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Thursday 4 June

Quantum Physics

On the Cryptographic Structure Required for Verifying Qubits

James Bartusek and Itay Shalit

Classically testing for the presence of anti-commuting operators on a quantum device is a critical tool underpinning recent progress in classical verification of quantum computation. While such tests can be based on cryptographic assumptions, known constructions rely on highly structured assumptions, e.g. trapdoor claw-free functions. In this work, we seek to explain this state of affairs by constructing strong cryptography from (certain forms of) classical tests of anti-commutation. In particular, we formulate the notion of a test of non-commutation (ToNC), an interactive protocol between a quantum prover and classical verifier in which the prover's final-round response is obtained by measuring one of two binary observables $P_0,P_1$ depending on the verifier's challenge bit $c$. We prove that, for a broad range of parameters, ToNC implies classical-communication key agreement (KA), and ToNC combined with one-way functions implies oblivious transfer (OT). Along the way, we develop tools for and provide the first known results on hardness amplification for post-quantum KA and OT, where communication is classical but adversaries may be quantum. In particular, we prove the following results of independent interest. - Post-quantum hard-core measure theorem: For any efficiently sampleable high-min-entropy distribution $D$ over pairs $(x,b)$ such that quantum circuits have advantage at most $\delta$ in predicting $b$ from $x$, there exists a sub-distribution $M\preceq D$ of density $(1-\delta)$ on which $b$ is nearly optimally quantum-hard to predict. - Post-quantum interactive XOR lemma: Given any classically-interactive protocol, if quantum adversaries have advantage at most $\delta$ in guessing a private challenger bit $b$, then two sequential repetitions reduce the advantage for predicting the XOR of the challenger bits $b_1\oplus b_2$ to at most $\delta^2+\rm{negl}(\lambda)$.
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Wednesday 3 June

Optics

Upconversion Dual-comb Passive Spectroscopy of Mid-IR Incoherent Light

Mingchen Liu, Matthew Heyrich, Sichong Ma et al. (+1 more)

We introduce cross-comb correlation spectroscopy, which correlates signals from asynchronous sum-frequency sampling of mid-IR incoherent light with two near-IR combs. We experimentally measure the frequency of phase-randomized mid-IR light with 100-MHz resolution using near-IR detectors.
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All authors Mingchen Liu, Matthew Heyrich, Sichong Ma, Scott A. Diddams

Quantum Physics

A Modular Approach to Succinct Arguments for QMA

James Bartusek, Jiahui Liu and Giulio Malavolta

Succinct argument systems are of central importance to modern crytpography, enabling the efficient verification of computational claims. In the classical setting, Kilian (STOC 92) established that any probabilistically checkable proof for NP can be transformed into a succinct argument system for NP using only collision-resistant hash functions. In the quantum setting, recent works have established the feasibility of (classically-verifiable) succinct arguments for QMA, capturing statements that require *quantum* proofs. However, known constructions all rely on the highly structured assumption of learning with errors (LWE), which stands in stark contrast with the unstructured assumptions that suffice for NP. In this work, we develop a new framework that broadens the cryptographic foundations of succinct arguments for QMA. We assume the existence of (i) an oblivious state preparation (OSP) protocol, which in turn can be constructed from *plain* trapdoor claw-free functions, and (ii) collapsing hash functions, the quantum analogue of collision-resistance. In particular, we obtain the first succinct, classically-verifiable argument system for QMA which does not rely on the hardness of LWE. Our construction proceeds in two steps. First, we design a *round-efficient* classically-verifiable argument system for QMA based only on the assumption of OSP. Second, we introduce a *generalized communication compression compiler*, which, assuming collapsing hash functions, transforms any $T$-round interactive protocol into one in which the communication size is bounded by $T \cdot \poly(\secp)$ for some fixed $\poly$ independent of the original size of each message. Our compiler extends a quantum rigidity-based communication compression technique of Zhang (QCrypt 25), and may be of independent interest.
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General Relativity and Quantum Cosmology

A Landscape of Cosmological Decoherence

S. Shajidul Haque and Bret Underwood

Current observations constrain primordial perturbations to be adiabatic, approximately Gaussian, and nearly-scale invariant. However, a generic mixed state satisfying these constraints has additional unconstrained degrees of freedom, which can be parameterized by the purity of the state and its momentum variance. This allowable parameter space reveals a unified geometric landscape of mixed states, allowing us to map and relate distinct models of decoherence and their respective pointer bases. Within this landscape we show that decoherence models that "classicalize" – in the sense of admitting a regular, positive-definite Glauber-Sudarshan $P$-function – must actively inject momentum into the system, exceeding that of the vacuum. The enhanced momentum sources the decaying mode of the curvature perturbation, backreacting on the Newtonian potential and radiation-era geometry. While this mode decays away fast enough to preserve the temporal coherence of the CMB acoustic peaks, requiring the potential to remain within linear perturbation theory places a model-independent bound on the momentum variance generated by any model of decoherence. This bound is definitively violated by decohered thermal states with more than $14$ e-folds of inflation, while a strong dependence on the number of e-folds restricts amplitude-basis decoherence to fewer than roughly $64$ e-folds of inflation in order to stay in the linear regime. Altogether, we present a unifying framework for evaluating the quantum-to-classical transition of the early universe.
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Chemical Physics

SC3: The Multi-Solvent Solubility Challenge and Benchmark

Vansh Ramani, Har Ashish Arora, Dhairya Kuchhal et al. (+4 more)

Solubility prediction is a standard benchmark in computational chemistry, yet multi-solvent models which reportedly approach the experimental-noise ceiling (i.e. the aleatoric limit) are not yet reliable enough to be deployed. We argue that this gap is partly artefactual: published benchmarks differ in curation policies, evaluate on count-weighted RMSE that hides failure on tail-heavy solvent distributions, and treat the widely cited 0.6-0.8 log S inter-laboratory figure as the aleatoric ceiling even though it reflects worst-case, not expected, disagreement. We introduce SC3, a multi-solvent solubility benchmark built on BigSolDB v2.1 with three contributions: (i) a reproducible curation pipeline yielding 101,535 measurements over 1,327 solutes and 206 solvents, with a recalibrated aleatoric floor of 0.106 log S-roughly 6 times tighter than the conventional figure; (ii) nested Gold/Silver/Bronze consensus tiers with per-point standard deviation, three leakage-checked splits, and a multi-solvent metric suite (PS-RMSE, Z-RMSE); and (iii) a 31-model benchmark across six families, whose best Bronze PS-RMSE sits at 5 times the aleatoric limit, and we observe this is a gap unclosed by any deep alternative tested. We perform three follow-on analyses: data scaling, transfer from quantum-chemistry solvation energies, and feature-level attribution, which demonstrates that calibrated per-point uncertainty is a reusable infrastructure for diagnosis beyond point prediction.
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All authors Vansh Ramani, Har Ashish Arora, Dhairya Kuchhal, Sergei Tatarin, Lev Krasnov, Sayan Ranu, Tarak Karmakar

Quantum Physics · Cross-listed from cs.AI

CARVE-Q: Quantum-Proposed, Classically Certified Interactive Driving Repair

Yifan Wang

The critical question after a correct driving veto is not only whether a maneuver is unsafe, but whether the blocked interaction admits a lawful, auditable, and responsibility-bounded repair. Prediction and game-theoretic planners can suggest plausible cooperation, yet they do not return a proof that the repair respects hard rules, right-of-way, cost allocation, and ego fallback. We introduce CARVE, Certified Affordable Repair of Vetoed maneuvers via Envelopes, a certificate architecture for prediction-free interactive repair. Given a vetoed maneuver, CARVE constructs a finite repair lattice and emits a structured certificate recording the binding rule, selected joint repair, right-of-way-scaled cooperation envelope, responsibility-weighted cost split, and ego-only fallback. This certificate view reveals the algorithmic bottleneck: multi-owner repair induces a product lattice $M = \prod_j |\mathcal{A}_j|$. We therefore introduce CARVE-Q, a verifier-shielded quantum-AI search layer that applies quantum minimum finding only to this black-box lattice while leaving all safety authority classical. In the conservative verifier-oracle model, exact classical minimum finding requires $\Theta(M)$ queries in the worst case, whereas Durr-Hoyer/Grover minimum finding uses $O(\sqrt{M})$ oracle queries with high probability. We prove verifier-shielded certificate soundness, priority non-elicitation, black-box query separation, and finite-precision reversible-oracle constructibility. We then demonstrate state-vector minimum finding on CARVE repair oracles up to 65,536 assignments and validate certificate preservation on Lanelet2-grounded INTERACTION replay with 100% right-of-way respect, 100% blame consistency, and zero priority false positives. The result is a trust-bounded quantum-AI pattern for certified autonomy: quantum proposes; CARVE certifies.
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Instrumentation and Methods for Astrophysics

Narrow spectral artifact investigation and mitigation in LIGO data from the fourth LIGO-Virgo-KAGRA observing run

E. Goetz, A. Neunzert, A. M. Knee et al. (+259 more)

We present efforts to identify, characterize, and mitigate narrow spectral artifacts in LIGO detector data during the fourth LIGO-Virgo-KAGRA observing run. Narrow spectral artifacts in gravitational-wave detectors are non-astrophysical noise sources that can degrade searches for narrowband persistent gravitational waves. Identifying and, where possible, mitigating these noise sources is one of the core efforts of the LIGO Detector Characterization group. Key software tools have been updated and new tools deployed for the fourth LIGO-Virgo-KAGRA observing run to facilitate investigations and data monitoring. We discuss these tool upgrades, and present several identified narrowband artifacts that have been successfully investigated and mitigated in LIGO data. Regardless of whether artifacts are mitigated or not, narrowband persistent gravitational-wave searches require information on which frequency bands contain non-astrophysical artifacts. Minimizing the number of bands containing non-astrophysical artifacts is essential to maximize the potential for discovery of a new class of gravitational-wave signals.
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All authors E. Goetz, A. Neunzert, A. M. Knee, A. Calafat, X. Fan, J-R. Mérou, K. A. Pham, T. Starkman, N. Aggarwal, Z. Bhalla, P. Baxi, J. Bayley, Y. Bu, J. B. Carlin, P. Charlton, X. Chen, G. Cheng, T. Cheunchitra, N. Christensen, A. Claveus, C. M. Compton, M. W. Coughlin, F. De Lillo, L. Dunn, S. E. Dwyer, A. Effler, T. A. Ferreira, B. Finkel, P. Goodarzi, A. E. Granados, H. Guo, C. Hsiung, K. Janssens, S. Kandhasamy, K. Kawabe, Y.-M. Kim, T. Kimpson, R. Krismer, M. Lalleman, Y. S. C. Lee, N. K. Y. Low, J. C. Martins, H. Middleton, C.-A. Miritescu, D. Nykamp, J. O'Leary, A. Renzini, K. Riles, A. Romero-Rodríguez, J. R. Sanders, R. M. S. Schofield, D. Singh, D. Singh, R. Slocum, Q. Song, J. Suresh, S. Suyamprakasam, J. D. Tasson, A. Tripathee, A. F. Vargas, A. Wang, K. Wu, J. Yee, J. Yi, Z. Zhang, R. Abbott, I. Abouelfettouh, R. X. Adhikari, A. Ananyeva, S. Appert, S. K. Apple, K. Arai, N. Aritomi, S. M. Aston, M. Ball, S. W. Ballmer, D. Barker, L. Barsotti, B. K. Berger, J. Betzwieser, D. Bhattacharjee, G. Billingsley, S. Biscans, C. D. Blair, N. Bode, E. Bonilla, V. Bossilkov, A. Branch, A. F. Brooks, D. D. Brown, J. Bryant, C. Cahillane, S. R. Callos, H. Cao, E. Capote, F. Clara, J. Collins, G. Connolly, R. Cottingham, D. C. Coyne, R. Crouch, J. Csizmazia, A. Cumming, L. P. Dartez, D. Davis, N. Demos, E. Dohmen, K. L. Dooley, J. C. Driggers, A. Ejlli, T. Etzel, M. Evans, J. Feicht, R. Frey, W. Frischhertz, P. Fritschel, V. V. Frolov, M. Fuentes-Garcia, P. Fulda, M. Fyffe, D. Ganapathy, B. Gateley, T. Gayer, J. A. Giaime, K. D. Giardina, J. Glanzer, R. Goetz, A. W. Goodwin-Jones, S. Gras, C. Gray, D. Griffith, H. Grote, T. Guidry, J. Gurs, E. D. Hall, J. Hanks, J. Hanson, M. C. Heintze, A. F. Helmling-Cornell, N. A. Holland, D. Hoyland, H. Y. Huang, Y. Inoue, A. L. James, A. Jamies, R. Jaume, A. Jennings, W. Jia, D. H. Jones, H. B. Kabagoz, S. Karat, S. Karki, M. Kasprzack, D. Keitel, N. Kijbunchoo, P. J. King, J. S. Kissel, K. Komori, A. Kontos, R. Kumar, K. Kuns, M. Landry, B. Lantz, M. Laxen, K. Lee, M. Lesovsky, F. Llamas Villarreal, M. Lormand, H. A. Loughlin, R. Macas, M. MacInnis, C. N. Makarem, B. M. Mannix, G. L. Mansell, R. M. Martin, K. Mason, F. Matichard, N. Mavalvala, N. Maxwell, G. McCarrol, R. McCarthy, D. E. McClelland, S. McCormick, T. McRae, F. Mera, E. L. Merilh, F. Meylahn, R. Mittleman, D. Moraru, G. Moreno, A. Mullavey, M. Nakano, T. J. N. Nelson, J. Notte, J. Oberling, T. O'Hanlon, R. Oram, C. Osthelder, D. J. Ottaway, H. Overmier, W. Parker, O. Patane, A. Pele, H. Pham, M. Pirello, J. Pullin, V. Quetschke, K. E. Ramirez, K. Ransom, J. Reyes, J. W. Richardson, M. Robinson, J. G. Rollins, C. L. Romel, J. H. Romie, M. P. Ross, B. I. Rotimi, K. Ryan, T. Sadecki, A. Sanchez, E. J. Sanchez, L. E. Sanchez, R. L. Savage, D. Schaetzl, M. G. Schiworski, R. Schnabel, E. Schwartz, D. Sellers, T. Shaffer, R. W. Short, D. Sigg, A. M. Sintes, B. J. J. Slagmolen, C. Soike, S. Soni, V. Srivastava, L. Sun, D. B. Tanner, M. Thomas, P. Thomas, K. A. Thorne, M. R. Todd, C. I. Torrie, G. Traylor, A. S. Ubhi, G. Vajente, J. Vanosky, A. Vecchio, P. J. Veitch, A. M. Vibhute, E. R. G. von Reis, J. Warner, B. Weaver, R. Weiss, C. Whittle, B. Willke, C. C. Wipf, J. L. Wright, V. A. Xu, H. Y. Yamamoto, L. Zhang, M. E. Zucker

Astrophysics of Galaxies

A Kinematic Study of Wolf-Rayet Stars at the Galactic Center I: Binary Candidates and Constraints on the Binary Fraction

Rory O. Bentley, Tuan Do, Andrea Ghez et al. (+13 more)

We report the binary fraction of Wolf-Rayet (WR) stars within 0.5~pc of the Galactic center obtained through the longest time-baseline (1994-2024) kinematic study of this population of stars. The new radial velocity ($v_{z}$) data we present is primarily from the W. M. Keck Observatory, with additional $v_{z}$ measurements from Gemini North Observatory. When combining our new $v_{z}$ measurements with literature measurements, we find $v_{z}$ variations suggesting the presence of a companion for five out of 27 WR stars, of which two are newly identified here (IRS~13E4, S8-181), along with three previously detected binaries (IRS~16SW, IRS~16NE, S4-258). Based on our experimental sensitivity and expected properties of the underlying population, we infer the binary fraction of the WR stars in the Galactic center to be 0.56$\pm$0.18. This is consistent with previous photometric studies of the young stars in the Galactic center, and with the binary fraction of field WR stars. When our results are combined with the results of previous photometric work, we find a binary fraction of 0.69$\pm$0.17 for the WR stars in the Galactic center.
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All authors Rory O. Bentley, Tuan Do, Andrea Ghez, Devin Chu, Anna Ciurlo, Abhimat K. Gautam, Zoë Haggard, Matthew W. Hosek Jr., Kelly Kosmo O'neil, Rebecca Lewis-Merrill, Gregory D. Martinez, Anna Pusack, Shoko Sakai, Jessica R. Lu, Mark R. Morris, Keith Matthews

Quantum Gases

A universal and efficient hybrid digital-analog fermionic quantum simulator

Hao-Tian Wei and Kaden R. A. Hazzard

We present a universal framework to harness fermionic ultracold atom platforms for quantum simulation, showing how variational algorithms on existing hardware can simulate many-body systems well beyond the hardware's native Hamiltonian. Our analysis provides evidence that one can quantum simulate the ground-state properties of a broad class of gapless target Hamiltonians of local observables in a quantum evolution time that grows polynomially with the inverse relative error, $T\sim O(\mathrm{poly}(1/\epsilon))$ up to logarithmic corrections, offering an exponential speedup over naïve classical algorithms such as exact diagonalization. We provide numerical evidence and theoretical argument that this holds for energy density, density-density, and spin-spin correlations in three qualitatively distinct models – the repulsive Hubbard model; a Hubbard model augmented with nearest-neighbor attractive interactions, which introduces the phenomenon of pairing; and the Hofstadter-Hubbard model, which introduces a gauge field and fractional quantum Hall physics. This work demonstrates quantum simulation using current fermionic platforms far beyond the models natively implemented in the hardware.
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High Energy Astrophysical Phenomena

Complex Analysis of Askaryan Radiation: UHECR Reconstruction

J. C. Hanson and D. Ibanez-Rodriguez

Ultra-high energy cosmic rays (UHECR) can produce relativistic cascades that emit radio-frequency (RF) pulses in the 0.1-1 GHz bandwidth via two distinct effects: the geomagnetic effect, and the Askaryan effect. The geomagnetic effect occurs when the magnetic field of the Earth causes cascade charges to form a transverse current that radiates linearly polarized radiation aligned with the Lorentz force direction. The Askaryan effect is caused by the net negative charge excess in the cascade that radiates linearly polarized radiation along the Cherenkov cone. When UHECR cascades enter solid, RF transparent matter at altitudes where the cascade develops, Askaryan radiation created in the solid medium can propagate to RF detectors. The Askaryan Radio Array (ARA) at the South Pole has observed 13 UHECR candidates in precisely this fashion. We present an analytical model that confirms the events are UHECRs. The model includes Askaryan radiation created within the ice sheet and the ARA RF channel response. The coherently summed waveforms (CSWs) from the UHECR candidates match our model with correlation coefficients between 0.69 and 0.86, and with minimal fractional power differences. Finally, we demonstrate how to obtain the Askaryan E-field from our model, and that it matches the results from the ARA collaboration.
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General Relativity and Quantum Cosmology

Black Bounce Solutions from a Self-Interacting 3-Form Field in General Relativity

Francisco S.N. Lobo and Manuel E. Rodrigues

We construct a new class of black-bounce solutions sourced by a self-interacting 3-form field minimally coupled to general relativity and a scalar field. The 3-form field, which naturally arises in string theory, supergravity, and cosmological models, provides the anisotropic effective stresses required to sustain regular geometries that interpolate smoothly between black holes and traversable wormholes. By exploiting the Hodge duality between a 3-form and a 1-form in four dimensions, we reduce the field equations and obtain exact solutions through the direct integration of the coupled equations of motion. In particular, the solutions are derived from algebraic combinations and manipulations of the Einstein, scalar, and 3-form field equations, starting from a complete action principle, without employing the usual reconstruction procedure in which the metric ansatz is imposed a priori and the matter sector is reconstructed afterwards. This approach reveals two distinct classes of solutions. The first one yields a globally phantom scalar field and a metric function with a characteristic arctangent dependence, reducing to the Schwarzschild-(anti) de Sitter spacetime in the limit of vanishing 3-form coupling. The second class produces a constant 3-form Lagrangian and, remarkably, a partially canonical scalar field, namely phantom only near the bounce and canonical outside the event horizon, a feature previously attainable mainly in modified theories of gravity, but which emerges here within pure general relativity. Both families are globally regular, as confirmed by the finiteness of the Kretschmann scalar, and exhibit an asymmetric horizon structure inherited from the 3-form energy-density distribution. These results demonstrate that the 3-form black-bounce framework is both mathematically consistent and observationally viable.
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General Relativity and Quantum Cosmology

Improved unimodular black holes with self-consistent renormalization scale identification

Christopher D. Carone

We consider the renormalization group improvement of unimodular black hole metrics with an identification of the renormalization scale as a function of the radial coordinate that is self-consistent in that it depends on parameters of the improved metric. Considering identifications that are motivated by minimality and dimensional analysis, we arrive at a number of non-singular unimodular black hole metrics. We determine the black hole mass gaps and note the qualitative similarities to other non-singular black hole metrics that have been discussed in the literature.
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High Energy Physics (Theory)

Dirichlet walls and the end of time

Hanako Helton, Gary T. Horowitz and Donald Marolf

We study evolution in Einstein-Hilbert gravity with Dirichlet boundary conditions imposed on a finite surface. We argue that there are open sets of initial data where such evolutions terminate at finite times due to singularities that reach the boundary. In any dimension, the simplest such examples occur in cosmologies. However, in 2+1 dimensions we also show that Dirichlet walls initially outside a BTZ black hole can fall through the horizon, and that this also leads to generic singularities. A similar construction in higher dimensions leads to trapped surfaces that reach the wall, though the end result of such evolutions is more difficult to study.
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Strongly Correlated Electrons

Complexity of the Laughlin wave function from the Dyson-orbital perspective

J. M. Zhang and Y. Liu

The Fermi sea is a simple and common concept in physics. However, a related and equally simple concept – the Dyson orbital – is far less discussed in physics, especially in textbooks. Yet, Dyson orbitals offer a valuable tool for characterizing the complexity of a fermionic wave functions, particularly in distinguishing between Fermi-sea-like and non-Fermi-sea-like states. As a preliminary application, we examine the Laughlin wave function and find the fortunate fact that the Dyson orbitals can be determined analytically. Further numerical data provides quantitative evidence that the Laughlin wave function describes a strongly correlated, non-Fermi liquid state.
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High Energy Physics (Theory)

The spectrum of the bosonic ambitwistor string revisited

José M. Figueroa-O'Farrill and Girish S. Vishwa

We revisit the calculation of the spectrum of the bosonic ambitwistor string, understood as the BRST cohomology or, equivalently, as the semi-infinite cohomology of the $\mathrm{BMS}_3$ Lie algebra relative to the centre with values in a particular module. We work in momentum space, which allows us to work algebraically and interpret the BRST cohomology as inducing representations of the Poincaré group. In agreement with the existing literature, we find that all the cohomology resides in the massless sector, but a careful representation-theoretic analysis of the spectrum reveals, in addition to the usual massless sector of the closed bosonic string (dilaton, metric and Kalb–Ramond field), also a massless vector. We devote a large part of the paper to describing the cohomology at a massless momentum $p$ as a module over the stabiliser $H$ of $p$ in the Lorentz group, a task which is made difficult due to $H$ not acting reducibly when $p\neq 0$. This allows us to conclude that the spectrum is not unitary, forbidding the interpretation of the extra massless vector as a Maxwell field.
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Statistical Mechanics

Dissipation-coherence tradeoff for stochastic oscillations

Jie Gu

Autonomous noisy oscillations in biochemical and mesoscopic systems require nonequilibrium driving and therefore dissipation. A striking conjecture by Oberreiter, Barato, and Seifert (OBS) proposes a universal lower bound on the entropy produced per oscillation period in terms of the coherence number of the slowest oscillatory mode. Here we derive a weaker but rigorous lower bound that preserves the OBS structure while introducing a mode-uniformity factor that quantifies how evenly the oscillatory eigenmode is distributed across states in the steady-state inner product. The result makes explicit that an eigenvalue-only prefactor can fail when the dominant oscillatory mode is localized. We also outline a proof-of-principle route for estimating this factor from low-dimensional data under single-mode dominance and sufficiently informative measurements, and derive an eigenvector-free corollary using only the smallest stationary probability. Translation-invariant Markov jump processes on a ring provide a symmetry-protected class with $\eta=1$, so the refinement reduces to the OBS form; the drift–diffusion limit on a circle saturates the bound.
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Strongly Correlated Electrons

Ideal Quantum Geometry for Fractional Chern Insulators

Jennifer Cano and Jie Wang

Quantum geometry plays a fundamental role in many aspects of condensed matter physics. Among its central objects are the Berry curvature and the quantum metric – quantities that, while distinct, are intertwined through geometric constraints. In this article, we survey recent progress in understanding when and how this bound is saturated, with particular emphasis on the emergence of momentum-space holomorphicity of Bloch states. These developments highlight a profound connection between certain ideal Bloch bands and the Hilbert space structure of the lowest Landau level. We elucidate this relationship through a review of quantum Hall physics in both homogeneous and spatially varying magnetic fields, and conclude by exploring its implications for the search for fractionalized phases in emerging platforms, including moiré materials.
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Cosmology and Nongalactic Astrophysics

On the potential for inhomogeneities to mimic an evolving dark energy

Hayley J. Macpherson and Georgios Valogiannis

In this work we explore the ability of inhomogeneities to result in an apparent dynamical evolution of dark energy. The idea that inhomogeneities may alter the expansion history of the Universe is not a new one. However, with the current excitement surrounding the inferred time-evolution of the equation of state of dark energy by the Dark Energy Spectroscopic Instrument (DESI), combined with Cosmic Microwave Background (CMB) and supernovae observations, it is worth revisiting. We use numerical relativity simulations of large-scale structure formation combined with nonlinear general-relativistic ray tracing to infer dark energy parameters for synthetic observers. We adopt a simplified set-up to roughly mimic the observational properties of the DESI plus supernovae and CMB constraints. In our small sample of 20 observers, we find one who infers parameters consistent with the DESI values at 2-$\sigma$ significance. While it is rare in our limited sample size, we show that it is at least possible for observers to infer significant non-LCDM parameters when their universe is well-described by a cosmological constant on average.
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Physics Education

Missing Data on Physics Exams: Demographic Patterns, Course-Level Predictions, and Implications for Equity

Cassandra Paul, David J. Webb and Mary Kate Chessey

In a previous quantitative retrospective study we showed that different demographic groups of students leave different numbers of problems blank on physics exams, leading to inequities in course outcomes. In that work we argued that there were good reasons to treat these blanks as missing data, rather than indicators of a lack of understanding. In this paper, we refine this analysis and show more detailed breakdowns of uncollected test item responses by race/ethnicity and first generation college student status, coming to the same conclusion: test item responses are uncollected for students with different ethnic and racial backgrounds at different rates, and these patterns are not exclusive to low-performing students. We also correct an error from our previous work, finding here that there is no significant gender difference in uncollected test item responses. Finally, we provide a more robust analysis of course level data illustrating that blanks are a variable controlled at the course level rather than the student level, providing more evidence for the use of a course deficit model (rather than a student deficit model) when examining equity disparities, and also suggesting that there are plausible means for instructors to minimize uncollected test item responses, and therefore reduce or even eliminate the bias associated with this missing data. We provide a couple suggestions for faculty who want to minimize the impacts of blanks.
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Mesoscale and Nanoscale Physics

Realistic quantum device data synthesized by consumer AI and how to identify it

S. M. Frolov and O. V. Kravchenko

With the advance of generative artificial intelligence (AI) synthetic texts and images have become commonplace. These capabilities offer clear benefits, but have also raised a number of ethical concerns that often have to do with misrepresenting AI outputs as genuine material. A lesser known capability of generative AI is to perform the basic analysis, processing and even synthesis of numerical data. This raises the question of whether AI can be used to imitate experimental data that an expert would consider scientifically meaningful and on par with data in the figures of peer-reviewed manuscripts? In this paper, we focus on synthesizing data inspired by well-known experiments done frequently on quantum electronic devices. This field is related to information technologies such as spintronics and quantum computing, and is considered data-rich and data-driven. We demonstrate that it is possible to generate dramatic signals associated with iconic effects such as quantum bit control, Majorana fermions, Josephson effects, quantum dots and wires using widely available ChatGPT. We find that because some of the clearest data from quantum devices can be expressed in terms of relatively basic mathematical models, AI does not need to learn on the specialized body of data. Instead, knowledge of the physics equations and of the basic features of experimental signals can go a long way towards building a realistic dataset. We also demonstrate that real data can be augmented by AI, and that AI can mimic the noise of common scientific instruments. To help assure that published data come from experiments and are not synthesized by AI, we recommend sharing large volumes of the primary data. While it is straightforward for AI to mimic a few sets of data, consistently generating long measured sequences poses sufficient barriers to the proliferation of undisclosed synthetic data.
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High Energy Physics (Phenomenology)

Diffractive open charm photoproduction in ultraperipheral lead-lead and proton-lead collisions at the LHC

Vadim Guzey, Gian Michele Innocenti, Anna M. Staśto et al. (+1 more)

We calculate diffractive $D^{0}$ photoproduction in ultraperipheral lead–lead (Pb–Pb) collisions at the Large Hadron Collider (LHC) within the recently developed G$\gamma$A–FONLL framework, where photon–lead diffraction is modeled using nuclear diffractive parton distributions obtained in the leading twist shadowing approach and the photon fluxes include corrections for independent electromagnetic dissociation accompanying the hard photoproduction process. We then use the predicted diffractive cross section to quantify the coherent diffractive contribution rejected by the $Xn0n$ neutron-tagged event selection adopted in the first measurement of $D^0$ photoproduction in Pb-Pb collisions at the LHC, which requires neutron emission from only one of the two lead nuclei. In this work, we also extend the G$\gamma$A–FONLL framework to proton–lead ($p$–Pb) UPCs and present predictions for inclusive and diffractive $D^{0}$ photoproduction at the LHC. In this case, the dominant configuration is photon emission from the lead ion followed by photon–proton scattering, and the diffractive contribution is evaluated using proton diffractive parton distributions constrained by HERA data.
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All authors Vadim Guzey, Gian Michele Innocenti, Anna M. Staśto, Mark Strikman

Materials Science

Interplay of non-local transport and local scattering during electron thermalization and spatial equilibration in laser-excited metals

Markus Uehlein, Tobias Held, Christopher Seibel et al. (+2 more)

Ultrafast laser excitation of metals induces electronic nonequilibrium both in space and locally in the energy distribution. The subsequent dynamics are governed by the interplay between non-local transport and local scattering of hot electrons, yet combined microscopic descriptions of these processes remain sparse. Here, we disentangle the influence of these processes on thermalization using a reformulation of the Boltzmann transport equation in energy space that consistently describes both spatial equilibration and scattering through full collision integrals. Our results reveal that transport accelerates the apparent thermalization observed at the irradiated surface by removing athermal carriers, while the same spatial redistribution delays complete equilibration of the full electron system. We analyze the experimentally accessible energy-dependent dynamics at the front and back surface and find that the dominant process varies, depending on both position and on the energetic window. Overall, our work improves the understanding of the interplay of electronic nonequilibrium processes occurring in optically thick laser-driven systems with relevant implications for future electronic applications.
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All authors Markus Uehlein, Tobias Held, Christopher Seibel, Sebastian T. Weber, Baerbel Rethfeld

General Relativity and Quantum Cosmology

Curvature conditions for generalized singularity theorems

Jeremías Daín and Gustavo Dotti

We study the curvature conditions introduced in [Class. Quant. Grav. 27, 152002] to predict focal points for trapped spacelike submanifolds in spacetimes of arbitrary dimensions, with the purpose of generalizing Penrose's singularity theorem to compact trapped submanifolds (CTMs) of codimension higher than two. We find that these conditions do not apply in general but may apply for specific CTMs. As a result, higher codimension CTMs may still work as singularity predictors, although the possibility that they intersect the domain of outer communications cannot be ruled out using standard arguments.
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Earth and Planetary Astrophysics

Ultraviolet-Driven Atmospheric Degeneracies Challenge Conventional Biosignature Frameworks for Terrestrial Planets with Ultracool M Dwarf Hosts: An Archean-Analog TRAPPIST-1 e Case Study

Evan L. Sneed, Edward W. Schwieterman, Sarah R. Peacock et al. (+2 more)

The ultraviolet (UV) spectrum of a host star strongly shapes the atmospheric composition and potential biosignatures of its planets. This relationship may be especially important for the planets orbiting TRAPPIST-1, an M8V star with substantially different published UV spectral energy distributions (SEDs). Using a one-dimensional photochemical model, we quantify how these SED uncertainties affect Archean Earth-like atmospheric analogs on TRAPPIST-1 e with and without biospheres. We emphasize Earth's Archean epoch because it represents a planet in transition from primarily abiotic to biotic controls on atmospheric composition. Different stellar spectra produce order-of-magnitude variations in the predicted abundances of CH4, CO, O2, and O3, thereby generating photochemical degeneracies that complicate the interpretation of potential biosignatures. For one TRAPPIST-1 UV reconstruction, a modeled atmosphere with abiotic deposition velocities and volcanic CH4 input can sustain simultaneous spectrally discernible CH4 and O3, yielding a potential false-positive disequilibrium biosignature. For all SEDs tested, surface deposition consistent with microbially-mediated CO consumption allows substantial O2 and O3 accumulation even without oxygenic photosynthesis, implying that oxygen-rich atmospheres around ultracool M dwarfs may not uniquely trace oxygenic ecosystems. Across our models, CO remains a powerful discriminator between abiotic and biotic surface boundary assumptions. Overall, we show that the abundances of co-occurring CH4, CO, and O3 can vary by orders of magnitude, depending on the assumed UV SED, creating ambiguities in interpreting atmospheric biosignatures, though observability may be challenging with current capabilities. Reducing UV spectral uncertainties is therefore essential for assessing surface-to-atmosphere interactions of temperate exoplanets around ultracool M dwarfs.
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All authors Evan L. Sneed, Edward W. Schwieterman, Sarah R. Peacock, Nicholas F. Wogan, Timothy W. Lyons

Geophysics

Learning and Inferring Multiphase Flow Dynamics in Porous Media using Scientific Machine Learning: Application to the "FluidFlower" CO2 Injection Experiment

Hannah Lu, Lluis Salo-Salgado, Yun-Ting Chou et al. (+2 more)

Accurate prediction and parameter identification of multiphase flow in porous media remain central challenges in geological carbon dioxide storage due to strong nonlinearities, high-dimensional parameter spaces, and limited observational data. We present a machine learning framework that integrates surrogate modeling and Bayesian inference to enable efficient forward prediction and inverse parameter estimation for CO2-brine flows in geological media. The approach is demonstrated using the "FluidFlower" experimental rig, a controlled laboratory system that provides high-resolution, time-resolved observations of CO2 migration in heterogeneous porous media. A convolutional neural network surrogate is trained on high-fidelity numerical simulations to learn the evolution of CO2 saturation and dissolved CO2 concentration fields over a wide range of multiphase flow properties. The trained surrogate is embedded within a Markov chain Monte Carlo framework for parameter inference conditioned on experimental observations. Results show that the surrogate accurately captures large-scale CO2 plume migration, dissolution dynamics, and multiphase flow behavior while providing orders-of-magnitude acceleration compared to traditional simulations. Embedding the surrogate within a Bayesian framework enables computationally tractable exploration of the parameter space and reveals both identifiable and non-identifiable parameter combinations that produce similar plume behavior. By leveraging spatially and temporally resolved full-field observations, the framework substantially improves agreement between simulations and experiments compared to previous manual calibrations based on limited plume-scale metrics. Analysis using progressively increasing observation horizons further shows that observations become more informative once the plume interacts with geological features such as faults and sealing layers.
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All authors Hannah Lu, Lluis Salo-Salgado, Yun-Ting Chou, Ehsan Haghighat, Ruben Juanes

Plasma Physics

Implementation and Verification of Toroidal Resistive Wall Boundary Conditions in the PIXIE3D MHD code using a Boundary Integral Method

Samuel Jones, Luis Chacón, Jason Hamilton et al. (+2 more)

We present the complete formulation of resistive wall boundary conditions in axisymmetric toroidal geometries as implemented in the PIXIE3D extended magnetohydrodynamics (MHD) code, along with a complete suite of analytical verification examples that demonstrate correctness in the implementation. The formulation centers around a thin wall approximation and a Boundary Integral Method to solve for the magnetic scalar potential in the immediately surrounding vacuum. This requires specialized quadrature rules derived from existing literature to handle the numerical integration of singular and hypersingular integrands (the Green's function of Laplace's equation and its derivatives), for which we provide the nodes and weights. Further, we describe an extension to the formalism to include the effect of a perfectly conducting second, outer wall exterior to the resistive (plasma-facing) wall and separated by vacuum, and exterior to the computational plasma mesh proper. Lastly, we describe an extension to include the effect of current-carrying coils also defined exterior to the plasma mesh in the resistive wall boundary condition treatment. For most aspects of the method, we present self-contained verification examples using analytic solutions in axisymmetric toroidal geometries (with both 2D and 3D plasmas) and show it to be accurate to second order. We demonstrate the algorithm with a vertical displacement event (VDE) using the ITER tokamak geometry.
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All authors Samuel Jones, Luis Chacón, Jason Hamilton, Dan Barnes, Andrés Yagüe-López

Computational Physics

Newton's Identity in Finite-Bead Fermionic Partition Function

A. Chaudhary and J. Valenzuela

For non-interacting fermions in a harmonic trap, the partition function at any discrete number of imaginary time slices (or beads) and for any choice of short-time propagator admits an exact recursion relation derived directly from the contracted determinant form of the path integral. This finite-bead recursion is distinct from earlier continuum-limit recursions, which do not apply to the discrete time partition functions. By identifying a direct correspondence between this recursion and Newton's identity, application of a closed-form result from the theory of partitions provides an exact expression for the one-dimensional $n$-fermion finite-bead partition function. From this, the Thermodynamic and Hamiltonian energies and specific heats are analytically calculated for any $n$, $N$, $\tau$, and propagator choice.
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High Energy Physics (Theory)

Optical properties of gravitating strings

Marcos Silva and Azadeh Mohammadi

We study the optical properties of gravitating Abelian-Higgs cosmic strings and compare them with those of the idealized infinitely thin string. We analyze the structure of the corresponding vortex solutions, characterizing their width, curvature profile, and approach to the ideal string limit. By investigating photon propagation in the string spacetime, we show that the finite core of the vortex gives rise to distinctive observational signatures absent in the ideal string approximation, including a characteristic triple-imaging configuration, strong demagnification of the central image, and a nontrivial Shapiro time delay between external and internal images. We determine how these effects depend on the parameters of the Abelian-Higgs model and show that the sign of the time delay is controlled by the ratio of the gauge boson mass to the Higgs boson mass, causing the string core to behave as either a temporal shortcut or a temporal barrier. Our results demonstrate that lensing effects can reveal information about the vortex formation and internal structure.
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General Relativity and Quantum Cosmology

On spherically symmetric Berwald vacuum solutions in Finsler gravity

Nicoleta Voicu, Diana - Maria Birla and Christian Pfeifer

Berwald-Finsler spacetimes are Finsler spacetimes that are closest to pseudo-Riemannian geometry, as their canonical nonlinear connection defines an affine connection on spacetime. In this paper, we find the first exact, non-Ricci flat, $SO(3)$-symmetric Berwald solutions to the Finsler gravity vacuum equation. To this aim, we first select from all spherically symmetric Berwald spacetimes, the only class that admits flat Finsler spacetime structures, making it particularly suitable for future investigations of asymptotic flatness. Then, for this class, we completely solve the Finsler gravity vacuum equation, and find three families of solutions. In particular, we show that in Finsler geometry there exist $SO(3)$-symmetric, vacuum solutions that are not Ricci-flat. These solutions are promising candidates to model the gravitational field around compact objects, beyond their Riemannian description.
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Mesoscale and Nanoscale Physics

A nanoscale magnetic spectrum analyzer based on qubit dressed states

Jan Rueschkamp, Shantam Ravan, Daniel Fernandez et al. (+6 more)

Magnetic field fluctuations on nanometer length scales manifest in a diverse range of phenomena – electron and spin dynamics in materials and devices, quantum many-body systems, and molecular chemistry. Measuring these phenomena requires sensors with a challenging combination of broad spectral bandwidth, high sensitivity, and nanoscale spatial resolution. Nitrogen-vacancy (NV) centers, atom-like quantum sensors in diamond, possess the requisite sensitivity and nanoscale sensing volume, but are typically limited in bandwidth by the practical speed of the applied quantum control sequence. Here, we overcome this limitation by exposing the NV qubit to a microwave dressing field during a dynamical decoupling sequence, which both amplifies and frequency-mixes target signals at arbitrary frequencies into the detection band of the dynamical decoupling protocol. We demonstrate this approach by using NV centers to detect both coherent and noisy nanoscale spin wave dynamics in a magnetic yttrium-iron-garnet (YIG) thin film over a broad frequency range. Our technique generalizes to other qubit platforms, providing a versatile framework for nanoscale spectroscopy across diverse physical and chemical systems.
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All authors Jan Rueschkamp, Shantam Ravan, Daniel Fernandez, Nazar Delegan, F. Joseph Heremans, David D. Awschalom, Ronald L. Walsworth, Nikola Maksimovic, Amir Yacoby