Cosmology and Nongalactic Astrophysics
Viability of Big Bang Nucleosynthesis in $f(R,L_m)$ Gravity
Kajal Phukan, Rajdeep Mazumdar, Kalyan Malakar et al. (+1 more)
We examine the viability of Big Bang Nucleosynthesis (BBN) constraints in $f(R,L_m)$
gravity, where the gravitational Lagrangian is an arbitrary function of the the Ricci scalar $R$ and matter Lagrangian density $L_m$. We derive stringent bounds on the underlying model parameters of four different $f(R,L_m)$
gravity models by examining both the primordial abundances of helium-4 ($^4\text{He}$) and the fractional variations in the
neutron–
proton freeze out temperature. Our results reveal that $f(R,L_m)$
gravity remains viable under the BBN constraints. With the freeze-out condition offering the most dominat constraint on the parameter space, whereas the bounds from $^4\text{He}$ abundance act as a separate abundance level consistency checks on the modified expansion rate. In summary, the presence of these feasible parameter regions demonstrates that $f(R,L_m)$
gravity models can successfully accommodate primordial element abundances without disrupting standard early Universe dynamics.
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All authors Kajal Phukan, Rajdeep Mazumdar, Kalyan Malakar, Kalyan Bhuyan
Solar and Stellar Astrophysics
A Systematic Gaia–ZTF Search for Short-Period Blue Compact-Binary Candidates
Jiamao Lin, Liangliang Ren, Yilong Li et al. (+7 more)
We present a catalog of 147 short-period (10.34–106.46~min) blue compact-binary candidates, identified by combining Gaia DR3 astrometry and photometry with ZTF DR23 light curves via a Gaia selection, period searches, and machine-learning morphology ranking. Of these, 111 lack prior compact-binary classifications. Multiwavelength data (DESI DR1, GALEX, AllWISE) reveal a heterogeneous sample: on the Gaia colour–magnitude diagram, 52 sources lie on the white-dwarf locus, 69 in the hot-subdwarf region, and 26 are intermediate. Among 26 sources with DESI spectra, only about one third follow the white-dwarf cooling sequence; the rest are more luminous blue
stars with white-dwarf-like low-resolution spectra. We highlight a prioritized subset of new white-dwarf-locus candidates for follow-up, including ten with periods below 40~min and none with existing radial-velocity data. Under fiducial binary assumptions, 17 of these newly identified white-dwarf-locus candidates would exceed the adopted LISA signal-to-noise threshold (led by a 37~pc white dwarf), with the count depending on chirp mass (9 for $0.15\,M_\odot$, 17 for $0.3\,M_\odot$, 21 for $0.6\,M_\odot$), assuming orbital modulation. However, for most of the white-dwarf-locus sample, observed modulation amplitudes exceed any plausible ellipsoidal signal by three to five orders of magnitude, implying that rotating
magnetic or chemically inhomogeneous single white dwarfs offer a viable alternative that ZTF photometry alone cannot rule out—the catalog includes at least one confirmed case. We release the full 147-source catalog, including periods, Gaia/spectroscopic classifications, harmonic/ellipsoidal diagnostics, and supplementary tables of fiducial GW estimates and UV–IR photometry.
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All authors Jiamao Lin, Liangliang Ren, Yilong Li, Bo Ma, Di-Chang Chen, Zi-Heng Yu, Sen Yang, Shun-Jia Huang, Yi-Ming Hu, Chengyuan Li
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
WIMP Freeze-Out in Diffusive Unimodular Gravity
Cesar Bonilla, Esteban Gonzalez and Carlos Maldonado
We study a non-standard cosmology (NSC) scenario within the Unimodular
Gravity (UG) framework, sourced by a scalar field $\phi$ that undergoes energy
diffusion, parametrized by the
diffusion parameter $x$, the initial energy densities rate $\kappa\equiv\rho_\phi/\rho_\gamma|_{\text{ini}}$, and the end-of-domination temperature $T_{\text{end}}$. We compare this UG+NSC scenario with standard NSC and $\Lambda$CDM cosmologies for WIMP Dark Matter (DM) production via the freeze-out mechanism. We find that energy
diffusion reshapes the allowed $(m_\chi, \langle\sigma v\rangle)$ parameter space, where $m_\chi$ is the DM mass and $\langle \sigma v \rangle$ is the thermally averaged annihilation cross section, opening regions otherwise excluded by DM overproduction in $\Lambda$CDM, and shifting the mass and cross-section ranges accessible to WIMP candidates depending on $x$, $\kappa$, $T_{\text{end}}$, and the barotropic index $\omega$ of $\phi$. As a concrete application, we implement this framework for the Real Singlet Scalar WIMP and test its $(m_\chi, \lambda_{HS})$ parameter space against current direct detection bounds from the LZ experiment, showing that energy
diffusion opens previously unconstrained regions in the
Higgs-portal coupling $\lambda_{HS}$ and thereby alters the detectability prospects of this
benchmark model in future searches.
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Solar and Stellar Astrophysics
Correlations with Magnetic Activity in the Solar Near-Surface Shear Layer. II. Radial Shear
M. Cristina Rabello Soares, Sarbani Basu, Richard S. Bogart et al. (+1 more)
Using Helioseismic and
Magnetic Imager ring-diagram measurements and building on the rotation-rate $\Omega$ inferences presented in Paper I for depths of 1-17 Mm, we examine the properties of the dimensionless radial shear $\partial\ln\Omega/\partial\ln r$. In the radial range overlapping global-mode analyses, the inferred shear agrees with previous results. The near-surface shear layer exhibits a three-region shear structure with an enhanced-shear middle layer, and the largest residual variations occur in the two shallowest regions not accessible to global-mode analyses. We parameterize the enhanced-shear layer by the depth of maximum shear, its amplitude, and its width, and find all three to be strongly correlated with a
magnetic activity index; increasing activity corresponds to a shallower, stronger, and modestly narrower layer, indicating that the flows and
magnetic fields are interconnected in these layers. This behavior is consistent with expectations that sufficiently strong toroidal fields can enhance the near-surface rotational shear and with inferences of a near-surface toroidal-field concentration near the radius where we observe the strongest shear. Moreover, the observed strengthening and upward shift of the strong-shear layer toward solar-cycle maximum suggest a corresponding solar-cycle dependence in the location of the strong toroidal field. We also highlight the importance of finite-resolution effects and instrumental calibration in interpreting small variations in the results.
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All authors M. Cristina Rabello Soares, Sarbani Basu, Richard S. Bogart, Charles S. Baldner
Instrumentation and Methods for Astrophysics
Fast Control for LIGO Interferometer Lock Acquisition
Masaya Ono, Nathan A. Holand, Radhika Bhatt et al. (+4 more)
Gravitational wave observatories are large scale
laser interferometers which are held on resonance to facilitate the detection of gravitational waves. Achieving this resonant condition is a time consuming process, and in the LIGO gravitational-wave observatories this procedure has a relatively low success rate. This limitation leads to a loss of observation time thereby reducing the number of observable astrophysical events. The primary cause of this problem is the coupling among the longitudinal degrees of freedom of the interferometer, particularly the coupling from the arm cavity lengths to the central degrees of freedom, such as the recycling cavities and the Michelson interferometer. We demonstrate a simpler and faster lock acquisition scheme at the 40-meter prototype interferometer, located at the California Institute of Technology. This scheme is achieved by controlling the arm cavity lengths with high bandwidth during the lock acquisition process. In this paper, we describe how this fast lock acquisition is realized, compare it with the current LIGO lock acquisition method, and discuss how our framework can be implemented in LIGO.
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All authors Masaya Ono, Nathan A. Holand, Radhika Bhatt, Peter G. Carney, Francisco Salces Càrcoba, Koji Arai, Rana X. Adhikari
Earth and Planetary Astrophysics
Finding Habitable Exoplanets with Binary Relative Astrometry: Planet Detection and Characterization with the Microarcsecond Astrometric Retrieval Algorithm (MARA)
William Roberson, Eric L. Nielsen, Jessie L. Christiansen et al. (+8 more)
Binary relative astrometry is a technique to search for rocky
planets in the habitable zone of nearby binary
stars using 1D relative astrometry at the microarcsecond level. This unprecedented precision would allow a custom-designed space
telescope to directly measure the occurrence rate of these
planets. The success of such a mission depends on our ability to recover and characterize
planets from the unique format of extreme precision binary relative astrometry data. We present MARA, the Microarcsecond Astrometric
Retrieval Algorithm, specifically designed for these data. We describe the design and format of the MARA pipeline, and demonstrate its accuracy and performance with a series of validation tests on simulated data, using the SHERA SMEx mission concept as an example. Our injection/recovery tests show that with these data, MARA is able to detect and characterize rocky
planets in the habitable zone of alpha Cen A, down to a coplanar mass of about 1 Earth mass in 1 year orbits. Expanding to a range of input
planet masses and periods for the same example mission, we find that the results from these injection/recovery tests generally agree with the analytic predictions of binary relative astrometry sensitivity. We use MARA to map out the expected completeness as a function of
planet mass and period, which in this case reaches down to about 0.5 M Earth masses at 3 year orbits around alpha Cen A. These depth-of-search calculations will be a vital ingredient in demographics calculations from the final data from a binary relative astrometry mission.
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All authors William Roberson, Eric L. Nielsen, Jessie L. Christiansen, Gautam Vasisht, Eduardo Bendek, Alex Davis, Eric E. Mamajek, Catherine A. Clark, Kaitlin M. Kratter, Juliette Becker, Michael R. Meyer
Astrophysics of Galaxies
Tracing Lyman alpha escape in the CRISTAL-02 galaxy at z~5.3
Arshi Ali, Lucia Guaita, Manuel Aravena et al. (+20 more)
We investigate the mechanisms regulating Lyman-alpha (Ly$\alpha$) escape in the
star-forming
galaxy CRISTAL-02 at z~5.3. The
galaxy has clumpy morphology, suggestive that it may be interacting with other system(s). Two clumps (A and B, hereafter) are suggested as a site for intense
star-formation or potential AGN candidates. We investigate how the local gas, dust, and feedback shape the escape of Ly$\alpha$
photons around these clumps. Using VLT/MUSE and JWST/NIRSpec IFU observations, complemented by NIRCam UV imaging, we constructed spatially matched emission-line maps. We derived flux, line-ratio, and extinction maps, together with spatially resolved Ly$\alpha$ escape fractions and ionizing
photon production efficiencies. We find that Ly$\alpha$ is significantly more extended than H$\alpha$ and UV, reaching ~33 kpc and preferentially extending along the cold molecular gas outflow traced by [C II] emission. Clumps A and B show contrasting Ly$\alpha$ properties: Clump A has lower dust attenuation and enhanced Ly$\alpha$/H$\alpha$ ratios and escape fraction, whereas Clump B is brighter in H$\alpha$ and UV but has suppressed Ly-$\alpha$ despite a higher ionizing
photon production efficiency. These results indicate that Ly$\alpha$ escape is strongly influenced by the local H I geometry, dust, and outflows and cannot be explained by ionizing
photon production alone. The observed Ly$\alpha$ morphology and zELDA radiative transfer modeling favor an outflow-driven escape scenario, while the available data cannot uniquely distinguish between AGN and
star formation-driven feedback.
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All authors Arshi Ali, Lucia Guaita, Manuel Aravena, Rebecca L. Davies, Jorge Gonzalez, Vicente Villanueva, Diego Oyarzun, Rodrigo Herrera-Camus, Ambra Nanni, Andreas Faisst, Anton M. Koekemoer, Deanne B. Fisher, Hanae Inami, Juan Molina, Justin Spilker, Lun-Jun Liu, Manuel Solimano, Michele Ginolfi, Michael Romano, Negin Nezhad, Poulomi Dam, Wuji Wang, Yuan Li
Solar and Stellar Astrophysics
Correlations with Magnetic Activity in the Solar Near-Surface Shear Layer. I. Rotation
M. Cristina Rabello Soares, Sarbani Basu and Richard S. Bogart
We used data from the Helioseismic and
Magnetic Imager to determine the rotation rate of the near-surface shear layer and its time variation. We applied the ring-diagram analysis technique allowing us to probe the layer between the depths of 1 Mm and 17 Mm. We find that the rotation rate increases inwards; it reaches values consistent with those inferred from global helioseismic analyses in the deeper layers, however, there are differences in the rotation rate of the northern and southern hemispheres. We show that the time variation of the rotation rate can be determined even without subtracting the time-averaged rotation rate from each epoch; however, such a subtraction is needed to get the canonical “torsional oscillation” signal. We find that even at depths as shallow as 1 Mm, the rotation rate shows the typical torsional oscillation pattern. The cumulative zonal displacement inferred from the residual flows exhibits a pronounced high-latitude hemispheric asymmetry and varies on solar-cycle timescales; at $75^\circ$ it shows an apparent temporal association with the polar
magnetic field. We find significant correlations between the cumulative displacement and
magnetic activity at a subset of latitudes, with multi-year lags: the displacement leads activity by ~5 years near $15^\circ$, whereas at higher latitudes activity leads by ~4 years. At mid to high latitudes, the inferred lags show a hemispheric dependence, with activity tending to lead in the north and lag in the south, suggesting possible hemispheric differences in the timing of cycle
evolution and motivating longer time series to test cycle-to-cycle variation.
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Cosmology and Nongalactic Astrophysics
Does Early Dark Energy Absorb the DESI Late-Time Dynamics Signal? A Combined Analysis
Mohammad Malekjani and Saeed Pourojaghi
While the recent Baryon Acoustic Oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) collaboration are largely consistent with a flat $\Lambda$CDM cosmology, the preferred parameters are in mild tension with those determined from the
cosmic microwave background (CMB). A late-time dynamical dark energy (DDE) solution has been proposed by the DESI collaboration to address this tension. In this work, we investigate whether the statistical preference for DDE is a genuine late-time phenomenon or an artifact of unresolved early-universe physics. To do so, we simultaneously allow for both early- and late-time modifications to the expansion history by combining the Early Dark Energy (EDE) framework with the Chevallier-Polarski-Linder (CPL) parametrization. Excluding the DESI BAO measurements, our joint analysis of the CMB+Pantheon+
datasets demonstrates that within an EDE-extended framework, the CPL parameters remain statistically consistent with the standard $\Lambda$CDM model. This supports the hypothesis that a DDE signal at low
redshifts can be effectively accounted for by an EDE component within the $\Lambda$CDM background. However, upon the inclusion of the DESI BAO measurements in the joint analysis, a statistically significant deviation from a cosmological constant emerges. Within this combined framework, the best-fit CPL parameters robustly indicate a departure from the standard $\Lambda$CDM model, favoring a phantom-to-quintessence transition in the DE equation of state. This demonstrates that the DESI preference for the late-time DDE is a robust signature that cannot be absorbed by modifying the physics of the early Universe.
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Astrophysics of Galaxies
Reconstructing orbits of galaxies in extreme regions (roger v2.0): an extension to intermediate mass systems
Martín de los Rios, Héctor J. Martínez, Andrés N. Ruiz et al. (+3 more)
In this paper, we present an updated version of the roger code, called roger v2.0, developed to perform the orbital classification of
galaxies residing in and around
galaxy groups and clusters. In addition to the projected phase-space coordinates, the new version incorporates the host
halo mass as an additional input parameter. Although the inclusion of the
halo mass leads to only modest changes in the classification, it contributes to improving the overall robustness of the method. We also extend the range of host
halo masses over which roger can be applied, enabling the analysis of systems with masses down to $10^{13.5} h^{-1} M_{\odot}$. We further provide a Python implementation of the new code, which will be made publicly available. This implementation enables users to efficiently and robustly classify arbitrary
galaxy samples using either version of the method. Moreover, it allows users to train a customized classifier on an alternative training set, providing the flexibility to adapt the method to different
datasets and scientific applications.
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All authors Martín de los Rios, Héctor J. Martínez, Andrés N. Ruiz, Selene Levis, Valeria Coenda, Hernán Muriel
Solar and Stellar Astrophysics
Responses of the X-ray spectrometer/imager STIX onboard Solar Orbiter
Hualin Xiao, Olivier Limousin, Ewan Dickson et al. (+1 more)
Solar
flares are explosive events that release X-rays from hot
plasma and accelerated electrons. The STIX instrument on the Solar Orbiter provides imaging spectroscopy of solar X-ray emissions from 4 to 150 keV. To interpret the STIX data accurately, understanding the instrument's response is crucial. Given the complexity of interactions of X-rays with the instrument, we developed a detailed Monte Carlo model for STIX based on Geant4. The model accurately depicts the instrument's components, such as grids, detectors, X-ray windows, and collimators, with their responses. We studied various effects, including grid shadowing, fluorescent X-rays emitted by materials in STIX, and grid transmission, to assess their impacts on STIX's scientific goals. Model validation was performed using Crab Nebula observations, a standard calibration source that provides reliable ground truth for X-ray instruments. Our simulations align with the Crab Nebula observations within the uncertainties, thereby validating the accuracy of the Geant4 model and showcasing its potential for interpreting STIX data. With the help of the generated response
matrices, which are indispensable for solar spectroscopy, we discuss the applications and limitations of the model for future STIX data analysis.
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All authors Hualin Xiao, Olivier Limousin, Ewan Dickson, Säm Krucker
Instrumentation and Methods for Astrophysics
Microlensify: a Transformer Based Machine Learning Classifier for Microlensing Events Trained on TESS Light Curves
Atousa Kalantari, Somayeh Khakpash, Sedighe Sajadian et al. (+3 more)
Microlensing can reveal populations of faint compact objects that are otherwise difficult to detect. Depending on their design, all-sky surveys have the potential to search for these objects across the sky. The Transiting
Exoplanet Survey Satellite (TESS), primarily designed to detect transiting
exoplanets, also provides near all-sky coverage with high cadence. In this work, we use TESS data to search for microlensing candidates using both traditional and machine-learning methods and to identify associated false positives in high-cadence surveys. Microlensify is a physics-informed,
transformer-based variational autoencoder trained on simulated single-lens microlensing light curves and real TESS Sector 12 data. The model classifies events, reconstructs light curves, and estimates microlensing event durations. Applied to $\sim 5.6$ million TESS light curves, it identified between $0.036\%$ and $1.89\%$ as microlensing candidates across different TESS pipelines. After applying microlensing detection metrics and cross-matching with SIMBAD, we obtained a final list of candidates and identified false positives including long-period variables, Mira variables, cataclysmic variables, red giants, and transients. We also found Gaussian-like peaks caused by asteroid crossings, a potential source of false positives in high-cadence microlensing surveys. The model also predicts event duration with an accuracy of $R^2 = 0.97$. The model was further tested on published events from different ground-based microlensing surveys, confirming 92.7% as microlensing, demonstrating its applicability across surveys with different cadences.
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All authors Atousa Kalantari, Somayeh Khakpash, Sedighe Sajadian, Hosein Haghi, Willow Fox Fortino, Rosanne Di Stefano
Instrumentation and Methods for Astrophysics
ADORA: a differentiable optical modeling and astrometric retrieval framework for SHERA
Dylan McKeithen, Stuart Shaklan, Gautam Vasisht et al. (+4 more)
Searching for Habitable
Exoplanets with Relative Astrometry (SHERA) is a proposed Small Explorer mission concept designed to measure the separation of nearby binary
stars at microarcsecond-class precision. Recovering this signal requires separating astrophysical motion from coupled changes in pointing, plate scale, wavefront error, spectral response, and detector calibration. We present the Astrometric Differentiable Optics and
Retrieval Algorithm (ADORA), an image-domain framework that combines a three-plane differentiable physical-optics model with a layered astrometric inference
algorithm. The forward model includes a diffractive pupil, mirror-specific wavefront error and beamwalk, polychromatic source and throughput models, and configurable detector effects. Per-frame registration states are treated locally and eliminated through Schur reduction before the slower astrometric and instrument state is updated in a prior-whitened Fisher eigenbasis. Five-minute matched-model simulations show no detected separation bias at the current Monte Carlo depth and approximately 11 uas realization-to-realization scatter. A SHERA target sweep reveals a more-than-fivefold variation in astrometric information between Alpha Centauri and 61 Cygni, motivating future target-dependent accumulation and update cadence. High-order-wavefront knowledge error can drive the
retrieval toward a strongly biased astrometric solution while leaving the local posterior sigma nearly unchanged, demonstrating that statistical
curvature alone does not capture unmodeled bias. Pixel-position errors across the tested range remain near the matched-model recovery scale indicating robustness to certain detector calibration errors. ADORA provides a flexible framework for studying astrometric extraction, calibration-bias diagnosis, and future SHERA requirements.
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All authors Dylan McKeithen, Stuart Shaklan, Gautam Vasisht, Joe Green, Rhonda Morgan, Louis Desdoigts, Peter Tuthill
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Bayesian Forecasts on Cosmic Superstring Searches with LISA
Satyabrata Datta and Rome Samanta
Cosmic superstrings are well-motivated early-Universe sources of
stochastic gravitational waves, with phenomenology controlled by the string tension $G\mu$ and the intercommutation probability $P$. We study whether LISA can reconstruct these parameters and distinguish different superstring signal models in the presence of instrumental noise and astrophysical foregrounds. We consider two phenomenological models. In Model I, reduced intercommutation acts only as an amplitude enhancement of a cusp-dominated spectrum, $\Omega_{\rm SS}^{\rm I}=P^{-\beta}\Omega_{\rm cusp}$. In Model II, the signal is a cusp–kink mixture, $\Omega_{\rm SS}^{\rm II} =P^{-\beta}[p_c\Omega_{\rm cusp}+(1-p_c)\Omega_{\rm kink}]$, so that $P$ controls both amplitude and spectral shape. Using simulated LISA data, we perform
Bayesian inference with noise uncertainties, unresolved extragalactic compact-binary backgrounds, and a flexible Galactic double-white-dwarf foreground. We compare the models using
Bayesian evidences and map the $(G\mu,P)$ posterior geometry with marginalized widths, correlations, covariance anisotropy, principal
eigenvalues, posterior area, and bias. We find that reduced intercommutation generically produces strong $G\mu$–$P$ correlations, because the data often constrain an amplitude-like combination. However, when the cusp–kink spectral difference lies in the LISA band and the signal is sufficiently loud, Model II can be favored and the posterior can retain genuine shape information. As an optimistic foreground scenario, we also compute the Bayes factor using a reduced tanh Galactic foreground template, finding improved model discrimination when the foreground shape is constrained.
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High Energy Astrophysical Phenomena
Modeling Relativistic Tidal Disruptions of MESA Stars
Liam M. Wang, Giovanni Maria Tomaselli and Zihan Zhou
Tidal disruption events (TDEs) occur when a
star passes so close to a black hole that its self-
gravity is overcome by the external tidal field. As the
star passes, it initially deforms, then is ripped apart, and some of its material eventually falls back on bound orbits, forming an
accretion disk around the black hole. A Newtonian model of TDEs, based on stellar perturbation theory of MESA
stars, was recently introduced as an alternative to computationally intensive hydrodynamical simulations. In this work, we add relativistic corrections to the model, incorporating equatorial Kerr geodesics, relativistic tidal fields, and relativistic fallback times. Compared to the Newtonian case, we find that
stars are disrupted earlier in their orbit, which gives them less time to accumulate physical deformations. Additionally, we find that the increased distance from the black hole at the time of disruption makes the fallback time longer. However, the black hole
spin has a negligible impact on fallback time, except for orbits with exceptionally close pericenter. Our results allow for a more accurate calculation of fallback rates than the Newtonian model, while also remaining computationally cheap. The code is available on GitHub.
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High Energy Astrophysical Phenomena · Cross-listed from physics.plasm-ph
Informing spectral models for dense plasmas with K-edge absorption measurements of warm dense copper
T. Cordova, E. V. Marley, D. A. Chin et al. (+14 more)
Warm dense matter remains a challenging regime to characterize experimentally and to model with predictive accuracy. Recent experimental platforms have been developed to generate, characterize, and diagnose uniform warm dense matter, enabling detailed comparisons with models. Here, we present experiments conducted at the OMEGA
laser facility that compress and heat a buried layer target to warm dense matter conditions, where the targets are heated to temperatures of approximately 20 eV and compressed to densities of 25 g/cm^3. We probe the warm dense
plasma using x-ray absorption spectroscopy, using the K-edge and bound-bound absorption features to constrain the temperature and charge state distribution of the
plasma. We compare these measurements with two types of models: collisional-radiative models with detailed electronic structure and ad-hoc density effects, and a multi-ion model based on density functional theory in combination with excited-state projector augmented-wave potentials. Neither approach fully reproduces the observed data, We show that the broad structure and position of the K-edge region can be modeled using density functional theory in combination with excited-state projector augmented-wave potentials. The density functional theory results are contrasted with a collisional-radiative model approach that incorporates ad-hoc density effects, which show incomplete agreement with the experimental observations, highlighting a need for improved density-dependent atomic modeling in warm dense
plasmas.
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All authors T. Cordova, E. V. Marley, D. A. Chin, R. A. London, S. B. Hansen, S. M. Vinko, J. E. Pask, H. A. Scott, H. P. Le, D. Aberg, M. K. G. Kruse, T. Döppner, F. N. Beg, J. Emig, P. M. Nilson, P. Sterne, M. J. MacDonald
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Stochastic Schwinger Effect: de Sitter and beyond
Lucas Vicente García-Consuegra and Azadeh Maleknejad
We develop a
stochastic formulation of the Schwinger effect in de Sitter spacetime using the Schwinger–Keldysh (in-in) formalism, tailored to particle production by non-stationary gauge backgrounds in the early Universe. Treating the gauge field as a prescribed classical
stochastic ensemble, we integrate out massless charged matter and derive the corresponding influence functional and particle-production kernel to leading non-trivial order in the gauge coupling. Conformal invariance allows the result to be extended directly from de Sitter to generic spatially flat FLRW spacetimes, without relying on asymptotic out states. We establish the infrared safety and classicality conditions of the
stochastic description and clarify its relation to the conventional static Schwinger effect. We further extend the framework to massless conformally coupled scalars and to weakly coupled non-Abelian gauge sectors, including Standard Model and hidden-sector examples, in regimes where thermal corrections are negligible. Our results provide a general framework for matter creation by
stochastic gauge fields in inflation, preheating, and non-thermal BSM sectors, connecting
quantum field theory in curved spacetime with early-Universe and high-energy phenomenology.
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Instrumentation and Methods for Astrophysics
Shaping SHAPE - A spectro-polarimeter onboard Chandrayaan-3 to observe Earth as an Exoplanet
Anuj Nandi, Swapnil Singh, Bhavesh Jaiswal et al. (+33 more)
Spectro-polarimetry of HAbitable
Planet Earth (SHAPE) is an experimental instrument onboard the Propulsion Module (Orbiter) of the Chandrayaan-3 mission, designed to perform disc-integrated spectro-polarimetric observations of Earth from lunar and highly elliptical Earth orbits. SHAPE is a compact, lightweight spectro-polarimeter comprising three subsystems: the Electro-Optical Detector System (EODS)-Optics, EODS-Electronics, and
Radio Frequency Source (RFS). An Acousto-Optic Tunable Filter (AOTF), driven by an in-house-developed 80$-$135 MHz RF source, provides spectral filtering in the near-infrared (NIR) wavelength range of 1.0$-$1.7 $\mu$m and produces two narrow-band beams with mutually perpendicular linear polarization states. The instrument optics, with a field of view of approximately 2.6{\deg}, focus the two beams onto InGaAs detectors. A spectral resolution of 2$-$4 nm is achieved using in-house-designed low-noise front-end electronics. The instrument also incorporates processing and power electronics for signal processing, detector biasing, and subsystem control. We present the overall instrument design, results from pre-launch ground-based testing, and in-orbit operational performance. The current configuration enables SHAPE to measure disc-integrated signatures of Earth over a range of phase angles, providing a test bed for characterizing Earth-like
exoplanets and benchmarking future
exoplanet observations.
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All authors Anuj Nandi, Swapnil Singh, Bhavesh Jaiswal, Anand Jain, Smrati Verma, Reenu Palawat, Ravishankar B. T., Brajpal Singh, Priyanka Das, Supratik Bose, Supriya Verma, Waghmare Rahul Gautam, Yogesh Prasad K. R., Bijoy Raha, Bhavesh Mendhekar, Sathyanaryana Raju K., Srinivasa Rao Kondapi V., Sumit Kumar, Mukund Kumar Thakur, Vinti Bhatia, Nidhi Sharma, Govinda Rao Yenni, Neeraj Kumar Satya, Venkata Raghavendra, Vivechana M. S., Evangelin Leeja Justin, Praloy Karmakar, Naga Manjusha J., Motamarri Srikanth, Abhishek Singh, Prabakaran B., Honey Gupta, Priyanka Mishra, Chinmay Kumar Rajhans, Kalpana K., Veeramuthuvel P
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
TeV-scale leptogenesis in a parity symmetric neutrino mass model
Keisuke Harigaya and Gio Leone
We study leptogenesis via out-of-
equilibrium decays of right-handed
neutrinos in a parity symmetric extension of the Standard Model with gauge group $SU(3)_c \times SU(2)_L \times SU(2)_R \times U(1)_X$, spontaneously broken to the Standard Model gauge group at a scale $v_R$. We focus on the minimal
Higgs realization, in which the strong CP problem is resolved without invoking additional
symmetries. In this framework, lepton number is violated through Yukawa interactions, while
neutrino masses arise only at higher loop order, a feature that permits the CP-violating
quantum corrections to right-handed
neutrino decays to be parametrically large. For thermal production of right-handed
neutrinos, we find that successful leptogenesis requires $v_R \gtrsim 6\times 10^{12}$ GeV. Non-thermal production, however, relaxes this bound dramatically, requiring only $v_R \gtrsim 10$ TeV, a scale accessible to
collider searches for new particles and searches for rare processes.
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