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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 7 November

Earth and Planetary Astrophysics

Why Estimating $\eta_\oplus$ is Difficult: A Kepler-Centric Perspective

Steve Bryson, Michelle Kunimoto, Ruslan Belikov et al. (+13 more)

$\eta_{\oplus}$, the occurrence rate of rocky habitable zone exoplanets orbiting Sun-like stars, is of great interest to both the astronomical community and the general public. The Kepler space telescope has made it possible to estimate $\eta_{\oplus}$, but estimates by different groups vary by more than an order of magnitude. We identify several causes for this range of estimates. We first review why, despite being designed to estimate $\eta_{\oplus}$, Kepler's observations are not sufficient for a high-confidence estimate, due to Kepler's detection limit coinciding with the $\eta_{\oplus}$ regime. This results in a need to infer $\eta_{\oplus}$, for example extrapolating from a regime of non-habitable zone, non-rocky exoplanets. We examine two broad classes of causes that can account for the large discrepancy in $\eta_\oplus$ found in the literature: a) differences in definitions and input data between studies, and b) fundamental limits in Kepler data that lead to large uncertainties and poor accuracy. We highlight the risk of large biases when using extrapolation to describe small exoplanet populations in the habitable zone. We discuss how $\eta_{\oplus}$ estimates based on Kepler data can be improved, such as reprocessing Kepler data for more complete, higher-reliability detections and better exoplanet catalog characterization. We briefly survey upcoming space telescopes capable of measuring $\eta_{\oplus}$, and how they can be used to supplement Kepler data.
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All authors Steve Bryson, Michelle Kunimoto, Ruslan Belikov, Galen J. Bergsten, Sakhee Bhure, William J. Borucki, Douglas A. Caldwell, Aritra Chakrabarty, Rachel B. Fernandes, Matthias Y. He, Jon M. Jenkins, Kristo Ment, Michael R. Meyer, Gijs D. Mulders, Ilaria Pascucci, Peter Plavchan

Astrophysics of Galaxies

Dynamical mirages: how bar-induced resonant trapping can mimic substructure clustering in dynamical parameter spaces

Michele De Leo, Davide Massari, Michele Bellazzini et al. (+3 more)

The complex task of unraveling the assembly history of the Milky Way is in constant evolution with new substructures identified continuously. To properly validate and characterise the family of galactic progenitors, it is important to take into account all the effects that can shape the distribution of tracers in the Galaxy. First among the often overlooked actors of galactic dynamics is the rotating bar of the Milky Way that can affect orbital tracers in multiple ways. We want to fully characterise the effect of the rotating bar of the Milky Way on the distribution of galactic tracers, provide diagnostics helpful in identifying its effect and explore the implications for the search and identification of substructures. We use the in-house Orbital Integration Tool (OrbIT), built to include the full effect of the bar and exploit its multidimensional output to perform a complete dynamical characterisation of a large sample of carefully selected Milky Way stars with very precise astrometry. We identify conspicuous overdensities in several orbital parameter spaces and verify that they are caused by the bar-induced resonances. We also show how contamination by trapped tracers provides local density enhancements that mimic the clumping usually attributed to genuine substructures. We provide a new and expedite way of identifying resonant loci and, consequently, to estimate the contribution of stars trapped into orbital resonances to phase-space overdensities previously identified as candidate relics of past merging events. Among those analysed here, we found that the detections of Cluster 3 and Shakti seem to have gained a non-negligible boost from resonance-trapped stars. Nyx is the most extreme case, with 70% of assigned member stars lying on resonant orbit, strongly suggesting that it is not the genuine relic of a merger event but an overdensity caused by bar-induced resonances
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All authors Michele De Leo, Davide Massari, Michele Bellazzini, Alessio Mucciarelli, Belén Acosta-Tripailao, Carlo Nipoti

Cosmology and Nongalactic Astrophysics

Probing Dark Energy Microphysics with kSZ Tomography

Julius Adolff, Selim Hotinli and Neal Dalal

The accelerated expansion of the Universe is well established by geometric probes, yet its physical origin remains poorly understood. Most constraints on dark energy arise from background observables – supernovae, baryon acoustic oscillations, and the cosmic microwave background – which mainly test the homogeneous expansion history. To move beyond this limitation, we examine how kinetic Sunyaev–Zel'dovich (kSZ) tomography, combined with galaxy clustering, can probe perturbative effects of dark energy and improve constraints on its background parameters. Using a Fisher-matrix analysis of the joint power spectra for LSST- and CMB-S4-like surveys, we quantify the additional information kSZ tomography contributes to dark-energy inference. Including kSZ data tightens constraints on $w_0$ by 15 % and on $w_a$ by 32 %, with parameter degeneracies distinct from those of geometric probes. We also assess the detectability of dark-energy perturbations through a two-parameter model, finding that for canonical sound speed ($c_s=1$) the effects are sub-percent and confined to horizon scales, while smaller sound speeds shift them to accessible $k$-ranges. Near-term kSZ measurements will primarily serve to test the consistency between background and perturbative signals, while future low-noise, high-resolution surveys may begin to uncover the microphysical properties of dark energy.
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Earth and Planetary Astrophysics

Knobs and dials of retrieving JWST transmission spectra. II. Impacts of pipeline-level differences on retrieval posteriors

Simon Schleich, Sudeshna Boro Saikia, Quentin Changeat et al. (+3 more)

Since the launch of JWST, observations of exoplanetary atmospheres have seen a revolution in data quality. Given that atmospheric parameter inferences depend heavily on the underlying data, a re-evaluation of current methodologies is warranted to assess the reliability of these results. We investigate the impact of variations in input spectra on atmospheric retrievals for the hot Jupiter WASP-39 b using JWST transit data. Specifically, we analyse the reliability of parameter estimations from random perturbations of the underlying spectrum and their sensitivity to three transmission spectra derived from the same observational data. Using the NIRSpec PRISM observation from a single transit of WASP-39 b, we perform retrievals with the TauREx framework. As a baseline, we use a spectrum derived with the Eureka! data reduction pipeline. To evaluate retrieval reliability, we analyse posterior distributions under deviations from this spectrum. We simulate random noise by performing retrievals on scattered instances of this spectrum and compare them with retrievals based on existing spectra reduced from the same raw observation. Our analysis identifies three types of posterior distributions: (1) Stable, Gaussian distributions for species constrained across the entire spectrum (e.g., H2O, CO2); (2) Uniform posteriors with upper bounds for weakly constrained species (e.g., CO, CH4); and (3) Unstable, heavy-tailed posteriors for species constrained by minor spectrum features (e.g., SO2, C2H2). We find that other parameters, such as the planetary radius and p-T profile, are stable under spectral perturbations. Posterior distributions differ for retrievals on independently reduced transmission spectra from the same raw data, complicating interpretation, particularly for skewed distributions. Based on this, we advocate for careful assessment and selection of credible interval sizes to reflect this.
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All authors Simon Schleich, Sudeshna Boro Saikia, Quentin Changeat, Manuel Güdel, Aiko Voigt, Ingo Waldmann

Astrophysics of Galaxies

Not all protoclusters host evolved galaxies: Evidence for reduced environmental effects in a lower halo mass protocluster at $z = 7.66$

Callum Witten, Pascal A. Oesch, Jake S. Bennett et al. (+5 more)

The progenitors of present-day galaxy clusters offer crucial insight into how galaxies and large-scale structure co-evolve in the early Universe. We present JWST/NIRCam grism spectroscopy of the photometrically identified $z=7.66$ protocluster core in the SMACS J0723.3-7327 lensing field, SMACS-PC-z7p7. We find six [O III]-emitters and five additional photometric candidates within a 0.3 arcmin$^2$ ($1.5\ {\rm cMpc}^2$) region, corresponding to an overdensity of $\delta \sim 200$. Despite the extreme overdensity, the resident galaxies exhibit star formation histories, UV slopes, and neutral hydrogen column densities that are consistent with those of field galaxies at similar redshifts. This is in stark contrast to the consistently high neutral hydrogen column densities, old stellar populations, and large dust masses of galaxies within a $z=7.88$ protocluster in the Abell 2744 field. Comparison with the TNG-Cluster and TNG300 simulations indicates a halo mass of ${\rm log_{10}}(M_{200{\rm c}}[{\rm M_{\odot}}]) = 11.4\pm0.2$ and implies that, on average, SMACS-PC-z7p7 will evolve into a present-day Fornax-like cluster (${\rm log_{10}}(M_{200{\rm c},\ z=0}[{\rm M_{\odot}}]) = 14.3\pm0.6$). The uniformly young, highly star-forming nature of the galaxy population of SMACS-PC-z7p7 suggests that environmental effects only become significant above halo masses of ${\rm log_{10}}(M_{200{\rm c}}[{\rm M_{\odot}}]) \gtrsim 11.5$. Comparison with other $z\gtrsim7$ protoclusters reveals that vigorous star formation persists in lower-mass protoclusters, whereas accelerated evolution and suppression of star formation emerge in more massive haloes. SMACS-PC-z7p7 therefore represents an early stage of protocluster assembly, in which residence within an overdense environment still enhances star formation and feedback processes have yet to exert a significant influence.
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All authors Callum Witten, Pascal A. Oesch, Jake S. Bennett, Romain A. Meyer, Emma Giovinazzo, Alba Covelo-Paz, William M. Baker, Lucy R. Ivey

Astrophysics of Galaxies

Figuring Out Gas & Galaxies In Enzo (FOGGIE). XIV. The Observability of Emission from Accretion and Feedback in the Circumgalactic Medium with Current and Future Instruments

Vida Saeedzadeh, Jason Tumlinson, Molly S. Peeples et al. (+11 more)

Observing the circumgalactic medium (CGM) in emission lines from ionized gas enables direct mapping of its spatial and kinematic structure, offering new insight into the gas flows that regulate galaxy evolution. Using the high-resolution Figuring Out Gas & Galaxies In Enzo (FOGGIE) simulations, we generate mock emission-line maps for six Milky Way-mass halos. Different lines (e.g., H$\alpha$, OVI) trace distinct CGM phases and structures, highlighting the importance of observations in multiple species. We quantify the observable CGM mass fraction as a function of instrument spatial resolution and surface brightness sensitivity, finding that sensitivity is the dominant factor limiting detectability across all ions. At fixed sensitivity, higher spatial resolution reveals more structures; at fixed spatial resolution, higher sensitivity recovers a higher percentage of the total mass. We explore CGM kinematics by constructing emissivity-weighted projected velocity maps and comparing line-of-sight velocities between emission lines. OVI shows the largest kinematic deviation from H$\alpha$, while MgII and SiII most closely follow HI velocities. Distinguishing these phases out to 50kpc from the galaxy center requires spectral resolution better than 30km/s for most ion pairs. Additionally, separating inflowing from outflowing gas based on projected kinematics also requires high spectral resolution: at 30km/s, more than 80% of gas above the emission detection threshold can be distinguished kinematically, but this fraction drops to <40% with a resolution of 200km/s. Our results provide predictions for future UV and optical instruments, showing that recovering the multiphase structure and kinematics of circumgalactic emission will require both high sensitivity and fine kinematic resolution.
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All authors Vida Saeedzadeh, Jason Tumlinson, Molly S. Peeples, Brian W. O'Shea, Cassandra Lochhaas, Lauren Corlies, Cameron W. Trapp, Britton D. Smith, Jessica K. Werk, Ayan Acharyya, Ramona Augustin, Andrew J. Fox, Nicolas Lehner, Anna C. Wright

Instrumentation and Methods for Astrophysics

Performance of the AstroPix Prototype Module for the Barrel Imaging Calorimeter at the ePIC Detector and in Space-Based Payloads

Bobae Kim, Regina Caputo, Manoj Jadhav et al. (+7 more)

AstroPix is a high-voltage CMOS (HV-CMOS) monolithic active pixel sensor originally developed to enable precision gamma-ray imaging and spectroscopy in the medium-energy regime (approximately 100 keV-100 MeV) based on the groundwork laid by ATLASpix and MuPix. It features a 500 um pixel pitch, in-pixel amplification and digitization, and low power consumption (around 3-4 mW/cm^2), making it scalable for large-area, multilayer telescope detector planes. The detectors have a designed dynamic range of 25 keV to 700 keV. With these features, AstroPix meets the requirements of future space-based high-energy telescopes and the imaging layers of the Barrel Imaging Calorimeter (BIC) in the Electron-Proton/Ion Collider (ePIC) detector at the future Electron-Ion Collider (EIC). For the space-based payload, AstroPix is being integrated into sounding rocket and balloon payloads to demonstrate the technical readiness of the devices. For BIC, AstroPix-based imaging layers interleaved within the lead/scintillating-fiber (Pb/SciFi) sampling calorimeter provide granular shower imaging, enabling key performance features such as electron/pion or gamma/neutral-pion separation. As part of the ongoing detector R&D efforts, we have been testing various AstroPix v3 configurations: the single chip, a quad-chip assembly, a three-layer stack of quad chips, and a nine-chip module that represents the smallest prototype unit of the BIC imaging layer. This presentation will highlight recent performance test results from these AstroPix detector configurations.
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All authors Bobae Kim, Regina Caputo, Manoj Jadhav, Sylvester Joosten, Adrien Laviron, Richard Leys, Jessica Metcalfe, Nicolas Striebig, Daniel Violette, Maria Żurek

Astrophysics of Galaxies · Cross-listed from gr-qc

Relativistic MOND Theory from Modified Entropic Gravity

A. Rostami, K. Rezazadeh and M. Rostampour

We derive a relativistic extension of Modified Newtonian Dynamics (MOND) within the framework of entropic gravity by introducing temperature-dependent corrections to the equipartition law on a holographic screen. Starting from a general modification of the surface degrees of freedom and employing the Unruh relation between acceleration and temperature, we obtain modified Einstein equations in which the geometric sector acquires explicit thermal corrections. Solving these equations for a static, spherically symmetric spacetime in the weak-field, low-temperature regime yields a corrected metric that smoothly approaches Minkowski space at large radii and naturally contains a characteristic acceleration scale. In the very-low-acceleration regime, the model reproduces MOND-like deviations from Newtonian dynamics while providing a relativistic underpinning for that phenomenology. We confront the theory with rotation-curve data for NGC~3198 and perform a Bayesian parameter inference, comparing our relativistic MOND (RMOND) model with both a baryons-only Newtonian dynamics (ND) model and a halo of dark matter (DM) model. We find that RMOND and DM models both fit the data significantly better than the baryons-only ND prediction, and that RMOND provides particularly improved agreement at $r\gtrsim 20\,\mathrm{kpc}$. These results suggest that temperature-corrected entropic gravity provides a viable relativistic framework for MOND phenomenology, motivating further observational tests, including gravitational lensing and extended galaxy samples.
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Cosmology and Nongalactic Astrophysics

Non-Gaussian Galaxy Stochasticity and the Noise-Field Formulation

Henrique Rubira and Fabian Schmidt

We revisit the stochastic, or noise, contributions to the galaxy density field within the effective field theory (EFT) of large-scale structure. Starting from the general, all-order expression of the EFT partition function, we elucidate how the stochastic contributions can be described by local nonlinear couplings of a single Gaussian noise field. We introduce an alternative formulation of the partition function in terms of such a noise field, and derive the corresponding field-level likelihood for biased tracers. This noise-field formulation can capture the complete set of stochastic contributions to the galaxy density at the field level in a normalized, positive-definite probability density which is suitable for numerical sampling. We illustrate this by presenting the first results of EFT-based field-level inference with non-Gaussian and density-dependent stochasticity on dark matter halos using LEFTfield.
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High Energy Astrophysical Phenomena

Chemical Evolution and Kilonova Implications of Post-Merger Accretion Disk Winds

Agnieszka Janiuk, Joseph Saji and Gerardo Urrutia

Several gamma ray bursts have recently been associated with a kilonova emission. We study the mechanisms which could account for this effect, by means of radioactive decay of elements synthesized in accretion disk wind. We model the r-process nucleosynthesis in the accretion disk wind system, asscociated with the prompt GRB phase. We compute the time-dependent GR MHD evolution of a GRB central engine where the newly formed black hole is accreting the mass from post-merger remnant. We explore the wind properties, for a range of the initial parameters of the system, and study representative cases for compact binary merger progenitors. We compute a suite of 2D and 3D time-dependent General Relativistic numerical simulations with a tabulated 3-parameter equation of state that allows for evolution of chemical composition evolution of the accretion flow. The neutrino emission is accounted for by incorporating the leakage scheme, where neutrino optical depth is calculated along the radial rays. We parameterize the optically thick and thin tori with different values of the pressure maximum and entropy in the disk, while the strength of large-scale poloidal magnetic fields is parameterized according to the chosen gas-to-magnetic pressure ratio. To probe the winds, we follow the particle trajectories. Upon this, we derive the nucleosynthetic yields of heavy elements in the outflows, and we map the regions of Lanthanide rich and poor ejecta. We find that the outflow carries high mass of neutron rich material expanding with mildly relativistic velocities. Our accretion disks operating under the SANE mode can power the GRB jets via neutrino annihilation, if the disk to BH mass ratio is larger than about 0.01 and the black hole is spinning. Slowly spinning black holes surrounded by massive post-merger disks can power these jets, and also be the sites of efficient nucleosynthesis of Lanthanides.
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Instrumentation and Methods for Astrophysics

$\texttt{unimpeded}$: A Public Nested Sampling Database for Bayesian Cosmology

Dily Duan Yi Ong and Will Handley

Bayesian inference is central to modern cosmology. While parameter estimation is achievable with unnormalised posteriors traditionally obtained via MCMC methods, comprehensive model comparison and tension quantification require Bayesian evidences and normalised posteriors, which remain computationally prohibitive for many researchers. To address this, we present $\texttt{unimpeded}$, a publicly available Python library and data repository providing DiRAC-funded (DP192 and 264) pre-computed nested sampling and MCMC chains with their normalised posterior samples, computed using $\texttt{Cobaya}$ and the Boltzmann solver $\texttt{CAMB}$. $\texttt{unimpeded}$ delivers systematic analysis across a grid of eight cosmological models (including $\Lambda$CDM and seven extensions) and 39 modern cosmological datasets (comprising individual probes and their pairwise combinations). The built-in tension statistics calculator enables rapid computation of six tension quantification metrics. All chains are hosted on Zenodo with permanent access via the unimpeded API, analogous to the renowned Planck Legacy Archive but utilising nested sampling in addition to traditional MCMC methods.
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Instrumentation and Methods for Astrophysics

Unsupervised Discovery of High-Redshift Galaxy Populations with Variational Autoencoders

Aayush Saxena

We apply variational autoencoders to automatically discover galaxy populations using publicly available high-redshift JWST spectra without prior classification knowledge. Our unsupervised method identifies distinct astrophysical classes of unique and exciting galaxy types, demonstrating automated discovery capabilities for large spectroscopic surveys.
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Solar and Stellar Astrophysics

Upper Limits on Radio Emission from the K2-18 System

Kelvin Wandia, Chenoa Tremblay, Michael A. Garrett et al. (+11 more)

Stellar and planetary magnetic fields play a crucial role in the habitability of a planet and the integrity of its atmosphere. The recently claimed detection of biosignatures, methane, carbon dioxide and dimethyl sulfide/disulfide, in the atmosphere of K2-18 b, a sub-Neptune orbiting an M dwarf star present an intriguing question regarding the stellar magnetic environment and the resistance of the planet's magnetosphere (if it exists) to erosion by magnetic activity from the host. To probe for radio emission from the system, we have conducted observations using the Karl G. Jansky Very Large Array (VLA) at S, C and X-bands (2-4, 4.5-7.5 and 8-10 GHz respectively) to search for coherent and incoherent radio emission. We detect no radio emission associated with incoherent emission mechanisms. We report $3\sigma$ Stokes I upper limits of $49.8\ \mu\rm{Jybeam}^{-1}$ at S-band, $17.7\ \mu\rm{Jybeam}^{-1}$at C-band and $18.0\ \mu\rm{Jybeam}^{-1}$ at X-band and an upper limit of the ratio of the radio to the total bolometric luminosity of $\log L_\text{R}/\log L_\text{bol}<-8.8$. We have also searched for short duration bursts associated with coherent emission mechanisms at C and X-bands . No signals above a $3\sigma$ significance threshold are detected. Although no signals are detected our radio observations offer constraints, albeit limited, on the stellar magnetic environment supporting recent X-ray observations indicating K2-18 is a very faint emitter. Our results also contextualise any planetary transmission spectra by providing constraints on the activity level of the host.
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All authors Kelvin Wandia, Chenoa Tremblay, Michael A. Garrett, Alex Andersson, Megan G. Li, Vishal Gajjar, Robert J. Beswick, Jack F. Radcliffe, David R. DeBoer, P.B. Demorest, Daniel Czech, Wael Farah, Ian Heywood, Andrew Siemion

Astrophysics of Galaxies

Investigating the imprints of tidal features on simulated galaxy outskirts in LSST-like mock observations

Aman Khalid, Sarah Brough, Garreth Martin et al. (+5 more)

Tidal features provide signatures of recent galaxy mergers, offering insights into the role of mergers in galaxy evolution. The Vera C. Rubin Observatory's upcoming Legacy Survey of Space and Time (LSST) will allow for an unprecedented study of tidal features around millions of galaxies. We use mock images of galaxies at $z\sim0$ ($z\sim0.2$ for NewHorizon) from NewHorizon, eagle, IllustrisTNG, and Magneticum Pathfinder simulations to predict the properties of tidal features in LSST-like images. We find that tidal features are more prevalent around blue galaxies with intrinsic colours $(g-i)\leq0.5$, compared to redder ones, at fixed stellar mass. This trend correlates with elevated specific star formation rates ($\mathrm{sSFR}>10^{-10}\mathrm{\:yr}^{-1}$), suggesting that merger-induced star formation contributes to the bluer colours. Tidal feature hosts in the red sequence appear to exhibit colour profiles offset to bluer colours for galaxies with stellar masses $10^{10}<M_{\star\mathrm{,\:30\:pkpc}}/\mathrm{M}_\odot<10^{11}$, similarly blue cloud tidal feature host galaxies appear to have their colour profiles offset to bluer colours for $10^{9.5}<M_{\star\mathrm{,\:30\:pkpc}}/\mathrm{M}_\odot<10^{10.5}$. However, the differences in colour profiles in either the red sequence or the blue cloud are not statistically robust and larger samples are needed to test if these differences are real. The predictions across the simulations are quantitatively distinct; therefore, LSST observations will allow us to further constrain the differences between different subgrid physics models.
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All authors Aman Khalid, Sarah Brough, Garreth Martin, Lucas C. Kimmig, Rhea-Silvia Remus, Claudia del P. Lagos, Louisa Canepa, Alice Desmons

High Energy Astrophysical Phenomena

Crossing the veil of the brightest radio relic in the sky MACS J0717.6+3745

A. Pasetto, O. Vilchis, A. Bonafede et al. (+3 more)

We present high-frequency, full-polarisation Jansky Very Large Array (VLA) radio data at X-band of the radio relic: MACS J0717.5+3745. Radio relics trace shock waves in the intracluster medium (ICM) produced during mergers. Understanding the physical characteristics of relics is important for determining their nature, whether for example they are thermal ICM electrons that are accelerated, or whether they are fossil electrons re-accelerated by a merger event. Radio spectropolarimetric analysis, such as the Stokes QU-fitting, provides a diagnostic of the nature and structure of the magnetized plasma internal or external to the source, with important implications for theoretical models. The high-frequency polarisation analysis presented here shows, for the first time, a change in the magneto-ionic structure compared to the low-frequency data available in the literature. These high-frequency, polarised data could be interpreted also with an internal depolarisation behaviour and this new finding may be used to investigate possible particle acceleration mechanism. If that is true, the change in the behaviour of the polarised signal could be tracing physical properties of a population of non-thermal particles that are undergoing to a re-acceleration of particles in the relic by large-scale internal shocks of Active Galactic Nuclei jet fossil particles ejected from the central Narrow Angle Tail radio galaxy. New upcoming broad-band VLA X- and Ku-bands data will clarify this. Finally, we conclude that high-frequency, high-sensitive, spectropolarimetric radio data should be explored further, as they can effectively trace shock fronts and thereby provide insights into the intrinsic magneto-ionic properties of radio components.
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All authors A. Pasetto, O. Vilchis, A. Bonafede, E. F. Jiménez-Andrade, K. Rajpurohit, E. Murphy

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Quantum Gravity, de Sitter Space, and Normalizability

Stephon Alexander, Heliudson Bernardo, Jacob Kuntzleman et al. (+1 more)

We propose a resolution to the longstanding problem of perturbative normalizability in canonical quantum gravity of the Lorentzian Chern-Simons-Kodama (CSK) state with a positive cosmological constant in four dimensions. While the CSK state is an exact solution to the Hamiltonian constraint in the self-dual formulation and semiclassically describes de Sitter spacetime, its physical viability has been questioned due to apparent nonnormalizability and CPT asymmetry. Starting from a nonperturbative holomorphic inner product derived from the reality conditions of the self-dual Ashtekar variables, we show that the linearization, in terms of gravitons, of the CSK state is perturbatively normalizable for super-Planckian cosmological constant. Furthermore, we demonstrate that a rotation in phase space, a generalization of Thiemann's complexifier, can render the full perturbative state normalizable for all $\Lambda$ by analytically continuing the non-convergent modes in phase space. This provides the first concrete realization of a CPT-breaking, yet normalizable, gravitational vacuum state rooted in a nonperturbative quantum gravity framework. Our results establish the CSK state-long thought formal-as a viable candidate for the ground state of quantum gravity in de Sitter space.
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All authors Stephon Alexander, Heliudson Bernardo, Jacob Kuntzleman, Max Pezzelle

Solar and Stellar Astrophysics

Recovering Ion Distribution Functions: II. Gyrotropic Slepian Reconstruction of Solar Wind Electrostatic Analyzer Measurements

Srijan Bharati Das and Michael Terres

Velocity distribution functions (VDF) are an essential observable for studying kinetic and wave-particle processes in solar wind plasmas. To experimentally distinguish modes of heating, acceleration, and turbulence in the solar wind, precise representations of particle phase space VDFs are needed. In the first paper of this series, we developed the Slepian Basis Reconstruction (SBR) method to approximate fully agyrotropic continuous distributions from discrete measurements of electrostatic analyzers (ESAs). The method enables accurate determination of plasma moments, preserves kinetic features, and prescribes smooth gradients in phase space. In this paper, we extend the SBR method by imposing gyrotropic symmetry (g-SBR). Incorporating this symmetry enables high-fidelity reconstruction of VDFs that are partially measured, as from an ESA with a limited field-of-view (FOV). We introduce three frameworks for g-SBR, the gyrotropic Slepian Basis Reconstruction: (A) 1D angular Slepian functions on a polar-cap, (B) 2D Slepian functions in a Cartesian plane, and (C) a hybrid method. We employ model distributions representing multiple anisotropic ion populations in the solar wind to benchmark these methods, and we show that the g-SBR method produces a reconstruction that preserves kinetic structures and plasma moments, even with a strongly limited FOV. For our choice of model distribution, g-SBR can recover $\geq90\%$ of the density when only $20\%$ is measured. We provide the package gdf for open-source use and contribution by the heliophysics community. This work establishes direct pathways to bridge particle observations with kinetic theory and simulations, facilitating the investigation of gyrotropic plasma heating phenomena across the heliosphere.
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High Energy Astrophysical Phenomena

Charge-dependent spectral softenings of primary cosmic-rays below the knee

DAMPE Collaboration: Francesca Alemanno, Qi An, Philipp Azzarello et al. (+145 more)

In most particle acceleration or propagation theories, the characteristic features of the cosmic ray spectra due to acceleration limits or propagation phase changes are charge dependent. Alternatively, the interaction scenario would expect mass dependent spectral features in general. The observational verification of which relation takes effect in nature is still lack due to the difficulty of measuring the spectra of individual particles up to very high energies. Here we report direct measurements of the carbon, oxygen, and iron spectra from ~20 gigavolts to ~100 teravolts (~60 teravolts for iron) with 9 years of on-orbit data collected by the Dark Matter Particle Explorer. Distinct spectral softenings have been directly detected in these spectra for the first time. Combined with the updated proton and helium spectra, the spectral softening appears universally at a rigidity of ~15 teravolts. A nuclei mass dependent softening is rejected at a confidence level of >99.999%. Possible interpretations of these results, including a nearby cosmic ray source and other models such as the propagation effect, are discussed.
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All authors DAMPE Collaboration: Francesca Alemanno, Qi An, Philipp Azzarello, Felicia-Carla-Tiziana Barbato, Paolo Bernardini, Xiao-Jun Bi, Hugo Valentin Boutin, Irene Cagnoli, Ming-Sheng Cai, Elisabetta Casilli, Jin Chang, Deng-Yi Chen, Jun-Ling Chen, Zhan-Fang Chen, Zi-Xuan Chen, Paul Coppin, Ming-Yang Cui, Tian-Shu Cui, Ivan De Mitri, Francesco de Palma, Adriano Di Giovanni, Tie-Kuang Dong, Zhen-Xing Dong, Giacinto Donvito, Jing-Lai Duan, Kai-Kai Duan, Rui-Rui Fan, Yi-Zhong Fan, Fang Fang, Kun Fang, Chang-Qing Feng, Lei Feng, Sara Fogliacco, Jennifer-Maria Frieden, Piergiorgio Fusco, Min Gao, Fabio Gargano, Essna Ghose, Ke Gong, Yi-Zhong Gong, Dong-Ya Guo, Jian-Hua Guo, Shuang-Xue Han, Yi-Ming Hu, Guang-Shun Huang, Xiao-Yuan Huang, Yong-Yi Huang, Maria Ionica, Lu-Yao Jiang, Wei Jiang, Yao-Zu Jiang, Jie Kong, Andrii Kotenko, Dimitrios Kyratzis, Shi-Jun Lei, Bo Li, Manbing Li, Wei-Liang Li, Wen-Hao Li, Xiang Li, Xian-Qiang Li, Yao-Ming Liang, Cheng-Ming Liu, Hao Liu, Jie Liu, Shu-Bin Liu, Yang Liu, Francesco Loparco, Miao Ma, Peng-Xiong Ma, Tao Ma, Xiao-Yong Ma, Giovanni Marsella, Mario-Nicola Mazziotta, Dan Mo, Yu Nie, Xiao-Yang Niu, Andrea Parenti, Wen-Xi Peng, Xiao-Yan Peng, Chiara Perrina, Enzo Putti-Garcia, Rui Qiao, Jia-Ning Rao, Yi Rong, Andrea Serpolla, Ritabrata Sarkar, Pierpaolo Savina, Zhi Shangguan, Wei-Hua Shen, Zhao-Qiang Shen, Zhong-Tao Shen, Leandro Silveri, Jing-Xing Song, Hong Su, Meng Su, Hao-Ran Sun, Zhi-Yu Sun, Antonio Surdo, Xue-Jian Teng, Andrii Tykhonov, Gui-Fu Wang, Jin-Zhou Wang, Lian-Guo Wang, Shen Wang, Xiao-Lian Wang, Yan-Fang Wang, Da-Ming Wei, Jia-Ju Wei, Yi-Feng Wei, Di Wu, Jian Wu, Sha-Sha Wu, Xin Wu, Zi-Qing Xia, Zheng Xiong, En-Heng Xu, Hai-Tao Xu, Jing Xu, Zhi-Hui Xu, Zi-Zong Xu, Zun-Lei Xu, Guo-Feng Xue, Ming-Yu Yan, Hai-Bo Yang, Peng Yang, Ya-Qing Yang, Hui-Jun Yao, Yu-Hong Yu, Qiang Yuan, Chuan Yue, Jing-Jing Zang, Sheng-Xia Zhang, Wen-Zhang Zhang, Yan Zhang, Ya-Peng Zhang, Yi Zhang, Yong-Jie Zhang, Yong-Qiang Zhang, Yun-Long Zhang, Zhe Zhang, Zhi-Yong Zhang, Cong Zhao, Hong-Yun Zhao, Xun-Feng Zhao, Chang-Yi Zhou, Xun Zhu, Yan Zhu

Solar and Stellar Astrophysics

Modeling Solar Atmosphere Dynamics with MAGEC

Anamaría Navarro, E. Khomenko, N. Vitas et al. (+1 more)

Modeling the solar atmosphere is challenging due to its layered structure and multi-scale dynamics. We aim to validate the new radiative MHD code MAGEC, which combines the MANCHA and MAGNUS codes into a finite-volume, shock-capturing framework, and to test its performance through 2D simulations of magneto-convection. MAGEC is MPI-parallelized and includes improvements for coronal modeling, such as LTE radiative losses and a hyperbolic treatment of thermal conduction that mitigates restrictive time steps. We also estimated its numerical viscosity and resistivity. To assess robustness, we performed 2D simulations covering a domain from 2 Mm below the surface to 18.16 Mm into the corona, using both open and closed magnetic-field configurations. For each case, we analyzed steady-state temperature profiles and the contributions to the internal-energy balance at different heights. A separate experiment examined the role of perpendicular thermal conduction. MAGEC reproduced the expected temperature stratification set by boundary conditions and magnetic geometry, and all simulations reached thermal equilibrium. Open-field cases produced higher coronal temperatures than closed, arcade-like fields. Analysis of the explicit and implicit energy terms clarified their relative effects on heating and cooling. Perpendicular thermal conduction, often neglected in coronal models, was found to influence plasma dynamics near reconnection; although local effects are small, they can cumulatively modify the average coronal temperature. These results show that MAGEC is a reliable and efficient tool for radiative MHD simulations, well suited to capturing the shocks and dynamic processes of the solar atmosphere.
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All authors Anamaría Navarro, E. Khomenko, N. Vitas, T. Felipe

Solar and Stellar Astrophysics

A scaling relationship for non-thermal radio emission from ordered magnetospheres - II. Investigating the efficiency of relativistic electron production in magnetospheres of BA-type stars

P. Leto, S. Owocki, C. Trigilio et al. (+19 more)

Magnetic BA stars host dipole-like magnetospheres. When detected as radio sources, their luminosities correlate with the magnetic field and rotation. Rotation is crucial because the mechanism undergirding the relativistic electron production is powered by centrifugal breakouts. CBOs occur wherever magnetic tension does not balance centrifugal force; the resulting magnetic reconnection provides particle acceleration. To investigate how physical conditions at the site of the CBOs affect the efficiency of the acceleration mechanism, we broadly explore the parameter space governing radio emission by increasing the sample of radio-loud magnetic stars. High-sensitivity VLA observations of 32 stars were performed in the hope of identifying new centrifugal magnetospheres and associated CBOs. We calculated gyro-synchrotron spectra using 3D modeling of a dipole-shaped magnetosphere. We evaluated combinations of parameters. The number of relativistic electrons was constrained by the need to produce the emission level predicted by the scaling relationship for the radio emission from magnetic BA stars. About half of the observed stars were detected, with luminosities in agreement with the expected values, reinforcing the robust nature of the scaling relationship for CBO-powered radio emission. Comparing the competing centrifugal and magnetic effects on plasma locked in a rigidly rotating magnetosphere, we located the site of CBOs and inferred the local plasma density. We then estimated the efficiency of the acceleration mechanism needed to produce enough non-thermal electrons to support the radio emission level. Given a constant acceleration efficiency, relativistic electrons represent a fixed fraction of the local thermal plasma. Thus, dense magnetospheres host more energetic particles than less dense ones; consequently, with other parameters similar, they are intrinsically brighter radio sources.
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All authors P. Leto, S. Owocki, C. Trigilio, F. Cavallaro, B. Das, M.E. Shultz, C.S. Buemi, G. Umana, L. Fossati, R. Ignace, J. Krticka, L.M. Oskinova, I. Pillitteri, C. Bordiu, F. Bufano, L. Cerrigone, A. Ingallinera, S. Loru, S. Riggi, A.C. Ruggeri, A. ud-Doula, F. Leone

Astrophysics of Galaxies

Linking Warm Dark Matter to Merger Tree Histories via Deep Learning Networks

Ilem Leisher, Paul Torrey, Alex M. Garcia et al. (+11 more)

Dark matter (DM) halos form hierarchically in the Universe through a series of merger events. Cosmological simulations can represent this series of mergers as a graph-like “tree” structure. Previous work has shown these merger trees are sensitive to cosmology simulation parameters, but as DM structures, the outstanding question of their sensitivity to DM models remains unanswered. In this work, we investigate the feasibility of deep learning methods trained on merger trees to infer Warm Dark Matter (WDM) particles masses from the DREAMS simulation suite. We organize the merger trees from 1,024 zoom-in simulations into graphs with nodes representing the merger history of galaxies and edges denoting hereditary links. We vary the complexity of the node features included in the graphs ranging from a single node feature up through an array of several galactic properties (e.g., halo mass, star formation rate, etc.). We train a Graph Neural Network (GNN) to predict the WDM mass using the graph representation of the merger tree as input. We find that the GNN can predict the mass of the WDM particle ($R^2$ from 0.07 to 0.95), with success depending on the graph complexity and node features. We extend the same methods to supernovae and active galactic nuclei feedback parameters $A_\text{SN1}$, $A_\text{SN2}$, and $A_\text{AGN}$, successfully inferring the supernovae parameters. The GNN can even infer the WDM mass from merger tree histories without any node features, indicating that the structure of merger trees alone inherits information about the cosmological parameters of the simulations from which they form.
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All authors Ilem Leisher, Paul Torrey, Alex M. Garcia, Jonah C. Rose, Francisco Villaescusa-Navarro, Zachary Lubberts, Arya Farahi, Stephanie O'Neil, Xuejian Shen, Olivia Mostow, Nitya Kallivayalil, Dhruv Zimmerman, Desika Narayanan, Mark Vogelsberger

Astrophysics of Galaxies

Intensive X-ray/UVOIR continuum reverberation mapping of the Seyfert AGN MCG+08-11-11

D. Kynoch, I. M. McHardy, E. M. Cackett et al. (+11 more)

We present results from intensive (x3 daily), three-month-long X-ray, UV and optical monitoring of the bright Seyfert active galactic nucleus (AGN) MCG+08-11-11 with Swift, supported by optical-infrared ground-based monitoring. The 12 resultant, well-sampled, lightcurves are highly correlated; in particular, the X-ray to UV correlation r_max = 0.85 is, as far as we know, the highest yet recorded in a Seyfert galaxy. The lags increase with wavelength, as expected from reprocessing of central high-energy emission by surrounding material. Our lag spectrum is much shallower than that obtained from an optical monitoring campaign conducted a year earlier when MCG+08-11-11 was approximately 4 times brighter. After filtering out long-term trends in the earlier optical lightcurves we recover shorter lags consistent with our own - demonstrating concurrent reverberation signals from different spatial scales and the luminosity dependence of the measured lags. We use our lag spectrum to test several physical models, finding that disc reprocessing models cannot account for the observed 'excess' lags in the u and r-i-bands that are highly indicative of the Balmer and Paschen continua produced by reprocessing in the broad line region (BLR) gas. The structure seen in both the variable (rms) and lag spectra, and the large time delay between X-ray and UV variations (approximately 2 days) all suggest that the BLR is the dominant reprocessor. The hard X-ray spectrum (Gamma approximately 1.7) and faint, red, UV-optical spectrum both indicate that the Eddington accretion ratio is low: approximately 0.03. The bolometric luminosity then requires that the black hole mass is substantially greater than current reverberation mapping derived estimates.
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All authors D. Kynoch, I. M. McHardy, E. M. Cackett, J. Gelbord, J. V. Hernández Santisteban, K. Horne, J. A. Miller, H. Netzer, C. Done, R. Edelson, M. M. Fausnaugh, M. R. Goad, B. M. Peterson, F. M. Vincentelli

Cosmology and Nongalactic Astrophysics

Reviving Quadratic Inflation: Minimal Deformation for CMB Compatibility and Reheating Consistency

Khedidja Djeha

We revisit the quadratic inflationary potential by introducing a minimal higher-order correction obtained through a simple field redefinition, leading to the potential V(chi) = (1/2) m^2 * (chi - (gamma/14) * chi^7)^2. While the uncorrected quadratic model predicts n_s approximately 0.967 and r approximately 0.13, in strong tension with CMB data, the corrected potential yields n_s approximately 0.965 and r approximately 0.036, fully consistent with Planck 2018 constraints. Beyond inflationary observables, the deformation also impacts the reheating phase. In the quadratic case, reheating corresponds to a matter-like regime with w_reh = 0, whereas the corrected potential gives w_reh approximately -0.011, a slightly softer equation of state. This modification raises the reheating temperature by a factor of about 3.4 (for N_reh = 10), or equivalently extends the reheating duration at fixed temperature. Our results demonstrate that even a minimal higher-order correction is sufficient to reconcile the quadratic model with observations while providing a more consistent post-inflationary history, highlighting the relevance of controlled deformations of simple inflationary scenarios.
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Earth and Planetary Astrophysics

EMPEROR I. Exoplanet MCMC parallel tempering for RV orbit retrieval

Pablo A. Peña and James S. Jenkins

We present EMPEROR, an open-source Python framework designed for efficient exoplanet detection and characterisation with radial velocities (RV). EMPEROR integrates Dynamic Nested Sampling (DNS) and Adaptive Parallel Tempering (APT) Markov Chain Monte Carlo (MCMC), supporting multiple noise models such as Gaussian Processes (GPs) and Moving Averages (MA). The framework enables systematic model comparison using statistical metrics, including Bayesian evidence ($\ln{\mathcal{Z}}$) and Bayesian Information Criterion (BIC), while providing automated, publish-ready visualisations. EMPEROR is evaluated across three distinct systems to assess its capabilities in different detection scenarios. Sampling performance, model selection, and the search for Earth-mass planets are evaluated in data for 51 Pegasi, HD 55693 and Barnard's Star (GJ 699). For 51 Pegasi, APT achieves an effective sampling increase over DNS by a factor 3.76, while retrieving tighter parameter estimates. For HD 55693 the stellar rotation $P_{\text{rot}}=29.72^{+0.01}_{-0.02}$ and magnetic cycle $P_{\text{mag}}=2557.0^{+70.1}_{-36.7}$ are recovered, while demonstrating the sensitivity of $\ln{\mathcal{Z}}$ to prior selection. For Barnard's star, several noise models are compared, and the confirmed planet parameters are successfully retrieved with all of them. The best model shows a period of 3.1536$\pm$0.0003~d, minimum mass of 0.38$\pm$0.03 M$_{\rm{\oplus}}$, and semi-major axis of 0.02315$\pm$0.00039~AU. Purely statistical inference might be insufficient on its own for robust exoplanet detection. Effective methodologies must integrate domain knowledge, heuristic criteria, and multi-faceted model comparisons. The versatility of EMPEROR in handling diverse noise structures, its systematic model selection, and its improved performance make it a valuable tool for RV exoplanetary studies.
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High Energy Astrophysical Phenomena

A subpopulation of low-mass, spinning black holes: signatures of dynamical assembly

Hui Tong, Thomas A. Callister, Maya Fishbach et al. (+5 more)

Gravitational-wave observations of massive, rapidly spinning binary black holes mergers provide increasing evidence for the dynamical origin of some mergers. Previous studies have interpreted the mergers with primary mass $\gtrsim45\,M_\odot$ as being dominated by hierarchical, second-generation mergers, with rapidly spinning primaries being the products of previous black hole mergers assembled in dense stellar clusters. In this work, we reveal confident evidence of another subpopulation with rapid and isotropic spins at low mass containing the two exceptional events GW241011 and GW241110, consistent with a hierarchical merger hypothesis. Our result suggests the mass distribution of the second-generation black holes is peaked at low primary masses of $\sim16\,M_\odot$ rather than $\gtrsim45\,M_\odot$ in the pair-instability gap. Such low-mass second-generation black holes must be formed from the merger of even lighter first-generation black holes, implying that dense, metal-rich stellar environments contribute to the binary black hole population. By separating the contamination of higher-generation black holes, our result reveals the primary mass distribution of first-generation black holes formed from stellar collapse, which shows a significant dip between $\sim12\,M_\odot$ to $\sim20\,M_\odot$. This may indicate a dearth of black holes due to variation in the core compactness of the progenitor.
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All authors Hui Tong, Thomas A. Callister, Maya Fishbach, Eric Thrane, Fabio Antonini, Simon Stevenson, Isobel M. Romero-Shaw, Fani Dosopoulou

Solar and Stellar Astrophysics

Near-degeneracy effects in Quadrupolar Mixed Modes. From an Asymptotic Description to Data Fitting

B. Liagre, A. Desai, L. Einramhof et al. (+1 more)

Dipolar (l=1) mixed modes revealed surprisingly weak differential rotation between the core and the envelope of evolved solar-like stars. Quadrupolar (l=2) mixed modes also contain information on the internal dynamics, but are very rarely characterised due to their low amplitude and the challenging identification of adjacent or overlapping rotationally split multiplets affected by near-degeneracy effects. We aim to extend broadly used asymptotic seismic diagnostics beyond l=1 mixed modes by developing an analogue asymptotic description of l=2 mixed modes, explicitly accounting for near-degeneracy effects that distort their rotational multiplets. We derive a new asymptotic formulation of near-degenerate mixed l=2 modes that describes off-diagonal terms representing the interaction between modes of adjacent radial orders. We implement the formalism within a global Bayesian mode-fitting framework, for a direct fit of all l=0,1,2 modes in the power spectrum density. We are able to asymptotically model the asymmetric rotational splitting present in various radial orders of l=2 modes observed in young red giant stars without the need for any numerical stellar modelling. Applied to the Kepler target KIC 7341231, our formalism yields core and envelope rotation rates consistent with previous numerical modelling, while providing improved constraints from the global and model-independent approach. We also characterise the new target KIC 8179973, measuring its rotation rate and mixed-mode parameters for the first time. The global fit allows for much better precision than standard methods, yielding better constraints for rotation inversions. We place the first observational constraints on the asymptotic l=2 mixed mode parameters (DPi_2,q_2,eps_g2), paving the way towards the use of asymptotic seismology beyond l=1 mixed modes.
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All authors B. Liagre, A. Desai, L. Einramhof, L. Bugnet

Instrumentation and Methods for Astrophysics

Optimizing broadband microwave absorbers for applications in the 70-200 GHz range

Gaganpreet Singh, Rustam Balafendiev, Mahesh Singh Bist et al. (+4 more)

We present results of an extensive suite of numerical simulations that probe square-tiled microwave absorber performance as a function of material properties, frequency, geometry, and unit cell size. The work, which probes both specular reflection and total absorption, highlights the critical importance of the absorber scale size relative to the incidence wavelength while suggesting that material properties have a comparatively weaker impact on overall performance. We show that some absorber designs can achieve 99.5-99.9% frequency-averaged absorption across the 70 to 200 GHz range for normal incidence and that low specular reflectance does not necessarily guarantee optimal absorption performance. Our results indicate that exponential, Klopfenstein, and linear impedance tapers provide comparable performance as long as a unit cell size of 1 to 4 mm is chosen. Simulation results are validated against measurements of specular reflectance.
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All authors Gaganpreet Singh, Rustam Balafendiev, Mahesh Singh Bist, Thomas J.L.J. Gascard, Gagandeep Kaur, Vid Primožič, Jon E. Gudmundsson

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Exact Renormalisation Group Evolution of the Inflation Dynamics: Reconciling $\alpha$-Attractors with ACT

Jean Alexandre, Lucien Heurtier and Silvia Pla

We present a non-perturbative framework for the dynamics of slow-roll inflation that consistently incorporates quantum corrections, based on an alternative functional renormalisation group (RG) approach. We derive the coupled Friedmann-RG flow equations governing the joint evolution of spacetime, the inflaton field, and its effective potential. Applying this formalism to $\alpha$-attractor E-models, we find that the RG flow induces a dynamical destabilisation of the inflationary trajectory, leading to a premature termination of slow roll. Remarkably, the resulting predictions bring $\alpha$-attractors into full agreement with the latest ACT data without introducing new physics beyond a consistent quantum-corrected treatment of the inflaton dynamics.
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High Energy Astrophysical Phenomena

Spectrum of PeV Cosmic-Ray Protons and Helium Nuclei with IceCube

Julian Saffer

The IceCube Observatory comprises a cubic-kilometer particle detector deep in the Antarctic ice and the cosmic-ray air-shower array IceTop at the surface above. Previous analyses of the cosmic-ray composition have used coincident events with IceTop detecting the electromagnetic shower footprint as well as GeV muons, while the sensors submerged in the ice measure the TeV muons from the same events. The energy range of previous composition analyses, however, has been limited to 3 PeV primary energy and above, whereas the IceTop all-particle energy spectrum has been extended down to 250 TeV. This contribution presents a method to reconstruct the combined spectrum of cosmic-ray protons and helium nuclei, starting at 200 TeV primary energy. The resulting H+He spectrum closes the gap in the measurements of light cosmic rays between IceCube as well as KASCADE and experiments measuring in the TeV energy range, such as DAMPE and HAWC.
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Cosmology and Nongalactic Astrophysics

Focus Point on Tensions in Cosmology from Early to Late Universe: Part II: New Directions in the Light of Observations from the Most Modern Astronomical Facilities

S. Capozziello, E. Di Valentino and V.G. Gurzadyan

The papers included in this Focus Point collection are devoted to the studies on the cosmological tensions and challenges stimulated by the latest observational data. The first results of the LARES-2 laser ranging satellite on the high precision testing of the frame-dragging effect predicted by General Relativity are presented. The data on the S-stars monitoring in the Galactic center obtained by GRAVITY collaboration were analysed within the Physics-informed neural network (PINN) approach. The results enabled to probe the role of the cosmological constant, of the dark matter, the star cluster in the core of the Galaxy obtaining an upper limit for the star density. The topics include the conversion of high-frequency relic gravitational waves into photons in cosmological magnetic field, cosmological gravitational waves stochastic background generation through the spontaneous breaking of a global baryon number symmetry, observational predictions of the Starobinsky inflation model and other studies.
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