Solar and Stellar Astrophysics
Frequent X-class Far UV Flares from a Young Solar Analog DS Tucanae A
Tristen Sextro, Kevin France, Vladimir Airapetian et al. (+4 more)
The young
solar analog DS Tuc A (~45 million years old, spectral type G6V) serves as an excellent proxy to the Sun during early stages of the Earth's
evolution. The young Sun's enhanced
magnetic activity in the form of X-ray and extreme UV emission,
stellar wind, and
flares likely affected the magnetospheric and atmospheric environments of early Venus, Earth and Mars. Studies of DS Tuc A help constrain
evolution of magnetospheric and atmospheric environments of early Venus, Earth, and Mars and create opportunities to study the impact of
flares on the transiting
exoplanet, DS Tuc Ab. We analyze ~11 hours of Far-ultraviolet (FUV; 1130 - 1450 $\mathring{A}$) observations taken by the Hubble Space
Telescope Cosmic Origins Spectrograph during late 2023 and early 2024. We find DS Tuc A exhibited 26
flares over ~11.1 hours of observations in the transition region lines Si IV (1394 $\mathring{A}$ + 1402 $\mathring{A}$), with durations ranging 90 - 960 seconds and FUV absolute energies ranging ~ 10$^{29}$ - 10$^{31}$ erg over the observed bandpass. Si IV
flares are accompanied by increases of other chromospheric and transition region lines, however the strongest Si IV
flares show no enhanced coronal emission traced by Fe XXI 1354 $\mathring{A}$. We present an analysis of each detected
flare, including X-ray and bolometric luminosities scaled from FUV
flare energies, electron density measurements for the strongest
flares, and the Far-UV continuum response to flaring. These results provide constraints on the frequency and energetics of
flares comparable to X100-class
solar flares and FUV-emitting regions in young
solar analogs.
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All authors Tristen Sextro, Kevin France, Vladimir Airapetian, Grace Sweetak, Randall McEntaffer, Kosuke Namekata, Yuta Notsu
Machine Learning
DSD: Learning Diverse and Reusable Motor Skills via Diffusion Skill Discovery
Sun Woo Kim and Xue Bin Peng
Humans efficiently learn new tasks by reusing a rich repertoire of motor skills across different goals and contexts. A similar strategy can also be used to enable simulated characters to efficiently perform new tasks by leveraging reusable motor skills. To support a wide range of downstream tasks, the learned repertoire should be diverse, consisting of distinct behaviors as well as spatial and temporal variation within each behavior. A commonly used method for learning diverse skills is by maximizing the mutual information between skill latents and the states produced by a policy. The marginal state
entropy promotes broad behavioral coverage, while the conditional
entropy encourages consistent behaviors from each latent. However, directly estimating the marginal state
entropy is intractable in high-dimensional control problems. Prior methods therefore rely on indirect latent-space approximations or coarse
estimators of the state distribution. These approximations may not effectively promote broad coverage of the state space, resulting in skills with limited behavioral diversity and reduced utility for downstream tasks. In this work, we propose
Diffusion Skill Discovery (DSD), a skill discovery method that uses a
diffusion model to approximate the
entropy gradient of the policy-induced state distribution through score matching. The resulting objective encourages the discovery of skills that produce a broader range of behaviors for high-dimensional
humanoid control. The learned skills are reused in two downstream control settings: hierarchical control with a task-specific high-level policy and zero-shot control through latent selection from offline trajectories. Our experiments show that DSD discovers a broader repertoire of reusable motor skills than prior skill discovery methods, leading to the emergence of complex and agile behaviors that can be reused across downstream tasks.
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High Energy Physics (Phenomenology)
Quantum Seesaw Cosmology: A Heating Phase from Pauli Blocking
Nicolás Bernal and Chee Sheng Fong
In Seesaw Cosmology, a scalar field reheats the Standard Model (SM) through right-handed
neutrinos (RHNs), which generate tiny
neutrino masses through the seesaw mechanism. When RHNs rapidly fill a restricted momentum-space region, expansion continually opens new fermionic states that are refilled by subsequent scalar decays, maintaining an approximately constant physical RHN density. This gives rise to a novel heating regime in which the SM temperature increases with the scale factor as $T \propto a^{+3/8}$, in sharp contrast to the conventional $T \propto a^{-3/8}$ scaling during matter-dominated reheating.
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Astrophysics of Galaxies
A dense, metal-rich absorber driven by a heavily dust-obscured galaxy: The direct evidence of CGM enrichment at $z\sim7$
Qinyue Fei, Seiji Fujimoto, Gabriel Brammer et al. (+22 more)
We report the serendipitous discovery of a dense, metal-enriched circumgalactic medium (CGM) absorber at z=7.03, together with its host
galaxy, identified along the sightline toward a red
quasar. The absorber exhibits the largest rest-frame equivalent widths and column densities observed to date at z>5, tracing a metal-enriched gaseous
halo. Using deep JWST/NIRSpec and NOEMA observations, we characterize the absorber's physical properties and identify its host, ND1, as a vigorously
star-forming
galaxy at an exceptionally close impact parameter of ~16kpc, so heavily
dust-obscured that it is detected only in the longest-wavelength NIRCam bands. Detections of [OIII]$\lambda$5007, H$\alpha$, and [CII]$\lambda 158\,\mu$m emission anchor the systemic
redshift to z~7.0321, revealing a coherent ~50km/s blueshift of the absorbing gas relative to the host, suggesting
outflow-driven metal transport into the
halo. The
outflow velocity, combined with the measured column density, implies an
outflow rate of $\dot{M}_{\rm out}=64 M_\odot\,yr^{-1}$ and a mass loading factor $\eta=3$, indicating an energetic, chemically-enriched wind launched from a
dust-obscured starburst. While the overall ionization state and [Mg/Fe] ratio align with empirical
cosmic evolutionary trends, the absorber displays an enhanced carbon-to-oxygen ([C/O]) ratio. This abundance pattern suggests the nucleosynthetic yields of Population~III
stellar explosions, and aligns with the host's
star-formation history extending to $z \gtrsim 8$, potentially offering a rare fossil record of
primordial metal enrichment. Our findings demonstrate that intense
star-formation feedback can rapidly and efficiently pollute the CGM/IGM well into the Epoch of Reionization. The NIR-dark nature of the host further implies that rest-UV surveys may systematically miss the dusty sources that drive CGM- and IGM-scale metal enrichment in the early Universe.
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All authors Qinyue Fei, Seiji Fujimoto, Gabriel Brammer, Lise Christensen, Marianne Vestergaard, Rohan P. Naidu, Robert A. Simcoe, Norman Murray, Luis C. Ho, Ruancun Li, Volker Bromm, Javier Álvarez-Márquez, Hollis B. Akins, Yoshihisa Asada, Simona Di Stefano, Kohei Inayoshi, Vasily Kokorev, Jorryt Matthee, Romain A. Meyer, Ava Polzin, Francesco Valentino, Fabian Walter, Marcel Neeleman, Yunjing Wu, Mengyuan Xiao
General Relativity and Quantum Cosmology
Exact Hairy Black Holes in Higher-Curvature Scalar–Tensor Gravity
Tianhao Wu
We construct exact hairy black holes in Lovelock–Horndeski
gravity and establish a relation between horizon
topology, scalar hair and covariant charges. Rooted in the dimensional reduction of higher-
curvature gravity, this framework connects scalar–tensor dynamics to the low-energy description of heterotic strings. In five dimensions, a single fixed theory admits a continuous planar family and two isolated
hyperbolic black holes. The
hyperbolic solutions share a locally AdS metric with distinct scalar dressings, while the planar family is Weyl curved and has a freely varying horizon scale. Both branches carry scalar hair regular on the future horizon. The
hyperbolic construction extends above four dimensions; compatibility of the displayed planar profile selects five and seven dimensions. Time translations of the scalar act through a global shift, which enters the complete covariant charge balance. Along the planar family, a changing bulk shift-charge density supplies this balance despite zero radial flux and vanishing horizon charge variation. The
hyperbolic roots admit no horizon-scale variation at fixed couplings.
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Statistical Mechanics
Brownian motion with geometry-dependent hydrodynamic memory
Benjamin Sorkin, Günther Turk and Howard A. Stone
Micron-sized particles moving through a fluid are subject to viscous resistance and thermal fluctuations. Beyond steady Stokes friction, colloids also exhibit hydrodynamic
memory effects arising from conservation laws of the surrounding fluid. Although fluid-flow problems in complex geometries and confinements are often highly involved, numerical or approximate solutions can be obtained; translating these solutions into closed-form equations of motion for individual colloids, however, is rarely possible. Here, we develop a theoretical framework that provides both underdamped and overdamped colloidal dynamics from the solution of an arbitrary flow problem: (i) Using the Lorentz reciprocal
theorem, we express the colloidal equation of motion in terms of the geometry's Green's function and the fluid-flow profile. This formulation yields both the corresponding Stokes drag as well as a Basset-like hydrodynamic
memory contribution. (ii) As colloid inertia is often negligible, we furthermore derive the corresponding overdamped (colloid-inertia-less) limit, which inherits the Stokes and Basset-like resistances and additionally gives rise to a spurious drift. We propose applications of this framework to passive and active particles subject to involved confinements and problem geometries.
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Statistical Mechanics
Hydrodynamic memory in overdamped colloidal dynamics
Benjamin Sorkin, Günther Turk and Howard A. Stone
Micron-sized colloid particles diffusing through a fluid experience hydrodynamic inertial and
memory effects, the latter causing velocity autocorrelation to decay as a power law. At the same time, many theoretical descriptions treat colloidal
diffusion in a fluid using overdamped Langevin dynamics for its convenience, eliminating velocity, omitting inertia, but also ignoring the power-law
memory. In this Letter, we show that hydrodynamic
memory survives in the overdamped (colloid-inertialess) limit. By identifying the dimensionless parameter controlling the crossover between early- and late-time dynamics, we derive in closed form the overdamped Langevin equation in the presence of hydrodynamic
memory. This provides a theoretical framework for realistically describing colloidal dynamics in a fluid, and establishes a rigorous basis for the positional
memory observed in high-resolution experiments. Our theory predicts that hydrodynamic
memory becomes increasingly pronounced for smaller particles and under stronger external forcing, and offers experimental probes for the crossover from conventional exponential relaxation to
memory-dominated power-law dynamics.
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Cosmology and Nongalactic Astrophysics
The galaxy-electron cross-spectrum with ACT, SPT-3G and DESILS LRGs
Selim C. Hotinli
The
galaxy–electron cross-power spectrum $P_{ge}(k)$ measures the small-scale distribution of gas around
galaxies, the quantity reshaped by feedback. We measure $P_{ge}$ from the kinetic Sunyaev–Zel'dovich (kSZ) signal of the photometric DESI Legacy Imaging Surveys luminous red
galaxies, cross-correlating a velocity-weighted
galaxy momentum template with the CMB temperature from ACT DR6 and, for the first time, SPT-3G. The absolute normalization of the cross-spectrum is fixed by a surrogate-field Monte Carlo that propagates the survey mask, lightcone
evolution, and photometric-
redshift weights, converting the measured pseudo-spectrum into $P_{ge}(k)$ in physical units. We detect $P_{ge}$ at $11.7\sigma$ with ACT and $8.4\sigma$ with SPT-3G, and at $12.3\sigma$ combining SPT-3G with the ACT northern cap, which it does not overlap. The two surveys have independent optics, beams, filtering and noise and share about two thirds of the SPT-3G
galaxies; their amplitudes agree channel by channel, the largest difference being $0.7\sigma$. All $26$ null tests on the adopted night maps are consistent with zero signal, among them the six ACT frequency differences, the three SPT-3G frequency differences, and the four ACT cap differences of the main selection. Turning the amplitude into a gas fraction requires the host
halo masses of the sample, which the cross-spectrum does not itself measure; taking them from its measured number density and from a published CMB-
lensing calibration of the same
galaxies, the gas within the virial radius is $25$–$33\%$ of the
cosmic baryon budget of the
halo.
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Earth and Planetary Astrophysics
Evidence for an Extended Hydrogen Outflow on WASP-12 b
Morgan Saidel, Shreyas Vissapragada, Heather A. Knutson et al. (+6 more)
Recent observations of atmospheric escape from
planets orbiting early-type
stars indicate that
planets with higher Roche filling factors have significantly higher mass loss rates. For three of these
planets, full-orbit observations have revealed the presence of large leading and trailing tails of escaping planetary material. These 3D
outflow geometries encode information about the underlying
outflow physics, and can also be used to constrain their
stellar wind properties and to predict their long-term orbital
evolution. We present new evidence for extended H$\alpha$ and H$\beta$ absorption from escaping hydrogen for a fourth
planet, WASP-12 b. We observed WASP-12 b with the Keck
Planet Finder on Keck I over a period of approximately eight hours centered on the transit. We find a H$\alpha$ and H$\beta$ absorption signal in the
stellar rest frame that is strongest during the transit (H$\alpha$ amplitude: $2.66\pm0.25\%$, H$\beta$ amplitude: $2.88\pm0.43\%$), with evidence of both pre- and post-transit absorption. This measurement is consistent with
outflow models where the escaping gas overflows the
planet's Roche lobe and is advected into the
stellar rest frame before being tidally sheared into extended tails. This
outflow behavior is qualitatively similar to previous H$\alpha$ observations of this
planet as well as observations of extended
outflows from other gas
giants orbiting early-type
stars.
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All authors Morgan Saidel, Shreyas Vissapragada, Heather A. Knutson, Aaron Householder, Morgan MacLeod, Adam Jensen, Howard Isaacson, Judah Van Zandt, Fei Dai
General Relativity and Quantum Cosmology
Massively parallel transdimensional sampling with data assimilation: an application to LISA galactic binaries
Gabriele Demasi and Walter Del Pozzo
Transdimensional
Bayesian inference is becoming a key ingredient in gravitational-wave astronomy. In many relevant applications, the number of components needed to describe the data is not known a priori and must be inferred jointly with their parameters. We present a transdimensional Sequential Monte Carlo (SMC) framework designed to exploit massive parallelism. The method evolves a population of particles through a sequence of tempered distributions and uses the No-U-Turn Sampler for the exploration of fixed-dimensional parameter space while reversible-jump birth and death moves allow the number of components to vary. The same SMC construction also enables posterior samples obtained from a shorter data segment to be updated as additional data become available, enhancing the overall efficiency of the analysis. We validate the approach on two proof-of-concept problems: the recovery of a sequence of Gaussian pulses and a simplified LISA
Galactic-binary inference problem. In both cases, the method recovers the injected number of components and produces consistent posterior estimates. These results indicate that the proposed method is a promising avenue toward scalable and parallel
Bayesian transdimensional inference for current and future gravitational-wave astronomy.
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Astrophysics of Galaxies
Chandra Lensing-cluster Ultradeep Extragalactic Survey (CLUES) I: A 2 Ms Point-Source Catalog of the Abell 2744 Field
Shouyi Wang, Fan Zou, Elena Gallo et al. (+10 more)
In the first paper of the Chandra
Lensing-cluster Ultradeep Extragalactic Survey (CLUES), we present an ultradeep 2 Ms X-ray survey of the Abell 2744 field constructed from 101 archival Chandra ACIS-I observations. With an exposure comparable to the Chandra Deep Fields and further boosted by strong-
lensing magnification from the Abell 2744 cluster at $z=0.3$, this field represents the third deepest extragalactic X-ray survey of the sky and also has rich synergy with extensive coverage by the Hubble Space
Telescope and James Webb Space
Telescope. We present the Chandra data reduction and detect sources in the soft (0.5-2 keV), hard (2-7 keV), and full (0.5-7 keV) bands over a total area of $369~\mathrm{arcmin^2}$. We perform dedicated image fitting with Chandra point spread functions to optimize point-source detections and improve X-ray positions and further screen the detections to address the impact of the central bright, structured intracluster medium. A total of 327 X-ray point sources are detected and cataloged, including their X-ray photometry and basic spectral properties. Detailed simulations are also conducted, based on which the expected 50% flux completeness reaches $6.3\times10^{-16}$, $2.8\times10^{-16}$, and $4.9\times10^{-16}~\mathrm{erg~cm^{-2}~s^{-1}}$ in the full, soft, and hard bands, respectively. The source number density as a function of flux is consistent with those in blank-field surveys within a factor of $\approx2$, with a slight excess above $\approx10^{-14}~\mathrm{erg~cm^{-2}~s^{-1}}$. All X-ray data products are publicly released, including the catalog, X-ray images, exposure maps, background maps, and sensitivity maps.
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All authors Shouyi Wang, Fan Zou, Elena Gallo, Bin Luo, W. N. Brandt, Yuxuan Pang, Tommaso Treu, Xue-Bing Wu, Dieu D. Nguyen, Guido Roberts-Borsani, Shengzhe Wang, Weiwei Xu, Zihao Zuo
High Energy Physics (Phenomenology)
WIMPs with Enhanced Annihilation from a Feebly Interacting Unstable Partner
Chance Hoskinson, Pearl Sandick and Barmak Shams Es Haghi
Weakly interacting massive particles (WIMPs) constitute one of the best-motivated dark matter (DM) candidates. In this study, we consider a simple extension of the WIMP paradigm in which WIMPs are coupled to a heavier particle that interacts only with them and can decay into WIMPs. In the early Universe, when WIMPs are in thermal
equilibrium with the Standard Model (SM) bath, they serve as a portal to populate the heavy partner through inverse decays. Depending on the lifetime of the partner particle, its eventual decay into WIMPs can significantly alter the WIMP abundance. If the partner decays into WIMPs before their freeze-out from
equilibrium, the standard thermal history remains unchanged. When the decay occurs after WIMP freeze-out, however, the injected non-thermal population of WIMPs can result in an overproduction of DM, therefore requiring a larger WIMP annihilation cross section relative to the standard scenario without the partner. For a given partner lifetime and WIMP annihilation cross section, freeze-out may be delayed due to re-annihilation or followed by a freeze-in phase. By solving the Boltzmann equations both semi-analytically and numerically, we explore these thermal histories and study the required enhancement in the WIMP annihilation cross section compared to the canonical value. This enhancement, which can reach up to three orders of magnitude, leads to stronger annihilation signals in the late Universe. As a result, current and upcoming indirect detection experiments are able to probe the lifetime of the partner particle. We briefly explore possible connections between our scenario and the
baryon asymmetry of the Universe. As an example, we show that the Next-to-Minimal Supersymmetric Standard Model (NMSSM) can provide a realization of our scenario, with the possibility of accommodating light higgsino DM with the correct relic abundance.
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Space Physics
Alfvénicity and Proximity to Parallel-Mode Marginal Stability in the Slow Solar Wind
Mani K Chettri, Rupak Mukherjee and Hemam D. Singh
The
proton temperature anisotropy in the
solar wind is bounded by the thresholds of pressure-anisotropy-driven kinetic instabilities, and the distance at which the
plasma settles from these thresholds is thought to be regulated by compressive fluctuations through the fluctuating anisotropy effect. We test whether the level of Alfvénicity is associated with this distance in the slow
solar wind. Using five years of Wind/SWE bi-Maxwellian
proton measurements (2004–2008), we separate slow-wind intervals into Alfvénic and non-Alfvénic populations on the basis of normalized cross helicity and residual energy. We compare their
magnetic compressive fraction and normalized compressive amplitude, and measure their proximity to marginal stability in the plane of parallel
proton beta and temperature anisotropy using the maximum growth rate over the scanned parallel wavenumbers, $\gamma_{\parallel,\max}$, from a Vlasov dispersion solver. At low matched parallel beta, the Alfvénic slow wind has lower normalized field-strength fluctuation amplitude and reaches the parallel-mode marginal-stability criterion more often than the non-Alfvénic slow wind. This association is consistent with a weaker fluctuating-anisotropy effect in the Alfvénic slow wind, but does not establish a causal relation.
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Statistical Mechanics
Structure of Measurement-Induced Entanglement in Infinite-Randomness Critical States
Oliver Breach
The impact of projective measurements on a many-body
quantum state is tightly linked to its underlying
entanglement structure. Critical states are particularly sensitive, as long-range
entanglement allows local measurements to have global consequences. This has been extensively studied in the context of critical states described by a conformal field theory (CFT), where measurements can alter critical properties in post-measurement quantities ('measurement-altered criticality') and induce long-range
entanglement with universal features ('measurement-induced
entanglement'). By contrast, little is known about the role of measurements on critical states with quenched disorder, which admit no CFT description. Here, we develop a theory of measurements on one-dimensional critical states governed by infinite-randomness fixed points (IRFPs), focusing on two closely related examples: the random XXZ chain and the random transverse-field Ising model. We show that the measurement-induced
entanglement decays as a power-law with universal exponent $(3-\sqrt{5})/2$ in both models, and that the minimum number of measurements required to establish this
entanglement obeys a universal scaling form. When only a finite density of measurements is made, we show that the critical properties of the state are remarkably robust: `measurement-altered criticality' is absent, with measurements either preserving the critical exponents, or destroying the criticality entirely. These results establish IRFPs as an analytically tractable arena for measurements on critical states, complementary to the CFT case. The outcome randomness that necessitates replica methods in clean systems becomes trivial at infinite randomness, with the universal response governed by the statistics induced by the quenched disorder.
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High Energy Physics (Theory)
Full Eigenstate Thermalization in Quantum Field Theory: Free Cumulants and Gravitational Scrambling
Ricardo Espíndola and Viktor Jahnke
Using thermal analyticity, we derive directional large-frequency bounds on the smooth functions entering full eigenstate thermalization in continuum
quantum field theory. The strongest directions reproduce the scales previously identified for
lattice systems, while the complete analyticity domain reveals a broader asymmetric multifrequency structure. In thermal two-dimensional conformal field theory, exact two- and three-point functions saturate the corresponding bounds. At fourth order, where genuine dynamical information first appears, we show that the
holographic CFTs studied here saturate the strongest full-ETH bounds. These results establish a direct connection between full ETH, free cumulants, and gravitational scrambling, and are consistent with the emergence of asymptotic freeness realized by the gravitational scrambling
algebra.
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High Energy Physics (Phenomenology)
Proper Time Shifts in Pulsar Timing Arrays
Vincent S. H. Lee
Pulsar timing arrays are a powerful tool for probing low-frequency gravitational phenomena and physics beyond the Standard Model. We establish a general, gauge-invariant framework for the timing residual by identifying the measurable quantity as the proper time interval between consecutive pulse arrivals at Earth. In linearized general relativity, we derive a general expression for this proper time shift and show that it decomposes into Doppler, Shapiro, and Einstein delay contributions whose sum is gauge invariant, similar to frameworks that have been developed for other gravitational-wave detectors such as
laser and atom interferometers. We also provide a recipe for computing the resulting timing residual for any specified perturbation, and we illustrate the method with several physically well-motivated sources, recovering known results where they exist in the literature. This recipe can be directly applied to search for new physics from real
pulsar timing data using existing numerical software.
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Astrophysics of Galaxies
On the clumpy nature of super-early galaxies
A. Ferrara, B. Das, M. Kohandel et al. (+2 more)
JWST has revealed that
galaxies during the Epoch of Reionization are composed of compact
stellar clumps spanning more than two orders of magnitude in mass and size. We present an analytical framework that connects the global properties of high-
redshift galactic disks to the formation, dynamical
evolution and visibility of these systems. Starting from the classical Toomre instability, we derive analytical mass-size and surface density-size relations together with, for the first time, the intrinsic clump mass spectrum obtained by integrating over the entire unstable branch of the dispersion relation. The observed clumps are naturally reproduced for turbulent velocity dispersions $\sigma\simeq 10-80\,{\rm km\,s^{-1}}$, while their location along the mass-size relation is determined by the compactness of the parent disk. The intrinsic spectrum extends over nearly two decades in mass, $5.5\lesssim\log(M_{\rm cl}/M_\odot)\lesssim7.3$, and is transformed by gas dynamical friction, which suppresses the high-mass tail ($t_{\rm df}\propto M_{\rm cl}^{-1}$) and reproduces the observed clump mass-function slope, $dN/dM\propto M^{-1.89}$.
Supernova feedback is insufficient to clear the dense natal gas, whereas radiation pressure provides a robust clearing mechanism: Ly$\alpha$ trapping dominates in
dust-poor clumps and infrared trapping takes over as they become enriched. The results provide the first self-consistent analytical framework connecting the formation, statistical properties and visibility of
stellar clumps in super-early
galaxies.
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All authors A. Ferrara, B. Das, M. Kohandel, A. Pallottini, E. Ntormousi
High Energy Physics (Theory)
Representation Theory of Three-dimensional Corner Symmetries
Giulio Neri and Ludovic Varrin
We study the representation theory of the three-dimensional extended corner
symmetry group associated with a circular corner. Using induced representation techniques, we construct families of representations of the infinite-dimensional corner
symmetry group and analyze their unitarity and irreducibility. We also determine the maximal central extension of the
symmetry group and construct the corresponding projective representations. The analysis is motivated by the role that corner
symmetries play in
quantum gravity, where boundary degrees of freedom — acted upon by the corner transformations — are expected to encode aspects of the
quantum structure of spacetime. In three dimensions, the representation-theoretic structures that emerge are closely related to
symmetry groups and
quantum theories that already appeared as central to the study of
gravity. This work provides a first step toward a systematic description of
quantum gravitational corner degrees of freedom in three dimensions.
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High Energy Astrophysical Phenomena
Unifying spatial correlation with hierarchical population inference to constrain the AGN channel for binary black hole mergers
Lucas Pouw, Lorenzo Speri, Niccolò Veronesi et al. (+1 more)
The origin of the
stellar-mass binary black holes (BBHs) observed in gravitational wave (GW) events by the LIGO-Virgo-KAGRA (LVK) detectors remains uncertain. One promising formation pathway is the active
galactic nucleus (AGN) channel, in which BBHs embedded in AGN
accretion discs experience enhanced merger rates and may produce rapidly spinning black holes in the upper mass gap. Previous constraints on the AGN contribution to the LVK merger population have relied either on spatial correlations between GW localisations and AGN catalogues or on modelling the intrinsic properties of GW sources. We develop a hierarchical
Bayesian framework that unifies these approaches within a single likelihood for the fraction of AGN-hosted GW events, $f_{\rm agn}$. This framework, combined with the latest gravitational wave transient catalogue GWTC-5.0 and the electromagnetic Quaia AGN catalogue, cannot exclude an AGN contribution to the observed merger rate. For unobscured AGN in the optical and infrared bands with bolometric luminosities $L_{\rm bol}\geq\{10^{44.5},10^{45.5},10^{46.5}\}\,\mathrm{erg\,s^{-1}}$, we exclude $f_{\rm agn} \geq \{0.52,0.41, 0.61\}$ at the 95 percent credible level under our fiducial model. The methodology and results presented in this work lay down the pathway for combining the full GW posterior with electromagnetic observations to infer the properties of GW populations and AGN discs.
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All authors Lucas Pouw, Lorenzo Speri, Niccolò Veronesi, Elena Maria Rossi
High Energy Physics (Phenomenology)
João Barata, Ying-Ying Li, Bo Wang et al. (+1 more)
Detector observables pose a fundamental challenge for nonperturbative
lattice methods due to their intrinsically real-time and asymptotic nature. We propose
quantum simulation platforms as an ideal setting for studying these observables. Using
quantum spin systems as a demonstration, we construct
lattice detector operators and establish their connection to continuum energy-flow observables. We demonstrate this framework in the $1+1$-dimensional
quantum Ising model, where finite
lattice calculations show quantitative agreement with conformal field theory expectations at criticality. These results support the interpretation of the
lattice flow operators as regulated counterparts of continuum detectors in the scaling and asymptotic limits, providing a concrete route toward realizing high-energy
collider physics on table-top
quantum platforms.
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All authors João Barata, Ying-Ying Li, Bo Wang, Hua Xing Zhu
High Energy Physics (Theory)
Full Eigenstate Thermalization in Quantum Field Theory and Gravitational Scrambling
Ricardo Espíndola and Viktor Jahnke
Using thermal analyticity, we derive directional large-frequency bounds on the smooth functions entering full eigenstate thermalization in continuum
quantum field theory. The strongest directions reproduce the scales previously identified for
lattice systems, while the complete analyticity domain reveals an asymmetric multifrequency structure. Thermal conformal correlators saturate the second- and third-order bounds, and the leading gravitational Regge contribution saturates the strongest fourth-order direction.
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Astrophysics of Galaxies
The relationship between morphology, density, and location in the cosmic web from massive to dwarf galaxies
Ilin Lazar, Sugata Kaviraj, Aaron E. Watkins et al. (+5 more)
We study how morphology relates to environment from massive to
dwarf galaxies using, for the first time, a mass-complete sample of ~13,000
galaxies, in the
stellar-mass and
redshift ranges 10^8 MSun < Mstar < 10^11.5 MSun and 0.2<z<0.4, respectively. By combining HST-derived visual morphological classifications with local density and
galaxy distances from nodes and filaments, we quantify how early-type and late-type
galaxies (ETGs and LTGs) differ with respect to environment. The overall ETG fraction decreases from ~65 per cent at Mstar ~ 10^11 MSun to ~20 per cent at Mstar ~ 10^8 MSun. Regardless of morphology, lower
stellar mass
galaxies lie further away from nodes and filaments than their more massive counterparts. While, at Mstar > 10^9 MSun, ETGs reside further away from nodes and filaments than LTGs, this segregation weakens as
stellar mass decreases, with ETGs and LTGs exhibiting similar locations at Mstar < 10^9 MSun. This diminishing difference at lower
stellar mass is likely driven by the fact that filaments have a finite extent and lower mass
galaxies, of all morphologies, lie further away from filament cores and are therefore confined to a smaller region of the filament itself. For high-mass
galaxies (where ETGs and LTGs show strong environmental segregation), greater proximity to nodes likely inhibits coherent angular momentum acquisition, while residing closer to filament cores increases the likelihood of interactions and mergers. Both make it easier to create dispersion-dominated systems, driving the sharp rise of the ETG fraction, in the high-mass regime, close to nodes (and, to a lesser extent) filaments. Our results show that
galaxy evolution is increasingly driven by internal processes as
stellar mass decreases.
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All authors Ilin Lazar, Sugata Kaviraj, Aaron E. Watkins, Christopher J. Conselice, Darshan Kakkad, Thomas M. Sedgwick, Garreth Martin, Sophie Koudmani
High Energy Astrophysical Phenomena
1D PIC Simulations of Resonant Scattering-Driven Pair Cascades in Magnetar Magnetospheres
Jens F. Mahlmann, Alexander A. Philippov, Adrien Soudais et al. (+2 more)
Hard X-rays in persistent magnetar emission originate from radiative processes in pair-loaded magnetospheric
plasma, yet self-consistent kinetic simulations of such radiation-rich systems remain limited. We perform 1D particle-in-
cell simulations of pair creation mediated by resonant inverse Compton scattering (RICS) along isolated field lines in twisted magnetospheres, capturing particle acceleration and radiative drag from first principles. The drag force, which strongly depends on the particle Lorentz factor and location, plays a key role in the magnetospheric
circuit. Strong RICS drag impedes the flow of electrons and positrons, particularly along extended field lines. Nevertheless, the
plasma sustains the
circuit by self-organizing into a single accelerating gap near the
star in one hemisphere. The accelerated
plasma flow from the gap becomes loaded with copious electron-positron pairs in extended RICS zones, and also carries ions extracted from the
star and accelerated in the gap. When radiative drag stops the pair-loaded flow at the
magnetic equator, the ion component transfers momentum through streaming instabilities, delivering a small
lepton population into the opposite hemisphere and sustaining the
circuit. The gap confined to a single (anode) hemisphere implies asymmetric hard X-ray production, possibly detectable in phase-resolved magnetar spectra.
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All authors Jens F. Mahlmann, Alexander A. Philippov, Adrien Soudais, Andrei M. Beloborodov, Lorenzo Sironi
High Energy Physics (Theory)
Bosonic String Amplitudes From Ribbon Graphs
Sam Christian, Ben Mazel, Yuchen Wang et al. (+2 more)
We develop a method for numerically computing higher genus CFT correlators and string amplitudes based on Kontsevich's ribbon graph parametrization of the
moduli space $\mathcal{M}_{g,n}$ of punctured Riemann surfaces. Using this method, we compute the compact
boson partition function up to genus 6 as well as the
moduli space integrand for bosonic string
vacuum amplitudes up to genus 3. Our results pass a number of nontrivial numerical checks. In particular, the
moduli space integrand of bosonic string amplitudes reproduce the Igusa cusp forms at genera 2 and 3.
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All authors Sam Christian, Ben Mazel, Yuchen Wang, Xi Yin, Yutai Zhang
High Energy Physics (Phenomenology)
Domain Adaptation against Background Sculpting in Anomaly Detection at the LHC
Vincent Benne, Marie Hein, Michael Krämer et al. (+3 more)
Weakly supervised anomaly detection has been shown to be an effective tool for model-agnostic searches for new physics, especially in the context of resonance searches. However, correlations between the anomaly score and the resonant mass can distort the background distribution after selecting on the anomaly score, complicating background estimation from the sidebands. To mitigate this background sculpting, we propose a domain-adaptation-based decorrelation of the anomaly score from the resonant mass. We study this approach using the LHC Olympics R&D data set and several weakly supervised anomaly detection methods. We find that domain adaptation can substantially reduce background sculpting while largely preserving the anomaly detection performance. When correlations between the input features and the resonant mass degrade the original method's performance, domain adaptation can also recover sensitivity.
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All authors Vincent Benne, Marie Hein, Michael Krämer, Humberto Reyes-Gonzalez, Philipp Soldin, Christopher Wiebusch
Instrumentation and Methods for Astrophysics
The OpenGadget3 Code for Cosmological Simulations
Klaus Dolag, Geray S. Karademir, Luca Tornatore et al. (+28 more)
We present the public release of OpenGadget3 (OG3), a substantially extended and re-organised version of the widely used Gadget-2/3 family of cosmological simulation codes. Since G2 was made publicly available, the absence of continued official development led to the creation of numerous, mutually incompatible developer versions of G3 across the community. This made it effectively impossible to track bug fixes, reproduce published results, or consistently credit the many individual contributors. OG3 addresses this by consolidating these disparate developments into a single, documented, and continuously maintained code base, released under the GNU GPLv3 through a GitLab repository (with an accompanying wiki), regularly synchronised with the active developer branch, and supported by a dedicated continuous-integration (CI) pipeline. OG3 retains the core algorithmic backbone of its predecessors, a Barnes&Hut oct-tree combined with a Particle-Mesh method for
gravity, and a choice of Smoothed Particle Hydrodynamics or Meshless-Finite-Mass solvers for gas dynamics, within a hybrid MPI/OpenMP parallelisation framework, extended with GPU offloading via OpenACC and OpenMP. The code integrates an extensive suite of sub-resolution and physical modules, including
primordial chemistry, radiative cooling,
star formation,
stellar feedback and chemical enrichment,
dust formation and
evolution, black hole growth and AGN feedback, MHD, thermal conduction, physical viscosity, SIDM, and massive
neutrinos. OG3 introduces new features improving robustness, reproducibility, and usability: a flexible mixed-precision framework spanning 16- to 128-bit representations; expert-level tagged parameters with restart-time change log; extensive consistency checks against invalid configurations; and FAIR-compliant reporting of all settings, parameters, and specific publications. (shortened and abridged)
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All authors Klaus Dolag, Geray S. Karademir, Luca Tornatore, Antonio Ragagnin, Milena Valentini, Ludwig M. Böss, Frederick Groth, Giuseppe Murante, Stefano Borgani, Volker Springel, Cenanda Arido, Javier Badía, Tiago Castro, Alice Damiano, Laura Di Federico, Moritz S. Fischer, Gian Luigi Granato, Nitya Hariharan, David Klemmer, Umberto Maio, Tirso Marin-Gilabert, Ilaria Marini, Yashraj Patil, Margarita Egelhofer, Cinthia Ragone-Figueroa, Luca Sala, Cecilia Scannapieco, Ludwig D. Schmidt, Ulrich P. Steinwandel, Giovanni Tedeschi-Prades, Marc Wiertel
High Energy Physics (Theory)
Quantum Dynamics of Probe Particles in Thermal Fields and the Emergence of Stochastic Dynamics
Bruno Scheihing-Hitschfeld
Starting from a general
Hamiltonian describing the
quantum dynamics of probe particles interacting with a set of environment degrees of freedom, we derive the
quantum master equation with which the reduced density
matrix of a probe particle evolves, the general equilibration condition that they satisfy when the environment is prepared in a thermal state – encoded in a KMS property for line operators extended in real time – and the Langevin description that emerges. The novelty of our results resides in their generality: We do not assume a specific form of the environment self-coupling, of the environment operator that couples the particle to it, of the statistics of its correlation functions, whether the statistics of the momentum transfer is Gaussian or not, or whether the probe particles move relativistically. Our results only require that spacetime translations, parity and time reversal be
symmetries of the
Hamiltonian, and that there exists a separation of scales between those characterizing the dispersion relation of the probe particle and those of the environment. We also discuss the limiting case in which Gaussian Brownian motion emerges. Overall, our results constitute a first-principles derivation of what properties of the underlying
quantum field theory govern the energy loss and momentum fluctuations of probe particles.
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High Energy Physics (Theory)
The Kerr/CFT energy gap
Robert Penna
Noether charges in
gravity are always defined with respect to a reference metric, but the near-horizon extremal Kerr (NHEK) solution does not come with an obvious choice of reference metric (it is not asymptotically flat, for example). We discuss a one parameter generalization of the NHEK solution due to Kinnersley and Kelley which interpolates between NHEK and an analytically continued version of Minkowski spacetime. We use this interpolating family of solutions to compute the conformal energy of NHEK above the Minkowski reference metric. We find an interesting order of limits issue when computing the conformal energy of the Minkowski
vacuum and we discuss a few natural prescriptions for fixing it, including one motivated by the Kerr/CFT correspondence.
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Data Structures and Algorithms
Efficient Robust Learning at the Information-Theoretic Limit
Adam R. Klivans, Konstantinos Stavropoulos, Sergei Tikhonov et al. (+1 more)
In an important recent work, Blanc (2026) gave an
algorithm for robustly learning Boolean concept classes with respect to a fixed distribution that outputs a (randomized) classifier achieving the optimal error of $\eta + \varepsilon$ where $\eta$ is the noise rate. In contrast, it is well known that deterministic hypotheses cannot achieve error less than $2\eta + \varepsilon$. Blanc's
algorithm is computationally inefficient, and the main problem left open in his work is to find a
polynomial-time
algorithm given access to an oracle for empirical risk minimization (ERM). Here we resolve this problem and give such an
algorithm. Additionally, we give an efficient
algorithm (no ERM oracle required) for robustly learning any function class that admits low-degree
polynomial approximators with respect to hypercontractive distributions. This captures basic settings including halfspaces with respect to Gaussian marginals. Our techniques make new connections to various types of online convex optimization
algorithms. As a surprising consequence, we show that efficient SQ learnability in the agnostic setting implies efficient learning with contamination (with respect to Gaussians or uniform over the hypercube).
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All authors Adam R. Klivans, Konstantinos Stavropoulos, Sergei Tikhonov, Arsen Vasilyan
Machine Learning
Regularized Least Squares Training of Quadratic Neural Networks with Applications to System Identification
Luis Rodrigues, Zachary Yetman Van Egmond and Mohammad R. Amiri Fard
This paper proposes a least squares approach for the training of quadratic neural networks with regularization. The proposed methodology yields a lower bound on the solution of the training optimization problem for the case where the regularization coefficient is positive. Moreover, it yields closed-form expressions for the approximate solution and its sensitivity The lower bound is tight and the approximate solution is the optimal solution when the regularization coefficient is zero. Having a closed-form expression for the weights reduces considerably the computational time when compared with iterative numerical methods such as backpropagation that can get stuck in local minima. The proposed approach has three main contributions, namely, (i) it yields an analytical expression for the weights, (ii) an analytical expression for the sensitivity of the weights to errors in the data is also provided, (iii) it establishes a connection between the optimization to compute a lower bound and
nuclear norm minimization. The proposed least squares training is successfully applied to a nonlinear system identification example where the proposed lower bound is compared with the optimal value.
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