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Thursday 17 September

Machine Learning

Efficient Bayes-Adaptive Reinforcement Learning with Temporal Logic Specifications

Jonathan Hau and Alessandro Abate

We present a novel end-to-end model-based Reinforcement Learning (RL) algorithm for efficient policy synthesis under given Linear Temporal Logic (LTL) specifications (e.g., safety or reachability) in unknown environments. To do so, a Limit-Deterministic Büchi Automaton (LDBA) representation of the LTL task is synchronised with a Bayes-Adaptive Markov Decision Process (BAMDP) representation of the environment, which allows us to leverage an enhanced exploration-exploitation trade-off that is achieved via Bayesian RL, as opposed to traditional non-Bayesian approaches. We further propose a novel Bayes-Adaptive Monte-Carlo Planning (BAMCP) algorithm to allow for approximate Bayes-optimal strategy synthesis in the synchronised BAMDP construct. A range of finite- and infinite-horizon task experiments demonstrate the effectiveness of our approach in terms of both property satisfaction and sample efficiency, when compared to traditional model-free approaches. Additional ablation studies also successfully highlight the value of the novel BAMCP algorithm in comparison to classical BAMCP for LTL task satisfaction. Finally, we also showcase a successful application of our approach for cautious RL, namely to reduce the number of task violations incurred during policy training.
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2609.20954 · 17 Sep · \copyright~2026 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

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High Energy Physics (Phenomenology)

Prospects for testing Lorentz symmetry with highly charged ions

Arnaldo J. Vargas

We investigate the prospects for testing Lorentz symmetry using highly charged ions. We derive the Lorentz-violating energy shifts relevant to Zeeman and Zeeman-hyperfine transitions within the ground state of H-like ions and to Zeeman and Zeeman-fine transitions within the ground state of B-like ions. The resulting signals include sidereal variations through the first harmonic of the sidereal frequency for H-like ions and through the third harmonic for B-like ions. For certain SME coefficients whose contributions scale with the fourth power of the electron momentum, the large electron momentum in H-like ions can provide sensitivity competitive with the best existing bounds at the precision achievable in H-like-ion spectroscopy. We also find that B-like-ion spectroscopy can provide competitive sensitivity to certain SME coefficients.
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Number Theory

On permutation-invariant construction of glued lattices

Maria Fernanda Zordan Bonini and Lenny Fukshansky

Given a permutation $\tau$ on $n$ letters, we consider lattices spanned by an orbit of one vector $\boldsymbol x$ in $\mathbb R^n$ under the action of $\tau$ by permutation of the coordinates. Such lattices generalize the important class of cyclic lattices and have previously been studied in~\cite{perm}, where a bound on their rank was established. We prove a sufficient condition on $\boldsymbol x$ for this bound to be achieved. We further investigate the structure of such permutation-invariant lattices, proving that they are glued by the permuted vector from the orthogonal cyclic blocks and giving a determinant formula for the lattice in terms of determinants of these blocks and the norm of the permuted vector. In the case $\boldsymbol x$ is an integer vector, these blocks are sublattices of the root lattices $A_k$ in respective dimensions with root lattices themselves and their glued direct sums also realizable by this construction. We also exhibit a glued construction of permutation-invariant algebraic integral lattices from collections of cyclic number fields. Finally, we prove a strengthened version of a previous result of~\cite{lf_ek} on a related construction of well-rounded lattices spanned by sets of algebraic conjugates.
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Quantum Physics

Nonlocal Magic Spreading in Many-body Quantum Dynamics: From Chaotic Evolution to Quasi-particle Picture in Integrable Models

Sreemayee Aditya, Piotr Sierant and Xhek Turkeshi

Entanglement and magic are resources that reveal complementary aspects of quantum many-body systems. Their interplay is captured by nonlocal magic, the magic that survives arbitrary local changes of basis. Yet their markedly different dynamical behavior leaves open how this irreducible component of magic spreads. Here we connect nonlocal magic to the capacity of entanglement, a tractable quantity measuring fluctuations of the entanglement Hamiltonian. This connection enables analytically controlled predictions across a wide range of many-body dynamics, from chaotic to integrable systems, which we investigate also using large-scale numerical simulations. In chaotic systems, nonlocal magic exhibits a transient buildup, with logarithmic growth in time followed by decay to a size-independent value. For integrable systems, we develop a quasiparticle picture in quantitative agreement with numerics, showing that the same initial growth instead leads to saturation at a value logarithmic in subsystem size. These contrasting behaviors have an operational consequence for entanglement embezzlement: the strongest scramblers embezzle only transiently, whereas free-fermionic dynamics can sustain universal embezzlement in the steady state.
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General Relativity and Quantum Cosmology

Zero Temperature, Degenerate Fermion Stars

S. Boatto, M. B. Paranjape, V. Pessanha et al. (+1 more)

We study a zero temperature, degenerate, fermion gas with fermions of rest mass $m$, that only interacts with itself, gravitationally. We describe a self-consistent novel approach to the formation of a degenerate, quantum mechanical, star. In this approach, the fermions occupy the energy levels that are determined by the self consistent gravitational interactions, according to the Pauli exclusion principle. Then the size of the highest occupied level determines the radius of the star. In the Newtonian gravitational limit, the fermions feel a potential corresponding to a simple harmonic well that smoothly attaches in the exterior to the usual $1/r$ Newtonian gravitational potential. We find analytically, solutions for stars with any radius and mass, parametrized by $m$ and $N_s$, the total number of fermions. In the Newtonian limit, we easily find that we can construct a star that is more compact than the Buchdahl bound and indeed can even be smaller than the Schwarzschild radius. Clearly, such cases are outside of the purview of the Newtonian limit. Therefore we expand our analysis to fermions in the general relativistic context, interacting gravitationally with a metric. We consider the metric corresponding to the interior Schwarzschild solution smoothly connecting to the usual exterior Schwarzschild metric. Treating matter semi-classically, we recover the Buchdahl bound in a completely independent analysis. We briefly discuss classical stability of the Newtonian solution, and its relation to Newtonian polytropic fluids.
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All authors S. Boatto, M. B. Paranjape, V. Pessanha, C. A. D. Zarro

High Energy Physics (Experiment)

First Measurement of Differential Cross Sections in Kinematic Imbalance Variables with Electron Neutrino Interactions Using the MicroBooNE Detector

MicroBooNE collaboration: P. Abratenko, D. Andrade Aldana, J. Asaadi et al. (+186 more)

We report the first measurement of flux-integrated cross sections as a function of kinematic imbalance variables for electron neutrino interactions on argon. Kinematic imbalance variables, applied here to electron neutrino interactions for the first time, are particularly interesting due to their sensitivity to effects such as Fermi motion, multinucleon processes, and final-state interactions, providing a detailed lens to study neutrino-nucleus interactions. These measurements are performed using MicroBooNE's full dataset of $1.3 \times 10^{21}$ protons on target from the Booster Neutrino Beam at the Fermi National Accelerator Laboratory. The measured cross sections are compared to several neutrino event generator configurations, revealing tensions between these models and data in the regions that are expected to be less dominated by final-state interactions.
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All authors MicroBooNE collaboration: P. Abratenko, D. Andrade Aldana, J. Asaadi, A. Ashkenazi, S. Balasubramanian, B. Baller, A. Barnard, G. Barr, D. Barrow, J. Barrow, V. Basque, J. Bateman, B. Behera, O. Benevides Rodrigues, S. Berkman, A. Bhat, M. Bhattacharya, V. Bhelande, A. Binau, M. Bishai, A. Blake, B. Bogart, T. Bolton, M.B. Brunetti, L. Camilleri, D. Caratelli, F. Cavanna, G. Cerati, A. Chappell, Y. Chen, J.M. Conrad, M. Convery, L. Cooper-Troendle, J.I. Crespo-Anadon, R. Cross, M. Del Tutto, S.R. Dennis, P. Detje, R. Diurba, Z. Djurcic, K. Duffy, S. Dytman, B. Eberly, P. Englezos, A. Ereditato, J.J. Evans, C. Fang, B.T. Fleming, W. Foreman, D. Franco, A.P. Furmanski, F. Gao, D. Garcia-Gamez, S. Gardiner, G. Ge, S. Gollapinni, E. Gramellini, P. Green, H. Greenlee, L. Gu, W. Gu, R. Guenette, L. Hagaman, M. D. Handley, O. Hen, A. Hergenhan, M. Harrison, S. Hawkins, C. Hilgenberg, G.A. Horton-Smith, A. Hussain, B. Irwin, M.S. Ismail, C. James, X. Ji, J.H. Jo, A. Johnson, R.A. Johnson, D. Kalra, G. Karagiorgi, W. Ketchum, A. Kelly, M. Kirby, T. Kobilarcik, K. Kumar, N. Lane, J.-Y. Li, Y. Li, K. Lin, B.R. Littlejohn, L. Liu, S. Liu, W.C. Louis, X. Luo, T. Mahmud, N. Majeed, C. Mariani, J. Marshall, D.A. Martinez Caicedo, F. Martinez Lopez, M. G. Manuel Alves, S. Martynenko, A. Mastbaum, I. Mawby, N. McConkey, B. McConnell, L. Mellet, J. Mendez, J. Micallef, T. Mohayai, A. Mogan, M. Mooney, A.F. Moor, C.D. Moore, L. Mora Lepin, M. A. Hernandez Morquecho, M.M. Moudgalya, S. Mulleria Babu, D. Naples, A. Navrer-Agasson, D. Nawarathne, N. Nayak, M. Nebot-Guinot, C. Nguyen, L. Nguyen, J. Nowak, N. Oza, O. Palamara, N. Pallat, V. Paolone, A. Papadopoulou, V. Papavassiliou, H. Parkinson, S.F. Pate, N. Patel, Z. Pavlovic, E. Piasetzky, K. Pletcher, I. Pophale, X. Qian, J.L. Raaf, V. Radeka, A. Rafique, M. Reggiani-Guzzo, J. Rodriguez Rondon, M. Ross-Lonergan, I. Safa, C. Sauer, D.W. Schmitz, A. Schukraft, W. Seligman, M.H. Shaevitz, R. Sharankova, L. Silva, E.L. Snider, S. Soldner-Rembold, J. Spitz, M. Stancari, J. St. John, T. Strauss, A.M. Szelc, K. Terao, C.Thorpe, D. Torbunov, D. Totani, M. Toups, A. Trettin, Y.-T. Tsai, J. Tyler, M.A. Uchida, T. Usher, B. Viren, M. L. Velazquez Fernandez, L. Wang, M. Weber, H. Wei, A.J. White, S. Wolbers, T. Wongjirad, K. Wresilo, W. Wu, E. Yandel, T. Yang, L.E. Yates, H.W. Yu, G.P. Zeller, J. Zennamo, C. Zhang, Y. Zhang

Optics

Physics-aware hyper-reduction for full-vector photonic waveguide mode solvers

Daniel Rodríguez-Guillén and Lorena Velázquez-Ibarra

Photonic waveguide design often requires repeated full-vector Maxwell eigenmode solves over wavelength and geometry, where the subpixel smoothing needed at dielectric interfaces makes operator assembly a substantial part of the cost. We present a physics-aware hyper-reduction framework for accelerating this assembly. The method exploits an exact affine dependence of the discrete operators on the locally sampled inverse-permittivity tensor, and chooses its strategy from how a parameter acts on the interface cells. We demonstrate two regimes. In wavelength sweeps at fixed geometry, tensor values change on a fixed set of cells, and proper orthogonal decomposition with matrix discrete empirical interpolation reproduces the operators from few snapshots. In moving-boundary sweeps, interface information relocates across the grid, and event-driven dynamic local sampling updates only the coefficients a geometric step changes, reproducing full assembly exactly. These results show that operator assembly can be reduced by more than an order of magnitude without approximating the moving boundary, shifting the cost of a photonic mode sweep to the eigensolver.
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Astrophysics of Galaxies

Euclid Quick Data Release (Q1) Euclid spectroscopy of quasars. 2. Physical properties from spectral fitting

Euclid Collaboration: J. Calhau, G. Calderone, A. Feltre et al. (+311 more)

A substantial volume of spectroscopic data has become available with the Euclid Data Release (Q1), which represents a unique opportunity to study quasars (QSOs) in the Euclid Deep Fields, provide spectroscopic measurements, and estimates of their physical properties. We present results from a spectroscopic analysis of QSOs with HE < = 22.5 using Q1. We use external catalogues from surveys such as the Dark Energy Spectroscopic Instrument (DESI), Gaia, Wide-field Infrared Survey Explorer (WISE), and the QUasars as BRIght beacons for Cosmology in the Southern hemisphere (QUBRICS) for the QSO selection and redshift determination, totaling 5489 QSOs. We provide measurements of the line fluxes, full widths at half-maximum, and respective uncertainties for the emission lines of Euclid spectra based on fitting statistica and signal-to-noise ratio (S/N). Of the total 5489 QSOs, 5387 are successfully fitted. We find that 45% of the total number of successfully fitted spectra are free of problematic artefacts allowing for trustworthy measurements. Our final Euclid QSO sample spans a redshift range of 0.01 < = z < = 4.8 and shows a median spectral index of {\alpha}{\lambda} = - 1.17. Finally, we estimate black hole masses with single epoch methods for 1213 sources, using the He I {\lambda}10830, Pa {\beta}, H {\alpha}, H {\beta}, and Mg II emission lines, obtainning a mean logarithmc mass of log10 (MBH / Msolar) = 8.7 and mean Edigton ratio of {\lambda}Edd = 0.34. The catalogue with the physical properties of this sample together with the software developed for the analysis is available online for scientific exploitation.
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All authors Euclid Collaboration: J. Calhau, G. Calderone, A. Feltre, M. Scialpi, V. Allevato, H. Landt, F. Ricci, Y. Fu, L. Spinoglio, F. Shankar, L. Nicastro, A. Viitanen, G. Zamorani, M. Mezcua, F. La Franca, D. Stern, E. Lusso, J. Wolf, A. Paulino-Afonso, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, X. Dupac, S. Dusini, A. Ealet, S. Escoffier, M. Farina, S. Ferriol, F. Finelli, S. Fotopoulou, N. Fourmanoit, M. Frailis, M. Fumana, L. Gabarra, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, W. G. Hartley, S. V. H. Haugan, S. Hemmati, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, M. Huertas-Company, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, V. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, N. Mauri, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, P. Monaco, A. Mora, M. Moresco, C. Moretti, L. Moscardini, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, I. Risso, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, C. Surace, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, D. Vibert, Y. Wang, J. Weller, A. Zacchei, E. Zucca, M. Ballardini, P. Bergamini, S. Borgani, E. Bozzo, C. Burigana, R. Cabanac, A. Cappi, T. Castro, J. A. Escartin Vigo, J. García-Bellido, T. Gasparetto, A. Loureiro, J. Macias-Perez, R. Maoli, R. B. Metcalf, M. Pöntinen, E. Sarpa, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, J. A. Acevedo Barroso, Y. Akrami, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, G. Arico, F. Atrio-Barandela, E. Aubourg, M. Baes, L. Baumont, L. Bazzanini, D. Bertacca, M. Bethermin, F. Beutler, L. Bisigello, A. Blanchard, L. Blot, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, T. E. Collett, S. Conseil, A. R. Cooray, P. Corcho-Caballero, B. Csizi, O. Cucciati, H. Dannerbauer, S. Davini, T. de Boer, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, V. Duret, A. Enia, Y. Fang, A. Farina, A. G. Ferrari, A. Finoguenov, F. Fontanot, A. Franco, K. Ganga, R. Gavazzi, E. Gaztanaga, Z. Ghaffari, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, N. A. Hatch, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, J. Kim, C. C. Kirkpatrick, A. Kovács, I. Kovačić, K. Koyama, S. Kruk, M. C. Lam, G. Leroy, J. Lesgourgues, L. Linke, S. J. Liu, X. Lopez Lopez, G. Maggio, F. Mannucci, F. R. Marleau, C. J. A. P. Martins, M. Migliaccio, M. Miluzio, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, A. Nersesian, S. Nesseris, F. Oppizzi, F. Pace, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, G. Rodighiero, K. Rojas, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, A. Schneider, D. Sciotti, E. Sellentin, S. Serjeant, J. G. Sorce, M. Talia, K. Tanidis, C. Tao, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, C. Uhlemann, C. Valieri, A. Venhola, G. Verza, S. Vinciguerra, M. von Wietersheim-Kramsta, L. Wang, A. H. Wright

Systems and Control

Optimal Day-Ahead Scheduling of Fast EV Charging Station With Multi-Stage Battery Degradation Model

Y. Wan, D. Gebbran, R. K. Subroto et al. (+1 more)

The paper proposes a day-ahead scheduling framework with a novel multi-stage battery degradation modeling method for an electric vehicle (EV) fast charging station (FCS) equipped with a battery energy storage system (BESS). Unlike previous studies, which employ a single battery degradation model to represent the aging process, this paper proposes a novel multi-stage battery degradation modeling method to accurately capture the degradation process across the whole lifespan. Subsequently, the multi-stage model is explicitly integrated into the proposed adaptive optimization framework in a computationally tractable way, thus having important practical implications in the field. The paper provides case studies to demonstrate the effectiveness of the proposed modeling method on a selected cycle aging model in reducing the operation cost of FCS with BESS operating in different stages. As a result, the overall operation cost with the multi-stage model is around 2.1% on average lower than the single-stage model counterpart. In addition, results show that with the increasing number of divided stages, the model error decreases and becomes stable, while the reduced operation cost compared with the single-stage model increases and saturates. Finally, we apply the multi-stage framework considering other conventional degradation models to show the superiority of the proposed method.
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All authors Y. Wan, D. Gebbran, R. K. Subroto, T. Dragičević

Computation and Language

$\mu^2$-Bench: A Multilingual Machine Unlearning Benchmark

Kyomin Hwang, Hyeonjin Kim, Hyunho Lee et al. (+3 more)

Undesired information such as harmful content and private data propagates through Multilingual Large Language Models (LLMs) via direct training and indirect cross-linguistic spread. Multilingual Machine Unlearning (MMU) aims to remove such information, yet its evaluation remains underexplored, leaving unclear whether unlearning truly eliminates target knowledge across all languages. To bridge this gap, we introduce $\mu^2$-Bench, an MMU benchmark that simulates the full pipeline of memorization, unlearning, and evaluation across diverse languages. It 1) spans a broad set of languages, 2) evaluates on both training and hold-out languages, and 3) assesses knowledge as dispersed across multiple languages. We show that successful MMU requires methods that reflect multilingual characteristics, and conduct analysis to provide deeper insights into MMU.
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All authors Kyomin Hwang, Hyeonjin Kim, Hyunho Lee, Yearim Kim, Yeji Song, Nojun Kwak

High Energy Astrophysical Phenomena

Systematic Uncertainties and Their Impact on Gamma-Ray Searches for Dark Matter in Dwarf Galaxies

Toni Bertólez-Martínez, Dan Hooper and Arifa Khatee Zathul

Gamma-ray observations of Milky Way dwarf galaxies provide some of the strongest constraints on dark matter annihilation and are approaching the sensitivity required to test dark matter interpretations of the Galactic Center Gamma-Ray Excess. The results, however, depend critically on the inferred dark matter distributions in these systems, conventionally described by their $J$-factors and spatial profiles. We review several sources of systematic uncertainty in dwarf galaxy $J$-factor determinations, including stellar membership, unresolved binaries, departures from equilibrium and spherical symmetry, and assumptions regarding the stellar and dark matter density profiles. Most $J$-factor determinations reported in the literature neglect several of these uncertainties, and the resulting measurements are often more dispersed than their quoted uncertainties would suggest. This indicates uncertainties of order $\Delta\log_{10}J\sim0.5$ or larger may be warranted for many of these systems. Using an ensemble of simulated Fermi-LAT observations of a stacked sample of 27 dwarf galaxies, we quantify how these unmodeled uncertainties affect the resulting constraints on the dark matter annihilation cross section. We find that adding an uncertainty of $\Delta\log_{10}J\sim 0.5$ or 1.0 in quadrature weakens the median upper limits of a stacked analysis by factors of 1.4 or 3.2, respectively. Furthermore, underestimating these uncertainties can cause such analyses to exclude the true annihilation cross section more frequently than the nominal confidence level would imply. Such undercoverage is especially pronounced in stacked analyses and persists even when the adopted and true $J$-factor uncertainties agree. Mismodeling spatially extended halos as point sources, as is sometimes done, further strengthens the resulting limits and increases the probability that true signals will be incorrectly excluded.
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Systems and Control

Source–Grid Coupling in Power System Oscillations: Observational Equivalence, Feedback Detectability, and Modal Interaction

Kai Sun and Bin Wang

The conventional distinction between forced and natural oscillations treats the oscillation source as external to a fixed power-system boundary. This paper develops a coupling-aware dynamical interpretation by explicitly accounting for the directionality of source-grid coupling. It examines when prescribed forcing and a one-way autonomous source are observationally equivalent, and when grid measurements can distinguish the presence of grid-to-source feedback. Matched interface signals yield exact equivalence under the same deterministic grid initial-value problem and measurement map. Bidirectional feedback enables source-grid eigenvalue interaction in the augmented autonomous model, while a reduced two-mode model shows that the interaction depends jointly on loop coupling and complex modal separation. The resulting framework establishes source-grid coupling directionality as a feedback-based dynamical boundary and clarifies when feedback can be inferred from grid-side measurements and why weak feedback may remain unresolved. Simulation studies on a two-area system demonstrate feedback detection within a calibrated source family, while source-model mismatch can be confounded with feedback. A WECC 243-bus system study demonstrates feasibility on a large system and shows that feedback detection need not require exact candidate selection.
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Machine Learning

When AI Reviews Train AI Reviewers: Scientific-Judgment Collapse and Mitigation

Sy-Tuyen Ho, Minghui Liu, Hieu Tran et al. (+1 more)

LLMs increasingly assist scientific peer review. This creates a feedback loop when generated reviews enter the training data of future LLMs. While recursive training has been studied broadly, its effects on scientific judgments remain poorly understood. We empirically study this effect in a controlled setting by varying synthetic-review exposure while fixing other training conditions. After one recursive step, increasing exposure from $0\%$ to $100\%$ makes recommendation ratings more concentrated, independently generated reviews of the same paper about $11\%$ more similar, and reviews across different papers about $5\%$ less diverse. A further step of recursive training amplifies homogenization when synthetic supervision is reintroduced. We characterize this task-specific phenomenon as $\textbf{scientific-judgment collapse}$. We also explore a training-free method using contrastive activation steering with a limited reference reviews. Controlled experiments show a partial recovery in recommendation agreement and judgment diversity across different papers, but not among independently generated reviews of the same paper. To explore this approach beyond controlled experiments, we develop $\textbf{TrustReviewer}$. We train the model on a large-scale curated data and apply activation steering at inference time. On held-out papers, steering increases exact recommendation match from $73.85\%$ to $75.40\%$, compared with $73.10\%$ for OpenReviewer on the same LLM backbone, while maintaining relatively diverse scientific judgments. Our findings quantify judgment homogenization under recursive training and motivate further research on preserving judgment diversity.
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All authors Sy-Tuyen Ho, Minghui Liu, Hieu Tran, Furong Huang

Solar and Stellar Astrophysics

White Dwarf Natal Kicks as Velocity-Space Random Walks. II. Binary Stellar Evolution and Observational Kick Constraints

Dang Pham, Stephen Majeski, Taeho Ryu et al. (+2 more)

Wide binaries containing white dwarfs (WDs) provide a pathway to exploring post-main-sequence (MS) natal kicks associated with asymmetric mass loss. In this work, we develop a binary population synthesis model that involves episodic mass loss and velocity kicks during the thermally-pulsing asymptotic-giant-branch (TP-AGB) phase of stellar evolution, when mass loss is expected to be most significant. We compare our synthesized populations against the Gaia DR2 and DR3 data for wide WD-MS and WD-WD binaries, varying the number, strength, and directionality of TP-AGB kicks. We find that the observed separation distribution can constrain the kick strength, but it alone is insufficient to also constrain the kick number and dimensionality. We therefore additionally constrain our models using the observed eccentricity distributions. Models where mass loss induces a random walk in the star's velocity are most consistent with observed eccentricity constraints for WD-MS binaries. No models are found to agree with the WD-WD eccentricity constraint. Our results suggest that at least 10 randomly directed kicks take place during the TP-AGB phase, leading to a cumulative root-mean-square kick velocity of approximately 0.7 km/s. These findings constrain the nature of WD natal kicks, connecting the orbital distributions of evolved wide binaries to asymmetric mass loss during the final stages of stellar evolution.
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All authors Dang Pham, Stephen Majeski, Taeho Ryu, Gabriel Tomassini, Andrea Chiavassa

Solar and Stellar Astrophysics

White Dwarf Natal Kicks as Velocity-Space Random Walks. I. Fokker-Planck Theory

Stephen Majeski, Dang Pham, Taeho Ryu et al. (+2 more)

White dwarfs are the most common end state of stellar evolution, including that of our own Sun, making their formation critical to completing a more comprehensive understanding of stellar evolution and even determining the eventual fate of the solar system. Wide binaries containing white dwarfs offer a powerful probe: their components evolve largely independently, yet stellar mass loss and velocity impulses (natal kicks) on the white dwarf progenitor leave measurable imprints on orbital properties. Previous population studies typically assume that each white dwarf receives only a single natal kick as it forms. While convenient, this simplification conflicts with simulations finding the formation process to be episodic. Therefore, a more realistic picture is that white-dwarf progenitors experience multiple stochastic kicks over their evolution. Here, we present a Fokker-Planck model for the evolution of binary orbital parameter distributions subject to many, randomly-oriented mass-loss-driven kicks. This model recovers key features of white-dwarf binary observations, including a -2 power law tail in the probability distribution of separations, and the thermalization of binary eccentricities beyond separations of 1000 au. We additionally investigate how white-dwarf kicks impact a myriad of other processes, such as binary dissolution, planetary system evolution, and even the production of interstellar objects.
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All authors Stephen Majeski, Dang Pham, Taeho Ryu, Gabriel Tomassini, Andrea Chiavassa

Data Structures and Algorithms

Prophet Inequalities and Online Contention Resolution for Matchoids

Calum MacRury, Pranav Nuti and Jan Vondrák

In the classical prophet inequality, an algorithm observes a sequence of random variables with known distributions in an online fashion, and it must select one of the random variables with the goal of maximizing the expected value of its selection. The performance of the algorithm is compared to an omniscient prophet who observes all of the random variables before having to make its selection. Combinatorial extensions of the classical prophet inequality in which the algorithm gets to pick a subset of the random variables (constrained to belong to some family of feasible sets) have been studied extensively. We study prophet inequalities with a $k$-matchoid constraint (a common generalization of a $k$-matroid intersection constraint and a $k$-bounded hypergraph matching constraint) in two common online arrival models. We give guarantees with respect to the ex-ante fractional relaxation of the omniscient prophet, obtaining an ex-ante competitive ratio of $\frac{1}{k+1}$ in the adversarial order case, and $\frac{1-e^{-k}}{k}$ in the random order case. Using the duality framework of Lee and Singla \cite{Lee2018}, this also yields online contention resolution schemes in these settings. Our adversarial-order prophet inequality can be viewed as a generalization of a recent $\frac12$-competitive matroid prophet inequality by Kalantarzadeh and Pashkovich, 2026. This generalization introduces a new framework: coordinated weighted principal partitions across multiple matroids. Our random-order prophet inequality is a generalization of the $k=1$ matroid case of Lee and Singla, 2018. The two results improve previously known competitive ratios for $k$-matroid intersection, which were $\frac{1}{(e+o(1))k}$ and $\frac{1}{k+1}$, respectively.
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Astrophysics of Galaxies

Cosmic web Ly$\alpha$ emission in a sample of overdense regions

Davide Tornotti, Michele Fumagalli, Matteo Fossati et al. (+7 more)

We present a complete and homogeneous analysis of the Ly$\alpha$ emission properties of the cosmic web at $3 \lesssim z \lesssim 5$ as a function of the overdensity of Ly$\alpha$ emitters (LAEs) in the MUSE Ultra Deep Field (MUDF) and the MUSE Extremely Deep Field (MXDF). We identify 41 overdensities, probing environments that are $\delta \approx 2 - 10$ times denser than the field. We search for extended emission down to surface brightness (SB) levels of $3 - 5 \times 10^{-20}\ \mathrm{erg\ s^{-1}\ cm^{-2}\ arcsec^{-2}}$, revealing filamentary structures beyond the scale of the circumgalactic medium, confirming that LAEs act as signposts of the cosmic web. A trend with overdensity emerges: non-detections are mainly at $\delta < 2$, a $\approx 1$ dex scatter in SB appears for $2 \lesssim \delta \lesssim 3.5$, and detections reach a maximum intrinsic SB of $\approx 2 \times 10^{-19}\ \mathrm{erg\ s^{-1}\ cm^{-2}\ arcsec^{-2}}$ for $\delta \gtrsim 3.5$. Emitting regions occupy a fraction of projected area $f_s \approx 0.20 - 0.25$ inside filaments, yielding a cosmological incidence for Ly$\alpha$ emission in the cosmic web $\ell(\mathrm{Ly}\alpha)$ of $\approx 1.22$, which is similar to the one of partially-neutral Lyman limit systems. This analysis indicates that the emitting gas is partially ionized at moderate densities ($n_{\mathrm{H}} \approx 10^{-3} - 10^{-1}\ \mathrm{cm}^{-3}$), likely tracing the denser spines of intergalactic filaments and embedded substructures. Finally, we forecast how oriented stacking in larger samples of overdensities from shallower observations could yield an expanded view of the cosmic web before the next-generation wide-field spectroscopic instruments become operational.
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All authors Davide Tornotti, Michele Fumagalli, Matteo Fossati, Roland Bacon, Fabrizio Arrigoni Battaia, Rajeshwari Dutta, Michele Fulghieri, Celine Peroux, Marc Rafelski, Mitchell Revalski

High Energy Physics (Phenomenology)

Thermal gravitino and axino rate from AutoTherm

Killian Bouzoud, Jacopo Ghiglieri and Greg Jackson

If ultrarelativistic supersymmetric particles are thermally produced in the early universe they would influence big-bang nucleosynthesis, dark matter and reheating constraints. While the basic framework for thermal gravitino and axino production is well established, the calculation is not completely settled. In this work, we revisit the problem using AutoTherm, a new tool which automates the computation of thermal rates from first-principles Thermal Field Theory, with control over the inherent theory uncertainty in Hard Thermal Loop resummation schemes. We demonstrate that the strict leading-order (LO) scheme, while unambiguous for hard momenta, can yield unphysical negative rates when extrapolated to soft momenta. To address this, we introduce a tuned scheme that ensures positivity and agreement with strict LO at high momenta, while avoiding gauge-dependent pathologies. We compare our results with existing parametrizations in the literature, identifying discrepancies and providing new, reliable fits for the gauge and Yukawa contributions to the gravitino and axino production rates. The choice of resummation scheme gives a theory uncertainty by a factor of $\sim 1.5$...$3$ depending on the temperature, which has been underappreciated until now. This residual spread should be taken into account in precision cosmological analyses of gravitino/axino abundancies.
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High Energy Physics (Phenomenology)

AutoTherm: Automated Thermal Field Theory rates for cosmology

Killian Bouzoud, Jacopo Ghiglieri and Greg Jackson

AutoTherm is a modular code automating the determination of thermal production and interaction rates for cosmology from Thermal Field Theory. This first release computes fully automatically the leading-order contribution from ultrarelativistic $2\leftrightarrow 2$ processes to the production rate of an off-equilibrium $\vartheta$ particle coupled to a thermal bath. It takes as input a FeynRules model file describing the Lagrangian of the bath-$\vartheta$ system. The AutoTherm program consists of a Wolfram package, which utilises FeynArts/FormCalc, together with a few Python modules for symbolic and numerical routines. Their combined usage leads from the model file to the rate, but each component can also be used in a standalone manner. The main strength of this release is the automated, model-independent handling of Hard Thermal Loop resummation, which is necessary whenever a $2\leftrightarrow 2$ process is mediated by a $t$-channel massless mediator. Developments in Thermal Field Theory reduce the apparently large model dependence to the determination of the thermal mass of the mediator, which we automate successfully. They further allow us to provide three leading-order-equivalent implementations of HTL resummation. Their spread provides a first estimate of the theory uncertainty from higher-order thermal corrections. We showcase the strength of our AutoTherm framework by successfully reproducing or correcting a host of results in the literature, such as the thermal production rate of ultrarelativistic right-handed neutrinos, of gravitons and gravitinos, of axions and of dark photons.
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Astrophysics of Galaxies

An Archival Calibration of JWST/MIRI Prism Wide-Field Slitless Spectroscopy: Methodology, Performance, and a Mid-Infrared Spectral Atlas of Galaxies at $z=0-4$ in the GOODS-N/S Fields

Fengwu Sun, Javier Álvarez-Márquez, Eiichi Egami et al. (+4 more)

Through the Low Resolution Spectroscopy (LRS) observing mode of JWST/MIRI, the P750L prism disperses the entire ~70"$\times$110" imager field, turning MIRI into a wide-field slitless spectrograph (WFSS) at 5-14 $\mu$m with spectral resolution $R\sim100$. Using archival MIRI LRS data taken in the GOODS-N/S deep fields and calibration programs, we present a complete and precise calibration suite for MIRI WFSS through an AI-assisted agentic workflow under human supervision. The calibration includes flat field, sky background, spectral tracing, wavelength calibration, flux calibration, and the large-scale flux flat (L-flat). We present the methodology of each calibration and quantify its accuracy. As a demonstration, we extract 5-14 $\mu$m slitless spectra of 180 spectroscopically confirmed galaxies at $z=0.08 - 3.71$ in the GOODS-N/S fields. We detect a large number of polycyclic aromatic hydrocarbon (PAH) bands and atomic lines (including Paschen $\alpha$ out to $z=3.71$) in individual sources. The PAH 3.3 $\mu$m luminosities correlate with the Paschen $\alpha$ luminosities (measured through NIRCam WFSS) for $z\sim1$ galaxies over a $\sim$1.5-dex range, supporting PAH 3.3 $\mu$m as a star-formation-rate tracer out to $z\sim1.6$. We release the calibration reference files, reduction scripts, and the mid-infrared spectral atlas. We also present caveats and lessons learned from our archival calibration work. Our empirical sensitivity characterization identifies a noise floor for deep MIRI WFSS integrations ($\gtrsim$ a few ks), whereas shallower integrations exceed the sensitivity predicted by the JWST Exposure Time Calculator. We also provide suggestions for the planning of future MIRI WFSS observing programs.
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All authors Fengwu Sun, Javier Álvarez-Márquez, Eiichi Egami, Román Fernández Aranda, Jakob M. Helton, Xiaojing Lin, Jianwei Lyu

General Relativity and Quantum Cosmology

Second-order scattering response of a Schwarzschild black hole

Bruno Bucciotti, Jaime Redondo-Yuste, Zhen Zhong et al. (+2 more)

Gravitational waves couple in a nonlinear fashion in the vicinity of a black hole. Black hole perturbation theory can be readily applied to compute the magnitude of this coupling, its dependence on the parity content, frequencies, and angular structure of the incoming gravitational waves. In this work we carry out this calculation, showing how the nonlinear coupling of gravitational waves generically peaks when the driven frequency matches the oscillation frequency of the fundamental quasinormal mode of the black hole. We also demonstrate how this excitation is largest at the maximal harmonics allowed, and study its dependence on the parity content of the incoming modes. At low frequencies, the quadratic response computed here encodes the nonlinear, dynamical tidal deformability of the black hole spacetime itself. We demonstrate numerically that the quadratic black hole coupling coefficient scales quadratically with the driving frequency, and recover this scaling from the 5-point Compton graviton scattering amplitude.
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All authors Bruno Bucciotti, Jaime Redondo-Yuste, Zhen Zhong, Adrien Kuntz, Vitor Cardoso

Solar and Stellar Astrophysics

Cause of chromospheric opposite polarity intrusions discovered in Sunrise III/SCIP data: MURaM-ChE simulations point to twisted flux ropes

Patrick A. Ondratschek, Damien F. Przybylski, Robert H. Cameron et al. (+33 more)

The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) instrument onboard the balloon-borne Sunrise III observatory provided new high-resolution observations of the solar chromosphere in the Ca II 854.2 nm line. The Stokes-V signal in magnetic network regions was found to show fine-structured details, which suggests the magnetic field above the network elements does not simply expand as a unipolar feature but displays opposite-polarity-intrusions (OPIs). These features appear as elongated structures in Stokes-V observations. In this work, we demonstrate that such features appear ubiquitously in a numerical simulation of the solar chromosphere. We use a simulation that is computed with the recently developed chromospheric extension of MURaM (MURaM-ChE) and resembles an enhanced network region. We find that OPIs appear ubiquitously in the vertical component of the magnetic field at around 1 Mm above the surface and are visible in the synthetic Stokes-V signal of the Ca II 854.2 nm line. The structures have lengths of 2 Mm to 7 Mm and widths of approximately 1 Mm. The magnetic field configurations associated with the OPI features appear to belong to twisted flux ropes (TFRs) and are visible for most of the time in the presented 21 min time series. Our results show that the magnetic structure of the chromosphere is more complex than previously thought, with even seemingly simple flux tubes showing embedded twisted fields pointing in the opposite direction. This may help in explaining new high-resolution observations from the Sunrise III mission.
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All authors Patrick A. Ondratschek, Damien F. Przybylski, Robert H. Cameron, H. N. Smitha, Sami K. Solanki, Masahito Kubo, Andreas Lagg, Achim Gandorfer, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alex Feller, Tino L. Riethmueller, Alberto Alvarez-Herrero, David Orozco Suarez, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentin Martinez Pillet, Laurent Gizon, Francisco Javier Bailen, Julian Blanco Rodriguez, Juan Sebastian Castellanos Duran, Edvarda Harnes, Johannes Hoelken, Francisco A. Iglesias, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dusan Vukadinovic, Hirohisa Hara, Toshifumi Shimizu

Superconductivity

Smectic Superconductivity

Grayson R. Frazier and Erez Berg

We identify a mechanism in which soft nonunitary fluctuations of the pair condensate can suppress phase coherence in a two-dimensional Rashba superconductor proximate to easy-plane ferromagnetic order. This spin polarization couples linearly to the supercurrent through a Lifshitz invariant, acting as an emergent gauge field for the superconducting $\mathrm{U}(1)$ phase. Integrating out soft magnetic fluctuations renormalizes the effective superfluid stiffness and drives the system into a "smectic" superconducting state, characterized by a finite-momentum helical phase texture and a long-wavelength stiffness that vanishes in one direction. Consequently, vortices no longer have a logarithmically divergent energy cost, and the quasi-long-range superconducting order is destroyed at any finite temperature. Weak lattice anisotropy pins the ferromagnetic order, cutting off the smectic-like behaviour at long wavelengths and thereby restoring a finite effective stiffness. Nonetheless, near the onset of magnetic order, the enhanced magnetic susceptibility leads to a vortex-deconfined regime for arbitrarily weak magnetoelectric coupling. The results provide insight into how intertwined superconducting and easy-plane ferromagnetic orders can reshape phase coherence, with relevance to rhombohedral graphene proximitized by a transition-metal dichalcogenide substrate.
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Astrophysics of Galaxies

Quiescent Galaxies at $z > 2$ from CAPERS spectroscopy and their Number densities

Lu Shen, Weida Hu, Casey Papovich et al. (+28 more)

Recent JWST observations have revealed an overabundance of quiescent galaxies at high redshift. Photometric methods, such as photometry-derived sSFRs, $UVJ$ colors, and synthetic $ugi_s$ colors, are commonly used to identify quiescent galaxies, but their completeness and purity remain poorly constrained. Here we present a spectroscopically selected sample of 19 quiescent galaxies at $2 \leq z \leq 4$ from the CANDELS-Area Prism Epoch of Reionization Survey (CAPERS). They are selected with $M_\ast > 10^{9.5} M_\odot$ and a specific star formation rate below 20% of the inverse cosmic age. These galaxies formed 50% of their stellar mass at $z \sim 3.0$–4.6 and quenched rapidly on timescales of $\sim0.1$–0.2 Gyr. These quenching timescales are comparable to those of other high-redshift QGs but shorter than those at lower redshift. Using the spectroscopic sample as a benchmark, we assess commonly adopted photometric QG selection methods. We find completeness of 63–89% and purities of only 40–63%, with strong emission-line galaxies constituting the dominant source of contamination. Applying completeness and purity corrections calibrated from the spectroscopic sample, we measure the number density of quiescent galaxies at $2 \leq z \leq 5$. The resulting number densities exceed the predictions of most current galaxy-formation simulations at $2<z<4$, with the largest discrepancy at $M_\ast \geq 10^{10.5} M_\odot$. This discrepancy suggests that current cosmological models may not assemble and quench massive galaxies sufficiently early or efficiently.
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All authors Lu Shen, Weida Hu, Casey Papovich, Justin Cole, Mark Dickinson, Pablo Arrabal Haro, Anthony J. Taylor, Adam C. Carnall, Ángel Chandro-Gómez, Yingjie Cheng, Nikko J. Cleri, James S. Dunlop, Carter Flayhart, Steven L. Finkelstein, Mauro Giavalisco, Michaela Hirschmann, Eric F. Jiménez-Andrade, Jeyhan S. Kartaltepe, Claudia D.P. Lagos, Ho-Hin Leung, Arianna S. Long, Ray A. Lucas, Eric J. Murphy, Lorenzo Napolitano, Pablo G. Pérez-González, Raymond C. Simons, Struan D Stevenson, Elizabeth Taylor, Xin Wang, L. Y. Aaron Yung, Jorge A. Zavala

Astrophysics of Galaxies

The Galactic Phosphorus Survey. I. Chemical Evolution across the Galactic Disk from $\sim$750 FGK Stars

Dionysios Gakis, Keith Hawkins, Zachary G. Maas et al. (+5 more)

Phosphorus (P) is an odd-$Z$ element produced primarily in massive stars and is also important for planetary chemistry as an element essential to life. However, its evolution over cosmic time remains poorly constrained because precise and homogeneous stellar P measurements are scarce. We determine the relationship between [P/Fe] and [Fe/H] over a range of metallicities across the Galactic disk and assess its variation between different stellar populations using the largest uniformly analyzed sample to date, comprising $\sim$750 FGK stars with high-resolution near-infrared spectra. Stellar parameters are determined through a spectro-photometric approach and P abundances are derived by fitting synthetic spectra to the P~I 10529.52~Å\ absorption feature. We confirm that [P/Fe] increases toward lower metallicities down to [Fe/H] $\sim$ -1.0 dex, where it appears to peak, broadly resembling the rise seen in $\alpha$-element abundance ratios over the same metallicity range and supporting a dominant contribution from massive stars on short core-collapse supernova timescales. When separating the sample into Galactic disk populations, thick-disk stars are systematically enhanced in [P/Fe] relative to the thin disk by $\sim$0.08 dex at fixed metallicity. We also measure a radial [P/Fe] gradient of $-0.124 \pm 0.006$ dex kpc$^{-1}$ and a vertical gradient of $+0.052 \pm 0.007$ dex kpc$^{-1}$. Although current chemical evolution models struggle to reproduce the observed trends, this survey increases the number of homogeneously measured stellar P abundances by approximately a factor of three, providing a new benchmark for Galactic chemical evolution models and the phosphorus inventory available to planetary systems.
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All authors Dionysios Gakis, Keith Hawkins, Zachary G. Maas, Christopher Sneden, Melike Afşar, Natalie R. Hinkel, Chenguang Sun, Wenwei Liang

Astrophysics of Galaxies

From IFS Maps to 3D Structure I: Constraining Geometry in the Circumgalactic Medium

Mandy C. Chen, Michael Rauch, Zhijie Qu et al. (+3 more)

The three-dimensional geometric structure of the cool (T~$10^4$ K) circumgalactic medium (CGM) – the line-of-sight depth and the number of discrete clumps – is poorly constrained. Existing inferences come predominantly from quasar absorption-line statistics, but these pencil-beam probes provide limited spatial and kinematic information. Here we show that spatially resolved emission-line maps from integral field spectrograph (IFS) observations provide complementary, novel constraints on cool CGM geometry when projection effects are accounted for. Observations of a sample of CGM nebulae yield measurements of the line-of-sight and the plane-of-sky velocity dispersions, with ratios $\sigma_{\rm los}/\sigma_{\rm pos}$ ranging from ~1 to ~2.5. Using direct numerical simulations of isotropic turbulence projected through emitting slabs of varying depth $L_{\rm los}$, we show that the ratio $\sigma_{\rm los}/\sigma_{\rm pos}$ allows us to probe $L_{\rm los}/L_{\rm neb}$, where $L_{\rm neb}$ is the nebular extent on the plane of the sky. We find that the inferred line-of-sight depth is typically ~0.1-$5\,L_{\rm neb}$, indicating that these nebulae are broadly comparable in depth and projected extent. Although the cool CGM is intrinsically clumpy, at the current IFS data resolution, each beam aggregates enough clumps that the projected dispersion ratio approaches its volume-filling value. Consequently, the emission kinematics provide little additional information on the detailed clump configuration beyond consistency with the clump incidence rates inferred from absorption-line surveys. These findings serve as a theoretical framework for the turbulence diagnostics developed in the companion paper (Paper II). Together, these papers demonstrate how IFS emission-line kinematics can provide a quantitative probe of the 3D CGM, complementary to absorption-line and emerging FRB approaches.
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All authors Mandy C. Chen, Michael Rauch, Zhijie Qu, Gwen C. Rudie, Hsiao-Wen Chen, James R. Beattie

Solar and Stellar Astrophysics

The Treasury of Extremely Metal-Poor O Stars

O. Grace Telford, Christiana Erba, Kristen B. W. McQuinn et al. (+10 more)

The Treasury of Extremely Metal-Poor O Stars (TEMPOS) is a Hubble Space Telescope survey of hot and massive O-type stars in nearby, low-metallicity galaxies ($\lesssim$20% of the solar metallicity, $Z_\odot$). Understanding massive-star physics in this regime is essential to interpret observations of metal-poor galaxies, including both low-mass dwarf galaxies and chemically unevolved galaxies in the early Universe. Yet, few far-ultraviolet (FUV) spectra of O stars of sufficient quality to characterize their fundamental properties and stellar winds exist below 20% $Z_\odot$, and heterogeneous observation design and incomplete coverage of parameter space pose significant barriers to progress. To remedy this, TEMPOS obtained new Cosmic Origins Spectrograph (COS) FUV spectra of 12 very metal-poor O stars, building upon archival data to assemble a spectroscopic atlas of 29 homogeneously observed stars that efficiently samples a wide range of spectral types and luminosity classes. Here, we describe the motivation, sample selection, and observation design for TEMPOS and present the first data release of reduced and coadded COS spectra. We then present initial results on the empirical properties of FUV O-star spectra below 20% $Z_\odot$, including radial velocities, equivalent widths of photospheric lines, and terminal wind velocities ($v_\infty$). We show that $v_\infty$ correlates with host galaxy metallicity across $\sim$5-50% $Z_\odot$ and find tentative evidence of a steeper decline in wind strength below $\sim$10% $Z_\odot$. The combined dataset of FUV spectra and planned releases of photometry and optical spectra from the TEMPOS Treasury program will advance our understanding of both stellar astrophysics and the interstellar medium in the extremely metal-poor regime.
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All authors O. Grace Telford, Christiana Erba, Kristen B. W. McQuinn, Calum Hawcroft, Andreas A. C. Sander, Julia Roman-Duval, John Chisholm, Danielle A. Berg, Varsha Ramachandran, Yong Zheng, Claus Leitherer, Abby Mintz, Evan N. Kirby

Statistical Mechanics

Bootstrapping Classical Systems with Quenched Disorder

Minjae Cho, Yaprak Önder, Eslam Khalaf et al. (+1 more)

We introduce a bootstrap method for deriving bounds on disorder-averaged observables in classical statistical systems with quenched disorder. The three main ingredients of the bootstrap are the positivity of ensembles of probability measures, disorder-averaged equations of motion, and explicit expectation values of random coupling variables. Together, these ingredients lead to a linear programming problem over the space of disorder averages. By further employing the positivity of the two-replica Gram matrix, we also formulate a semidefinite programming problem that produces bounds on two-replica correlators. We demonstrate the method using two examples: the two-dimensional random site-diluted Ising model and the one-dimensional disordered contact process. For the latter example, the bootstrap bounds exhibit a region of multiple kinks that we relate to the Griffiths region, whose finite-size scaling analysis yields a typical correlation length exponent in good numerical agreement with the known value.
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All authors Minjae Cho, Yaprak Önder, Eslam Khalaf, Michael G. Scheer

Astrophysics of Galaxies

ALMA Chemical Evolution (ACE) survey: dust-to-gas ratios in sub-solar metallicity galaxies at cosmic noon

N. N. Geesink, G. Popping, L. A. Boogaard et al. (+11 more)

Dust is a fundamental component of the interstellar medium and provides a key tracer of the baryon cycle that regulates galaxy evolution. The dust-to-gas ratio links metals in the gas phase to those locked into dust grains, making it a sensitive diagnostic of dust production, grain growth, and destruction. We present measurements of the dust-to-molecular-gas ratio ($\rm DGR_{mol}$), for typical star-forming galaxies ($\log M_\star \approx 10$) at sub-solar metallicites, at $z\simeq2-2.5$ from the ALMA Chemical Evolution (ACE) survey. By combining ALMA CO and dust-continuum observations with robust gas-phase metallicity measurements, ACE extends direct dust and molecular-gas measurements to lower stellar masses and lower metallicities than previously available at this epoch, reaching down to $0.4\,Z_{\odot}$. This enables the first constraints on the $\rm DGR_{mol}$–metallicity relation for typical unlensed galaxies at cosmic noon. We find that $\rm DGR_{mol}$ increases with metallicity, with a log-space slope of $1.2 \pm 0.7$, indicating that metal-poor galaxies have systematically lower $\rm DGR_{mol}$ than their more metal-rich counterparts. For the detected ACE galaxies, we measure a mean value of $\log_{10}(M_{\rm dust}/M_{\rm mol})=-2.37\pm0.05$ for a mean metallicity of 12+$\log (\rm O/H) = 8.45 \pm 0.02$. We find agreement with $\rm DGR_{mol}$ in the local Universe at fixed metallicities, indicating that the same dust-growth physics, likely grain growth in the ISM, dominates at metallicities of $8.3 \leq 12+\log(\rm O/H) \leq 8.7$ at cosmic noon. These measurements provide novel empirical constraints for models of dust enrichment and galaxy evolution during the peak epoch of cosmic star formation. Additionally, ACE provides a sub-solar metallicity reference for the calibration of dust continuum as tracer of molecular gas, essential for studying metal-poor, high-redshift systems.
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All authors N. N. Geesink, G. Popping, L. A. Boogaard, I. Langan, A. Pope, R. Popescu, I. Shivaei, M. Solimano, M. Kaasinen, B. Mobasher, D. Narayanan, M. Parente, N. Reddy, R. L. Sanders

High Energy Physics (Theory)

Cosmological Correlators from Resurgence

Yuanzhao Li and Zhong-Zhi Xianyu

Integrating out heavy particles is generally viewed as an irreversible procedure that erases some physical information above the cutoff scale of the resulting effective theory. However, this does not preclude the possibility of recovering the heavy propagating degrees from the low-energy effective theory with appropriate boundary data supplied. A classic example is the recovery of Schwinger pair production from the resummed Euler-Heisenberg effective action. In this work, we perform a similar exercise in a cosmological setting. We show that it is possible to reconstruct the inflationary correlators with massive exchanges, for a discrete heavy spectrum and arbitrary tree topologies, from the low-energy effective theory together with unitarity and Bunch-Davies boundary conditions. The divergent EFT series is resummed in three ways: the boundary differential operators, spectral representation, and Borel resummation, and the exponentially suppressed cosmological collider signals are recovered via analytic continuation. Our construction provides a resurgent relation between the local EFT background and the nonanalytic heavy-particle production, and may also be viewed as an inverse problem for the dispersive bootstrap.
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