but old, high-gravity brown dwarf ZTF J0038+2030 B (T_day = 1049 K, log g = 5.4) shows a deep, field-T-dwarf-like dayside methane band, implicating gravity rather than irradiation as the dominant control. CO2-to-CO diagnostics place transiting and directly imaged planetary-mass companions at stronger relative CO2 absorption than field brown dwarfs, consistent with metallicity enhancement from planetesimal accretion. These CMD sequences provide a unified, model-testable map for self-luminous and irradiated atmospheres.

Measurements of Newton's gravitational constant remain limited by environmental and apparatus-dependent systematics whose treatment is often less explicit than that of instrumental noise. Among these, atmospheric density fluctuations generate unshieldable gravity gradients that couple directly to torsion-balance observables as atmospheric Newtonian noise. Here, we develop a GUM-consistent framework for propagating this contribution through the torque estimator into the uncertainty budget of torsion-balance measurements. We derive closed-form spatial transfer functions for two benchmark geometries: a two-mass dumbbell, which provides an upper-coupling reference, and a perfectly symmetric cross, which serves as an idealized rejection limit and exposes the trade-off between suppressing low-order environmental coupling and preserving signal response. We also separate stationary correlated inputs from non-stationary baseline drift, using the Ornstein--Uhlenbeck process only as a benchmark for the former. Atmospheric pressure benchmarks indicate that the resulting background contribution is below present reference uncertainty levels, but can become relevant as systematic floors approach the part-per-million regime. This framework provides a practical route for incorporating site-specific environmental gravity gradients into future torsion-balance uncertainty budgets.

We present the first atmospheric retrieval analysis of two compositional benchmark mid-L dwarfs -- SDSSJ141659.78+500626.4 and GJ 499 C -- using the \textit{Brewster} retrieval framework, where the wide benchmark nature of these systems provides independent constraints on age and bulk composition from their stellar primaries. These targets were observed with JWST using NIRSpec Prism and MIRI LRS, providing low-resolution ($R$ $\sim$ 100) spectra between 0.6--14.0 $\mathrmμ$m with high signal-to-noise ratios (SNR $\sim$100 -- 600). For SDSSJ141659.78+500626.4, the retrieved cloud combination of a high-altitude enstatite slab and low-altitude iron deck clouds matches phase-equilibrium predictions based on the primary star's Mg/Si ratio. We retrieve a super-solar C/O = 0.71$^{+0.01}_{-0.01}$ and slightly metal-rich [M/H] = 0.22$^{+0.03}_{-0.03}$. This C/O ratio can only be reconciled with the value inferred for the primary if additional oxygen sequestration beyond the retrieved cloud mass is present, or if there are uncertainties in the adopted opacities or other model deficiencies. The inferred [C/H] and [O/H] are 0.31$\pm$0.03 and 0.19$\pm$0.03, respectively, which are consistent within the relatively large uncertainties of the host star abundances. For GJ 499 C, the retrieved silicon-monoxide and forsterite slab clouds are difficult to explain with simple phase-equilibrium assumptions, yielding Mg/Si $\sim$ 1.9. We estimate C/O = 0.69$^{+0.02}_{-0.02}$ and [M/H] = 0.13$^{+0.04}_{-0.06}$. For both objects, the inferred radii of 0.85$^{+0.01}_{-0.01}$ $R_{\mathrm{Jup}}$ and 1.00$^{+0.02}_{-0.02}$ $R_{\mathrm{Jup}}$ and masses of 73.7$^{+4.9}_{-9.2}$ $M_{\mathrm{Jup}}$ and 68.0$^{+8.5}_{-12.7}$ $M_{\mathrm{Jup}}$ are consistent with evolutionary models and system ages, highlighting the plausibility of our results.

Ideal attached points are a core concept in general relativity for pseudo-Riemannian manifolds, and whether the spacetime can be extended with certain properties is a central consideration in their choice. This paper establishes a sufficient condition for the separability between singularities and points at infinity for any maximally extended pseudo-Riemannian manifold. We focus on the incomplete geodesics of $(\mathcal{M},g)$, and produce an envelopment $(\mathcal{M},g,\hat{\mathcal{M}})$ of the spacetime such that an incomplete geodesic $γ:[0,1) \rightarrow \mathcal{M}$ has an endpoint $q$ in $\hat{\mathcal{M}}$. If there is no pair of geodesics approaching $q$ which is intertwined, then $q$ is a singularity. Additionally, $q$ will not be approached by any geodesic with infinite affine parameter, and therefore cannot cover a point at infinity, thereby rendering it a {\it pure singularity} in the abstract boundary framework. We apply the Endpoint Theorem to the maximal g-boundary introduced by Graf and Beld-Serrano in arXiv:2307.11034, and also provide a result on the separability between directional singularities and pure singularities. This analysis is then applied to the Schwarzschild spacetime.

Following the work by Rowan et al., I found that a large fraction of systems presented as triple/quadruple stars are in fact only blends. After careful inspection of 225 candidate systems from Rowan et al., I found that one-third of them are, in fact, only blended signals of two different eclipsing binaries, well separated from each other on the sky. Their typical angular separation is dozens of arcsec, reaching up to more than 100 arcsec for some targets. This is probably due to relatively large TESS pixels and insufficient cross-checking of all available catalogues and photometric data. I present a list of 76 confirmed blends with their correct identification and respective periods. Such a high fraction (33.8 per cent) of reported false-positive systems should be taken into account in future studies, when reporting to new discoveries of doubly eclipsing candidates.

We prove mode stability for the massless scalar wave equation on Kerr-de Sitter black hole spacetimes in the full subextremal range. In combination with recent work by Petersen-Vasy, this proves, unconditionally, that sufficiently regular solutions of the scalar wave equation decay exponentially fast to constants.

I present a novel physics result generated entirely autonomously by ChatGPT 5.6 Sol. The Lyth bound relates an observable primordial tensor amplitude to a lower limit on the field excursion during single-field slow-roll inflation. We show that non-attractor evolution obeys a complementary upper bound. For a canonically normalized scalar field, the nonconstant superhorizon curvature mode is anti-damped whenever the second Hubble-flow parameter satisfies $ε_2\equiv d\lnε/dN<-3$. The same condition requires the inflaton kinetic energy to decrease sufficiently rapidly that the field-space distance traversed during a non-attractor interval obeys $Δφ_{\rm NA} / M_{\text{P}} < \left(2\sqrt{2ε_{\rm in}}/3\right) \left(1-e^{-3ΔN/2}\right) < \left(2\sqrt{2ε_{\rm in}}/3\right)$.The result is independent of the potential and does not require the slow-roll approximation. If $ε_2=-p<-3$ is constant, the stronger bound $Δφ/M_{\text{P}}<2\sqrt{2ε_{\rm in}}/p$ is saturated asymptotically. In ultra-slow-roll inflation, $p=6$, giving $Δφ<\sqrt{2ε_{\rm in}}M_{\text{P}}/3$. We derive an exact relation between field excursion and amplification of the velocity of the nonconstant curvature mode, and give the corresponding scalar-power relation in the quasi-de Sitter limit. In contrast with the usual Lyth relation, arbitrarily large non-attractor amplification approaches a finite field distance. This provides a model-independent field-range constraint on canonical single-field mechanisms for amplifying primordial fluctuations.

This paper re-examines the Dark Matter (DM) problem through the lens of physical principles. We first develop a functionalist account and taxonomy of principles. We propose to define principles in terms of their intended functions or purposes. Their argumentative force boils down to context-sensitive and often tentative reasons for believing them adequate for those purposes. In research contexts in which novel theories or models are sought which push the boundaries of knowledge into new domains, reliance on well-motivated principles as principal building blocks is a historically widespread, natural, and methodologically prudent research strategy---what we'll dub "principled inquiry". In a second step, we apply this methodological machinery to the DM problem. Through detailed analyses of four mainstream DM approaches---supersymmetric WIMPs, axions, sterile neutrinos, and primordial black holes---we substantiate four claims. (C1) The DM paradigm is formed by the framework of possibilities, circumscribed by a shared cluster of regulative and constitutive principles of gravitational and non-gravitational physics. (C2) Besides those common principles, the four DM models also depart from other principles of orthodox physics in distinct ways. (C3) They do so to different degrees---displaying different forms and extents of "minimal mutilation" with respect to some of the principles of established non-gravitational physics. (C4) The guidelines of principled inquiry clarify the sense in which the DM problem constitutes an ever-more disconcerting crisis: worries are growing that the principles on which DM researchers have routinely and rationally relied may have run out of heuristic steam. Pressure is mounting to "leave no stone unturned" (Bertone and Tait 2018): scientists ought to increasingly explore ideas that stray more radically from the cautious explorations of principled inquiry.

The purpose of the paper is to place Whiting's classical growing mode stability argument, extended to real frequencies by Shlapentokh-Rothman for the scalar wave equation and by Andersson, Ma, Paganini and Whiting in general, in the framework of classical PDE theory. The key steps are: a description of the dual or adjoint modes, a singular phase space pairing argument which is technically executed via the Fourier transform, followed by a standard unique continuation result. One part of our description of the dual modes connects them directly to the standard mode solutions which are smooth over the event horizon. In the zero spin case, there is a geometric interpretation of this: quasinormal modes (for non-zero real frequencies) which are smooth across the future event horizon can be extended as distributional QNM solutions by 0 through the past event horizon. We also describe the behavior of mode solutions at the bifurcate sphere.

We investigate the problem of confinement of massive ghost, which violates the unitarity of the physical S-matrix, in quadratic gravity on the basis of a manifestly covariant and local canonical operator formalism. First, we reconsider the manifestly covariant quantization of quadratic gravity in the de Donder gauge (the harmonic gauge) from the viewpoint of dipole fields. Next, we also reconsider a possible mechanism of confinement of the massive ghost and derive an effective Lagrangian for asymptotic fields of a BRST quartet where the asymptotic field corresponding to the massive ghost is found to obey a dipole field equation as in the Froissart model, which is a characteristic feature in our formalism. To understand quantum aspects of our theory, we perform a manifestly covariant quantization of the effective Lagrangian in two different ways based on the three-dimensional Fourier transform and the four-dimensional Fourier transform, and derive the same result that the quantum Fock space is spanned by multipole states.

Elemental and isotopic abundances are key tracers of planet formation, stellar evolution, and Galactic chemical evolution. Very low-mass stars are particularly interesting in this regard, because unlike more massive or evolved stars their photospheric abundances retain the star's natal composition. Cool dwarf spectra have historically been challenging to use for measurements of chemical abundances because of the blending of molecular and atomic features. However, recent advances in molecular line lists, atmospheric models, fitting techniques and IR spectrographs have enabled the successful measurement of elemental and isotopic ratios in a few dozen very low-mass stars. Here, we present near-infrared high-resolution spectroscopy of TRAPPIST-1 covering the fundamental and overtone bands of carbon monoxide and its prominent isotopologues. From the joint analysis of the $K$-band (CFHT/SPIRou) and $M$-band (Keck/NIRSPEC) spectra, we derive the first stellar C/O ratio and the first carbon and oxygen isotope ratios for this star. We obtain a metallicity of $[\mathrm{M/H}] = 0.00 \pm 0.06$, a C/O ratio of $0.60 \pm 0.02$, $^{12}\mathrm{C}/^{13}\mathrm{C} = 154{}^{+17}_{-16}$, and $^{16}\mathrm{O}/^{18}\mathrm{O} = 490{}^{+78}_{-64}$. TRAPPIST-1 has generally solar-like elemental abundances, with a $^{12}\mathrm{C}/^{13}\mathrm{C}$ ratio that is higher than the solar value and may be modestly elevated relative to some nearby cool dwarfs at similar metallicity. While C/O is most tightly constrained by the $K$-band, the isotopic detections are driven by the $M$-band data.