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163c886c8d24e035dd2e6cdcdd20eb84f6b0c5127934ea786c591f56da95a212
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2026-01-13T00:00:00-05:00
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Timing Gamma-ray Pulsars using Gibbs Sampling
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arXiv:2601.07592v1 Announce Type: new Abstract: Timing analyses of gamma-ray pulsars in the Fermi Large Area Telescope data set can provide sensitive probes of many astrophysical processes, including timing noise in young pulsars, orbital period variations in redback binaries, and the stochastic gravitational wave background (GWB). These goals can require careful accounting of stochastic noise processes, but existing methods developed to achieve this in radio pulsar timing analyses cannot be immediately applied to the discrete gamma-ray arrival time data. To address this, we have developed a new method for timing gamma-ray pulsars, in which the timing model fit is transformed into a weighted least squares problem by randomly assigning each photon to an individual Gaussian component of a template pulse profile. These random assignments are then numerically marginalised over through a Gibbs sampling scheme. This method allows for efficient estimation of timing and noise model parameters, while taking into account uncertainties in the pulse profile shape. We simulated Fermi-LAT data sets for gamma-ray pulsars with power-law timing noise processes, showing that this method provides robust estimates of timing noise parameters. We also describe a Gaussian-process model for orbital period variations in black-widow and redback binary systems that can be fit using this new timing method. We demonstrate this method on the black-widow binary millisecond pulsar B1957+20, where the orbital period varies significantly over the LAT data, but which provides one of the most stringent gamma-ray upper limits on the GWB.
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https://arxiv.org/abs/2601.07592
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Academic Papers
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7eff29e4ab5c9407ffc803ea03ddc716fe09175dbb746a59be1b79d009b3bd13
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2026-01-13T00:00:00-05:00
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Deep Search for Joint Sources of Gravitational Waves and High-Energy Neutrinos with IceCube During the Third Observing Run of LIGO and Virgo
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arXiv:2601.07595v1 Announce Type: new Abstract: The discovery of joint sources of high-energy neutrinos and gravitational waves has been a primary target for the LIGO, Virgo, KAGRA, and IceCube observatories. The joint detection of high-energy neutrinos and gravitational waves would provide insight into cosmic processes, from the dynamics of compact object mergers and stellar collapses to the mechanisms driving relativistic outflows. The joint detection of multiple cosmic messengers can also elevate the significance of the common observation even when some or all of the constituent messengers are sub-threshold, i.e. not significant enough to declare their detection individually. Using data from the LIGO, Virgo, and IceCube observatories, including sub-threshold events, we searched for common sources of gravitational waves and high-energy neutrinos during the third observing run of Advanced LIGO and Advanced Virgo detectors. Our search did not identify significant joint sources. We derive constraints on the rate densities of joint sources. Our results constrain the isotropic neutrino emission from gravitational-wave sources for very high values of the total energy emitted in neutrinos (> $10^{52} - 10^{54}$ erg).
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https://arxiv.org/abs/2601.07595
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Academic Papers
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b12cbb1f1b2f031367dfedc64c862035e5b2629ac1fa82fc93118f1898090576
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2026-01-13T00:00:00-05:00
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Galaxy Mergers in UNIONS -- II: Predicting Timescales in the Post-Merger Regime
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arXiv:2601.07604v1 Announce Type: new Abstract: Galaxy mergers are critical events that influence galaxy evolution by driving processes such as enhanced star formation, quenching, and active galactic nucleus (AGN) activity. However, constraining the timescales over which these processes occur in the post-merger phase has remained a significant challenge. This study extends the MUlti-Model Merger Identifier (\textsc{Mummi}) framework to predict post-merger timescales ($T_{PM}$) for galaxies, leveraging machine learning models trained on realism-enhanced mock observations derived from the IllustrisTNG simulations. By classifying post-merger galaxies into four temporal bins spanning 0 to 1.76 Gyr after coalescence, \textsc{Mummi} achieves time classification accuracies exceeding 70 per cent. We apply this framework to the Ultraviolet Near Infrared Optical Northern Survey (UNIONS), yielding a catalog of 8,716 post-merger galaxies with $T_{PM}$ predictions and stellar masses $\log(M_*/M_\odot) \geq 10$ at redshifts 0.03 < z < 0.3. These results provide a robust methodology to connect galaxy interaction timescales with physical processes, enabling detailed studies of galaxy evolution in the post-merger regime.
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https://arxiv.org/abs/2601.07604
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Academic Papers
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0c53dc68f92b218aee2fd87258f96715fffb4f497ad3373baa393b5fc2388256
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2026-01-13T00:00:00-05:00
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Impact of Nuclear Reaction Rates on Calcium Production in Population III Stars: A Global Analysis
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arXiv:2601.07623v1 Announce Type: new Abstract: We investigate the sensitivity of calcium production to nuclear reaction rates of a 40 solar-mass Population III star using 1D multi-zone stellar models. A comprehensive nuclear reaction network was constructed, and all $(p,\gamma)$ and $(p,\alpha)$ reaction rates were individually varied by a factor of 10 up and down, identifying 13 preliminary key reactions for calcium production. To propagate the reaction rate uncertainties on calcium production, two sets of Monte Carlo simulations were performed for these key reactions: one adopting STARLIB reaction rates and the other incorporating updated rates from recent experimental data and evaluations. Our results show that Monte Carlo simulations using the updated rates show good agreement with the observed calcium abundance of the extremely iron-poor star SMSS J031300.36-670839.3 within the 68% confidence interval predicted by the models. In contrast, the observed calcium abundance lies marginally outside the 68% C.I. when using the STARLIB rates. Spearman rank-order correlation analysis and SHAP values show that the $(p,\gamma)$ and $(p,\alpha)$ reactions of F18 and F19 exhibit strong coupled effects on calcium production. These reaction-rate uncertainties need to be reduced to constrain the stellar model predictions. Our study provides insights for future nuclear physics experiments aimed at reducing reaction rate uncertainties in the nucleosynthesis of Population III Stars. Additionally, comparisons between 20 solar-mass and 40 solar-mass Population III stellar models confirm that the latter, with updated reaction rates, is more capable of reproducing the observed Ca abundance and [Ca/Mg] ratio.
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https://arxiv.org/abs/2601.07623
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Academic Papers
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6663c503b66728ff8e2b02deb691d68635ad9bca1b354ac836dbde8da58c8ec6
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2026-01-13T00:00:00-05:00
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CHEX-MATE: Relationship between X-ray and millimetre inferences of galaxy cluster temperature profiles
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arXiv:2601.07653v1 Announce Type: new Abstract: Thermodynamic profiles from X-ray and millimetre observations of galaxy clusters are often compared under the simplifying assumptions of smooth, spherically symmetric intracluster medium. These approximations lead to expected discrepancies in the inferred profiles, which can provide insights about the cluster structure or cosmology. Motivated by this, we present a joint XMM-\textit{Newton} and \textit{Planck} analysis of 116 CHEX-MATE clusters to measure $\eta_T = T_X/T_{SZ,X}$, the ratio between spectroscopic X-ray temperatures and a temperature proxy derived from Sunyaev-Zel'dovich (SZ) pressures and X-ray densities. We considered relativistic corrections to the thermal SZ signal and implemented X-ray absorption by Galactic molecular hydrogen. The $\eta_T$ distribution has a mean of $1.01 \pm 0.03$, with average changes of $8.1\%$ and $2.7\%$ when relativistic corrections and molecular hydrogen absorption are not included, respectively. The $\eta_T$ distribution is positively skewed, with the scatter mostly affected by cluster morphology: relaxed clusters are closer to unity and less scattered than mixed and disturbed systems. We find little or no correlation with redshift, mass, or temperature.
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https://arxiv.org/abs/2601.07653
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Academic Papers
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d29335dab1357609dc9a2392f60d932443308e0e9bb6520cd203c834110ddc0e
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2026-01-13T00:00:00-05:00
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Tachyonic gravitational dark matter production after inflation
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arXiv:2601.07670v1 Announce Type: new Abstract: We propose a novel gravitational mechanism for the non-thermal production of dark matter driven by curvature-induced tachyonic instabilities after inflation. Departing from the commonly studied non-minimal couplings to gravity, our framework considers a real spectator scalar field coupled quadratically to spacetime curvature invariants. We show that the rapid reorganization of spacetime curvature at the end of inflation can dynamically render the dark matter field tachyonic, triggering a short-lived phase of spontaneous symmetry breaking and explosive particle production. As a concrete and theoretically controlled example, we focus on the Gauss-Bonnet topological invariant. By combining analytical estimates with fully non-linear $3+1$ classical lattice simulations, we track the out-of-equilibrium evolution of the system and compute the resulting dark matter abundance. We find that this purely gravitational mechanism can robustly reproduce the observed dark matter relic density over a wide range of masses and inflationary scales, providing also a simple fitting function that enables a lattice-independent application of our results.
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https://arxiv.org/abs/2601.07670
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Academic Papers
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40864e1324d2523dc66d26562e8082e4f5e96fd6abd09c863a0fc9813f13a4ca
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2026-01-13T00:00:00-05:00
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Brightest GRB flare observed in GRB 221009A: bridge the last gap between flare and prompt emission in GRB
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arXiv:2601.07688v1 Announce Type: new Abstract: Flares are usually observed during the afterglow phase of Gamma-Ray Bursts (GRBs) in soft X-ray, optical and radio bands, but rarely in gamma-ray band. Despite the extraordinary brightness, GECAM-C has accurately measured both the bright prompt emission and flare emission of GRB 221009A without instrumental effects, offering a good opportunity to study the relation between them. In this work, we present a comprehensive analysis of flare emission of GRB 221009A, which is composed of a series of flares. Among them, we identify an exceptionally bright flare with a record-breaking isotropic energy $E_{\rm iso} = 1.82 \times 10^{53}$ erg of GRB flares. It exhibits the highest peak energy ever detected in GRB flares, $E_{\rm peak} \sim 300$ keV, making it a genuine gamma-ray flare. It also shows rapid rise and decay timescales, significantly shorter than those of typical X-ray flares observed in soft X-ray or optical band, but comparable to those observed in prompt emissions. Despite these exceptional properties, the flare shares several common properties with typical GRB flares. We note that this is the first observation of a GRB flare in the keV-MeV band with sufficiently high temporal resolution and high statistics, which bridges the last gap between prompt emission and flare.
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https://arxiv.org/abs/2601.07688
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Academic Papers
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0cd9a3bb020f4e74ed5c3e3e80b5b1ce9562e392ac295d88a1d06e75e2c4304d
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2026-01-13T00:00:00-05:00
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Brightness Characterization and Modeling for Amazon Leo Satellites
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arXiv:2601.07708v1 Announce Type: new Abstract: The mean apparent magnitude of Amazon Leo satellites is 6.28 based on 1,938 observations. For spacecraft in their operational mode, 92% exceeded the brightness limit recommended by the IAU for interference with research, while 25% distract from aesthetic appreciation of the night sky. The reflective characteristics are similar to Version 1 Starlink spacecraft.
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https://arxiv.org/abs/2601.07708
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Academic Papers
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8847f77ca060c478d3f4e2fdf850b00a843d8cc3a20a4864f74eb8f1541c6e48
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2026-01-13T00:00:00-05:00
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Induced gravitational waves - beyond linear cosmological perturbation theory
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arXiv:2601.07716v1 Announce Type: new Abstract: This thesis focuses on gravitational waves (GWs) that arise beyond linear order in cosmological perturbation theory. In recent years, scalar-induced GWs have attracted significant attention because they may serve as the observational signature of primordial black holes (PBHs) formed in the early universe. The formation of PBHs requires large density perturbations, which can naturally emerge in some models of inflation. When these large density fluctuations couple, they act as a source for scalar-induced GWs at second order. In this work, we extend the existing formalism by including linear tensor fluctuations as an additional source term. This gives rise to two new classes of second-order GWs: those sourced by scalar-tensor couplings (scalar-tensor induced GWs) and those quadratic in tensor modes (tensor-tensor induced GWs). We find that the scalar-tensor contribution becomes significant if first-order tensor modes are enhanced, whilst the tensor-tensor contribution remains subdominant. Moreover, we demonstrate that the spectrum of scalar-tensor induced GWs exhibits an unphysical enhancement in the UV limit when the primordial scalar power spectrum is insufficiently peaked. To investigate whether this can be resolved, we study third-order induced GWs and their correlation with primordial GWs. We find that this new contribution suppresses the overall signal but does not cancel the unphysical enhancement. Possible explanations for this behaviour are discussed and left for future work. Finally, we explore the effect of primordial scalar non-Gaussianity on the spectrum of scalar-tensor induced GWs, building on previous results showing its impact on scalar-induced GWs.
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https://arxiv.org/abs/2601.07716
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Academic Papers
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4a804a10ad4d8a6405e2374671ad1f9d54a489757ce5fc3d8eb1824776335b2e
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2026-01-13T00:00:00-05:00
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A COLIBRI Photometric Study of SN 2025bvm: A Normal, Slowly Declining Type Ia Supernova
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arXiv:2601.07745v1 Announce Type: new Abstract: We present 121 days of multi-band (\Bband, \gband, \rband, \iband) optical photometry of the Type Ia supernova SN 2025bvm, obtained with the COLIBRI telescope at OAN-SPM. The light curves show a photometric decline of $\Delta m_{15}(B) = 0.867 \pm 0.051$~mag, characteristic of a slow-declining Type Ia supernova. After correcting for host galaxy extinction ($E(B-V)_{host} = 0.308 \pm 0.030$~mag) and adopting a distance of 70~Mpc, we derive a peak absolute magnitude of $M_B = -19.13 \pm 0.40$~mag. This luminosity is fully consistent with its slow decline rate, placing SN 2025bvm within the population of normal Type Ia supernovae. We conclude that SN 2025bvm is a normal Type Ia supernova, whose photometric properties, such as a slow late-time decline and a prominent \iband-band secondary maximum, suggest an explosion that resulted in a particularly massive ejecta.
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https://arxiv.org/abs/2601.07745
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Academic Papers
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9a3d375463910b8855b3efce397d7d49ea047b8d3b80ec18ffdec01b5f4b17a2
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2026-01-13T00:00:00-05:00
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Core Scouring Dynamics and Gravitational Wave Consequences: Constraints on Supermassive Black Hole Binary Hardening
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arXiv:2601.07762v1 Announce Type: new Abstract: In this paper we perform a multi-messenger investigation of the efficiency of stellar scattering in tightening supermassive black hole binaries by jointly comparing models to the observed galaxy stellar core population and to results of nanohertz gravitational wave observations. Our model uses merger trees from the IllustrisTNG cosmological suite of simulations to predict stellar mass deficits in core galaxies. We take into account dynamical friction, stellar scattering, and gravitational wave emission and compare to the observed relation between core mass deficit and galaxy stellar mass. We find that to match observations, binary hardening in the stellar scattering regime must be about 1.6 times faster than N-body experiments suggest. Most importantly we find that, even assuming a full loss-cone, hardening by stellar scattering alone is insufficient to explain the low frequency turnover seen in the gravitational wave background. This strongly suggests that gas-dynamics play an important role in hardening and provides a reason to be optimistic about electromagnetically visible binary AGN.
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https://arxiv.org/abs/2601.07762
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Academic Papers
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737d110842709c9b8db4d0e4aa4a74c99a7ad0aff8d7980aae98501151b79aac
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2026-01-13T00:00:00-05:00
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Popcorn in the sky: Identifying primordial black holes in the gravitational-wave background
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arXiv:2601.07774v1 Announce Type: new Abstract: Primordial black holes (PBHs) are possible sources of a gravitational-wave background (GWB), detectable with the next observing runs of LIGO--Virgo--KAGRA. In case of a detection, it will be crucial to distinguish the possible sources of this GWB. One under-explored possibility is to exploit the duty cycle that quantifies the number of sources present in the time domain signal, which can be very different depending on the nature and population of the sources. We compute the duty cycle for a realistic population of PBH binaries, isolating the shot-noise, popcorn and continuous contributions to the GWB. We identify the dependence of the duty cycle on the signal frequency, duration and amplitude as a crucial metric for distinguishing PBHs from other sources in the GWB and constraining PBH models. Our work motivates the development of specific analysis tools to extract these observables, in order to unlock new cosmological insights with upcoming GW data.
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https://arxiv.org/abs/2601.07774
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Academic Papers
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81b0c42b55f766ff33b93a1a044fcf1ae103e6282674cbd38348cecbd2fc7aa7
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2026-01-13T00:00:00-05:00
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Euclid preparation. Testing analytic models of galaxy intrinsic alignments in the Euclid Flagship simulation
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arXiv:2601.07784v1 Announce Type: new Abstract: We model intrinsic alignments (IA) in Euclid's Flagship simulation to investigate its impact on Euclid's weak lensing signal. Our IA implementation in the Flagship simulation takes into account photometric properties of galaxies as well as their dark matter host halos. We compare simulations against theory predictions, determining the parameters of two of the most widely used IA models: the Non Linear Alignment (NLA) and the Tidal Alignment and Tidal Torquing (TATT) models. We measure the amplitude of the simulated IA signal as a function of galaxy magnitude and colour in the redshift range $0.1<2.1$. We find that both NLA and TATT can accurately describe the IA signal in the simulation down to scales of $6$-$7 \,h^{-1}\,$Mpc. We measure alignment amplitudes for red galaxies comparable to those of the observations, with samples not used in the calibration procedure. For blue galaxies, our constraints are consistent with zero alignments in our first redshift bin $0.1 < z < 0.3$, but we detect a non-negligible signal at higher redshift, which is, however, consistent with the upper limits set by observational constraints. Additionally, several hydrodynamical simulations predict alignment for spiral galaxies, in agreement with our findings. Finally, the evolution of alignment with redshift is realistic and comparable to that determined in the observations. However, we find that the commonly adopted redshift power-law for IA fails to reproduce the simulation alignments above $z=1.1$. A significantly better agreement is obtained when a luminosity dependence is included, capturing the intrinsic luminosity evolution with redshift in magnitude-limited surveys. We conclude that the Flagship IA simulation is a useful tool for translating current IA constraints into predictions for IA contamination of Euclid-like samples.
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https://arxiv.org/abs/2601.07784
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Academic Papers
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700e71e37f938a6be475ea52ba0ee5a4931d10895b1ef4331a2bbabe6cfe069f
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2026-01-13T00:00:00-05:00
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Euclid preparation. Calibrated intrinsic galaxy alignments in the Euclid Flagship simulation
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arXiv:2601.07785v1 Announce Type: new Abstract: Intrinsic alignments of galaxies are potentially a major contaminant of cosmological analyses of weak gravitational lensing. We construct a semi-analytic model of galaxy ellipticities and alignments in the \Euclid Flagship simulation to predict this contamination in Euclid's weak lensing observations. Galaxy shapes and orientations are determined by the corresponding properties of the host haloes in the underlying $N$-body simulation, as well as the relative positions of galaxies within their halo. Alignment strengths are moderated via stochastic misalignments, separately for central and satellite galaxies and conditional on the galaxy's redshift, luminosity, and rest-frame colour. The resulting model is calibrated against galaxy ellipticity statistics from the COSMOS Survey, selected alignment measurements based on Sloan Digital Sky Survey samples, and galaxy orientations extracted from the Horizon-AGN hydrodynamic simulation at redshift $z=1$. The best-fit model has a total of 12 alignment parameters and generally reproduces the calibration data sets well within the $1\sigma$ statistical uncertainties of the observations and the \flagship simulation, with notable exceptions for the most luminous sub-samples on small physical scales. The statistical power of the calibration data and the volume of the single \flagship realisation are still too small to provide informative prior ranges for intrinsic alignment amplitudes in relevant galaxy samples. As a first application, we predict that \Euclid end-of-mission tomographic weak gravitational lensing two-point statistics are modified by up to order $10\,\%$ due to intrinsic alignments.
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https://arxiv.org/abs/2601.07785
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Academic Papers
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a7feda51a383f18ce932b86c3a0b3ea864c62b21cce5ffff4d53026b02c06293
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2026-01-13T00:00:00-05:00
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Testing subhalo abundance matching with galaxy kinematics
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arXiv:2601.07799v1 Announce Type: new Abstract: The rotation velocities of disc galaxies trace dark matter halo structure, providing direct constraints on the galaxy--halo connection. We construct a Bayesian forward model to connect the dark matter halo population predicted by $\Lambda$CDM with an observed sample of disc galaxies (SPARC) through their maximum rotation velocities. Our approach combines a subhalo abundance matching scheme (accounting for assembly bias) with a parameterised halo response to galaxy formation. When assuming no correlation between selection in the SPARC survey and halo properties, reproducing the observed velocities requires strong halo expansion, low abundance matching scatter ($<0.15$ dex at $1\sigma$) and a halo proxy that strongly suppresses the stellar masses in satellite haloes. This is in clear tension with independent clustering constraints. Allowing for SPARC-like galaxies to preferentially populate low $\Vmax$ haloes at fixed virial mass greatly improves the goodness-of-fit and resolves these tensions: the preferred halo response shifts to mild contraction, the abundance matching scatter increases to $\sint = 0.19^{+0.13}_{-0.11}$ dex and the proxy becomes consistent with clustering. However, the inferred selection threshold is extreme, implying that SPARC galaxies occupy the lowest ${\sim}16$ per cent of the $\Vmaxhalo$ distribution at fixed $\Mvir$. Moreover, even with selection, the inferred scatter remains in statistical disagreement with the low-mass clustering constraints, which are most representative of the SPARC galaxies in our sample. Our analysis highlights the advantage of augmenting clustering-based constraints on the galaxy--halo connection with kinematics and suggests a possible tension using current data.
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https://arxiv.org/abs/2601.07799
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Academic Papers
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9827e054a4d63fd2a1a26cb2d48e5b50179e41b6e34db217988fa0dbcd0ed65a
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2026-01-13T00:00:00-05:00
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Cosmoglobe DR2. V. Spatial correlations between thermal dust and ionized carbon emission in Planck HFI and COBE-DIRBE
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arXiv:2601.07818v1 Announce Type: new Abstract: We fit five tracers of thermal dust emission to ten Planck HFI and COBE-DIRBE frequency maps between 353 GHz and 25 THz, aiming to map the relative importance of each physical host environment as a function of frequency and position on the sky. Four of these correspond to classic thermal dust tracers, namely H i (HI4PI), CO (Dame et al. 2001a), H{\alpha} (WHAM, Haffner et al. (2003a, 2016)), and dust extinction (Gaia; Edenhofer et al. 2024), while the fifth is ionized carbon (C ii) emission as observed by COBE- FIRAS. We jointly fit these five templates to each frequency channel through standard multi-variate linear regression. At frequencies higher than 1 THz, we find that the dominant tracer is in fact C ii, and above 10 THz this component accounts for almost the entire fitted signal; at frequencies below 1 THz, its importance is second only to H i. We further find that all five components are well described by a modified blackbody spectral energy density (SED) up to some component-dependent maximum frequency ranging between 1 and 5 THz. In this interpretation, the C ii-correlated component is the hottest among all five, with an effective temperature of about 25 K. The H{\alpha} component has a temperature of 18 K, and, unlike the other four, is observed in absorption rather than emission. Despite the simplicity of this model, which relies only on external templates coupled to spatially isotropic SEDs, we find that it captures 98 % of the full signal root mean squared (RMS) below 1 THz. This high efficiency suggests that spatial variations in the thermal dust SED, as for instance reported by Planck and other experiments, may be more economically modelled on large angular scales in terms of a spatial mixing of individually isotropic physical components.
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https://arxiv.org/abs/2601.07818
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Academic Papers
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79786448e1c9e3062a02e98fe426505f0d15685bf3bfa4bc48eddb69553ebe28
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2026-01-13T00:00:00-05:00
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Cosmoglobe DR2. VII. Towards a concordance model of large-scale thermal dust emission for microwave and infrared frequencies
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arXiv:2601.07822v1 Announce Type: new Abstract: We fit a four-component thermal dust model to COBE-DIRBE data between 3.5 and 240 micron within the global Bayesian end-to- end Cosmoglobe DR2 reanalysis. Following a companion analysis of Planck HFI, the four components of this model correspond to "hot dust", "cold dust", "nearby dust", and "Halpha correlated dust", respectively, and each component is modelled in terms of a fixed spatial template and a spatially isotropic spectral energy density (SED) defined by an overall free amplitude for each DIRBE channel. Except for the cold dust amplitude, which is only robustly detected in the 240 micron channel, we measure statistically significant template amplitudes for all components in all DIRBE channels between 12 and 240 micron. In the 3.5 and 4.9 micron channels, only the hot component is detected, while the 1.25 and 2.2 micron channels are too dominated by starlight emission to allow robust dust detections. The total number of DIRBE-specific degrees of freedom in this model is 25. Despite this low dimensionality, the resulting total SED agrees well with recent astrodust predictions. At both low and high frequencies, more than 95 % of the frequency map variance is captured by the model, while at 60 and 100 micron about 70 % of the signal variance is successfully accounted for. The hot dust component, which in a companion paper has been found to correlate strongly with C ii emission, has the highest absolute amplitude in all DIRBE frequency channels; in particular, at 3.5 micron, which is known to be dominated by polycyclic aromatic hydrocarbon emission, this component accounts for at least 80 % of the total signal. This analysis represents an important step towards establishing a joint concordance model of thermal dust emission applicable to both the microwave and infrared regimes.
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https://arxiv.org/abs/2601.07822
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Academic Papers
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b1b7fa31b4c200bd57d63496f4366d914f8dcada9d0dd8304b21beb9ae8d6665
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2026-01-13T00:00:00-05:00
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Cosmoglobe DR2. IV. Modelling starlight in DIRBE with Gaia and WISE
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arXiv:2601.07831v1 Announce Type: new Abstract: We present a model of starlight emission in the Diffuse Infrared Background Explorer (DIRBE) data between 1.25 and 25$\,\mu$m based on \textit{Gaia} and WISE measurements. We include two classes of compact objects, namely bright stars with individual spectral energy densities (SEDs) measured by \textit{Gaia}, and a combined diffuse background of dim point source emission. Of the 424\ 829 bright sources that we fit, the number of stars with a flux density detected by WISE at Galactic latitudes $|b|>20^{\circ}$ at more than $5\,\sigma$ is 94\,680, for an average of 1.36~stars per DIRBE beam area. For each star, we adopt physical parameters ($T_{\mathrm{eff}}$, $\log g$, and [M/H]) from \textit{Gaia}; use these to identify a best-fit effective SED with the PHOENIX stellar model library; convolve with the respective DIRBE bandpass; and fit an overall free amplitude per star within the Bayesian end-to-end \texttt{Cosmoglobe} DR2 framework. The contributions from faint sources are accounted for by coadding all 710\ 825\ 587 WISE sources not included as bright stars, and fit one single overall amplitude per DIRBE band. Based on this model we find that total star emission accounts for 91\,\% of the observed flux density at 2.2\,$\mu$m; 54\,\% at 4.9$\,\mu$m; and 1\,\% at 25\,$\mu$m. As shown in companion papers, this new model is sufficiently accurate to support high-precision measurements of both the Cosmic Infrared Background monopole and zodiacal light emission in the three highest DIRBE frequencies.
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https://arxiv.org/abs/2601.07831
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Academic Papers
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9ebf328763c96531f925f2f2e740fb6fae1a57e7ba501d5dbdbe4f32140e398d
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2026-01-13T00:00:00-05:00
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Axion misalignment as a synchronization phenomenon
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arXiv:2601.07836v1 Announce Type: new Abstract: We propose a dynamical reinterpretation of axion misalignment as an emergent collective phenomenon. Drawing an explicit parallel between axion field dynamics and synchronization in coupled oscillator systems, we show that a macroscopic axion phase can arise dynamically from initially incoherent configurations through gradient-driven ordering in an expanding Universe. In this framework, the misalignment angle is not a fundamental initial condition but a collective variable that becomes well defined only once phase coherence develops. Using a simple lattice model, we illustrate how the collective phase is selected prior to the onset of axion oscillations, providing a dynamical basis for the standard misalignment picture. This perspective offers a new way of organizing axion initial-condition sensitivity, reframes anthropic small-angle arguments in terms of phase-ordering efficiency, and suggests a broader connection between fine-tuning and emergent collective dynamics in the early Universe.
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https://arxiv.org/abs/2601.07836
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Academic Papers
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31827bc40a589bb0ab250dd1dc0608a6777f59fe0f2836e27ae4e9956e0387ae
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2026-01-13T00:00:00-05:00
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Temperature-Dependent CPT Violation: Constraints from Big Bang Nucleosynthesis
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arXiv:2601.06259v1 Announce Type: cross Abstract: In this study, we explore temperature-dependent CPT violation during Big Bang Nucleosynthesis (BBN) through electron-positron mass asymmetries parametrized by $b_0(T) = \alpha T^2$. The $T^2$ scaling naturally evades stringent laboratory bounds at zero temperature while allowing for significant CPT violation at MeV scales in the early universe \cite{ParticleDataGroup:2024cfk}. Using a modified version of the BBN code \faGithub \href{https://github.com/vallima/PRyMordial}{\,\texttt{PRyMordial}} with dynamically-solved chemical potentials and appropriate finite-mass corrections, we constrain electron-positron mass differences from observed abundances of Helium-4, Deuterium, and $N_{\rm eff}$. We find that $\alpha$ must be greater than or approximately equal to $10^{-6}$ GeV$^{-1}$ for keV-scale mass differences at BBN. All three observables show no simultaneous $1\sigma$ overlap, though pairwise combinations allow for constrained regions of parameter space. We present three toy models demonstrating how $b_0(T) \propto T^2$ arises from field-theoretic mechanisms, including temperature-driven phase transitions. These results provide the most stringent constraints on early-universe CPT violation in this regime, probing parameter space inaccessible to laboratory experiments.
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https://arxiv.org/abs/2601.06259
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f1c74ffb2e870a58daffcfe6a9a8bfe3642e13a3cbd81d1e57db7633eef2639c
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2026-01-13T00:00:00-05:00
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Cosmological Dynamics on a Novel $f(Q)$ Gravity Model with Recent DESI DR2 Observation
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arXiv:2601.06438v1 Announce Type: cross Abstract: In this article, we investigate the cosmological viability of a modified symmetric teleparallel gravity model within the $f(Q)$ framework. We derive observational constraints on the model parameters by performing a Markov Chain Monte Carlo analysis using a combined dataset consisting of cosmic chronometers, PantheonPlus SH0ES, and DESI BAO DR2. Our analysis yields the best-fit values for the model parameters $m=-0.386 \pm 0.090$ and $n=-1.055 \pm 0.047$, along with the cosmological parameters at present: $H_0 = 73.19 \pm 0.25$, $q_0 = -0.51 \pm 0.6$, and $\omega_{0} = -0.73 \pm 0.3$, at 68\% CL. Furthermore, we examine the physical behavior of the model, focusing on the effective equation of state and deceleration parameter. Our findings indicate that the model experiences a transition from the early deceleration phase to the late-time cosmic acceleration, and the transition occurs at a redshift $z_{tr} = 0.573$. We also analyse the $om(z)$ diagnostic, which reflects a positive slope, supporting the behavior of the equation of state parameter in the quintessence region.
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https://arxiv.org/abs/2601.06438
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240912f63a5ee03051715d2625a46c547417c2681678c2184b3c095d9caf3f50
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2026-01-13T00:00:00-05:00
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Kerr-Newman-de Sitter black holes in $f(R)$ gravity with constant curvature: horizon structure and extremality
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arXiv:2601.06661v1 Announce Type: cross Abstract: The theory of $f(R)$ gravity with constant curvature (i.e. constant scalar curvature) admits rotating and charged black hole solutions obtained from the Kerr-Newman-(A)dS metrics of general relativity through appropriate rescalings of the metric parameters. In this paper, we focus on the Kerr-Newman-de Sitter case and present a unified analytic treatment of the horizon structure and its physical properties, allowing for a transparent comparison between general relativity and $ f(R)$ gravity with constant curvature. We solve the quartic equation determining the horizon locations and derive closed analytic expressions for the horizon radii. Focusing on extremal configurations, we obtain analytic formulas for the squared rotation parameter $ a^2 $ and the inverse square of the curvature radius $ l^{-2} $ as functions of the horizon location and the electric charge. For generic values of these parameters, the extremality conditions are non-universal, reducing to the familiar Kerr-Newman bound only in the limit of vanishing background curvature. We identify an ultra-extremal configuration in which $ a^2 $ attains its maximal value at zero charge and decreases monotonically to zero as the charge approaches its limiting value, while $ l^{-2 }$ increases correspondingly. As an illustrative example, we show that black holes with charge $ q=M/2 $ necessarily possess a minimum rotation, which emerges naturally as an intersection point in our analytic description of $ a^2 $ and $ l^{-2 }$, when embedded in a universe characterized by a critical value of $ l^{-2} $ (equivalently, the scalar curvature or the cosmological constant). Finally, we demonstrate that when the mass satisfies $ M^2= (a^2+q^2)(1-a^2/l^2)$, the quartic horizon equation factorizes, leading in the extremal regime to a chiral-like horizon structure that allows only the outer-cosmological horizon merger.
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https://arxiv.org/abs/2601.06661
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49087afdbd1e12b027283303fdb20f84bbf35671f23d1c81e02047ad4386ebb0
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2026-01-13T00:00:00-05:00
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Limits of vacuum-template subtraction for LISA massive black hole binary sources in realistic environments
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arXiv:2601.06684v1 Announce Type: cross Abstract: We investigate the impact of gravitational wave (GW) dephasing due to gas accretion on the subtraction of massive black hole (MBH) binary signals over 4 yr of LISA data in the context of the global-fit. Based on state of the art predictions for the population of merging MBHs, we show that imperfect subtraction with vacuum waveform templates leaves a GW residual with an SNR of $3.2^{+5.4}_{-1.9}\times \sqrt{f_{\rm Edd} \langle \dot n \rangle/(20\, {\rm yr}^{-1})}$, where $f_{\rm Edd}$ is the typical Eddington ratio and $\langle \dot n \rangle$ the mean merger rate of LISA MBH binaries. We characterize the dependence of the residual on key population hyper-parameters, provide a simple fitting function and discuss detection and mitigation strategies.
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https://arxiv.org/abs/2601.06684
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5e60cd727b5104a58cceb64534acceae014006279b581e9c35c6af2234dc7b3c
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2026-01-13T00:00:00-05:00
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Numerical Study of Polytropes with n=1 and Differential Rotation
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arXiv:2601.06905v1 Announce Type: cross Abstract: The solution space of differentially rotating polytropes with n=1 has been studied numerically. The existence of three different types of configurations: from spheroids to thick tori, hockey puck-like bodies and spheroids surrounded by a torus, separate from or merging with the central body has been proved. It has been shown that the last two types appear only at moderate degrees of rotation differentiality, sigma~2. Rigid-body or weakly differential rotation, as well as strongly differential, have not led to any "exotic" types of configurations. Many calculated configurations have had extremely large values of parameter tau, which has raised the question of their stability with respect to fragmentation.
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https://arxiv.org/abs/2601.06905
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267240e23c58d34c9070127a24aad910f6b75de6c2f0086b0640a45356917120
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2026-01-13T00:00:00-05:00
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Strong Einstein-Hilbert Gravity Inflation and ACT Phenomenology
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arXiv:2601.06946v1 Announce Type: cross Abstract: In this work we study rescaled effective single scalar field theories, and we confront these with the ACT constraint on the spectral index of the scalar primordial perturbations and the updated BICEP/Planck constraint on the tensor-to-scalar ratio. Rescaled scalar theories of gravity may be the result of an effective $f(R,\phi)$ gravity at strong curvature regimes, which may result on a rescaling of the Einstein-Hilbert term of the form $\sim \alpha R$. It turns out that canonical scalar field theories with stronger gravity compared to standard Einstein-Hilbert gravity can be compatible with the ACT and updated Planck/BICEP constraints, with stronger gravity meaning that the rescaling parameter $\alpha$ takes values smaller than unity.
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https://arxiv.org/abs/2601.06946
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58a30b06b92d3b2b567f904680a6015b3fda52c21cc9ff5ad9b8237f928c1675
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2026-01-13T00:00:00-05:00
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Viable f(R) Scenarios Unifying Inflation with Realistic Dynamical Dark Energy
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arXiv:2601.06949v1 Announce Type: cross Abstract: Two $F(R)$ gravity models are tested on the basis of their viability during all stages of cosmological evolution. It is shown that these models can describe both the early-time inflationary epoch and the dark energy epoch. The models are confronted with the latest observational data, including the Pantheon+ catalogue with Type Ia supernovae, the Dark Energy Spectroscopic Instrument measurements of baryon acoustic oscillations, the Hubble parameter estimations and data from cosmic microwave background radiation. Investigation of the viability conditions for these models, in particular, the condition $\frac{dF}{dR}>0$ required a deep analysis. Both models appeared to be viable during the early-time era, but for the late-time evolution the viability conditions are not fulfilled in definite domains in the parameter spaces of these models. However the best fitted parameters, determined in confrontation with the mentioned observational data, lie far from the forbidden domains for both models. These $F(R)$ gravity models describe the observations with the large advantage over the $\Lambda$-Cold-Dark-Matter model, not only in $\chi^2$ statistics, but also with Akaike and Bayesian information criteria. This success of the two $F(R)$ gravity scenarios is connected with their capability to mimic dynamical dark energy, similarly to models with variable equation of state, that is necessary for describing the latest Pantheon+ and DESI observational data.
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https://arxiv.org/abs/2601.06949
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005bb1e0551c183abb83deb0c66288f1d1afb4f9955441b0784d4ba2ef6bd311
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2026-01-13T00:00:00-05:00
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IndIGO-D: Probing Compact Binary Coalescences in the Decihertz GW Band
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arXiv:2601.06956v1 Announce Type: cross Abstract: We study IndIGO-D, a decihertz gravitational-wave mission concept, focusing on a specific configuration in which three spacecraft fly in formation to form an L-shaped interferometer in a heliocentric orbit. The two orthogonal arms share a common vertex, providing a space-based analogue of terrestrial Michelson detectors, while operating in an optimised configuration that yields ppm-level arm-length stability. Assuming 1000 km arm length, we analyse the orbital motion and antenna response, and assess sensitivity across the [0.1 - 10] Hz band bridging LISA and next-generation ground-based interferometers. Using fiducial sensitivity curves provided by the IndIGO-D collaboration, we compute horizon distances for different source classes. Intermediate-mass black-hole binaries with masses $10^{2}$ - $10^{3} \, M_\odot$ are detectable to redshifts $z \sim 10^{3}$, complementing the reach of LISA and terrestrial detectors. Binary neutron star systems are observable to a horizon distance of $z \lesssim 0.3$, allowing continuous multi-band coverage with Voyager-class interferometers from the decihertz regime to merger. A Bayesian parameter-estimation study of a GW170817-like binary shows that the sky localization area improves from $\sim 21 \,\mathrm{deg}^2$ at one month to $0.3 \,\mathrm{deg}^2$ at six hours pre-merger! These sky areas are readily tiled by wide-field time-domain telescopes such as the Rubin Observatory, whose $9.6 \,\mathrm{deg}^2$ field of view and r-band depth enable high-cadence, repeated coverage of GW170817-like kilonovae at this distance and beyond. IndIGO-D exploits the rapid evolution of binaries in the decihertz band to bridge the gap between millihertz and terrestrial observations, enabling early warnings on timescales from months to hours and enhancing the prospects for multi-band and multi-messenger discoveries.
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https://arxiv.org/abs/2601.06956
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f0e31ff6b7444252232c2fffc425dd77d81edba1ae2c292f58844c4363f40934
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2026-01-13T00:00:00-05:00
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Oscillatory Freeze from Inertial Holographic Dark Energy
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arXiv:2601.07007v1 Announce Type: cross Abstract: We study a generalized holographic dark energy model in which the infrared cutoff depends on the Hubble parameter and its first two time derivatives. The inclusion of the $\ddot H$ term introduces a finite relaxation timescale for the horizon degrees of freedom, which can be interpreted as an effective entropic inertia of the holographic vacuum energy. The resulting background dynamics admit late--time solutions in which the cosmic expansion gradually halts. In the underdamped regime, the Hubble parameter undergoes exponentially damped oscillations and asymptotically approaches $H\to0$. The scale factor grows monotonically but by a finite amount, while curvature invariants decay exponentially, leading to an asymptotically Minkowski spacetime without future singularities. We confront the full nonlinear background evolution with cosmic chronometer measurements of the Hubble parameter and find good agreement with current late--time expansion data, with a reduced chi--squared $\chi^2/\nu\simeq0.52$. At observable redshifts, oscillatory features are strongly suppressed and remain consistent with existing constraints.
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https://arxiv.org/abs/2601.07007
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91ba92a131070926164b65f2eacbf39ebb6f45628d4105cc2ac31d30b9e57eff
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2026-01-13T00:00:00-05:00
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Multi-Physics Bayesian Analysis of Neutron Star Crust Using Relativistic Mean-Field Model
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arXiv:2601.07722v1 Announce Type: cross Abstract: We study the properties of neutron-star crust within a Bayesian framework based on a unified relativistic mean-field (RMF) description of dense matter. The analysis focuses on the posterior distributions of crust properties, constrained by nuclear experimental data, chiral effective field theory, and multimessenger neutron-star observations. In the inference, the outer crust is fixed using the AME2020 nuclear mass table, supplemented by Hartree--Fock--Bogoliubov mass models, while the inner crust is described using a compressible liquid-drop model consistently coupled to the RMF interaction. The same RMF framework is used to describe the uniform core, ensuring a unified treatment across all density regimes. From the resulting posteriors, we extract key crustal observables, including the crust--core transition density and pressure, crust thickness, crust mass, and the fractional crustal moment of inertia. We find that the transition density is primarily governed by the symmetry-energy slope $L$ and curvature $K_{\rm sym}$ evaluated at sub-saturation densities, while the transition pressure plays a central role in determining global crustal properties. The inner-crust equation of state reflects a collective interplay between isovector nuclear-matter properties rather than a dependence on any single parameter. We also assess the impact of using matched crust--core constructions and show that they can introduce systematic differences in predicted neutron-star properties when compared with fully unified treatments.
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https://arxiv.org/abs/2601.07722
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c5303c781a50879e0eac653fc80d9852592be161af83fcfd3461643d23cf5fdb
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2026-01-13T00:00:00-05:00
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Learning the relations between neutron star and nuclear matter properties with symbolic regression
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arXiv:2601.07727v1 Announce Type: cross Abstract: The equation of state (EOS) of dense matter in neutron stars (NSs) remains uncertain, particularly at supra-nuclear densities where complex nuclear interactions and the potential presence of exotic matter, like hyperons, come into play. The complex relationships existing between nuclear matter and neutron star properties are investigated. The focus is on their nonlinearities and interdependencies. In our analysis, we apply a machine learning algorithm known as symbolic regression, paired with principal component analysis, to datasets generated from Bayesian inference over relativistic mean-field models. A systematic Principal Component Analysis has allowed to break down the percentage contribution of each element or feature in the relationships obtained. This study examines two main models (datasets): the NL model, which includes nucleonic degrees of freedom; and the NL-hyp model, which includes hyperons in addition to nucleons. Our analysis confirms a robust correlation between the tidal deformability of a 1.4 \(M_\odot\) neutron star and $\beta$-equilibrium pressure at twice the nuclear saturation density. This correlation remains once hyperons are included. The contribution of the different nuclear matter properties at saturation to the radius and tidal deformability was calculated. It was shown that the isovector properties have the largest impact, with a contribution of about 90\%. We also studied the relationship between the proton fraction at different densities and various symmetry energy parameters defined at saturation density. For the hyperon data set, we took into account the effects of the negatively charged hyperon $\Xi$ in order to recover the relationships. Our study reveals the individual impact of various symmetry energy parameters on proton fractions at different densities.
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https://arxiv.org/abs/2601.07727
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4a24d051a1b950d89bf64244543a6617530a3a2ebc2aa80a5b9c048f6a878e88
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2026-01-13T00:00:00-05:00
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Rotation-dependent $I$-Love-$Q$-$\delta M$ relations in perturbation theory
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arXiv:2601.07734v1 Announce Type: cross Abstract: The so-called $I$-Love-$Q$ relations link some normalized versions of the moment of inertia, the Love number, and the quadrupole moment of a star. These relations, in principle, enable the inference of two of the quantities given the third. However, their use has been limited because the normalized versions of the multipole moments rely on the static mass derived from the Tolman-Oppenheimer-Volkoff equation, which is not directly observable. In this work, using perturbation theory, we find that the $I$-Love-$Q$ relations can also be formulated in terms of an alternative set of normalized quantities that do not depend on the static mass, but on the actual (observable) mass.
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https://arxiv.org/abs/2601.07734
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dc60e753a9ca21b53f9d20b53517a0e9bccbdeaa06309f3dfbf57b98fc0cc257
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2026-01-13T00:00:00-05:00
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Systematic Biases in Gravitational-Wave Parameter Estimation from Neglecting Orbital Eccentricity in Space-Based Detectors
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arXiv:2601.07739v1 Announce Type: cross Abstract: Accurate modeling of gravitational-wave signals is essential for reliable inference of compact-binary source parameters, particularly for future space-based detectors operating in the milli- and deci-Hertz bands. In this work, we systematically investigate the parameter-estimation biases induced by neglecting orbital eccentricity when analyzing eccentric compact-binary coalescences with quasi-circular waveform templates. Focusing on the deci-Hertz detector B-DECIGO and the milli-Hertz detector LISA, we model eccentric inspiral signals using a frequency-domain waveform that incorporates eccentricity-induced higher harmonics and the time-dependent response of spaceborne detectors. We quantify systematic biases in the chirp mass, symmetric mass ratio, and luminosity distance using both Bayesian inference and the Fisher-Cutler-Vallisneri (FCV) formalism, and assess their significance relative to statistical uncertainties. By constructing mock gravitational-wave catalogs spanning stellar-mass and massive black-hole binaries, we identify critical initial eccentricities at which systematic errors become comparable to statistical errors. We find that for B-DECIGO, even very small eccentricities, $e_0\sim 10^{-4}-10^{-3}$ at 0.1 Hz, can lead to significant biases, whereas for LISA such effects typically arise at larger eccentricities, $e_0\sim 10^{-2}-10^{-1}$ at $10^{-4}$ Hz, due to the smaller number of in-band cycles. Comparisons between FCV predictions and full Bayesian analyses demonstrate good agreement within the regime where waveform mismatches remain small, especially when extrinsic parameters are pre-aligned to minimize mismatches. Our results highlight the necessity of incorporating eccentricity in waveform models for future space-based gravitational-wave observations.
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https://arxiv.org/abs/2601.07739
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ead935e00b64f5593b37bb753075fb95ccbde2413bee3b73ad933abb2aac2b23
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2026-01-13T00:00:00-05:00
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Exploring Lorentz Invariance Violation from Ultra-high-energy Gamma Rays Observed by LHAASO
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arXiv:2106.12350v2 Announce Type: replace Abstract: Recently the LHAASO Collaboration published the detection of 12 ultra-high-energy gamma-ray sources above 100 TeV, with the highest energy photon reaching 1.4 PeV. The first detection of PeV gamma rays from astrophysical sources may provide a very sensitive probe of the effect of the Lorentz invariance violation (LIV), which results in decay of high-energy gamma rays in the superluminal scenario and hence a sharp cutoff of the energy spectrum. Two highest energy sources are studied in this work. No signature of the existence of LIV is found in their energy spectra, and the lower limits on the LIV energy scale are derived. Our results show that the first-order LIV energy scale should be higher than about 10^5 times the Planck scale M_{pl} and that the second-order LIV scale is >10^{-3}M_{pl}. Both limits improve by at least one order of magnitude the previous results.
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https://arxiv.org/abs/2106.12350
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3dc5c00e4acb768fdb942cc024f2b97acab82b23553ae9e67b49c5e557171b90
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2026-01-13T00:00:00-05:00
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Self-consistent 3D radiative transfer for kilonovae: directional spectra from merger simulations
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arXiv:2306.17612v5 Announce Type: replace Abstract: We present three-dimensional radiative transfer calculations for the ejecta from a neutron star merger that include line-by-line opacities for tens of millions of bound-bound transitions, composition from an r-process nuclear network, and time-dependent thermalization of decay products from individual $\alpha$ and $\beta^-$ decay reactions. In contrast to expansion opacities and other wavelength-binned treatments, a line-by-line treatment enables us include fluorescence effects and associate spectral features with the emitting and absorbing lines of individual elements. We find variations in the synthetic observables with both the polar and azimuthal viewing angles. The spectra exhibit blended features with strong interactions by Ce III, Sr II, Y II, and Zr II that vary with time and viewing direction. We demonstrate the importance of wavelength-calibration of atomic data using a model with calibrated Sr, Y, and Zr data, and find major differences in the resulting spectra, including a better agreement with AT2017gfo. The synthetic spectra for near-polar inclination show a feature at around 8000 A, similar to AT2017gfo. However, they evolve on a more rapid timescale, likely due to the low ejecta mass (0.005 M$_\odot$) as we take into account only the early ejecta. The comparatively featureless spectra for equatorial observers gives a tentative prediction that future observations of edge-on kilonovae will appear substantially different from AT2017gfo. We also show that 1D models obtained by spherically averaging the 3D ejecta lead to dramatically different direction-integrated luminosities and spectra compared to full 3D calculations.
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https://arxiv.org/abs/2306.17612
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6c578c9a1e3673b70ddb81e77fbd2a2368ee7583ec3d46cc46bb9415447a132f
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2026-01-13T00:00:00-05:00
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Exploring the interplay between star formation efficiency and dust in regulating the UV luminosity of early systems in the JWST and ALMA era
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arXiv:2409.10613v2 Announce Type: replace Abstract: Recent observations by the James Webb Telescope (JWST) have unveiled numerous galaxy candidates between $z \sim 9 - 16.5$, hinting at an over-abundance of sources at the bright-end of the UV Luminosity Function (UV LF) at z $\gtrsim$ 11. Complementarily, the Atacama Large Millimetre Array (ALMA) has started yielding dust mass estimates at $z \sim 5 - 7$. In this work, we develop an analytic formalism baselined against the latest ALMA results, jointly exploring the impact of bursty star formation and its associated dust enrichment, on the visibility of early galaxies, while also modelling sources scattered off the main sequence of star formation. We incorporate dust production in type II Supernovae, dust destruction, ejection, growth and sputtering. Our key results are: (i) explaining the UV LF at $z \sim 5 - 13$ requires an average star formation efficiency that evolves as $f_*(z) = 10^{0.13z-3.5}$, with a number of observations exceeding this main sequence by a factor of 10. (ii) The dust enrichment of early systems is driven by dust production in SNII ejecta, while growth and sputtering impact the dust mass by 60\% and 40\% respectively at $z \sim 7$. (iii) galaxies at $z \gtrsim 9$ can retain significant dust, reaching average dust-to-stellar mass ratios of 0.19\% (0.14\%) at $z \sim 9$ ($z \sim 11$). Dust attenuation decreases with redshift as dust becomes more dispersed within halos. (iv) observations by ALMA at $z \sim 5$ and 7 are not representative of the average population that makes up the UV LF.
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https://arxiv.org/abs/2409.10613
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e0a768c9c7f6ad71a173c70d3c87fc7649ba20867c1e82237bc1c580c6b1d9f5
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2026-01-13T00:00:00-05:00
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A model of the heliocentric dust ring on Venus orbit
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arXiv:2504.16610v2 Announce Type: replace Abstract: A heliocentric dust ring on Venus orbit was discovered following observations by the Helios spacecraft, and then confirmed thanks to observations by STEREO and the Parker Solar Probe. The impact risk it poses needs to be evaluated for any spacecraft crossing the ring. This study aims to provide a first model of the dust ring, in terms of distribution of particles (including size distribution), velocity, density of the ring, and deduce a first estimation of the impact risk to spacecrafts crossing the ring. We seek to describe the orbits of dust particles in the ring. We explore a first simple model, that leads us to propose a second, more elaborate, model. This model is then populated by particles that we integrate for 2000 years. We demonstrate that the dust ring will persist over the next 2000 years, only slightly extending radially and perpendicularly to the Venus orbital plane. We show that particles tend to accumulate at Venus orbit, but that along it the differences in density is negligible. We compute the number of particles we can expect to find in the ring. Finally, as an example, we apply this model to Bepi-Colombo to obtain a first estimate of the impact flux in function of radius and mass, for radii between 2 $\mu$m and 2 cm (i.e. for masses between 10^-2 kg and 10^-14 kg). We also present the impact velocity and direction of impacts with respect to Bepi-Colombo. We are able to conclude that the ring seems to present a low risk for spacecrafts using Venus as a gravity assist.
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https://arxiv.org/abs/2504.16610
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59c66e7ce4cb94403c07d531e52de6c3a6d1fe799f89ab3db425f3522342755c
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2026-01-13T00:00:00-05:00
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Time-evolving coronal modelling of the solar maximum around the solar storms in May 2024 by COCONUT
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arXiv:2505.11990v2 Announce Type: replace Abstract: Time-evolving MHD coronal models deliver more realistic results than traditional quasi-steady-state models. The fully implicit time-evolving coronal model COCONUT performs efficiently enough for real-time coronal simulations during solar minimum. However, during solar maxima, the coronal magnetic field is more complex and stronger, and coronal structures evolve more rapidly than during solar minima. Time-evolving MHD coronal modelling of solar maxima often struggles with poor numerical stability and low computational efficiency. We enhanced the numerical stability of the time-evolving coronal model COCONUT to mitigate these issues with the aim to evaluate the differences between the time-evolving and quasi-steady-state coronal simulation results, and to assess the impact of the spatial resolution on global MHD coronal modelling of solar maxima. After enhancing the positivity-preserving property of COCONUT, we employed it to simulate the evolution of coronal structures within 0.1 AU in an inertial coordinate system over two CRs around the solar storms in May 2024. These simulations were performed on unstructured geodesic meshes containing 6.06, 1.52, and 0.38 M cells. We also conducted a quasi-steady-state coronal simulation that treated the solar surface as a rigidly rotating spherical shell. A comparison with observations further validated the reliability of the time-evolving coronal modelling technique. It shows that incorporating the evolution of the magnetic field on the solar surface can significantly improve the fidelity of global MHD coronal simulations around a solar maximum. A simulated magnetic field strength using a mesh with 6.06 M cells can be stronger by more than 40% than that in a mesh with 0.38 M cells. The fully implicit time-evolving model COCONUT shows promise for accurately conducting real-time global coronal simulations of solar maxima.
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https://arxiv.org/abs/2505.11990
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d835685ed5b141c15b27f6fdbaac35af99f1e170503a52ac70af6fd10b0231c6
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2026-01-13T00:00:00-05:00
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The PAU Survey: Measuring intrinsic galaxy alignments in deep wide fields as a function of colour, luminosity, stellar mass and redshift
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arXiv:2505.15470v3 Announce Type: replace Abstract: We present the measurements and constraints of intrinsic alignments (IA) in the Physics of the Accelerating Universe Survey (PAUS) deep wide fields, which include the W1 and W3 fields from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) and the G09 field from the Kilo-Degree Survey (KiDS). Our analyses cover 51deg$^{2}$, in the photometric redshift (photo-$z$) range $0.1 < z_{\mathrm{b}} < 1$ and a magnitude limit $i_{\mathrm{AB}}<22$. The precise photo-$z$s and the luminosity coverage of PAUS enable robust IA measurements, which are key for setting informative priors for upcoming stage-IV surveys. For red galaxies, we detect an increase in IA amplitude with both luminosity and stellar mass, extending previous results towards fainter and less massive regimes. As a function of redshift, we observe strong IA signals at intermediate ($z_{\mathrm{b}}\sim0.55$) and high ($z_{\mathrm{b}}\sim0.75$) redshift bins. However, we find no significant trend of IA evolution with redshift after accounting for the varying luminosities across redshift bins, consistent with the literature. For blue galaxies, no significant IA signal is detected, with $A_{1}=0.68_{-0.51}^{+0.53}$ when splitting only by galaxy colour, yielding some of the tightest constraints to date for the blue population and constraining a regime of very faint and low-mass galaxies.
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https://arxiv.org/abs/2505.15470
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6b4a13fdc4269437646b1605a0b9e57bfd5248282ac3414c15909bff61d569cb
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2026-01-13T00:00:00-05:00
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PEARLS: 21 Transients Found in the Three-Epoch NIRCam Observations in the Continuous Viewing Zone of the James Webb Space Telescope
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arXiv:2506.12175v2 Announce Type: replace Abstract: We present 21 transients from our three-epoch, four-band NIRCam observations covering 14.16 arcmin^2 in the Spitzer IRAC Dark Field (IDF), taken by the JWST Prime Extragalactic Areas for Reionization and Lensing Science program with a time cadence of ~6 months. A separate Hubble Space Telescope program provided Advanced Camera for Surveys optical imaging contemporaneous with the second and third epochs of the NIRCam observations. The NIRSpec spectroscopy on three transients confirmed a Type Ia supernova at z=1.63 and the host galaxies of the other two at z=2.64 and 1.90, respectively. Combining these with the photometric redshifts (z_ph) of the host galaxies in the rest of the sample, we find that the transients are in either a "mid-z" group at z>1.6 with M_V -14.0 mag. The mid-z transients are consistent with supernovae. In contrast, the low-z transients' luminosities fall in the range of the so-called "gap transients" between supernovae and novae. However, this latter conclusion is only tentative due to possible catastrophic failures in z_ph that could bias them to low-z. Conversely, if they are indeed at z < 0.4, it would be worth studying similar transients in the future. Our work further demonstrates the power of NIRCam in transient science and also shows that it would be more fruitful to carry out a long-term monitoring program with more passbands, a higher cadence and prompt follw-up spectroscopy. Being in the continuous viewing zone of the JWST, the IDF is an ideal field for this purpose.
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https://arxiv.org/abs/2506.12175
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dcd39445125ac8b9524ea129a524e51fa9d8a1fc8f10af521e01c786a137d087
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2026-01-13T00:00:00-05:00
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JWST Reveals a Candidate Jellyfish Galaxy at z=1.156
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arXiv:2506.14117v2 Announce Type: replace Abstract: We report the discovery of COSMOS2020-635829 as a candidate jellyfish galaxy undergoing ram pressure stripping in a (proto)cluster at $z > 1$. High-resolution imaging from the James Webb Space Telescope reveals a symmetric stellar disk coupled to a unilateral tail of star-forming knots to the south. Using Gemini GMOS IFU observations, we show that these extra-planar continuum sources are embedded within an ionized gas tail that is kinematically connected to the disk of COSMOS2020-635829. If confirmed, this represents the highest-redshift discovery of a ram pressure stripped ionized gas tail. The tail sources are characterized by extremely young stellar populations ($\lesssim 100\,\mathrm{Myr}$), have stellar masses of ${\sim}10^8\,\mathrm{M_\odot}$, and star formation rates of $0.1\text{--}1\,\mathrm{M_\odot\,yr^{-1}}$. This work shows that ram pressure stripping can potentially perturb group and cluster galaxies at $z > 1$ and may contribute to environmental quenching even near Cosmic Noon.
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https://arxiv.org/abs/2506.14117
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6930c9d42bfb8aa8c78abd35ec260d985606b9d0f39f1c447f4ecc5c16535a02
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2026-01-13T00:00:00-05:00
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Bayesian constraints on quark stars from multi-messenger observations
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arXiv:2506.22781v2 Announce Type: replace Abstract: We perform a systematic Bayesian analysis of quark star equations of state under current multimessenger constraints, investigating the impact of prior assumptions and extreme-mass observations. Quark matter is modeled within an interacting MIT bag framework that consistently accommodates color-superconducting phases (2SC, 2SC+s, and CFL) and perturbative QCD corrections. We find that quark star models exhibit a distinct advantage in naturally accommodating the ultra-low mass object HESS J1731-347, a configuration that is challenging for standard neutron star models. In the high-mass regime, the interpretation of the secondary component of GW190814 is shown to be strongly prior-dependent: only broad priors allow for the substantial stiffness required to support such a massive object ($\sim$2.6 M$_\odot$), while more restrictive priors favor a softer equation of state consistent with standard pulsar populations. Microscopically, we demonstrate that current data tightly constrain the effective bag constant and the overall stiffness, but cannot distinguish between different color-superconducting phases. Furthermore, we validate a reduction of the model to two effective parameters without loss of information. Our results indicate that if quark stars exist, their sound speeds consistently exceeds the conformal limit ($c_s^2>1/3$) at stellar densities.
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https://arxiv.org/abs/2506.22781
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929a92f9ef1a0221d69c70746215b7097876a929ad172de9f281548ecb7f77bc
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2026-01-13T00:00:00-05:00
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Angular correlation functions of bright Lyman-break galaxies at $\mathbf{3 \lesssim z \lesssim 5}$
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arXiv:2507.02515v2 Announce Type: replace Abstract: We investigate the clustering of Lyman-break galaxies at redshifts of 3 $\lesssim z \lesssim$ 5 within the COSMOS field by measuring the angular two-point correlation function. Our robust sample of $\sim$60,000 bright ($m_{\rm UV}\lesssim 27$) Lyman-break galaxies was selected based on spectral energy distribution fitting across 14 photometric bands spanning optical and near-infrared wavelengths. We constrained both the 1- and 2-halo terms at separations up to 300 arcsec, finding an excess in the correlation function at scales corresponding to $<20$ kpc, consistent with enhancement due to clumps in the same galaxy or interactions on this scale. We then performed Bayesian model fits on the correlation functions to infer the Halo Occupation Distribution parameters, star formation duty cycle, and galaxy bias in three redshift bins. We examined several cases where different combinations of parameters were varied, showing that our data can constrain the slope of the satellite occupation function, which previous studies have fixed. For an $M_{\rm{UV}}$-limited sub-sample, we found galaxy bias values of $b_g=3.18^{+0.14}_{-0.14}$ at $z\simeq3$, $b_g=3.58^{+0.27}_{-0.29}$ at $z\simeq4$, $b_g=4.27^{+0.25}_{-0.26}$ at $z\simeq5$. The duty cycle values are $0.62^{+0.25}_{-0.26}$, $0.40^{+0.34}_{-0.22}$, and $0.39^{+0.31}_{-0.20}$, respectively. These results suggest that, as the redshift increases, there is a slight decrease in the host halo masses and a shorter timescale for star formation in bright galaxies, at a fixed rest-frame UV luminosity threshold.
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https://arxiv.org/abs/2507.02515
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41968668c63a3a0232ae517c631237a1fee8da36760a2649240af6045881b7a6
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2026-01-13T00:00:00-05:00
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Confronting Mukhanov Parametrization of Inflationary Equation-of-State with ACT-DR6
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arXiv:2507.05648v2 Announce Type: replace Abstract: We provide a simple yet effective semi-analytical approach to confront Mukhanov Parametrization of inflationary equation-of-state, $1+\omega =\frac{\beta}{({N}+1)^\alpha}$, with the latest ACT-DR6 data employing Hamilton-Jacobi formulation. We find that equation-of-state formalism comes up with excellent fit to the latest data. In the process we are also able to put stringent constraint on the two model parameters. In order to get the bounds of $\alpha$ and $\beta$ we have also made use of the recent finding $r<0.032$. We have further utilized results from the joint analysis of ACT-DR6, Planck-2018 and DESI-Y1 data to find the observationally viable region for $\alpha$ and $\beta$. We have also employed the predictions on primordial gravity waves from forthcoming CMB missions in the likes of CMB-S4 and LiteBIRD along with results from the combination of ACT-DR6, Planck-2018 and DESI-Y1 data to further restrict the model parameters. We find that detection of gravity waves would help us narrow the viable parameter space for Mukhanov parametrization. But in the absence of detection of primordial gravity waves signal by those CMB missions parameter space is reduced significantly for $\beta$, while the range for $\alpha$ is slightly increased. In addition we observe that, $\alpha$ is primarily dependent on the observationally viable range for scalar spectral index while other model parameter $\beta$ is resting heavily on the restriction upon the amplitude of primordial gravity waves. We find that equation-of-state formalism has a wide range of parameter values consistent with recent observational data set along with futuristic CMB missions in the likes of CMB-S4 and LiteBIRD.
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https://arxiv.org/abs/2507.05648
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aec71c8a752313c376e1d907d05518c2c6b3e114484f2483771c06abc3c8d978
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2026-01-13T00:00:00-05:00
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MrMARTIAN: A Multi-resolution Mass Reconstruction Algorithm Combining Free-form and Analytic Components
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arXiv:2508.13262v4 Announce Type: replace Abstract: We present ${\tt MrMARTIAN}$ (Multi-resolution MAximum-entropy Reconstruction Technique Integrating Analytic Node), a new hybrid strong lensing (SL) modeling algorithm. By incorporating physically motivated analytic nodes into the free-form method ${\tt MARS}$, ${\tt MrMARTIAN}$ enables stable and flexible mass reconstructions while mitigating oversmoothing in the inner mass profile. Its multi-resolution framework increases the degrees of freedom in regions with denser strong lensing constraints, thereby enhancing computational efficiency for a fixed number of free parameters. We evaluate the performance of ${\tt MrMARTIAN}$ using publicly available simulated SL data and find that it consistently outperforms ${\tt MARS}$ in recovering both mass and magnification. In particular, it delivers significantly more stable reconstructions when multiple images are sparsely distributed. Finally, we apply ${\tt MrMARTIAN}$ to the galaxy cluster MACS J0416.1-2403, incorporating two analytic nodes centered on the northeastern and southwestern BCGs. Our mass model, constrained by 412 multiple images, achieves an image-plane rms scatter of ~0".11, the smallest to date for this dataset.
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https://arxiv.org/abs/2508.13262
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242ebeb514074cea7106627fdac624fc4fca006bf6380ce74229a3e3a6ae8361
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2026-01-13T00:00:00-05:00
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Little Red Dots and their Progenitors from Direct Collapse Black Holes
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arXiv:2508.14155v2 Announce Type: replace Abstract: The James Webb Space Telescope (JWST) has discovered a new population of objects, the Little Red Dots (LRDs), characterized by V-shaped spectra indicative of strong breaks around the Balmer limit and compact morphology that gave them their name. A popular explanation is that they are a sub-population of active galactic nuclei/supermassive black holes (AGN/SMBHs) predominantly found in the high-redshift Universe ($z\gtrsim3$). Similarly, direct collapse black holes (DCBHs), theorized to form from collapsing massive, extremely metal-poor gas clouds, have been invoked to explain high-redshift quasars, the most massive AGN sub-population. Here, we employ the semi-analytical code A-SLOTH to produce a population of DCBHs and compare them against observed LRD demographics and properties. Specifically, we compare the DCBH-seeded SMBH population against the standard stellar-remnant seeds and find that DCBH models agree better with observed LRD population statistics and host halo properties. Furthermore, for the most extreme and earliest LRD detections, interpreted to be systems with an AGN but little stellar component, DCBHs are able to reproduce the observed spectral shape and properties under multiple scenarios - high dust attenuation or AGN surrounded by dense gas - that have been proposed to explain the unique shape of LRD spectra. Even when super-Eddington accretion, invoked previously to explain the nature of LRDs, is enforced on stellar remnant seeds, the spectral characteristics of extreme LRDs cannot be reproduced. We emphasize the importance of gas-metallicity observations as an additional dimension besides the widely used SMBH-stellar mass ratios to further constrain the progenitors of LRDs.
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https://arxiv.org/abs/2508.14155
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5e944644769d09531fb5c85a628cb791a2bd8b3fbf5fbd3785c608e2a6b618f1
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2026-01-13T00:00:00-05:00
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What determines the $\gamma$-ray luminosities of classical novae?
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arXiv:2508.15900v2 Announce Type: replace Abstract: Classical novae in the Milky Way have now been well-established as high-energy GeV $\gamma$-ray sources. In novae with main-sequence companions, this emission is believed to result from shocks internal to the nova ejecta, as a later fast wind collides with an earlier slow outflow. To test this model and constrain the $\gamma$-ray production mechanism, we present a systematic study of a sample of recent Galactic novae, comparing their $\gamma$-ray properties ($\gamma$-ray luminosity and duration) with their outflow velocities, peak $V$-band magnitudes, and the decline times of their optical light curves ($t_2$). We uniformly estimate distances in a luminosity-independent manner, using spectroscopic reddening estimates combined with three-dimensional Galactic dust maps. Across our sample, $\gamma$-ray luminosities ($>$100 MeV) vary by three orders of magnitude, spanning $10^{34}-10^{37}$ erg s$^{-1}$. Novae with larger velocity of the fast outflow (or larger differential between the fast and slow outflow) have larger $\gamma$-ray luminosities, but are detectable for a shorter duration. The optical and $\gamma$-ray fluxes are correlated, consistent with substantial thermal emission in the optical from shock-heated gas. Across six novae with $\gamma$-ray and infrared light curves, evidence for dust formation appears soon after the end of the detected $\gamma$-ray emission. Dusty and non-dusty novae appear to have similar $\gamma$-ray luminosities, though novae that have more material processed by the shocks may be more likely to form dust. We find that the properties of the $\gamma$-ray emission in novae depend heavily on the ejecta properties, and are consistent with expectations for internal shocks.
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https://arxiv.org/abs/2508.15900
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bbf3c7b49f2b11042123ecb41c3a2c326341ccfe5c1a1b6ca975c30c22a56904
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2026-01-13T00:00:00-05:00
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COCONUT: A coronal model with an energy decomposition strategy
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arXiv:2508.20423v2 Announce Type: replace Abstract: In this paper, we propose an energy decomposition method combined with an HLL Riemann solver that includes an additional dissipation term in the energy equation to improve the numerical stability of the fully implicit, time-evolving coronal model COCONUT and extend its applicability to solar-maximum phases. In MHD simulations that evolve conservative variables in time, the thermal pressure is typically computed by subtracting the magnetic and kinetic energies from the total energy. In low-beta (the ratio of thermal to magnetic pressure; $< 10^{-3}$) regions, discretization errors of magnetic energy can be comparable to the thermal pressure, potentially leading to negative thermal pressure and causing the simulation to crash. Therefore, we update the decomposed energy, excluding the magnetic energy, at each time step. It avoids subtracting a large magnetic energy from the total energy to obtain a very small thermal pressure in low-$\beta$ regions, thereby improving the numerical stability of MHD models. We validate the algorithm using a time-evolving solar-maximum Carrington rotation simulation in 2025, which the previous code failed to run to completion. We also perform quasi-steady-state coronal simulations and 2D benchmark tests to further assess the algorithm's performance. The simulation results show that the algorithm produces results nearly identical to those obtained using the traditional full energy equation during solar minimum, while significantly improving COCONUT's ability to simulate coronal evolution under strong magnetic fields, even including fields exceeding 100 Gauss with $\beta<10^{-3}$. This method provides a promising approach for performing quasi-realistic coronal simulations during solar maxima.
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https://arxiv.org/abs/2508.20423
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9231c538873c1bd4ddf7bd672121546c071c1570815ac57126d3e3b6f92972bb
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2026-01-13T00:00:00-05:00
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Accelerated calibration of semi-analytic galaxy formation models
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arXiv:2509.00143v2 Announce Type: replace Abstract: We present an accelerated calibration framework for semi-analytic galaxy formation models, demonstrated with Galacticus. Rather than fitting directly to properties such as the low-redshift stellar mass function (SMF) - which requires evolving thousands of halos per likelihood evaluation - we construct a fast likelihood from the stellar-to-halo mass relation (SHMR; mean and scatter) evaluated at a small set of target halo masses, reducing each evaluation to simulating only tens of galaxies. We sample the posterior over Galacticus parameters with Markov Chain Monte Carlo and show that the resulting calibration reproduces the low-redshift SMF. We then extend the method to additional datasets, using a higher-redshift SHMR and the low-redshift stellar mass-size relation as examples, and assess performance for large scale structure survey-relevant properties: stellar masses, sizes, and emission-line strengths. The SMF matches data well at low redshift, but toward higher redshift the model yields too few massive galaxies and too many low-mass galaxies. Size evolution with redshift is approximately correct, but the mass-size relation is too flat, producing massive galaxies that are too small. The H$\alpha$ luminosity function is well reproduced at z~2, but by z~0.4 the model overproduces highly star-forming, H$\alpha$-bright systems. These discrepancies suggest the model lacks sufficient flexibility (e.g. in gas cooling/recycling or feedback) to reconcile all datasets simultaneously. Our strategy complements emulator-based methods for calibrating semi-analytic models by enabling rapid, low-cost scans of model choices and parameterisations - a capability we envision leveraging to supply calibrated starting points for more detailed follow-up inference.
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https://arxiv.org/abs/2509.00143
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197aad598cc3f7be76459f96ca7ac4056bdf5298c6d91ff4863baa848413c766
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2026-01-13T00:00:00-05:00
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Needlets and foreground removal for SKAO hydrogen intensity maps
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arXiv:2509.02644v2 Announce Type: replace Abstract: Intensity Mapping (IM) of the 21-cm line of the neutral hydrogen (\textsc{Hi}) has become a compelling new technique to map the large-scale structure of the Universe. One of the main challenges is the presence of strong foreground emissions of several orders of magnitude larger than the \textsc{Hi}~signal. Here, we implement a version of the Principal Component Analysis, a blind component-separation technique, based on a kind of spherical wavelets called needlets. These functions exploit double localization both in real and in harmonic space. We test Need-PCA performances on a set of maps that simulates the SKA MID radio telescope in the AA4 configuration. We compare our results with other component separation methods such as Generalised Morphological Component Analysis (GMCA) and Generalized Needlet Internal Linear Combination (GNILC). All the methods have comparable results, recovering the \textsc{Hi}~signal within 10\% accuracy across the frequency channels, in the multipole range 30 $\lesssim \ell \lesssim$ 136. We also test our pipeline in the presence of systematics such as polarization leakage. We find that the cleaning methods are insensitive to the presence of such systematic, yielding the same results as in the leakage-free case. Finally, under the assumption of a realistic telescope beam with sidelobes, we find that standard PCA and GMCA fails to recover the \textsc{Hi}~signal at larger scales, while the Need-PCA and Need-GMCA are less affected. GNILC tends to over-clean, yielding to a loss of the signal.
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https://arxiv.org/abs/2509.02644
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57a7e710f8148fa5a0bf8f3a3de31032cb84f8cb79d05e0078010072c299e131
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2026-01-13T00:00:00-05:00
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$\texttt{Jipole}$: A Differentiable $\texttt{ipole}$-based Code for Radiative Transfer in Curved Spacetimes
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arXiv:2509.07065v2 Announce Type: replace Abstract: Recent imaging of supermassive black holes by the Event Horizon Telescope (EHT) has relied on exhaustive parameter-space searches, matching observations to large, precomputed libraries of theoretical models. As observational data become increasingly precise, the limitations of this computationally expensive approach grow more acute, creating a pressing need for more efficient methods. In this work, we present $\texttt{Jipole}$, an automatically differentiable (AD), $\texttt{ipole}$-based code for radiative transfer in curved spacetimes, designed to compute image gradients with respect to underlying model parameters. These gradients quantify how parameter changes-such as the black hole's spin or the observer's inclination-affect the image, enabling more efficient parameter estimation and reducing the number of required images. We validate $\texttt{Jipole}$ against $\texttt{ipole}$ in two analytical tests and then compare pixel-wise intensity derivatives from AD with those from finite-difference methods. We then demonstrate the utility of these gradients by performing parameter recovery for an analytical model using a conjugate gradient optimizer in three increasingly complex cases for the injected image: ideal, blurred, and blurred with added noise. In most cases, high-accuracy fits are obtained in only a few optimization steps, failing only in cases with extremely low signal-to-noise ratios and large blurring size kernels. These results highlight the potential of AD-based methods to accelerate robust, high-fidelity model-data comparisons in current and future black hole imaging efforts.
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https://arxiv.org/abs/2509.07065
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3848e90cc38ace5948eda01c1bf9035888bc6660f1091eb687857f727a5300f5
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2026-01-13T00:00:00-05:00
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A Pristine Star-Forming Complex at z=4.19
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arXiv:2509.07073v2 Announce Type: replace Abstract: We report the discovery of a faint (M_1700 ~ -12.2), oxygen-deficient strongly-lensed ionizing source -- dubbed LAP2 (Lensed And Pristine 2) -- at a spectroscopic redshift of z=4.19. LAP2 appears to be isolated and lies very close to the caustic produced by the lensing galaxy cluster Abell 2744. It was observed with the James Webb Space Telescope (JWST) NIRSpec MSA in prism mode as part of the UNCOVER program. The NIRSpec spectrum reveals prominent Lya emission (7.1 sigma), clear Ha emission (6.2 sigma), tentative Hb emission (2.8 sigma), and no detectable [OIII]4959,5007 (~ 7 times fainter than Ha). The inferred [OIII] 2 sigma upper limit corresponds to an R3 index <0.85 (assuming the Ha/Hb ~ 2.86 case~B recombination ratio), which, under high-ionization conditions, implies a metallicity of Z < 6 X 10^(-3) Z_sun. The combination of faint ultraviolet luminosity, large rest-frame Ha equivalent width (~ 650 A), and extremely compact size (< 10 pc) suggests that LAP2 is being caught in an early, pristine formation phase consistent with an instantaneous-burst scenario, with an estimated stellar mass of at most a few 10^4 Msun. Deep VLT/MUSE observations further reveal copious Lya emission forming an arclet that straddles the critical line. LAP2 thus joins the rare class of extremely metal-poor star-forming complexes that JWST has started to unveil at redshifts 3 - 7, and provides a rare glimpse into a still very poorly explored faint-luminosity regime.
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https://arxiv.org/abs/2509.07073
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1335fc419a50df53fcd2dac8e948e10e56a0a7f5417f9042093bab1f5dbadc1c
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2026-01-13T00:00:00-05:00
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Gaia Barium Dwarfs and Their Ostensibly Ordinary Counterparts
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arXiv:2509.13413v2 Announce Type: replace Abstract: The recently identified Gaia population of main-sequence--white dwarf (MS+WD) binaries at separations of ${\sim}\,1~{\rm AU}$, often with moderate eccentricities, is not readily reproduced by binary population synthesis models. Barium stars represent a closely related population whose enrichment in $s$-process elements both confirms the presence of a WD companion and attests to past binary interaction. It also indicates that mass transfer occurred at least during the late- and post-AGB phases of the WD progenitor, when $s$-process elements are dredged up. In this work, we further explore the connection between the astrometrically identified Gaia MS+WD binaries and the classical barium star population. To achieve this, we used high-resolution FEROS spectroscopy to measure abundances for 30 Gaia DR3 non-single-star binaries, identifying 10 as Ba-enriched. Together with our recent analysis of archival GALAH data, this yields a sample of 38 barium dwarfs with dynamically measured WD masses, compared to only 6 previously known systems with known WD masses at these separations. We find that, in cases where metallicity is sufficiently low to facilitate efficient $s$-process production, barium and yttrium enrichment is often detected. This enrichment is also identified in eccentric systems, suggesting that post-AGB mass transfer mechanisms are capable of pumping eccentricity into the orbit or occur without erasing it. Our results indicate that the Gaia MS+WD binaries trace the population from which barium stars emerge. Treating the large Gaia-discovered population as an extension of known $s$-process enriched dwarfs opens an avenue to empirically constrain their formation and evolution.
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https://arxiv.org/abs/2509.13413
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e74d179c9bbb62ecd1e1b209bff9737ec31b93318a922fa9036ce82c9eeae2a7
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2026-01-13T00:00:00-05:00
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Measuring the Central Dark Mass in NGC 4258 with JWST/NIRSpec Stellar Kinematics
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arXiv:2509.20519v2 Announce Type: replace Abstract: We present a new stellar dynamical measurement of the supermassive black hole (SMBH) mass in the nearby spiral galaxy NGC 4258, a critical benchmark for extragalactic mass measurements. We use archival JWST/NIRSpec IFU data (G235H/F170LP grating) to extract high-resolution two-dimensional stellar kinematics from the CO bandhead absorption features within the central $3'' \times 3''$. We extract the stellar kinematics after correcting for instrumental artifacts and separating the stellar light from the non-thermal AGN continuum. We employ Jeans Anisotropic Models (JAM) to fit the observed kinematics, exploring a grid of 12 models to systematically test the impact of different assumptions for the point-spread function, stellar mass-to-light ratio ($M/L$) profile, and orbital anisotropy. All 12 models provide broadly acceptable fits, albeit with minor differences. The ensemble median and 68% (1$\sigma$) bootstrap confidence intervals of our 12 models yield a black hole mass of $M_{\rm BH} = (4.08^{+0.19}_{-0.33}) \times 10^7$ M$_\odot$. This paper showcases the utility of using the full model ensemble to robustly account for systematic uncertainties, rather than relying on formal errors from a single preferred model, as has been common practice. Our result is just 5% larger than, and consistent with, the benchmark SMBH mass derived from water maser dynamics, validating the use of NIRSpec stellar kinematics for robust SMBH mass determination. Our analysis demonstrates JWST's capability to resolve the SMBH's sphere of influence and deliver precise dynamical masses, even in the presence of significant AGN continuum emission.
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https://arxiv.org/abs/2509.20519
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7685e381e1c3dd789f265ec2f23d20438b22f7b90951d2138869afa5593e12f6
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2026-01-13T00:00:00-05:00
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Modeling gravitational wave sources in the MillenniumTNG simulations
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arXiv:2510.06311v2 Announce Type: replace Abstract: (Edited) We introduce a flexible framework for building gravitational wave (GW) event catalogs in hydrodynamic simulations of galaxy formation. Our framework couples the state-of-the-art binary population synthesis code SEVN with Arepo-GW -- a module fully integrated into the moving-mesh code Arepo -- to assign merger events of binary compact objects to stellar particles in simulations by stochastically sampling merger tables generated with SEVN. Arepo-GW supports both on-the-fly operation, producing event catalogs during simulations, and post-processing, using snapshots from existing runs. The algorithm is fully parallel and can be adapted to outputs from other simulation codes. To demonstrate the capabilities of our new framework, we applied Arepo-GW in post-processing to simulations from the MillenniumTNG suite, including its flagship box. We investigate key properties of the resulting GW event catalog, built on SEVN predictions, focusing on comoving merger rates, formation efficiencies, delay-time distributions, and progenitor mass and metallicity distributions. We also examine how these properties vary with simulated volume. We find that GW progenitor rates closely track simulated star formation histories and are generally consistent with current observational constraints at low redshift, aside from a factor of $\sim 4.5$ excess in binary black hole mergers. Moreover, our binary black hole merger rates decline more slowly with redshift than current observational estimates for $z \lesssim 1$. Finally, the analysis of progenitor mass functions across different formation channels reveals only mild redshift evolution, while the binary black hole mass function displays features compatible with current observational determinations. These findings highlight the potential of our novel framework to enable detailed predictions for upcoming GW surveys within a full cosmological context.
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https://arxiv.org/abs/2510.06311
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6f32844014cdbc8963be4900ccead6995bb0733fdc2b525838572ac1848dc710
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2026-01-13T00:00:00-05:00
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New ultralight scalar particles and the mass-radius relation of white dwarfs -- the important role of Sirius B
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arXiv:2510.06312v2 Announce Type: replace Abstract: We present the equation of state for two classes of new ultralight particles, a scalar field coupling to electrons and a light $\mathbb{Z}_\mathcal{N}$ QCD axion field coupling to nucleons. Both are potential candidates for dark matter. Using the scalar modified equations of state, we calculate models for white dwarf stars and compare their radii and masses with observed mass-radius data. The comparison results in stringent constraints on the masses of the particles and the coupling parameters. For a wide range of particle masses and coupling parameters, constraints from the white dwarf equation of state surpass existing limits, outperforming also dedicated laboratory searches. The remarkable accuracy of modern white-dwarf mass-radius relation data, exemplified by Sirius B, now allows stringent tests of dense-matter physics and constraints on new particle scenarios.
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https://arxiv.org/abs/2510.06312
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d4b45afbf77c99e292978cb4fcaf61384b2693f3a560bd82cf97e01ca086dfd8
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2026-01-13T00:00:00-05:00
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MESA-QUEST: Tracing the formation of direct collapse black hole seeds via quasi-stars
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arXiv:2510.11772v3 Announce Type: replace Abstract: The origin of the first supermassive black holes (SMBHs) observed at redshifts $z\geq 9$ remains one of the most challenging open questions in astrophysics. Their rapid emergence suggests that massive ``heavy seeds'' must have formed early, possibly through the direct collapse of pristine gas clouds in the first galaxies. We present MESA-QUEST, a new framework built upon the Modules for Experiments in Stellar Astrophysics (MESA) code, designed to model the structure and evolution of quasi-stars -- massive, radiation-supported envelopes hosting accreting black holes at their cores -- believed to be the progenitors of direct-collapse black hole (DCBH) seeds. Our implementation introduces flexible boundary conditions representing both Bondi accretion and saturated-convection regimes, and explores the impact of several stellar wind and mass-loss prescriptions, including Reimers, Dutch, and super-Eddington radiation-driven winds. We find that quasi-stars can grow central black holes to $\geq 10^3\,M_{\odot}$ under favorable conditions, with saturated-convection models yielding BH-to-total mass ratios up to 0.55$M_*$ -- five times higher than Bondi-limited cases. However, strong radiation-driven winds can dramatically curtail growth, potentially quenching heavy-seed formation unless balanced by sustained envelope accretion. Our results delineate the physical limits under which quasi-stars can remain stable and produce heavy seeds capable of evolving into the earliest SMBHs detected by JWST and Chandra. Future extensions will incorporate rotation, magnetic fields, and GR-radiation hydrodynamics to refine accretion physics and constrain the viability of the quasi-star pathway for early SMBH formation.
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https://arxiv.org/abs/2510.11772
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3a0005fda0f7b7c3e78b06db53091823b84024a9531dac2014f6bcb1fc54d209
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2026-01-13T00:00:00-05:00
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Born to be recycled: a comprehensive population synthesis of the Galactic millisecond pulsars
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arXiv:2510.15661v2 Announce Type: replace Abstract: Millisecond pulsars (MSPs) are the oldest but fastest pulsars known to date. In the 1980s, to explain how these pulsars could be formed, a new hypothesis was formulated: the recycling of pulsars, i.e the fact that a pulsar could accrete matter from a companion and been spun up. In this paper, we developed a population synthesis algorithm for pulsars which belong to a binary, in order to check whether most of the observed recycled pulsars were formed via an accretion mechanism and derive statistics about their properties, that are difficult to obtain through observations. We also make predictions for future surveys. Toward the presented objectives, we use the code Stellar EVolution for N-body (SEVN) to take into account all the binary processes and our own code to evolve each pulsar self-consistently by taking into account the secular evolution of a force-free magnetosphere, the magnetic field decay, gravitational braking and spatial evolution. Each pulsar is born in binary with a main sequence companion, and evolve to present time. The radio and $\gamma$-ray emission locations were modeled by the polar cap geometry and striped wind model, respectively. Our simulations seem to reproduce well the population of radio and $\gamma$-ray pulsars observed in the selected surveys. We also found that there should be less than $220$ unidentified pulsars in the Fourth Fermi-LAT catalogue of $\gamma$-ray sources (4FGL). High values of the viewing angle $\zeta$ seem to be needed to be able to observe the recycled pulsars, and it also seems difficult to observe recycled pulsars with an aligned rotation axis and magnetic axis (i.e., $\chi \leq 10${\deg}). We find that only a small fraction, approximately $\sim 7.6\times10^{-3}$ %, of oxygen-neon white dwarfs (ONeWDs) in binary systems appear to contribute to the population of mildly recycled pulsars through accretion-induced collapse.
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https://arxiv.org/abs/2510.15661
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9eb24b2f3f63d68646b8eea16582dc1f5a3f0f08ef581b6680ad21c0e374c733
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2026-01-13T00:00:00-05:00
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Implications of Joint Spectral Analysis of Gamma-Ray Bursts detected by Fermi Large Area Telescope and Gamma-ray Burst Monitor on Phenomenological Correlations
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arXiv:2510.16475v2 Announce Type: replace Abstract: Gamma-ray bursts (GRBs) have emerged as powerful cosmological probes for exploring the distant Universe, owing to their immense luminosities and detectability at high redshifts. Several empirical correlations have been established, particularly involving their energy properties. This work aims to enhance the precision of these correlations through joint spectral analysis, focusing on reducing uncertainties in both the spectral indices and the peak energy ($E_{\rm p}$) derived from spectral fitting. We extend previous studies using both traditional and novel spectral models, utilizing a sample of 37 GRBs observed by the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT), incorporating the LAT Low-Energy (LLE) technique, over the period 2008-2024. Our analysis compares results from joint fits (GBM-LAT-LLE) against those from GBM-only fits. The study focuses on fitting time-integrated ${\rm T}_{90}$ and peak flux in the rest frame. Among the observable phenomenological correlations, we revisit the Amati and Yonetoku relations: the Amati relation links the intrinsic peak energy ($E_{i,\rm p}$) to the total isotropic energy ($E_{\rm iso}$) emitted during ${\rm T}_{90}$, while the Yonetoku relation connects $E_{i,\rm p}$ to the isotropic luminosity ($L_{\rm iso}$). Refining these correlations aims to deepen our understanding of GRB energetics and improve the precision of cosmological parameter estimates derived from GRB observations.
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https://arxiv.org/abs/2510.16475
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5ff02a9977eed67a0704f9714a5407fa9550b0eb4bc5b8cac0b312a6014ef77c
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2026-01-13T00:00:00-05:00
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Evolutionary Tracks and Spectral Properties of Quasi-stars and Their Correlation with Little Red Dots
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arXiv:2510.17952v2 Announce Type: replace Abstract: JWST has revealed a population of red, compact, high-redshift (${z\sim3-10}$) objects referred to as ``Little Red Dots'' (LRDs). These objects exhibit unusual spectral features reminiscent of stellar spectra with blackbody-like SEDs, large hydrogen Balmer breaks, Balmer line absorption, and classical stellar absorption features such as calcium H&K and the calcium triplet. Following the recent suggestion that these may be actively accreting direct-collapse black holes in the process of assembly, i.e. quasi-stars, we present evolutionary models of quasi-stars using our recently released, publicly available MESA-QUEST modeling framework. We compute a grid of models spanning a range of black hole masses and predict the luminosities, temperatures, surface gravities, and lifetimes of these objects. We find that these models lie along a Hayashi track once they hit their ``late-stage'' which constitutes the majority of their lives ($\sim 20$~Myr). We present scaling relations for estimating the mass of a quasi-star as a function of the bolometric luminosity, as well as the bolometric luminosity as a function of the effective temperature for the Hayashi track. The short lifetimes in tandem with the observed number density of LRDs imply the possibility that every supermassive black hole was once a quasi-star. We compare synthetic spectra of our quasi-star models to observations of LRDs, and show that these models are broadly capable of reproducing the continuum spectra of observed LRDs. These results indicate that quasi-stars are promising candidates for the origin of supermassive black holes via direct collapse in the early universe.
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https://arxiv.org/abs/2510.17952
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d89997386f0f25d858f7ffb70ba762ef07ac8ab988c326b4b22052f977e31d6c
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2026-01-13T00:00:00-05:00
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Stellar Wind-Blown Bubbles as Environments for Late-Time Rebrightening of Gamma-Ray Burst Afterglows
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arXiv:2510.22891v2 Announce Type: replace Abstract: We presented the multi-wavelength afterglow fitting results for three events that exhibit late afterglow rebrightening behavior: EP240414a ($z=0.401$), GRB 240529A ($z=2.695$), and GRB 240218A ($z=6.782$), which span a broad range of redshifts, from the local to the high-redshift universe.We prove that the peculiar afterglow light curves of three bursts can be well fitted by structured jets propagated in free-to-shocked stellar wind environment of stellar wind blown bubbles. This scenario offers a self-consistent explanation for the observed subclass of afterglows that exhibit rebrightening that is characterized by steep rises and rapid decays. It also provides a unified solution for such events and offers pathways to study both the jet generation mechanism and the propagation process of jets through the envelope of the progenitor. This study reveals that the structured jets produced by such events exhibit a narrow jet core and a steep angle-dependent energy decay index, suggesting highly magnetized jets. The derived transition radii from free stellar winds to shocked stellar winds for all three events are smaller than 0.5 pc, with statistical analysis of similar events indicating a median value of 0.1 pc, which conflicts with numerical simulation results. We anticipate that future observations by EP and SVOM missions will enhance the understanding of analogous events and further reveal information about progenitors and their circum-environments.
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https://arxiv.org/abs/2510.22891
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60ca942d557091ef471475984eaf6425030a5d07a2a1f69106f7e73d76094769
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2026-01-13T00:00:00-05:00
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Cosmic Vine: High abundance of massive galaxies and dark matter halos in a forming cluster at z=3.44
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arXiv:2510.23549v2 Announce Type: replace Abstract: The Cosmic Vine is a massive protocluster at z=3.44 in the JWST CEERS field, offering an ideal laboratory for studying the early phases of cluster formation. Using the data from the DAWN JWST Archive, we conduct a comprehensive study on the large-scale structure, stellar mass function (SMF), quiescent members, and dark matter halos in the Cosmic Vine. First, we spectroscopically confirm 136 galaxies in the Vine at z=3.44, and an additional 47 galaxies belonging to a diffuse foreground structure at z=3.34 which we dub the Leaf. We identify four subgroups comprising the Cosmic Vine and two subgroups within the Leaf. Second, we identified 11 quiescent members with log(M*/Msun)=9.5-11.0, the largest sample of quiescent galaxies in overdense environments at z>3, which gives an enhanced quiescent galaxy number density 2x10^(-4)cMpc^(-3) that is three times above the field level at log(M*/Msun) > 10. Notably, these quiescent members form a tight red sequence on the color-magnitude diagram, making it one of the earliest red sequences known to date. Third, by constructing the SMFs for both star-forming and quiescent members, we find that both SMFs are top-heavy, with a significantly enhanced quiescent fraction at log(M*/Msun)>10.5 compared to field counterparts. The stellar mass-size analysis reveals that star-forming members are more compact at higher masses than their field counterparts. Finally, we estimate a halo mass of log(Mh/Msun)=13.2+-0.3 for the protocluster core, and log(Mh/Msun)=11.9-12.4 for satellite subgroups. The phase-space analysis indicates that three subgroups are likely infalling to the core. This work reveals a high abundance of massive galaxies and dark matter halos in a forming cluster, demonstrating the accelerated assembly of massive galaxies in massive halos when the Universe was less than 2 billion years old.
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https://arxiv.org/abs/2510.23549
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0399a82e88388e17a7b9ad64a7d8032f012b3e6ecd322e1d2e6cb1ee226de3bd
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2026-01-13T00:00:00-05:00
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First Cosmological Constraints from the Joint Analysis of Galaxy Clustering and the Kinetic Sunyaev-Zel'dovich Effect
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arXiv:2510.27227v2 Announce Type: replace Abstract: We perform the first joint analysis of galaxy clustering (GC) and the kinetic Sunyaev-Zel'dovich (kSZ) effect to simultaneously constrain cosmological and astrophysical parameters in this work, utilizing a combination of the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) map and the Constant Stellar Mass (CMASS) galaxy sample. As a complementary probe to the galaxy density power spectrum, we incorporate the pairwise kSZ power spectrum detected with a high signal-to-noise ratio (S/N $\sim 7$) to derive constraints on cosmological parameters ($H_0 = 70.82^{+4.94}_{-5.01}$, $\Omega_{\rm m} = 0.290^{+0.092}_{-0.068}$, $w_0 = -1.038^{+0.245}_{-0.437}$) and the average optical depth of the galaxy sample ($\lg\bar{\tau} = -4.24 \pm 0.10$). Compared to the GC-only analysis, the joint analysis yields tighter constraints on these cosmological parameters: the Figures of Merit improve by 20.5\%, 19.7\% and 10.0\% for the $H_0$--$\Omega_{\rm m}$, $H_0$--$w_0$ and $\Omega_{\rm m}$--$w_0$ contours, respectively. For the first time, we demonstrate the complementary applicability of the kSZ effect in constraining cosmological parameters from real observational data.
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https://arxiv.org/abs/2510.27227
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ef6c77ca6a98ad8857ecde06180e7cb4b01263072c52e1fe156b277cc912d34c
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2026-01-13T00:00:00-05:00
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Machine-Learning Estimation of Energy Fractions in MHD Turbulence Modes
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arXiv:2511.04119v2 Announce Type: replace Abstract: Magnetohydrodynamic (MHD) turbulence plays a central role in many astrophysical processes in the interstellar medium (ISM), including star formation and cosmic-ray transport and acceleration. MHD turbulence can be decomposed into three fundamental modes-fast, slow, and Alfv\'en-each contributing differently to the dynamics of the medium. However, characterizing and separating the energy fractions of these modes was challenging due to the limited 2D information available from observations. To address this difficulty, we use 3D isothermal and multiphase MHD turbulence simulations to examine how mode energy fractions vary under different physical conditions. Overall, we find that the Alfv\'en and slow modes carry comparable kinetic-energy fractions and together dominate the turbulent energy budget in multiphase media, while the fast mode contributes the smallest fraction. Relative to isothermal conditions, multiphase simulations exhibit an enhanced fast-mode energy fraction. We further introduce a machine-learning-based approach that employs a conditional Residual Neural Network to infer these fractions directly from spectroscopic data. The method leverages the fact that the three MHD modes imprint distinct morphological signatures in spectroscopic maps owing to their differing contributions to density and velocity fluctuations. Our model is trained on a suite of isothermal and multiphase simulations covering typical ISM conditions. We demonstrate that our machine learning model can recover the mode fractions from spectroscopic observables, achieving mean relative normalized errors of approximately 0 and standard deviation of 0.01 - 0.02 for seen data and 0.1 - 1.8 for unseen data.
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https://arxiv.org/abs/2511.04119
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dcb8dc3920aa45348198e1ae34eb422702366f9e0c3f19e61c0f6a81104dd142
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2026-01-13T00:00:00-05:00
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The HITRAN2024 methane update
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arXiv:2511.21840v3 Announce Type: replace Abstract: Spectroscopic parameters of methane from many different studies were gathered to improve the HITRAN database towards its 2024 version. After a validation process using high-resolution FTS and CRDS spectra, about 80,000 lines of the four most abundant isotopologues were replaced from the dyad to the triacontad regions. These changes amount to 51,000 transition wavenumbers, 18,000 line intensities, 33,000 pressure-broadening half-widths, and 3300 assignments. 44,000 new lines were added with 16,000 old lines removed, extending the database from 12,000 cm$^{-1}$ up to 14,000 cm$^{-1}$, and covering some gaps. A greater focus was brought on the pentad, octad, and tetradecad regions, targeted by several remote sensing instruments. In these regions, comparisons of spectral fits from multiple line lists were performed, taking only the parameters that provide best fit for each line. In the $\nu _3$ band, in addition to replacing the previous values, speed-independent pressure broadening parameters of $^{12}$CH$_4$ were gathered and used to fit Pad\'e-approximant functions. These functions then replaced any outdated experimental data in $\nu _3$, missing data in the new lines, as well as the values that were determined to be outside their physical boundaries. The CH$_3$D broadening parameters were replaced in the same manner, for missing and low or high values, using a semi-empirical formula instead.
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https://arxiv.org/abs/2511.21840
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3b8478f472cf60d7dce20bf68a8ee4963c9c7f5b4490435462b6e2f94e4392e8
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2026-01-13T00:00:00-05:00
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Large Language Models for Limited Noisy Data: A Gravitational Wave Identification Study
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arXiv:2512.04031v2 Announce Type: replace Abstract: This work investigates whether large language models (LLMs) offer advantages over traditional neural networks for astronomical data processing, in regimes with non-Gaussian, non-stationary noise and limited labeled samples. Gravitational wave observations provide an suitable test case, using only 90 LIGO events, finetuned LLMs achieve 97.4\% accuracy for identifying signals. Further experiments show that, in contrast to traditional networks that rely on large simulated datasets, additional simulated samples do not improve LLM performance, while scaling studies reveal predictable gains with increasing model size and dataset size. These results indicate that LLMs can extract discriminative structure directly from observational data and provide an efficient assessment for gravitational wave identification. The same strategy may extend to other astronomical domains with similar noise properties, such as radio or pulsar observations.
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https://arxiv.org/abs/2512.04031
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c6ff2cd00871852e9180594cd8f29e5a4f644697d2309527f098714f0057df8e
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2026-01-13T00:00:00-05:00
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ExoMol line lists -- LXIII: ExoMol line lists for 12 isotopologues of CO$_2$
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arXiv:2512.13889v2 Announce Type: replace Abstract: Extensive rovibrational line lists are constructed for 12 isotopologues of carbon dioxide: $^{12}$C$^{16}$O$_2$, $^{13}$C$^{16}$O$_2$, $^{12}$C$^{17}$O$_2$, $^{13}$C$^{17}$O$_2$, $^{12}$C$^{18}$O$_2$, $^{13}$C$^{18}$O$_2$, $^{16}$O$^{12}$C$^{17}$O, $^{16}$O$^{12}$C$^{18}$O, $^{16}$O$^{13}$C$^{17}$O, $^{16}$O$^{13}$C$^{18}$O, $^{17}$O$^{12}$C$^{18}$O, and $^{17}$O$^{13}$C$^{18}$O. The variational program TROVE was employed together with an exact kinetic energy operator, accurate empirical potential energy surface (Ames-2) and the ab initio dipole moment surface Ames-2021-40K. Empirical energy levels from the most recent MARVEL analyses, as well as from the HITRAN and CDSD databases, are used to replace calculated values where available. The line lists are further supplemented by assigning AFGL quantum numbers using machine-learning based estimators. The resulting data were employed to generate opacities with four radiative transfer codes, TauREx, ARCiS, NEMESIS, and petitRADTRANS, both for individual isotopologues and for CO$_2$ at terrestrial isotopic natural abundance. All line lists and associated data are available at www.exomol.com.
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https://arxiv.org/abs/2512.13889
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102c79c8b3f6c728104b944da591624bbb15335850f74ddf3b34d45cb85e5a26
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2026-01-13T00:00:00-05:00
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First reverberation mapping of a Bowen fluorescence line
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arXiv:2512.15497v2 Announce Type: replace Abstract: Reverberation mapping (RM) is a powerful tool to determine the extent, structure, and kinematics of the broad-line region (BLR) of active galactic nuclei (AGN). So far, RM of the BLR has only been performed for recombination lines responding to the varying ionizing continuum. We tested whether OI 8446, attributed to Bowen fluorescence driven by Ly$\beta$ pumping, varied on short (day- to week-long) timescales during a 2016 HST/STIS campaign of NGC 4593, and examined how it relates to other emission lines and the ionizing UV continuum. We quantified the variability of OI 8446 by calculating its rms amplitude. We then extracted integrated light curves of OI 8446 and other UV and optical emission lines, and compared them with each other and with the UV continuum light curve using correlation analyses. In addition, we used archival near-infrared spectra to assess the dominant excitation mechanism of OI 8446. We detect, for the first time, variability in OI 8446 on day timescales. The fractional rms amplitude is $\sim 4$% over the 4-week campaign. The OI 8446 light curve reverberates with a delay of $\sim 2.5$ days relative to Ly$\alpha$, used as a proxy for Ly$\beta$, detected at a false-alarm probability of 0.6% (significance of $\sim 2.8\sigma$) under our adopted null hypothesis. It closely tracks H$\alpha$ with only a minor additional delay of $\sim0.3$ days, placing its emission region at essentially the same distance as the Balmer-line weighted BLR. Line ratios indicate that Ly$\beta$ pumping is the dominant excitation mechanism for O I 8446. Our results establish OI 8446 as the first Bowen-fluorescence line reverberation-mapped, responding directly to variations in Ly$\beta$ flux. We propose that in future campaigns targeting AGN with larger BLRs, O I could enable dual-driver RM using both the continuum and the pumping line as drivers.
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https://arxiv.org/abs/2512.15497
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ea99972b05487a65fbc9d7ec0f01af87b15babf0a040bb5091c589b246ed540e
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2026-01-13T00:00:00-05:00
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Multiband Gravitational Wave Detection Prospects for M31 UCXB-1 System in Low and Middle Frequency Band
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arXiv:2512.21520v2 Announce Type: replace Abstract: The recent discovery of M31 UCXB-1, the first extragalactic ultracompact X-ray binary (UCXB) with an orbital period of $T_{\rm orb} \sim 465$ s, presents a unique laboratory for studying close binary evolution and an unprecedented target for continuous gravitational wave (GW) searches. Its identification as a strong candidate black hole-white dwarf (BH-WD) system, combined with its exceptionally short period and high X-ray luminosity, suggests it may be one of the most vital low-frequency GW sources in M31. In this \textit{Letter}, we investigate the detectability of its GW signal for future space-borne detectors in multiband GW detection. We find that while its signal-to-noise ratio (S/N) for low-frequency detectors remains marginal for high-confidence detection, middle-frequency detectors such as DECIGO and BBO are far more promising, potentially achieving S/N $\varrho>8$ within reasonable observational duration. With a primary mass of only $m_1 > 5.4M_\odot$ (or $6.6M_\odot$), the network of all low and middle frequency detector (or BBO alone) is capable of detecting GW from this system with a $\varrho > 8$, during 10-year observation. Furthermore, orbital eccentricity can enhance the GW strain at higher harmonics, further improving its detectability, especially for middle-frequency detectors. This study establishes M31 UCXB-1 as a key prototype of short-period UCXBs, cementing its role as a cornerstone for multiband, multi-messenger astrophysics and a vital bridge between X-ray astronomy and the future GW era.
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https://arxiv.org/abs/2512.21520
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90cda64f85a4bad18fda7b6ad8a56703c546ef277aca73b208d335baeaad25f9
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2026-01-13T00:00:00-05:00
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Particle production and Higgs reheating
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arXiv:2512.21658v2 Announce Type: replace Abstract: Reheating is essential for transforming the cold, vacuum dominated Universe at the end of inflation into the hot thermal bath required by the Standard Model. In many well motivated inflationary models, however, the inflaton has no direct couplings to other fields, raising the question of how the Universe becomes repopulated with particles. We address this question within the framework of geometric reheating, where energy transfer occurs purely through gravitational effects. Focusing on a Higgs inflationary scenario with a non-minimal curvature coupling $\xi \phi^2 R$, we derive the post-inflationary dynamics and compute particle production using the Bogoliubov formalism. We show that the rapid, oscillatory evolution of the curvature scalar after inflaton acts as a time dependent gravitational pump, creating scalar spectator particles even in the absence of explicit interactions. This curvature driven production mechanism provides a natural and efficient route to reheating, demonstrating that gravity alone can initiate the standard thermal history and bridge inflation with radiation domination in minimal, coupling free models of the early Universe.
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https://arxiv.org/abs/2512.21658
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915423822da6019bd737405bf9b8c95208d37f0fb2ca14bf85c79047795bffe0
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2026-01-13T00:00:00-05:00
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A global view of post-interaction white dwarf-main sequence binaries
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arXiv:2601.00439v2 Announce Type: replace Abstract: Common-envelope evolution (CEE) is among the most uncertain phases in binary evolution. To empirically constrain CEE, we construct a uniformly selected sample of eclipsing post--common-envelope binaries (PCEBs). Starting from an unresolved white dwarf-main-sequence (WDMS) candidate sample within 200 pc selected from the Gaia color-magnitude diagram, we identify 39 detached eclipsing WDMS binaries using ZTF light curves. The binaries contain cool M dwarfs orbiting warm white dwarfs with orbital periods ($P_{\rm orb}$) of 0.1-2 d. The sample's simple selection function allows us to model observational incompleteness and infer intrinsic properties of the PCEB population. We find an orbital-period distribution consistent with being log-uniform over 0.1-2 d, contrary to recent reports of a bimodal distribution. The companion-mass distribution peaks around $0.25~{\rm M_\odot}$ and declines steeply toward larger masses. The estimated local space density is $7.2\times10^{-5}~{\rm pc^{-3}}$, corresponding to a Galaxy-wide birth rate of 0.01 per year. Combining our results with recent Gaia-based constraints on wider WDMS binaries, we construct an empirical period distribution of post-interaction WDMS binaries spanning 0.1-1000 d. The emerging period distribution is roughly log-flat (d$N/{\rm d}\log P_{\rm orb}\propto P_{\rm orb}^0$) at $P_{\rm orb} < 2$ d and log-increasing (d$N/{\rm d}\log P_{\rm orb}\propto P_{\rm orb}^1$) at $P_{\rm orb} = 100-1000$ d. The 10-100 d regime remains poorly constrained, but a few nearby systems suggest it is also well-populated. Short-period PCEBs ($P_{\rm orb}<2$ d) with M dwarf companions are roughly 2-3 times more common than wide ($P_{\rm orb} = 100-1000$ d) WDMS binaries with FGK companions, which likely formed through stable mass transfer. These results provide direct observational constraints on CEE and an empirical benchmark for binary-population models.
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https://arxiv.org/abs/2601.00439
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b8aadf295702cf646d895fe56b81fab4ae759d7928fa23665676b861a732c593
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2026-01-13T00:00:00-05:00
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Vetting and False Positive Analysis of TOI 864.01: Evidence for a Likely Hierarchical Eclipsing Binary Masked by Dilution
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arXiv:2601.02171v3 Announce Type: replace Abstract: We present a detailed vetting analysis of the TESS candidate TOI 864.01, initially identified as a potential ultra-short-period ($P \approx 0.52$ d) Earth-sized planet orbiting an M-dwarf. Using 12 sectors of TESS photometry spanning a multi-year baseline, we recover a robust periodic transit-like signal. While the recovered transit depth is attenuated by detrending ($\approx 158$ ppm), the SPOC pipeline reports an undiluted depth of $\approx 640$ ppm. Stellar characterization based on Gaia DR3 astrometry yields a nominally single-star solution (RUWE = 1.18), highlighting the limitations of astrometric vetting for tight companions. Incorporating archival high-resolution imaging from the TESS Follow-up Observing Program (TFOP SG1) reveals a stellar companion at a separation of 0.04", unresolved by both Gaia and TESS. Accounting for this close contaminant renders statistical validation inapplicable, as False Positive Probability calculations fail to converge in this regime of extreme dilution. Bayesian model comparison between planetary and eclipsing binary scenarios yields an inconclusive result ($\Delta \ln Z \approx 0.09$), consistent with the strong degeneracy introduced by unresolved blending. Ground-based follow-up photometry further supports significant dilution, with a measured transit depth ($\approx 0.37$ ppt) shallower than predicted under an undiluted planetary scenario ($\approx 0.64$ ppt). Notably, ground-based observations also reveal a transit timing offset of 6.3 minutes late compared to the SPOC ephemeris, further supporting a non-planetary interpretation. Taken together, the available evidence favors a hierarchical eclipsing binary interpretation. We therefore classify TOI 864.01 as a probable False Positive and recommend its retirement from planetary candidate lists.
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https://arxiv.org/abs/2601.02171
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c67e198e0cd5a987ba00517df056757778b235567d4f97643851a790286c1ff0
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2026-01-13T00:00:00-05:00
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Energetic particles accelerated via turbulent magnetic reconnection in protoplanetary discs - I. Ionisation rates
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arXiv:2601.05060v2 Announce Type: replace Abstract: Context. Ionisation controls the chemistry, thermal balance, and magnetic coupling in protoplanetary discs. However, standard ionisation vectors such as stellar UV, X-rays, Galactic cosmic rays (GCRs) might not be efficient enough, as UV/X-rays are attenuated rapidly with depth, while GCRs are modulated. Turbulence-induced magnetic reconnection in disc atmospheric layers offers a physically motivated, in situ source of energetic particles (EPs) that has never been considered. Aims. We quantify the ionisation and heating produced by EPs accelerated by turbulent reconnection, identify where they dominate over X-rays and GCRs, and determine energetic thresholds for their relevance. We provide scalable diagnostics tied to the local energy budget. Methods. We adopt a Fermi-like acceleration model with parameters linked to a turbulent reconnection geometry trigger by the magneto-rotational instability, yielding a steady-state energy distribution of the EP forming a power-law of index $p=2.5$. We propagate electrons and protons through the disc and compute primary and secondary ionisation and associated heating on a fiducial T Tauri disc model background. The non-thermal normalisation is set by the fraction of local viscous accretion energy dissipation channelled to EPs, parametrised by $\kappa$. Results. For $\kappa\gtrsim 0.4\%$, EPs ionisation overpass standard ionisation sources in the disc atmosphere and intermediate/deep layers out to radii of a few tens of astronomical units. Even at $\kappa\sim 0.025\%$, EPs contribute at the few-percent level, thus are chemically and dynamically relevant. These results identify EPs accelerated by turbulence-induced magnetic reconnection as a rather robust, disc-internal ionisation channel that should be included in thermo-chemical models of protoplanetary discs.
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https://arxiv.org/abs/2601.05060
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a21a2f1b63ce8e40db3ab9b72cf74ec7b8e4263ec73c0b4fe1332fccbd27a6ae
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2026-01-13T00:00:00-05:00
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Hidden pattern of self-invariant cosmic expansion: Empirical evidence from Hubble diagram of supernovae
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arXiv:2601.05512v2 Announce Type: replace Abstract: We present empirical evidence extracted from the Pantheon Catalog of SNeIa demonstrating that the speed of light varies as the universe expands. Moreover, the speed of light must vary in a specific quantifiable manner. Departing from the standard $\Lambda$CDM model, we reformulate the kinematics of late-time acceleration by employing Dolgov's power-law cosmology $a=\left(t/t_{0}\right)^{\mu}$ [Phys. Rev. D 55, 5881 (1997)] and Barrow's varying speed of light $c=c_{0}\,a^{-\zeta}$ [Phys. Rev. D 59, 043515 (1999)]. In this cosmology, light traveling through an expanding universe undergoes an additional refraction caused by the varying c along its path, resulting in a modified Lemaitre redshift formula $1+z=a^{-(1+\zeta)}$. Despite its parsimony, the model achieves a high-quality fit to the Pantheon Catalog of SNeIa and exhibits a strong degeneracy along the locus $(1+\zeta)\,\mu=1$. This empirical relation indicates a self-invariant cosmic evolution: at all instants during the late-time epoch, the speed of light is exactly proportional to the rate of cosmic expansion, viz. $c=\mu^{-1}c_{0}\,t_{0}\,\frac{da}{dt}$, a characteristic that is absent in the $\Lambda$CDM model. This synchronous behavior between $c$ and $da/dt$ has profound cosmological implications that we will discuss, regarding (i) the nature of late-time acceleration; (ii) the horizon problem; (iii) Kolb's coasting universe model [Astrophys. J. 344, 543 (1989)]; (iv) a generalization of the cosmological principle to the time domain; and (v) the emergence of a novel conformally flat metric applicable to cosmology. This newfound kinematic $c\propto da/dt$ relation, if further corroborated, will represent a stringent requirement that any viable dynamical model of cosmology must satisfy -- a requirement that the $\Lambda$CDM model does not fulfill.
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https://arxiv.org/abs/2601.05512
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8a5d94d361aca5bd63fa0682ce65aeed0524545d0689d785862ee90b7ed51c3d
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2026-01-13T00:00:00-05:00
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Corrections to the Black hole entropy from a Bose Einstein condensate: a semi-classical phenomenological approach
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arXiv:2501.04358v2 Announce Type: replace-cross Abstract: In this paper we obtain logarithmic corrections to the black hole entropy. Motivated by our recent proposal concerning the nature of the degrees of freedom leading to the black hole entropy in terms of a Bose Einstein (BEC) condensate of gravitons, we study how to introduce logarithmic corrections. In fact we show that, after modifying the internal energy by means of simple by physically sound arguments dictated by ordinary quantum mechanics and possible non-commutative effects at Planckian scales, a logarithmic term does appear in the Bekenstein Hawking entropy law. We also obtain that the entropy $S_{BH}$ of a ball of Planckian areal radius is $2\pi K_B$, i.e. $S_{BH}(R=L_P)=2\pi K_B$. Our approach show that the possibility that the interior of a black hole is composed with a BEC of gravitons is a viable physically motivated possibility.
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https://arxiv.org/abs/2501.04358
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2c3b01e8698b09bbb557fd76ba3c6aba96a2cbb557088f73b7bada002e92baff
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2026-01-13T00:00:00-05:00
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Supernova constraints on lepton flavor violating ALPs
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arXiv:2501.12075v3 Announce Type: replace-cross Abstract: Supernovae offer a unique hot and dense environment to probe new physics beyond the Standard Model. We investigate supernova cooling constraints on lepton-flavor-violating (LFV) axions and axion-like particles (ALPs) that couple to electrons and muons. For LFV-ALP production in supernovae, muon decay and lepton bremsstrahlung have been considered previously. In this work, we identify the electron-muon coalescence channel as an efficient new production mechanism in the high-mass regime. We also include the semi-Compton scattering process, which has recently been shown to provide sizable contributions for electron-coupled ALPs. We find that muon decay dominates in the low-mass regime, electron-muon coalescence becomes the leading channel at high masses, and semi-Compton scattering provides the dominant contribution in the intermediate mass range. We find that the electron-muon coalescence process yields the strongest constraints in the mass range of $\sim (115,280)$ MeV, probing the ALP-electron-muon coupling down to $\sim 4\times 10^{-10}$ for an ALP mass of $\sim200$ MeV.
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https://arxiv.org/abs/2501.12075
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8af56bfaa92241f334e426e8ad5744ef8fbf26f7367c30e4bd3577f3e7f7b410
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2026-01-13T00:00:00-05:00
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Enhancing gravitational-wave detection: a machine learning pipeline combination approach with robust uncertainty quantification
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arXiv:2504.17587v3 Announce Type: replace-cross Abstract: Gravitational-wave data from advanced-era interferometric detectors consists of background Gaussian noise, frequent transient artefacts, and rare astrophysical signals. Multiple search algorithms exist to detect the signals from compact binary coalescences, but their varying performance complicates interpretation. We present a machine learning-driven approach that combines results from individual pipelines and utilises conformal prediction to provide robust, calibrated uncertainty quantification. Using simulations, we demonstrate improved detection efficiency and apply our model to GWTC-3, enhancing confidence in multi-pipeline detections, such as the sub-threshold binary neutron star candidate GW200311_103121.
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https://arxiv.org/abs/2504.17587
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2198e6e31a73dd55571a930fde27112433c943d1abd26dab01b866fc3e3c93a7
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2026-01-13T00:00:00-05:00
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Dark Matter in X-rays: Revised XMM-Newton Limits and New Constraints from eROSITA
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arXiv:2506.02310v3 Announce Type: replace-cross Abstract: We investigate two classes of dark matter (DM) candidates, sub-GeV particles and primordial black holes (PBHs), that can inject low-energy electrons and positrons into the Milky Way and leave observable signatures in the X-ray sky. In the case of sub-GeV DM, annihilation or decay into $e^+e^-$ contributes to the diffuse sea of cosmic-ray (CR) leptons, which can generate bremsstrahlung and inverse Compton (IC) emission on Galactic photon fields, producing a broad spectrum from X-rays to $\gamma$-rays detectable by instruments such as eROSITA and XMM-Newton. For PBHs with masses below $\sim10^{17}$ g, Hawking evaporation similarly yields low-energy $e^\pm$, leading to comparable diffuse emission. Using the first data release from eROSITA and incorporating up-to-date CR propagation and diffusion parameters, we derive new constraints on both scenarios. For sub-GeV DM, we exclude thermally averaged annihilation cross sections in the range $\sim 10^{-27}-10^{-25} \ \mathrm{cm^3/s}$ and decay lifetimes of $\sim 10^{24}-10^{25}$ s for masses between 1 MeV and 1 GeV, with eROSITA outperforming previous X-ray constraints below $\sim$ 30 MeV. For asteroid-mass PBHs, we set new bounds on the DM fraction based on their Hawking-induced emission. Finally, we revisit earlier constraints from XMM-Newton, finding that they were approximately four orders of magnitude too stringent due to the use of the instrument's geometric solid angle rather than its exposure-weighted solid angle. Upon using the exposure-weighted solid angle, we show that the revised XMM-Newton limits are slightly weaker than those from eROSITA.
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https://arxiv.org/abs/2506.02310
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2952ba4e7346bc51a4e7125aecd6769dec6ba58ae1bbf1b5f441f0926c4501af
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2026-01-13T00:00:00-05:00
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Diffuse astrophysical neutrinos from dark matter around blazars
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arXiv:2506.06416v2 Announce Type: replace-cross Abstract: Neutrinos from blazars can originate from inelastic scatterings between protons within their jets and sub-GeV dark matter (DM) around them, explaining IceCube detections of neutrinos from TXS 0506+056 that are otherwise challenging for models of its jet. In this paper we calculate such DM-induced high-energy neutrinos, from TXS 0506+056 as well as from a stacked blazar sample, in the four cases where DM-quark interactions are mediated by a new massive vector, axial, scalar, and pseudoscalar particle. Intriguingly, we find that this mechanism can saturate the diffuse astrophysical neutrino flux observed by IceCube at high energies. Our mechanism will be tested by additional blazar observations and by various searches for sub-GeV DM.
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https://arxiv.org/abs/2506.06416
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24967a7adc06c9665b3d0a4e749f2c036fc8180ee5e148550c9cdffeefc73bb1
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2026-01-13T00:00:00-05:00
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Stability of Thin Shell and Wormhole Configurations: Schwarzschild, Schwarzschild -- (Anti-) de Sitter, and FLRW Spacetimes
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arXiv:2507.00315v2 Announce Type: replace-cross Abstract: The stability of thin shell wormholes and black holes to linearized spherically symmetric perturbations about a static equilibrium is analyzed. Thin shell formalism is explored and junctions formed from combinations of Schwarzschild, Schwarzschild - de Sitter, and Schwarzschild - anti-de Sitter, as well as Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetimes are considered. The regions of stability for these different combinations are thoroughly described and plotted as a function of mass ratios of the Schwarzschild masses and radii of the wormhole throats. A taxonomy of the qualitative features of the various configurations and parameter spaces is developed, illustrating the stability regions when present. The considered wormholes are all found to be unstable in the causal region.
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https://arxiv.org/abs/2507.00315
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d36e92ec7b1e10da0412572962f5cf256eaeaad1b37bc9be9ae199f8a31bbd6b
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2026-01-13T00:00:00-05:00
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Quasi-Normal Modes and Nonlinear Electrodynamics in Black Hole Phase Transitions
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arXiv:2508.00404v5 Announce Type: replace-cross Abstract: We investigate the connection between thermodynamic phase transitions and quasi-normal modes (QNMs) in charged black holes with a positive curvature constant, within the framework of $F(R)$-Euler-Heisenberg gravity. Nonlinear electromagnetic fields lead to rich thermodynamic phase structures and significantly affect the QNMs of massless scalar fields. By analyzing the QNMs spectrum, we find that the transition point marking the disappearance of the divergence in the QNMs slope parameter $K$ aligns with the change of the thermodynamic phase structure described by the heat capacity, within the bounds of computational uncertainty. This precise matching holds under variations of the curvature parameter and charge. Furthermore, we show that larger angular quantum number $l$ diminishes this correspondence, while higher overtone number $n$ restores it beyond a threshold. These findings demonstrate that thermodynamic phase transitions of black holes carry embedded dynamical information, uncovering a fundamental link between black hole thermodynamic and dynamical properties.
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https://arxiv.org/abs/2508.00404
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3b3529fcde06d2b213faeb835ad5064a15ef08ab91684f23edcce33a9bcfab35
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2026-01-13T00:00:00-05:00
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Color-superconducting quarkyonic matter
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arXiv:2509.03517v2 Announce Type: replace-cross Abstract: We explore the role of color superconductivity in quarkyonic matter under the conditions of color and electric neutrality at $\beta$- and strong equilibrium, as relevant for neutron stars. By explicitly incorporating the color-superconducting pairing gap into the phenomenological model of a smooth transition from hadron to quark matter, we extend the known quarkyonic framework to include this essential aspect relevant at high densities. The momentum dependence of the pairing gap, motivated by the running of the QCD coupling and introduced similarly to chiral quark models with nonlocal interaction, is a novel element of the model that is crucial for enabling the simultaneous onset of all color-flavor quark states in the presence of color superconductivity. While asymptotically conformal behavior of the present model is ensured by construction, we demonstrate that reaching the conformal limit in agreement with the predictions of perturbative QCD is provided by the proper momentum dependence of the thickness of the hadron shell in momentum space. We employ the flexible meta-modeling approach to nuclear matter, analyzing the structure of the hadron shell in momentum space and focusing on the effects of color superconductivity in quarkyonic matter. Similar to the effects induced by the onset of the quarkyonic phase, color superconductivity leads to stiffening of the equation of state of the NS matter. This causes a significant impact on observable properties of neutron stars, which are analyzed and compared to recent astrophysical and theoretical constraints. We argue that the developed model of color-superconducting quarkyonic matter provides a new, consistent tool for studying the scenario of smooth quark-hadron transition in NSs.
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https://arxiv.org/abs/2509.03517
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1bbb7122ece2762983b1abfa744bf0eb0a5cad2678ede5053643a1bc048363ab
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2026-01-13T00:00:00-05:00
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Uncertainty in predicting the stochastic gravitational wave background from compact binary coalescences
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arXiv:2510.02163v2 Announce Type: replace-cross Abstract: The stochastic gravitational-wave background from compact binary coalescences is expected to be the first detectable stochastic signal via cross-correlation searches with terrestrial detectors. It encodes the cumulative merger history of stellar-mass binaries across cosmic time, offering a unique probe of the high-redshift Universe. However, predicting the background spectrum is challenging due to numerous modeling choices, each with distinct uncertainties. In this work, we present a comprehensive forecast of the astrophysical gravitational-wave background from binary black holes, binary neutron stars, and neutron star-black hole systems. We systematically assess the impact of uncertainties in population properties, waveform features, and the modeling of the merger rate evolution. By combining all uncertainties, we derive credible bands for the background spectrum, spanning approximately an order of magnitude in the fractional energy density. These results provide thorough predictions to facilitate the interpretation of current upper limits and future detections.
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https://arxiv.org/abs/2510.02163
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66cb383e1e57b95b49512796e31c68c1595951e2841145f01b172ec2dc4de7a0
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2026-01-13T00:00:00-05:00
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Cavity Multimodes as an Array for High-Frequency Gravitational Waves
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arXiv:2601.03341v2 Announce Type: replace-cross Abstract: Microwave cavities operated in the presence of a background magnetic field provide a promising avenue for detecting high-frequency gravitational waves (HFGWs). We demonstrate for the first time that the distinct antenna patterns of multiple electromagnetic modes within a single cavity enable localization and reconstruction of key properties of an incoming HFGW signal, including its polarization ratio and frequency drift rate. Using a 9-cell cavity commonly employed in particle accelerators as a representative example, we analyze the time-domain response of 18 nearly degenerate modes, which can be sequentially excited by a frequency-drifting signal. The sensitivity is further enhanced by the number of available modes, in close analogy to the scaling achieved by a network of independent detectors, enabling sensitivity to astrophysically plausible binary sources.
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https://arxiv.org/abs/2601.03341
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e0de43bc63b5385d587795d8bf8a2c100be1abce90863158f4e1b3075ccf1c0a
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2026-01-13T00:00:00-05:00
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Resolving the automation paradox: falling labor share, rising wages
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arXiv:2601.06343v1 Announce Type: new Abstract: A central socioeconomic concern about Artificial Intelligence is that it will lower wages by depressing the labor share - the fraction of economic output paid to labor. We show that declining labor share is more likely to raise wages. In a competitive economy with constant returns to scale, we prove that the wage-maximizing labor share depends only on the capital-to-labor ratio, implying a non-monotonic relationship between labor share and wages. When labor share exceeds this wage-maximizing level, further automation increases wages even while reducing labor's output share. Using data from the United States and eleven other industrialized countries, we estimate that labor share is too high in all twelve, implying that further automation should raise wages. Moreover, we find that falling labor share accounted for 16\% of U.S. real wage growth between 1954 and 2019. These wage gains notwithstanding, automation-driven shifts in labor share are likely to pose significant social and political challenges.
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https://arxiv.org/abs/2601.06343
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3a10023b68d7cef6fbc072a6533f5c95391e3884cde8519909381a5385585d78
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2026-01-13T00:00:00-05:00
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Long-Term Causal Inference with Many Noisy Proxies
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arXiv:2601.06359v1 Announce Type: new Abstract: We propose a method for estimating long-term treatment effects with many short-term proxy outcomes: a central challenge when experimenting on digital platforms. We formalize this challenge as a latent variable problem where observed proxies are noisy measures of a low-dimensional set of unobserved surrogates that mediate treatment effects. Through theoretical analysis and simulations, we demonstrate that regularized regression methods substantially outperform naive proxy selection. We show in particular that the bias of Ridge regression decreases as more proxies are added, with closed-form expressions for the bias-variance tradeoff. We illustrate our method with an empirical application to the California GAIN experiment.
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https://arxiv.org/abs/2601.06359
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7e3173974c2d9452d3152a70e40b191748ad2b082b6f6098841a42e3dca0208d
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2026-01-13T00:00:00-05:00
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The Promise of Time-Series Foundation Models for Agricultural Forecasting: Evidence from Marketing Year Average Prices
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arXiv:2601.06371v1 Announce Type: new Abstract: Forecasting agricultural markets remains a core challenge in business analytics, where nonlinear dynamics, structural breaks, and sparse data have historically limited the gains from increasingly complex econometric and machine learning models. As a result, a long-standing belief in the literature is that simple time-series methods often outperform more advanced alternatives. This paper provides the first systematic evidence that this belief no longer holds in the modern era of time-series foundation models (TSFMs). Using USDA ERS data from 1997-2025, we evaluate 17 forecasting approaches across four model classes, assessing monthly forecasting performance and benchmarking against Market Year Average (MYA) price predictions. This period spans multiple agricultural cycles, major policy changes, and major market disruptions, with substantial cross-commodity price volatility. Focusing on five state-of-the-art TSFMs, we show that zero-shot foundation models (with only historical prices and without any additional covariates) consistently outperform traditional time-series methods, machine learning models, and deep learning architectures trained from scratch. Among them, Time-MoE delivers the largest accuracy gains, improving forecasts by 45% (MAE) overall and by more than 50% for corn and soybeans relative to USDA benchmarks. These results point to a paradigm shift in agricultural forecasting: while earlier generations of advanced models struggled to surpass simple benchmarks, modern pre-trained foundation models achieve substantial and robust improvements, offering a scalable and powerful new framework for highstakes predictive analytics.
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https://arxiv.org/abs/2601.06371
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feafa60ecf4cf76f3a348f5c97fe63b23af86b0be84bef9c466b36e8823f94cf
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2026-01-13T00:00:00-05:00
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Bounded Rationality with Subjective Evaluations in Enlivened but Truncated Decision Trees
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arXiv:2601.06405v1 Announce Type: new Abstract: In normative models a decision-maker is usually assumed to be Bayesian rational, and so to maximize subjective expected utility, within a complete and correctly specified decision model. Following the discussion in Hammond (2007) of Schumpeter's (1911, 1934) concept of entrepreneurship, as well as Shackle's (1953) concept of potential surprise, we consider enlivened decision trees whose growth over time cannot be accurately modelled in full detail. An enlivened decision tree involves more severe limitations than a mis-specified model, unforeseen contingencies, or unawareness, all of which are typically modelled with reference to a universal state space large enough to encompass any decision model that an agent may consider. We consider a motivating example based on Homer's classic tale of Odysseus and the Sirens. Though our novel framework transcends standard notions of risk or uncertainty, for finite decision trees that may be truncated because of bounded rationality, an extended and refined form of Bayesian rationality is still possible, with real-valued subjective evaluations instead of consequences attached to terminal nodes where truncations occur. Moreover, these subjective evaluations underlie, for example, the kind of Monte Carlo tree search algorithm used by recent chess-playing software packages. They may also help rationalize the contentious precautionary principle.
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https://arxiv.org/abs/2601.06405
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b3530a940b1943a0912b0b1c63d324b31c8875527deb743038e38b4fd4c33d2d
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2026-01-13T00:00:00-05:00
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Sign Accuracy, Mean-Squared Error and the Rate of Zero Crossings: a Generalized Forecast Approach
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arXiv:2601.06547v1 Announce Type: new Abstract: Forecasting entails a complex estimation challenge, as it requires balancing multiple, often conflicting, priorities and objectives. Traditional forecast optimization criteria typically focus on a single metric -such as minimizing the mean squared error (MSE)- which may overlook other important aspects of predictive performance. In response, we introduce a novel approach called the Smooth Sign Accuracy (SSA) framework, which simultaneously considers sign accuracy, MSE, and the frequency of sign changes in the predictor. This addresses a fundamental trade-off (the so-called accuracy-smoothness (AS) dilemma) in prediction. The SSA criterion thus enables the integration of various design objectives related to AS forecasting performance, effectively generalizing conventional MSE-based metrics. We further extend this methodology to accommodate non-stationary, integrated processes, with particular emphasis on controlling the predictor's monotonicity. Moreover, we demonstrate the broad applicability of our approach through an application to, and customization of, established business cycle analysis tools, highlighting its versatility across diverse forecasting contexts.
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https://arxiv.org/abs/2601.06547
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16addfa2d460e275fea90a3f223804acee7d85dd4507cfd0ac56147e3178eacc
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2026-01-13T00:00:00-05:00
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Empirical Bayes Estimation in Heterogeneous Coefficient Panel Models
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arXiv:2601.07059v1 Announce Type: new Abstract: We develop an empirical Bayes (EB) G-modeling framework for short-panel linear models with multidimensional heterogeneity and nonparametric prior. Specifically, we allow heterogeneous intercepts, slopes, dynamics, and a non-spherical error covariance structure. We establish identification and consistency of the nonparametric maximum likelihood estimator (NPMLE) under general conditions, and provide low-level sufficient conditions for several models of empirical interest. Conditions for regret consistency of the resulting EB estimators are also established. The NPMLE is computed using a Wasserstein-Fisher-Rao gradient flow algorithm adapted to panel regressions. Using data from the Panel Study of Income Dynamics, we find that the slope coefficient for potential experience is substantially heterogeneous and negatively correlated with the random intercept, and that error variances and autoregressive coefficients vary significantly across individuals. The EB estimates reduce mean squared prediction errors relative to individual maximum likelihood estimates.
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https://arxiv.org/abs/2601.07059
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6997270a0d2cd9e8f37981ec206f32362752d21b02da9b78ee9e54ec117c33f9
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2026-01-13T00:00:00-05:00
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A Note on 'The Limits of Price Discrimination' by Bergemann, Brooks, and Morris
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arXiv:2601.07452v1 Announce Type: new Abstract: This note revisits the analysis of third-degree price discrimination developed by Bergemann et al. (2015), which characterizes the set of consumer-producer surplus pairs that can be achieved through market segmentation. This was proved by means of market segmentation with random prices, but it was claimed that any segmentation with possibly random pricing has a corresponding direct segmentation, where a deterministic price is charged in each market segment. However, the latter claim is not correct under the definition of market segmentation given in the paper, and we provide counterexamples. We then propose an alternative definition to resolve this issue and examine the implications of the difference between the two definitions in terms of the main result of their paper.
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https://arxiv.org/abs/2601.07452
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668f622d3e9cce7dc2766c25b7503724b45089d57a7a239ca689611720b81c01
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2026-01-13T00:00:00-05:00
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Modelling Distributional Impacts of Carbon Taxation: a Systematic Review and Meta-Analysis
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arXiv:2601.07713v1 Announce Type: new Abstract: Carbon taxes are increasingly popular among policymakers but remain politically contentious. A key challenge relates to their distributional impacts; the extent to which tax burdens differ across population groups. As a response, a growing number of studies analyse their distributional impact ex-ante, commonly relying on microsimulation models. However, distributional impact estimates differ across models due to differences in simulated tax designs, assumptions, modelled components, data sources, and outcome metrics. This study comprehensively reviews methodological choices made in constructing microsimulation models designed to simulate the impacts of carbon taxation and discusses how these choices affect the interpretation of results. It conducts a meta-analysis to assess the influence of modelling choices on distributional impact estimates by estimating a probit model on a sample of 217 estimates across 71 countries. The literature review highlights substantial diversity in modelling choices, with no standard practice emerging. The meta-analysis shows that studies modelling carbon taxes on imported emissions are significantly less likely to find regressive results, while indirect emission coverage has ambiguous effects on regressivity, suggesting that a carbon border adjustment mechanism may reduce carbon tax regressivity. Further, we find that estimates using older datasets, using explicit tax progressivity or income inequality measures, and accounting for household behaviour are associated with a lower likelihood of finding regressive estimates, while the inclusion of general equilibrium effects increases this likelihood.
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https://arxiv.org/abs/2601.07713
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2f67474cb63a02dc22b376b59ac0850ae58f0b08eda0a427ba084c0a15bf3ee4
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2026-01-13T00:00:00-05:00
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Who sets the range? Funding mechanics and 4h context in crypto markets
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arXiv:2601.06084v1 Announce Type: cross Abstract: Financial markets often appear chaotic, yet ranges are rarely accidental. They emerge from structured interactions between market context and capital conditions. The four-hour timeframe provides a critical lens for observing this equilibrium zone where institutional positioning, leveraged exposure, and liquidity management converge. Funding mechanisms, especially in perpetual futures, act as disciplinary forces that regulate trader behavior, impose economic costs, and shape directional commitment. When funding aligns with the prevailing 4H context, price expansion becomes possible; when it diverges, compression and range-bound behavior dominate. Ranges therefore represent controlled balance rather than indecision, reflecting strategic positioning by informed participants. Understanding how 4H context and funding operate as market governors is essential for interpreting cryptocurrency price action as a rational, power-mediated process.
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https://arxiv.org/abs/2601.06084
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2133c5c7ce4d5125321ec880e62ad310ca29f28cf4d81f82b7caa16657267ba9
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2026-01-13T00:00:00-05:00
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Crypto Pricing with Hidden Factors
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arXiv:2601.07664v1 Announce Type: cross Abstract: We estimate risk premia in the cross-section of cryptocurrency returns using the Giglio-Xiu (2021) three-pass approach, allowing for omitted latent factors alongside observed stock-market and crypto-market factors. Using weekly data on a broad universe of large cryptocurrencies, we find that crypto expected returns load on both crypto-specific factors and selected equity-industry factors associated with technology and profitability, consistent with increased integration between crypto and traditional markets. In addition, we study non-tradable state variables capturing investor sentiment (Fear and Greed), speculative rotation (Altcoin Season Index), and security shocks (hacked value scaled by market capitalization), which are new to the literature. Relative to conventional Fama-MacBeth estimates, the latent-factor approach yields materially different premia for key factors, highlighting the importance of controlling for unobserved risks in crypto asset pricing.
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https://arxiv.org/abs/2601.07664
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cfb17773ade5cbee88897d490f3f316c31e6723b5b17f842e3fdc42715ac5908
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2026-01-13T00:00:00-05:00
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Recursive Score and Hessian Computation in Regime-Switching Models
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arXiv:2205.01565v2 Announce Type: replace Abstract: This study proposes a recursive and easy-to-implement algorithm to compute the score and Hessian matrix in general regime-switching models. We use simulation to compare the asymptotic variance estimates constructed from the Hessian matrix and the outer product of the score. The results favor the latter.
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https://arxiv.org/abs/2205.01565
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8ebb856fb39e6f77b26a77df0112030cffdd03bef665dfc2ebd508ca114c9979
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2026-01-13T00:00:00-05:00
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Regulation and Frontier Housing Supply
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arXiv:2208.01969v5 Announce Type: replace Abstract: Regulation is a major driver of housing supply, yet often difficult to observe directly. This paper estimates frontier cost, the non-land cost of producing housing absent regulation, and regulatory tax, which quantifies regulation in money terms. Working within an urban environment of multi-floor, multi-family housing and using only apartment prices and building heights, we show that the frontier is identified from the support of supply and demand shocks without recourse to instrumental variables. In an application to new Israeli residential construction, and accounting for random housing quality, the estimated mean regulatory tax is 48% of housing prices, with substantial variation across locations. The regulatory tax is positively correlated with centrality, density, and prices. We construct a lower bound for the regulatory tax that allows quality to differ systematically over location and time, by assuming (weak) complementarity between quality and demand. At the end of our sample, when prices are highest and our bound is most informative, we bound the regulatory tax between 40% (using a 2km radius) and 53%.
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https://arxiv.org/abs/2208.01969
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b7e918bee3b8e1959ec0866bce96cc48ae7966b4dc0a365bd0ea77f45308b608
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2026-01-13T00:00:00-05:00
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Forecasted Treatment Effects
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arXiv:2309.05639v4 Announce Type: replace Abstract: We consider estimation and inference of the effects of a policy in the absence of an untreated or control group. We obtain unbiased estimators of individual (heterogeneous) treatment effects and a consistent and asymptotically normal estimator of the average treatment effect. Our estimator averages, across individuals, the difference between observed post-treatment outcomes and unbiased forecasts of their counterfactuals, based on a (short) time series of pre-treatment data. The paper emphasizes the importance of focusing on forecast unbiasedness rather than accuracy when the end goal is estimation of average treatment effects. We show that simple basis function regressions ensure forecast unbiasedness for a broad class of data generating processes for the counterfactuals. In contrast, forecasting based on a specific parametric model requires stronger assumptions and is prone to misspecification and estimation bias. We show that our method can replicate the findings of some previous empirical studies but it does so without using an untreated or control group.
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https://arxiv.org/abs/2309.05639
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Academic Papers
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svg
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b39ece6e4089bf46422e212b00aeceb60270a4477ef5798a485c9246cda963f3
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2026-01-13T00:00:00-05:00
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Identifying Causal Effects in Information Provision Experiments
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arXiv:2309.11387v5 Announce Type: replace Abstract: Standard estimators in information provision experiments place more weight on individuals who update their beliefs more in response to new information. This paper shows that, in practice, these individuals who update the most have the weakest causal effects of beliefs on outcomes. Standard estimators therefore understate these causal effects. I propose an alternative local least squares (LLS) estimator that recovers a representative unweighted average effect in a broad class of learning rate models that generalize Bayesian updating. I reanalyze six published studies. In five, estimates of the causal effects of beliefs on outcomes increase; in two, they more than double.
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https://arxiv.org/abs/2309.11387
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Academic Papers
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svg
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38ee63e655541fc41b1c913131841b64cdce332142a7d635166e74ea144c9267
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2026-01-13T00:00:00-05:00
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New Compensating and Equivalent Variation Closed-form Solutions for Non-Separable Public Goods
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arXiv:2401.15493v3 Announce Type: replace Abstract: This study finds exact closed-form solutions for compensating variation (CV) and equivalent variation (EV) for both marginal and non-marginal changes in public goods given homothetic, but non-separable, utility where a single sufficient statistic summarizes consumer preferences. The closed-form CV and EV expressions identify three economic mechanisms that determine magnitudes. One of these mechanisms, the relative preference effect, helps explain the disparity between willingness to pay (WTP) and willingness to accept (WTA) for public goods. We also show how our closed-form solutions can be employed to calculate WTP and WTA across income groups using estimates from existing empirical studies.
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https://arxiv.org/abs/2401.15493
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Academic Papers
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svg
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0a66b8583ca7a58b3496d16b789907daa4fdd6903097ac25858268c15f303401
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2026-01-13T00:00:00-05:00
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On Causal Inference with Model-Based Outcomes
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arXiv:2403.19563v5 Announce Type: replace Abstract: We study the estimation of causal effects on group-level parameters identified from microdata (e.g., child penalties). We demonstrate that standard one-step methods (such as pooled OLS and IV regressions) are generally inconsistent due to an endogenous weighting bias, where the policy affects the implicit weights (e.g., altering fertility rates). In contrast, we advocate for a two-step Minimum Distance (MD) framework that explicitly separates parameter identification from policy evaluation. This approach eliminates the endogenous weighting bias and requires explicitly confronting sample selection when groups are small, thereby improving transparency. We show that the MD estimator performs well when parameters can be estimated for most groups, and propose a robust alternative that uses auxiliary information in settings with limited data. To illustrate the importance of this methodological choice, we evaluate the effect of the 2005 Dutch childcare reform on child penalties and find that the conventional one-step approach yields estimates that are substantially larger than those from the two-step method.
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https://arxiv.org/abs/2403.19563
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Academic Papers
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svg
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41a31e0362f7ee3c060fe65bb761a96fd8f747712b67bc1eedb6f2bb07904ae5
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2026-01-13T00:00:00-05:00
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Simulation in discrete choice models evaluation: SDCM, a simulation tool for performance evaluation of DCMs
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arXiv:2407.17014v3 Announce Type: replace Abstract: Discrete choice models (DCMs) have been widely utilized in various scientific fields, especially economics, for many years. These models consider a stochastic environment influencing each decision maker's choices. Extensive research has shown that the agents' socioeconomic characteristics, the chosen options' properties, and the conditions characterizing the decision-making environment all impact these models. However, the complex interactions between these factors, confidentiality concerns, time constraints, and costs, have made real experimentation impractical and undesirable. To address this, simulations have gained significant popularity among academics, allowing the study of these models in a controlled setting using simulated data. This paper presents multidisciplinary research to bridge the gap between DCMs, experimental design, and simulation. By reviewing related literature, the authors explore these interconnected areas. We then introduce a simulation method integrated with experimental design to generate synthetic data based on behavioral models of agents. A utility function is used to describe the developed simulation tool. The paper investigates the discrepancy between simulated data and real-world data.
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https://arxiv.org/abs/2407.17014
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Academic Papers
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