High Energy Physics (Theory)
On the Universality of Probe Complexity in $\mathcal{N}=4$ SYM
Eric L. Graef, Jeff Murugan, Horatiu Nastase et al. (+1 more)
We investigate Krylov complexity for single-trace operators dual to open strings attached to
giant gravitons in planar $\mathcal{N}=4$ super Yang-Mills theory. We show that in protected and few-body sectors, Krylov dynamics is governed by orthogonal
polynomial theory associated to the seed spectral measure, leading to bounded Lanczos coefficients determined solely by spectral support. In particular, for fixed
magnon number $M$ and open-string length $L\rightarrow\infty$, we derive $a_n=2Mg$ and $b_n\rightarrow Mg$, demonstrating integrable, band-limited dynamics. This establishes that such sectors are insufficient to test recently proposed
gravity-side universality of operator complexity growth. We therefore formulate a finite-density program in which
magnons scale with system size, and propose a concrete universality test: whether the leading Krylov growth depends only on coarse thermodynamic data $(\rho,\varepsilon)$ and not on microscopic probe structure. This provides a precise boundary-field-theory framework for testing gravitational universality
conjectures.
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All authors Eric L. Graef, Jeff Murugan, Horatiu Nastase, Hendrik J.R. Van Zyl
High Energy Astrophysical Phenomena
Subgrid Modelling for Relativistic Magnetohydrodynamics with Machine Learning
William Cook and Sebastiano Bernuzzi
Resolving the impact of
magnetic field instabilities in triggering small scale turbulent flow and the associated rearrangement of the field is of critical importance in understanding multimessenger observables in binary
neutron star mergers, and angular momentum transport in
neutron stars and
accretion disks. Direct simulation of these instabilities are unfeasible, however large-eddy simulations can incorporate the impact of this
turbulence with a subgrid model. We present the first machine-learning-based subgrid model for special relativistic magnetohydrodynamics, trained using a neural network. We demonstrate its performance in online simulations of the 3D Kelvin-Helmholtz instability through both a priori and a posteriori tests. Evaluated in a low resolution simulation, our model captures
magnetic field amplification of a simulation at 4 times the resolution with a speed-up of a factor 44. This demonstrates the applicability of such methods in general relativistic simulations of
neutron star mergers and other scenarios.
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High Energy Physics (Experiment)
Towards LLM-Powered Automation of a Dark Matter Constraint Repository
Lanqing Yuan and Karthik Ramanathan
Dark matter constraint repositories are critical community infrastructure, yet the most widely-used are volunteer-maintained, a sustainability risk as results accelerate. Limits are typically published as figures rather than machine-readable records, compounding the burden. We present a large
language model (LLM) system that monitors arXiv, extracts limit curves, integrates them as code, and opens pull requests for human review. Extraction uses a tool-using
agent that interprets physical conventions and checks its results, with a fixed multi-channel pipeline evaluated as an alternative. We evaluate both approaches on a 329-paper
benchmark of measured limits graded against the upstream-curated repository. An extraction is considered successful when the extracted and reference mass ranges overlap by more than 90%, with at least 90% of compared values agreeing within a factor of two. For Fable 5, 52.6% of eligible curve comparisons meet this criterion with the
agent, compared with 20.9% with the pipeline. Deployed, the pipeline has generated limit proposals, but none have merged: governance of AI-generated scientific data is itself unsolved.
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Astrophysics of Galaxies
The $M$-$\sigma$ Relation Has to Break
Omri Nitzan and Re'em Sari
We revisit the growth of central black holes via
tidal disruption events (TDEs) and plunges of
stellar-mass black holes (sBHs). Our model incorporates the current understanding of mass segregation, where sBHs sink to the center, enhancing the rates of both TDEs and plunges. We demonstrate that in dense cluster cores, with densities exceeding $10^6\,\mathrm{M_\odot\,{pc}^{-3}}$, seeds of initial mass $M_0\gtrsim100\,M_\odot$ undergo runaway growth. This runaway terminates once the black hole radius of influence surpasses the core radius, or equivalently, most of the core mass has been consumed. This typically results in an intermediate-mass black hole (IMBH), within a few $\mathrm{Gyr}$. Subsequent growth proceeds as a power law. In contrast to observed supermassive black holes (SMBHs), which tightly follow the famous $M \propto \sigma^\beta$ with $\beta \cong5$, our derived sBH
accretion rates, integrated over a
galactic lifetime, predict final masses of $M\approx10^5\,M_\odot \times(\sigma/50\mathrm{km\;s^{-1}})^{2.5}$. While our prediction for the contribution of plunges to the growth of the IMBH is robust, the TDE contribution can be negligible if only a small fraction of their mass is actually accreted or up to 3 times higher than the plunges contribution if half a
stellar mass gets accreted in each event. Below $M\sim10^5\,M_{\odot}$ this accreted
star and sBH mass exceeds the extrapolation of the observed $M$-$\sigma$ relation. This predicts that the $M$-$\sigma$ scaling must flatten below $M \sim 10^5\,M_{\odot}$ to a shallower, $2.26<\beta<2.5$ profile. If confirmed by observations, this would indicate capture-driven growth.
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High Energy Physics (Phenomenology)
Globally Charged Vacuum Decay
Giulio Barni and Jose R. Espinosa
Vacuum decay at zero temperature is generically described by a real $O(4)$-symmetric Coleman bounce. When the scalar field driving the decay carries a conserved global charge, this picture changes qualitatively: the path integral must be projected onto a definite charge sector, the Euclidean field obeys twisted boundary conditions, and the saddle is complex. For the simplest case of a $U(1)$ global
symmetry, we first reformulate this problem in a two-field real Euclidean description with a real saddle. We then solve the resulting two-dimensional partial differential equation problem describing the decay of a homogeneous charged medium to a deeper
vacuum via bubble nucleation. At finite charge the bounce departs from $O(4)$
symmetry, the barrier between
vacua is lowered, and the decay rate increases. Continuing the solution to real time, we find that charge rearrangement around the expanding wall costs phase-gradient energy and drives the bubble to a subluminal terminal velocity even in
vacuum. We also clarify how the fixed-charge construction interfaces with finite-temperature and finite-chemical-potential descriptions.
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Strongly Correlated Electrons
Omri Lesser and Chao-Ming Jian
Fermions with opposite
spins occupying half-filled conjugate Chern bands exhibit interaction physics distinct from their multi-component Landau-level counterparts with the same chirality. This is largely due to unavoidable inter-species collisions that preclude the Halperin-type wavefunctions available in multi-component Landau levels. In this work, we propose and evaluate a variational wavefunction for a fractional
quantum spin Hall state with Z_4 topological order in a pair of conjugate Landau levels. This Z_4 topological order has previously been shown to be the minimal topological order compatible with charge conservation, $S_z$ conservation, time-reversal
symmetry, and the fractional
spin Hall conductance 1/2 suggested by previous twisted MoTe$_2$ experiments. Our construction is based on the condensation of an anyonic
exciton formed by the neutral fermionic excitations in a decoupled pair of Moore-Read Pfaffian state and its conjugate. By coupling the
chiral and anti-
chiral Ising conformal field theories associated with the two
spin species, we introduce a variational mass parameter in the Z_4 trial wavefunction that captures the inter-
spin-species s-wave pairing of composite
fermions alongside the intra-
spin-species p-wave pairing. We assess the energetics of this trial state using Monte Carlo sampling on a spherical geometry. Because the coupled state intrinsically involves Landau-level mixing, we explicitly evaluate the resulting kinetic energy penalty. Our phase diagram reveals that the proposed Z_4 state becomes energetically favorable in a sizable region of parameter space, over both the decoupled pair of conjugate Pfaffian states and an alternative
exciton condensate state. These results provide a concrete microscopic wavefunction realization of this Z_4 fractional
quantum spin Hall phase, and propose a route to constructing additional families of such states.
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Astrophysics of Galaxies
Resolved Ages and Stellar Metallicities in Progenitors of Milky Way Analogs: A Closer Look at their Star Formation Histories since $z=5$
Vivian Yun Yan Tan, Adam Muzzin, Naadiyah Jagga et al. (+12 more)
We present the
evolution of the resolved mass-weighted age,
stellar metallicity, and sSFR of 872 Milky Way Analog (MWA) progenitors up to
redshift $z=5$ from the Canadian Unbiased Cluster Survey (CANUCS). The
metallicity and mass-weighted ages were obtained via spatially resolved SED-fitting with the non-parametric code Dense Basis. We split the sample into mergers versus non-mergers using the merger parameter from the Gini-$M_{20}$ plane obtained through Gini-$M_{20}$ analysis of the morphology of the
stellar mass maps with Statmorph. Across our
redshift range, non-mergers have negative or flat average age gradients from $-0.022$ to 0.005 dex/kpc, and positive or flat sSFR gradients from $-0.089$ to 0.092 dex/kpc, consistent with inside-out assembly. The average $\log(Z/\Zsun)$ gradients for non-mergers range from $-0.029$ to 0.044 dex/kpc, however, positive gradients only appear between $2 < z < 3$. At every
redshift epoch, mergers typically have flatter age gradients, more negative sSFR gradients, and similar
metallicity gradients compared to non-mergers. We divide the property maps of ongoing mergers into separate regions based on their component
galaxies, and find little to no difference between the components' average ages or
metallicities, but the less massive of the merging system is on average $0.1-0.4$ dex higher in sSFR. Our results point to major mergers contributing some momentary disruption to the general trend of inside-out mass assembly, but does not upend the overall picture of MWA disks growing inside-out over
cosmic time.
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All authors Vivian Yun Yan Tan, Adam Muzzin, Naadiyah Jagga, Visal Sok, Ghassan T. E. Sarrouh, Gregor Rihtaršič, Roberto Abraham, Yoshihisa Asada, Maruša Bradač, Kartheik Iyer, Nicholas S. Martis, Gaël Noirot, Marcin Sawicki, Chris J. Willott, Sunna Withers
High Energy Physics (Theory)
Quantum Gravity Cutoff from Axions: A Type IIB Landscape Study
Matthew Reece, Tom Rudelius and Christopher Tudball
Extra-dimensional
axions have coupling strength related to fundamental, ultraviolet physics. It has been proposed that the properties of such
axions imply a bound on the
quantum gravity cutoff: $\Lambda_\mathrm{QG} \lesssim 2\pi \sqrt{S} f$, where $f$ is the
axion decay constant and $S$ is the instanton action. In the context of weakly-coupled string theory, we identify $\Lambda_\mathrm{QG}$ with the string scale $M_s$. In this paper, we carry out a quantitative study of this bound on the string scale in the context of Calabi-Yau compactifications of Type IIB string theory, considering both $C_2$ and $C_4$
axions. We show, both analytically and numerically, that the bound holds even near boundaries of the Kähler
moduli space, including those where the co-scaling relationship for
axion strings fails. This evidence bolsters previous arguments, based on naturalness and on unitarity, that the bound is a general feature of extra-dimensional
axions in
quantum gravity.
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Strongly Correlated Electrons
Jason Y. Yan, Xiaoyu Guo, R. Bhandia et al. (+3 more)
Quantum geometry has emerged as a unifying concept across condensed matter physics, underlying phenomena from nonlinear topological response to flat-band superconductivity. While usually formulated within band theory,
quantum geometry remains meaningful in disordered interacting systems~\cite{resta1999electron}. Here we show that the first negative moment of the optical conductivity – proportional to the zero temperature
quantum Fisher information as a bound on the multipartite
entanglement – provides an experimental probe of
quantum geometry across the three-dimensional metal-
insulator quantum phase transition in phosphorus-doped silicon. We extract a
quantum geometric length $\ell$ that characterizes the local wavefunctions. Far from the transition, this length is almost coincident with the Bohr radius of the hydrogenic phosphorus donors, reflecting their atomic-scale
quantum geometry. Approaching the transition, $\ell$ is enhanced, but does not diverge continuously like a correlation length; it jumps discontinuously to infinity at the critical point. This reflects the UV domination of the sum rule in three dimensions that renders it insensitive to the critical fluctuations driving the diverging dielectric constant and correlation length. Its enhancement demonstrates a “puffing" of the donor polarizability volume of
quantum geometric origin, which yields a
quantum geometric corrected Clausius-Mossotti description in closer agreement with the diverging dielectric response and provides a
quantum mechanical foundation for the century-old Herzfeld metallization criterion.
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All authors Jason Y. Yan, Xiaoyu Guo, R. Bhandia, T.F. Rosenbaum, Natalia Drichko, N. P. Armitage
Mathematical Physics
Integrating Polchinski's equation by convergent binary tree expansions
Paul Obernolte and Manfred Salmhofer
We give a solution to Polchinski's equation for the Wilsonian effective action in terms of an expansion in binary trees, and prove that this expansion converges in fermionic field theories, provided the fermionic covariance has finite determinant and decay constants. A novel element of the proof are detailed combinatorial estimates for the number of leaf trees associated to binary trees. The method can be used on standard models of fermionic
quantum field theory and
quantum statistical mechanics.
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High Energy Physics (Phenomenology)
Probing Light Dark Fermions in $B \to D^{(*)}\ell X_{\rm inv}$ via Rate Distributions
Lipika Kolay, Soumitra Nandi, Shantanu Sahoo et al. (+1 more)
Experimental analyses of the semileptonic decays $ B \to D^{(*)} \ell \bar{\nu}$ typically rely on the assumption that the missing energy originates from a massless
neutrino, as predicted by the Standard Model. However, this assumption may not hold in scenarios where the invisible final-state particle is instead massive, such as a sterile
neutrino or a dark-sector
fermion. In this work, we explore how the presence of a massive dark sector
fermion modifies the kinematic and angular distributions of these decays. Our analysis is carried out within the framework of a general weak effective theory, and we also discuss effective and simplified models in which these interactions may arise. In addition, we study the implications of these effects for the extraction of the CKM
matrix element $ |V_{cb}|$. Overall, our results show that relaxing the standard assumption of a massless
neutrino can lead to observable effects and provide a framework for systematically investigating their impact on semileptonic $B$- decay distributions.
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All authors Lipika Kolay, Soumitra Nandi, Shantanu Sahoo, Ria Sain
Fluid Dynamics
Receptivity of the flow on the stagnation streamline of a blunt body in supersonic flow
Iliya Milman and Michael Karp
The receptivity of the inviscid flow on the stagnation streamline of a blunt body in supersonic flow is investigated theoretically for incoming freestream disturbances. The wave transmission and coupling are quantified by solving the linearized shock-fitting problem with a spectral method, whereas the steady base flow is obtained using a nonlinear shock-fitting spectral solver. Revisiting previous theoretical work, we identify and correct an error in a key coefficient in the analysis by Morkovin (J. Appl. Mech., 27, 1960), overturning the prior conclusion of body-induced damping and revealing amplification instead. The post-shock
entropy disturbances display singular behavior near the stagnation point, which is treated analytically. Acoustic disturbances dominate pressure and velocity responses, while density is affected by both acoustic and
entropy modes. The base flow pressure gradient introduces weak coupling between the acoustic and entropic components of the response. The actual stagnation-line base flow amplifies all disturbances more than the simplified model of uniform post-shock flow; as well as a shock without a body, and the differences are quantified for a range of Mach numbers. The responses to
entropy, fast acoustic, and slow acoustic waves are compared as functions of the freestream Mach number.
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Materials Science
Fine-Tuning a Universal Machine-Learned Interatomic Potential for Oxygen Plasma Interactions with WS$_2$
Jaehong Kwon, Andrew S. Rosen and David B. Graves
Molecular dynamics simulation of
plasma-surface interactions requires an interatomic potential that is simultaneously accurate, computationally efficient, and able to describe many elements and bonding types in reactive systems. In principle, a foundation model for machine-learned interatomic potential (MLIP) can meet these demands. We explore the use of the Universal Models for Atoms (UMA) model, developed by Meta FAIR, for the interactions of oxygen
plasma species on a multilayer of WS$_2$, a promising 2D material. Starting from the pretrained uma-s-1p1 model under the Open Catalyst 2020 (OC20) task, we apply an iterative fine-tuning loop. Even in the absence of fine-tuning, the pretrained model reproduces the production-scale observables of interest, namely, chemisorbed S and O coverage under 15 eV O$^+$ and O$_2^+$ bombardment. These results were obtained without
spin polarization and Hubbard $U$ correction. Nonetheless, fine-tuning with
spin polarization and a Hubbard $U$ correction reduces the energy and force mean absolute error (MAE) to $4.5\times10^{-3}$ eV/atom and $0.076$ eV/angstrom, respectively.
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Optics
Coherent Control of a Polariton Continuous Time Crystal
I. Carraro-Haddad, G. Usaj, A. Fainstein et al. (+3 more)
Spontaneous breaking of time-translation
symmetry and the emergence of self-sustained oscillations in
quantum driven-dissipative systems is the hallmark of continuous time
crystals (CTCs). An outstanding challenge is to achieve precise, coherent control of such dynamical phases, whose complex nonlinear dynamics makes them inherently difficult to manipulate. Here, we experimentally demonstrate coherent control of a solid-state CTC realized in a non-resonantly excited
spin-polarized
exciton-polariton condensate in a Ga(Al)As microcavity. We exploit two complementary control channels: an additional weak control
laser and the optomechanical interaction with confined GHz
phonons. By tuning the control
laser energy and power, we stabilize distinct dynamical regimes, including frequency pushing, injection locking with continuous tuning of the limit-cycle frequency, and full suppression of the autonomous dynamics via phase locking. Under appropriate detuning conditions, the control excitation generates coherent mechanical self-oscillation through the polariton–
phonon deformation-potential interaction, evidenced by spectral sidebands. The resulting dynamical back-action provides a
phonon-mediated locking channel that fixes the frequency of the CTC. Together, the two channels dramatically enhance the temporal coherence of the GHz limit-cycle dynamics, as established through linewidth narrowing and time-resolved first-order correlation measurements $\gone(\tau)$. Our work establishes a way to harness the unique aspects of CTCs for practical applications in the GHz-range.
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All authors I. Carraro-Haddad, G. Usaj, A. Fainstein, K. Biermann, P. V. Santos, A. S. Kuznetsov
Quantum Physics
Systematic derivation of Tsirelson bounds in arbitrary dimensions
Lorenzo Coccia, Matteo Padovan and Giuseppe Vallone
The study of Bell nonlocality and the bounds of
quantum correlations, the so-called Tsirelson bounds, is fundamental to
quantum information science and the exploration of the limits of
quantum theory. While
quantum bounds for
qubit systems have been extensively characterized, determining tight
quantum bounds for correlations attainable with high-dimensional
quantum states and measurements remains a significant challenge. In this work, we propose a systematic derivation of bipartite Tsirelson and local bounds written in terms of sum-of-squares decompositions. Using this method, we discover novel bounds and recover established results for maximally entangled states of
qubits and qu$d$its.
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Earth and Planetary Astrophysics
The GAPS Programme at TNG LXXIV. A reanalysis of the planetary systems TOI-1272 and TOI-1694 with HARPS-N and retraction of the planetary interpretation of TOI-1272 c
L. Mancini, L. Naponiello, M. Damasso et al. (+14 more)
Hot Neptunes are close-in
exoplanets that occupy a sparsely populated region of parameter space known as the "hot-Neptune desert". Their presence in this extreme environment is puzzling as it implies a complex history involving intense
stellar radiation, atmospheric loss, and unique migration patterns, different from Neptunes at larger orbital periods. We are running an observational programme conceived to enlarge the number of close-in Neptune-sized
planets, with well-measured physical and orbital parameters, with the aim of contributing to obtaining a statistically significant sample needed to clarify what the formation and migration pathways of this class of
exoplanets are. We used currently available TESS photometry, along with new (HARPS-N) and archival (HIRES) high-precision radial-velocity measurements, to review the main properties of the planetary systems TOI-1272 and TOI-1694 by means of joint-fit analyses that, in the case of TOI-1272, included Gaussian-process regressions for carefully modelling
stellar activity. Our final estimates of the parameters of the two systems are consistent with previous measurements but have smaller uncertainties. We identified the radial-velocity variation of TOI-1272 found in the HIRES data as
stellar activity rather than planetary in nature and, therefore, rejected the non-transiting
planet TOI-1272c. This opens up the possibility that TOI-1272b's eccentricity is the result of high-eccentricity migration. The larger number of data at our disposal also allowed us to point out that both TOI-1694b and TOI-1694c move on slightly eccentric orbits. The current orbital architecture of TOI-1694 suggests a history of migration driven by both disc and dynamical interactions.
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All authors L. Mancini, L. Naponiello, M. Damasso, K. Biazzo, A. S. Bonomo, A. F. Lanza, J. Lillo-Box, M. Pinamonti, R. Cosentino, A. Bignamini, W. Boschin, A. Fiorenzano, P. Giacobbe, F. Manni, M. Rainer, G. Scandariato, A. Sozzetti
Solar and Stellar Astrophysics
Transonic Solutions for Recombination-Driven Stellar Winds
Ilan Strusberg, Re'em Sari and Jim Fuller
We present an analytical stationary isentropic solution of the spherically symmetric Euler equations in the gravitational field of a
star using an equation of state of ionizable monatomic gas. The solution consists of a fully ionized hydrostatic inner region, followed by a thick hydrostatic recombination region where the density decreases by orders of magnitude, the radius increases by about an order of magnitude and the temperature decreases by a factor of two. Within this recombination region, a large portion of the recombination energy is used for lifting the gas subsonically. This region ends at a critical point, located roughly at $10-100~\rm{AU}$, where the gas is mostly recombined, beyond which it flows supersonically as a wind. We find the position and the quantities of the gas at the critical point and derive the mass-loss rate of the solution. We apply our solution to evolved
stars, with a compact core surrounded by a high
entropy envelope. We derive the mass-loss rate as a function of time. As the
star is losing mass, it goes through a sequence of our solutions, in a runaway manner which ends once most of the high
entropy envelope is lost. The recombination-driven winds are initiated once the
stars expands to a radius of about $1~\rm{AU}~M/M_\odot$ and are terminated on a timescale of $10^1-10^4~\rm{years}$. We discuss the implications for common envelope
evolution.
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Nuclear Theory
Hyperonic equation of state for neutron stars: A systematic Bayesian comparison of density-dependent and non-linear relativistic mean-field models
Pedro Sanson, Tuhin Malik and Constança Providência
A systematic
Bayesian inference study of the equation of state (EOS) of dense matter with strangeness is presented, extending five relativistic mean-field (RMF) models with both constant and density-dependent couplings to include the full
baryon octet. The hyperon-nucleon couplings in the scalar channel are varied within ranges informed by hypernuclear data, while vector isoscalar couplings are fixed by the SU(6)
symmetry quark model. Observational constraints from NICER (PSR J0030, J0437, J0740) and GW170817, theoretical constraints from
chiral effective field theory ($\chi$EFT) and perturbative QCD (pQCD), and experimental constraints from
nuclear saturation properties are imposed simultaneously. We find that the inclusion of hyperons systematically reduces the maximum
neutron star mass by $0.05$-$0.10,M_\odot$ across all models while increasing the radius at $1.4,M_\odot$ by $0.5$-$0.8$ km. The speed of sound exhibits a characteristic softening at densities $2$-$3,\rho_{\rm sat}$ coinciding with hyperon onset. All hyperonic models remain consistent with the $2,M_\odot$ constraint. Models with a more flexible isovector channel span a larger
proton fraction when only nucleons are included. However, the extra flexibility is visibly suppressed by hyperons, meaning that the average
proton distribution is independent of model flexibility when hyperons are included. Less flexible models show comparable or slightly increased
proton fractions due to EOS stiffening when hyperons are included. Only a residual number of hyperonic equations of state give rise to a mass-radius curve with a negative slope at low masses. A $1.8,M_\odot$
neutron star with a radius larger than or similar to the radius of a $1.2,M_\odot$
star would provide strong evidence that the
star contains baryonic degrees of freedom beyond nucleons.
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Astrophysics of Galaxies
Little Red and Blue Dots: AGN-excited narrow lines, Lyman-$\alpha$ emission, and resemblance to standard quasars
Sophia Geris, Roberto Maiolino, Xihan Ji et al. (+35 more)
We present an analysis of a sample of 36 Little Red and Blue Dots (LRDs and LBDs) at $2.26<z<7.89$, identified by JWST in the GOODS fields. While both categories are selected to have broad Balmer lines, both of them are extremely X-ray weak. Both classes share the same location on various diagnostic diagrams, consistent with AGN excitation (with some deviations which can be ascribed to low
metallicity), although their weak HeII emission suggests a generally softer ionizing spectrum than ordinary AGN. LRDs display Ly$\alpha$ emission stronger than normal
star-forming
galaxies, and with a broad component consistent with the broad component of H$\alpha$. Overall, these findings indicate that LRDs and LBDs are both powered by growing black holes and their ionizing radiation escapes to ionize the surrounding interstellar medium (ISM). The broad Balmer lines ($H\alpha_b$ and $H\beta_b$) have different apparent properties: LBDs have EW(H$\alpha _b$) and $H\alpha_b/H\beta_b$ broadly consistent with normal AGN, while LRDs have higher values of both quantities, although still in the tail of the
quasars distribution. LRD models in which a gas envelope completely encases the black hole, are inconsistent with these results – these scenarios need modification to include clumpiness, or a (classical) equatorial geometry, letting ionizing
photons reach the ISM. The different broad Balmer properties imply that LBDs cannot simply be LRDs with more
galaxy contribution. Scenarios in which LRDs are simply
dust-obscured LBDs seem broadly consistent with the observations. Finally, these results indicate that LRDs' bolometric luminosities estimated assuming isotropic emission and complete covering by the absorber are inadequate. The few X-ray-detected LRDs suggest no deviation from the standard AGN bolometric corrections, once absorption is accounted for.
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All authors Sophia Geris, Roberto Maiolino, Xihan Ji, Guido Risaliti, Giorgio Lanzuisi, Francesco D'Eugenio, Yuki Isobe, Gareth Jones, Anishya Harshan, Matilde Brazzini, Ignas Juodžbalis, Jan Scholtz, Pierluigi Rinaldi, Hannah Übler, William Baker, Andrew J. Bunker, Marcella Brusa, Stefano Carniani, Stephane Charlot, Mirko Curti, Andrea Comastri, Emma Curtis Lake, Roberto Gilli, Kevin Hainline, Piero Madau, Stefano Marchesi, Giovanni Mazzolari, Lorenzo Napolitano, Eleonora Parlanti, Laura Pentericci, Cristina Ramos Almeida, Brant Robertson, Maddie S. Silcock, Roberta Tripodi, Giacomo Venturi, Cristian Vignali, Fabio Vito, Yongda Zhu
Mathematical Physics · Cross-listed from math.AP
On the traces of the L_2-solution of a general linear differential equation in the domain
Burskii V.P
This paper pertains to the general theory of boundary value problems for general linear differential equations with smooth coefficients in a bounded domain with a smooth boundary and contains new advances in the general theory related to the boundary properties of solutions. Specifically, conditions on the traces of a solution to a general differential equation on the boundary of the domain are found and studied, allowing the solution to be reconstructed from its traces and the right-hand side of the equation. For the case of a general equation with constant coefficients, the resulting conditions on the traces of the solution take the form of a generalized moment problem.
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Earth and Planetary Astrophysics
Investigation of Split Comet 240P/NEAT
David Jewitt, Jane Luu and Yoonyoung Kim
We present time-series observations of the split comet 240P/NEAT near perihelion, obtained using the Nordic Optical
Telescope. The brighter component, 240P-A, has an estimated radius in the range 400 m to 600 m, and loses
dust at the peak rate 130 kg/s. The ejected
dust has characteristic size 50 micron, is expelled sunward at 25 m/s, with a total ejected mass in the period of observation 1.5x10^9 kg. Mass loss from the fainter component, 240P-B, peaks at 35 kg/s and the total ejected mass was 2.3x10^8 kg. The radius of 240P-B is uncertain, with a best estimate about 300 m and an absolute lower limit 50 m. 240P-A and 240P-B are currently separating at about 1 m/s, a speed that is likely accelerating as a result of differential outgassing forces, and have a separation age over 3 years. The splitting of 240P is incompatible with the action of tides, impact, and internal pressure build up. 240P fits a developing picture, in which small comets are destroyed by rotational instabilities triggered by outgassing torques, an explanation that can be tested in 240P by future observations.
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Instrumentation and Methods for Astrophysics
Carruthers Data Processing Pipeline: Instrument Effect Correction
Alex Zhang, Heather Filippini, Lara Waldrop et al. (+1 more)
The Carruthers Geocorona Observatory – launched in September 2025 – is NASA's first mission devoted to investigating the fundamental nature of Earth's exosphere from its distant vantage in
halo orbit around the Earth-Sun L1 Lagrange point. Its primary payload, the GeoCoronal Imager, consists of two coaligned photometric imagers that measure ultraviolet Lyman-alpha emission radiance from exospheric hydrogen simultaneously at wide- and narrow- fields of view. The imagers use MicroChannel Plate intensified Complementary Metal
Oxide Semiconductor detectors, which are known to add various artifacts to the final image telemetered from the spacecraft, hereby known as instrument effects. This paper details the
algorithms used to retrieve and remove instrument effects from raw telemetry on-orbit, including detector voltage bias, thermal dark current, particle radiation, flat-field, and distortion. Finally, the science data processing pipeline from raw telemetry to instrument-effect corrected images is detailed.
Algorithm performance is measured via a synthetic numerical image generator or validated on pre-launch experiments.
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All authors Alex Zhang, Heather Filippini, Lara Waldrop, Jason McPhate
General Relativity and Quantum Cosmology
Consistency Conditions and the Derivation of Harmonic Structure in Einstein-Maxwell-dilaton Theory
Bardia H. Fahim and Joshua G. Fenwick
Many exact solutions of Einstein-Maxwell and Einstein-Maxwell-dilaton theory share a common structural pattern in which the metric functions are built from harmonic functions on a specified spatial base, often taken to be flat. We investigate this pattern by considering the Einstein-Maxwell-dilaton theory in arbitrary dimensions, where the dilaton field is non-trivially coupled to the Maxwell field and to a Liouville-type potential proportional to the cosmological parameter. Without imposing either the base geometry or the harmonic form of the metric function in advance, we show that for the generic branch, the field equations force the dilaton couplings to be equal, restrict the spatial base geometry to be
Ricci flat, and make the metric function harmonic on this base. The resulting spacetime can then be written in terms of a conformal potential. We also consider a purely spatial branch, which instead leads to a distinct constraint on the coupling constants. These results provide a unified field-equation derivation of the harmonic behavior and conformal structure that appear in several classes of solutions, including multi-center geometries, cosmological solutions, and dynamical black holes.
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Medical Physics · Cross-listed from eess.IV
Deep Unrolled Networks in Representation Space Applied to MRI Reconstruction
Efe Il{\i}cak, Baris Imre, Chloé Najac et al. (+4 more)
Deep unrolled networks (DUNs) integrate physical forward models with learned regularization in cascaded network architectures, achieving exceptional performance in inverse problems while maintaining interpretability. While most DUNs operate in the object domain (e.g., image space), recent variants explored representation spaces for improved information flow. However, these methods rely on heuristic methods for data consistency (DC), sacrificing fidelity with measurements. In this work, we introduce DUNE (Deep Unrolled Networks in rEpresentation space), a framework that maintains exact adherence to physical measurements while operating in learned representation spaces. By deriving the DC gradient via the chain rule and implementing it through the Vector-Jacobian Product (VJP), we enable exact backpropagation of measurement residuals into the representation space. This formulation supports diverse architectural backbones, including pre-trained encoders to guide the iterative process. We assess DUNE against state-of-the-art baselines on accelerated MRI reconstruction tasks, demonstrating that exact VJP-based gradients yield superior reconstruction quality and structural fidelity across both single-channel portable low-field and multi-channel clinical high-field MRI acquisitions. The code will be available upon publication at https://github.com/EfeIlicak/DUNE.
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All authors Efe Il{\i}cak, Baris Imre, Chloé Najac, Ruben van den Broek, Beatrice Lena, Andrew Webb, Marius Staring
Mesoscale and Nanoscale Physics
Subgap Linear Thermoelectricity in Superconducting Quantum Hall Systems
Leonardo Pierattelli, Fabio Taddei, Alessandro Romito et al. (+1 more)
We show that an integer
quantum Hall setup proximized by
superconductors can exhibit subgap thermoelectric effects in the linear-response regime when triplet superconducting correlations are present. We devise a minimal setup that enables a nonzero Seebeck effect mediated by Andreev processes and predict that the corresponding Seebeck coefficient can reach values on the order of $k_B/e$ in the middle of the
quantum Hall plateau. We analytically show that both triplet correlations and
spin polarization are essential for the emergence of the thermoelectric effect, which arises despite the linear band dispersion of the edge states. We characterize the dependence of the thermoelectric response on the
Hamiltonian parameters and the system's temperature regime.
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All authors Leonardo Pierattelli, Fabio Taddei, Alessandro Romito, Alessandro Braggio
Nuclear Theory
One-Body and Two-Body Density Matrix Elements in a Symplectic Many-Body Basis
Jakub Herko and Mark A. Caprio
The
symplectic no-core configuration interaction (SpNCCI) framework is an ab initio many-body method for
nuclear structure which makes use of the approximate
symplectic symmetry of
nuclei by appropriate choice of many-body basis states. In this paper we derive recurrence relations allowing for calculation of one-body and two-body density
matrix elements between the SpNCCI basis states. Availability of these
matrix elements allows for integration of the SpNCCI framework with other modern many-body methods and for calculation of
matrix elements of any one-body or two-body operator.
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Mathematical Physics · Cross-listed from math.SP
Ambarzumian-type theorems for Hermitian matrices with applications
Matthias Hofmann and Joachim Kerner
A foundational result in inverse spectral theory due to Ambarzumian (1929) states that the Neumann
Laplacian on an interval is not isospectral to the Neumann
Laplacian with an additional non-zero potential. In this note, our aim is to investigate Ambarzumian-type
theorems for certain classes of Hermitian
matrices, including well-known
matrices such as the discrete
Laplacian on finite graphs. In addition, using different methods, we establish an Ambarzumian-type
theorem for
matrices with vanishing diagonal, in particular, the adjacency
matrix on finite graphs. In this way, we generalize existing results on Ambarzumian-type
theorems to general finite discrete graphs.
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History and Philosophy of Physics
Cosmology as Representation: Informational Invariance and the Limits of Scientific Realism
Stefano Profumo
Modern cosmology is often taken to provide an increasingly accurate description of the universe's underlying ontology through progressively refined mathematical models. I challenge this interpretation by arguing that the empirical success of cosmology underdetermines not only ontology but also the mathematical and conceptual frameworks used to represent observational data. I propose instead that the objective content of cosmology is best identified with cross-representational informational invariants-features of observational structure that persist across empirically adequate descriptions. These invariants can be characterized in information-theoretic terms, including correlation structure, statistical distinguishability, and limits on accessible information, and formalized using tools such as the Fisher-Rao metric on model space. On this view, cosmological models are best understood as efficient encodings of observational structure rather than uniquely privileged descriptions of fundamental reality. Scientific progress, accordingly, consists not in convergence toward a fixed ontology, but in the progressive refinement of the informational structure accessible to observation.
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Statistical Mechanics
Nonreciprocal Disorder Prevents Zero-Temperature Freezing in a Ferromagnet
Noah Grodzinski, Robert L. Jack and Sarah A. M. Loos
Nonreciprocal interactions underpin diverse nonequilibrium phenomena, yet the effects of quenched nonreciprocity in extended systems remain largely unexplored. We study a $2d$ Ising model with randomly distributed nonreciprocal bonds at density $p$, finding a continuous nonequilibrium transition down to $T=0$ with finite $p_c$. A gauge-invariance argument yields $p_c(T)\leq1/2$, and mean-field theory predicts a qualitatively correct phase diagram. Unlike
equilibrium disordered models, the zero-temperature dynamics remains active, with athermal rare-region reversals and logarithmic "activated" coarsening.
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Mesoscale and Nanoscale Physics
Assessing Majorana states and qubits through quantum capacitance
Rodrigo A. Dourado, Ramón Aguado, Jeroen Danon et al. (+2 more)
Quantum capacitance (QC) has recently emerged as a promising tool for parity readout in topological
qubits based on Majorana bound states (MBSs). Here, we show that this capability can be extended further: by employing an auxiliary
quantum dot (QD) as a sensor, we demonstrate that QC measurements simultaneously resolve two fundamental figures of merit of the device, the ground-state energy splitting and the MBS overlap, thus providing direct access to the underlying internal degrees of freedom. Using a low-energy effective model, we provide analytic expressions for these two figures of merit that can be determined from the relative position and magnitude of the QC maxima in the even and odd parity sectors as functions of the auxiliary-QD energy. We further validate these results with a microscopic model of QD-based Kitaev chains and
qubits, demonstrating their applicability in a wide range of MBS-based devices. Our results establish QC as a probe of MBS quality and a tool for topological-device optimization that preserves
fermion parity.
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All authors Rodrigo A. Dourado, Ramón Aguado, Jeroen Danon, Martin Leijnse, Rubén Seoane Souto