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Physics

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Wednesday 26 August

Soft Condensed Matter

Dynamical and conformational behavior of a polymer in a crowded solution

Setarehalsadat Changizrezaei and Colin Denniston

We investigate the structure and dynamics of a polymer in a fluid containing mobile spherical colloidal crowders of radius $R$. We compare and contrast the behavior with Langevin dynamics (LD) and lattice–Boltzmann molecular dynamics (LBMD), the latter incorporating long-range hydrodynamic interactions. Both the colloid size relative to the monomer radius $r$ and the volume fraction $\phi$ are varied to determine how crowding modifies polymer behavior. Increasing volume fraction induces polymer compaction, with the mechanism strongly dependent on the size ratio $R/r$. Small colloids primarily modify the short-wavelength polymer conformation, causing self-avoiding-walk-like behavior to persist to shorter length scales, whereas large colloids reduce the effective long-wavelength Flory exponent, indicating degraded solvent quality consistent with a confinement-blob picture. Polymer diffusion exhibits distinct behavior in LD and LBMD. In LD, diffusion decreases rapidly and depends strongly on $R/r$; a phenomenological scaling involving $\ln(1+R/r)$ captures this size dependence, and additional scaling with $R_g$ reduces scatter, indicating polymer-scale correlations induced by crowding. In contrast, LBMD diffusion follows an effective-medium-like exponential dependence on concentration, governed by hydrodynamic coupling. Rouse-mode analysis identifies three regimes: scaling breakdown at low volume fraction, Zimm-like behavior at intermediate density in both LD and LB, and at high density hydrodynamic screening in LB with confinement-dominated dynamics in LD.
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Tuesday 25 August

Quantum Physics

A Frame-Spread Lower Bound for Quantum Entropy Estimation under Fixed Rank-One Measurements

Xinyu Song

We study estimation of the von Neumann entropy of a $d$-dimensional quantum state from independent outcomes of a fixed rank-one measurement. Let $\kappa_\nu\in[1,d+1]$ denote the normalized trace-zero frame spread; $\kappa_\nu=1$ for exact complex projective $2$-designs. For any fixed rank-one measurement and $n\le c_2d^2/\kappa_\nu$, the minimax mean-squared error is at least $c_1\log^2\{d^2/(\kappa_\nu n)\}$. For bounded frame spread and every fixed $0<a<2$, the minimax risk is of order $\log^2 d$ throughout $n\lesssim d^{2-a}$; hence fixed uniform accuracy requires $\Omega(d^2)$ observations. Existing tomography bounds give bounded risk from $O(d^3\log^3 d)$ observations for finite equal-weight exact designs and the Haar covariant measurement, while the intermediate minimax regime remains open. The results concern a fixed measurement repeated independently across copies; adaptive and collective protocols, and protocols that reuse common randomness across copies, are not covered.
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Geophysics

Higher–order gradient modeling of velocity dispersion in tight sandstones with implications to agroseismology

Rafael Abreu, Ashay Motghare, Chahana Nagesh et al. (+2 more)

Modeling frequency-dependent shear-wave propagation in fluid-saturated porous rocks remains a challenge today because existing poroelastic theories generally rely a large number of constitutive parameters that are difficult to constrain from seismic observations. We propose a dynamically consistent higher-gradient continuum model that reproduces shear-wave dispersion using only three effective material parameters: the macroscopic shear velocity and two characteristic length scales governing higher-order elasticity and gradient inertia. We validate the model against laboratory measurements of glycerin-saturated tight sandstone over a wide range of effective pressures. The inversion reproduces the measured shear-wave dispersion, including positive, weak and negative dispersion regimes. We finally discuss the relationship between the proposed formulation and micropolar theories, the computational challenges and the potential of reduced-order generalized continuum models for seismic exploration, reservoir characterization, and emerging agroseismology applications.
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All authors Rafael Abreu, Ashay Motghare, Chahana Nagesh, Alireza Nadi, Hassam Khan

Physics and Society

When Edge Importance Disagrees: Resistance-Ranked versus Betweenness Pruning on Urban Road Networks

Jianru Shen

Sparsifying large road-network graphs by removing a fraction of their edges is a common way to reduce storage and accelerate spatial queries, but the choice of which edges to remove can quietly degrade the network that remains. We compare three edge-importance criteria for deciding what to prune, namely uniform random removal, low edge-betweenness removal, and low-effective-resistance removal, on 27 urban road networks drawn from OpenStreetMap that span a wide range of sizes and street-network morphologies. At edge-removal ratios from five to thirty percent we evaluate each criterion along three complementary axes: length-weighted routing utility, a topology-only measure given by the retention of the second-smallest eigenvalue of the normalized Laplacian of the largest connected component, and the fraction of an externally defined arterial backbone, taken from OpenStreetMap road classes, that each criterion destroys. The criteria disagree. Low-effective-resistance ranking, which targets electrically redundant edges, preserves connectivity well only below ten percent removal; beyond this level, retention falls below that of random removal in a growing majority of cities, and by thirty percent the method removes a larger share of the arterial backbone than random deletion does. Betweenness removal is consistently the best of the three on all three axes, at every removal ratio. Resistance-based redundancy is therefore not a safe proxy for routing importance when compressing real road networks, and a routing-oriented criterion is the more dependable choice.
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Quantum Physics

The entanglement of purification is not additive

Artus Krohn-Grimberghe

The entanglement of purification $E_P$, introduced by Terhal, Horodecki, Leung, and DiVincenzo in 2002, measures the total correlations of a bipartite state by the entanglement needed to purify it; whether it is additive on tensor powers has been open since its introduction. In 2012 Chen and Winter argued "beyond reasonable doubt", from numerical evidence, that the two-qubit Werner state at singlet fraction $f = 1/200$ is a counterexample, and explicitly left a completely rigorous proof to future work. To our knowledge we give the first rigorous proof: for this state $W$, $E_P^\infty(W) \le 0.9663\ldots < 97/100 < E_P(W)$, hence the entanglement of purification is strictly nonadditive at some finite tensor power. The lower bound is a finite certificate: analytic reductions send the Schmidt spectrum of every purification in the complete complex Stiefel domain to a point satisfying explicit necessary inequalities in a three-dimensional box, and an exact-rational subdivision of that box has 25,383 leaves, each of which either excludes nonphysical points or proves the entropy bound. The upper bound combines an exact symmetric-support endpoint, an explicit feasible isometry, and a convexity theorem for the regularized quantity, closed by two directed rational logarithm certificates. Every computer-assisted certificate reduces to integer comparisons; a dependency-free program verifies all of them from the supplementary artifact.
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High Energy Physics (Phenomenology)

Finite-Volume Non-extensive statistical in QCD phase

M. A. A. Ahmed and H. Zainuddin

Recently, some research has emerged that used the Tsallis statistics in Quantum Chromodynamics (QCD). In Tsallis statistics, the Tsallis parameter $\mathfrak{q}$ reflects long-range interactions, non-Markovian memory, and multifractal boundary effects, linking directly to temperature variance in fluctuating systems, which vanish in the Boltzmann-Gibbs limit. This is our motivation to investigate the thermodynamical variables of a hot and dense system. Within a non-extensive color QCD MIT-Bag Model and using the Tsallis distributions to describe the thermal response functions related to the equation of state. The study focuses on the deconfinement phase transition from a hadronic gas to a quark-gluon plasma in order to analyze the behavior of thermodynamical quantities of the system, such as the energy density, the pressure and the interaction measure at finite volume under Tsallis statistics. Furthermore, the effect of the $\mathfrak{q}$-parameter on the phase transition point is investigated. We find that the transition point is significantly affected by the $\mathfrak{q}$-parameter in the framework of non-extensive statistics.
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Plasma Physics

Physics-Informed Neural Operator Surrogate for 2D Magnetohydrodynamic Reconnection

Kushaal Kumar Pothula and Arunav Kumar

Direct numerical simulation of magnetic reconnection is limited by the scale separation of resistive magnetohydrodynamics. At large Lundquist numbers $S$ the current layer thins as $S^{-1/2}$, forcing fine grids and short time steps that make parameter scans prohibitively expensive. Deep learning neural operators offer an alternative by learning the map between function spaces rather than individual solutions, so that a single trained model returns the state for any parameter and time at inference cost. We have developed a Fourier Neural Operator (FNO) based Physics-Informed Neural Operator (PINO) surrogate for two-dimensional compressible, viscous, resistive reconnection in a wall bounded domain. We condition on the initial state, the Lundquist number, and a continuous query time. Predicting the magnetic flux function makes $\grad\!\cdot\!\bB=0$ exact, direct time queries remove autoregressive error accumulation, and parity-aware spectral differentiation matches the wall treatment of the reference solver. Trained across $10^{3}\le S\le2\times10^{5}$ with two values withheld, the surrogate recovers density, pressure, and guide field to better than $0.2\%$, velocity to $3.2$ to $3.9\%$, the flux function to $1.0\%$, and the spectral current density to $7.5\%$. It resolves the thin, narrow current sheet, Alfvénic jets, and spectral resolution beyond mode cutoff. Our surrogate reproduces the layer-averaged reconnection rate to within $3\%$ through $S=1.1\times10^{4}$, recovering a reconnection time exponent of $0.497$ consistent with Sweet-Parker scaling. When queried zero-shot on the $2049^{2}$ solver mesh, a full trajectory run is on the order of seconds on one GPU against several hours for the DNS, over two orders of magnitude faster, establishing learned operators as a practical route to surveying reconnection across parameter space.
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Quantum Physics

QEVOLVE-Bench: A Seed Benchmark for Quantum SDK Evolution and Repair Planning

Krishna Bhatia and Gautami Sanjay Naik

Quantum software is increasingly built on fast-moving Python SDKs such as Qiskit, PennyLane, and Cirq. When these SDKs evolve, user programs can fail because execution helpers are removed, import paths change, simulator abstractions shift, device names are deprecated, or circuit export interfaces are revised. Although some failures surface as simple missing-symbol errors, repairing them is not only a syntactic problem: developers must identify the replacement workflow, preserve the quantum-facing intent, and validate behavior under pinned framework versions. This paper presents QEVOLVE-Bench, a small executable seed benchmark for quantum SDK evolution. The current public release contains 14 controlled migration tasks across Qiskit, PennyLane, and Cirq. Each task is a self-contained Python project with pinned dependencies, failing and passing outputs, pytest acceptance checks, metadata, and benchmark notes. The artifact also includes a manifest, sanity checker, representative smoke-test logs, Zenodo archive, screencast, and a lightweight QEVOLVE-Agent prototype that converts task evidence into structured repair proposals. QEVOLVE-Bench is intentionally not a statistically powered benchmark; instead, it is an extensible seed artifact that lowers the setup cost for studying automated repair, LLM-based software engineering, and maintenance of quantum SDK-based projects.
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Quantum Physics

Local and Global Risk Bounds for Quantum Entropy Estimation under Projective-Design Measurements

Xinyu Song

We establish a lower bound for estimating the von Neumann entropy from independent outcomes of any fixed rank-one POVM. A rotation-averaged van Trees argument gives a global minimax risk of at least $(d/n)\log^2\{n/(4d)\}$ when $d\ge C$ and $n\ge Cd$, without a projective-design assumption. We also characterize risk on an operator-norm ball of radius $r$ around the maximally mixed state. We allow an approximate second moment: on the trace-zero Hermitian subspace, the measurement frame may differ by $\varepsilon<1$ from the tight projective frame. A clipped estimator based on canonical dual shadows and the complete U-statistic for purity has risk at most $d^3r^2/n+d^4/n^2+d^6r^6$. Lower bounds under the same frame control yield the local minimax rate $d^3r^2/n+d^4/n^2$ when $n\ge Cd^2$ and $r$ lies in an explicit matching range. For every fixed upper bound on $\varepsilon$, approximation changes only the constants, not the powers of $d,n,r$. At the critical radius $r=n^{-1/2}$, the local risk is asymptotically negligible relative to the global risk when $n\log^2(n/d)\gg d^3$. This separation holds for projective 2-designs, including global Clifford measurements in qubit dimensions, and for their uniformly well-conditioned frame approximations. Finite-sample experiments in dimension four illustrate the critical-radius benchmark and the effect of a nonexact frame.
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Quantum Physics · Cross-listed from math.CO

Discrete Concavity of Token-Graph Spectral Radii via Lorentzian Semigroups

Weiqi Jiang

Let $F_k(G)$ be the $k$-token graph of a finite graph with nonnegative edge weights, and let $A_k$ and $D_k$ be its weighted adjacency and degree matrices. For every $-1\leq\vartheta\leq1$, we prove that $k\mapsto\lambda_{\max}(A_k+\vartheta D_k)$ is discretely concave. Complement symmetry then makes this sequence nondecreasing up to the middle level. At $\vartheta=1$ and $\vartheta=0$, this gives the signless-Laplacian and adjacency spectral-radius monotonicity conjectures of Apte, Parekh, and Sud. The spectral result follows from a finite-time theorem: for every $t\geq0$, the heat contents $\binom{n}{k}^{-1}\mathbf{1}^{*}e^{t(A_k+\vartheta D_k)}\mathbf{1}$ are log-concave in $k$. We encode all token levels in one Lorentzian polynomial. A four-variable operator symbol proves preservation by each edge heat gate, and the Lie-Trotter formula passes this preservation to the full semigroup. Large-time growth rates recover the top eigenvalues. The same construction also yields Lorentzian polynomials from top spectral projections. Finally, we show that the local symbol certifies exactly the parameter range $[-1,1]$.
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Quantum Physics

Energy-Constrained Commutator Variance for Weyl Pairs

Hassan Nasreddine

Let $W$ be a representation of the Weyl relations on a separable Hilbert space and write $\mathcal R_W(K)=\{W(f):f\in K\}''$. If the symplectic pairing of $K_1$ and $K_2$ is nonzero, there is a self-adjoint unitary $B\in\mathcal R_W(K_2)$ such that, for every normal state $\rho$, one can choose a self-adjoint unitary $A_\rho\in\mathcal R_W(K_1)$ with $\operatorname{Var}_\rho(-i[A_\rho,B])=4$. Hence the optimized mean-input-energy-constrained coefficient equals $4$ at every admissible energy threshold. For the fixed trigonometric Weyl witness $h$, an exact identity for $4-h^2$ reduces the deficit to a phase-fixed problem for commuting squared Weyl translations. For the one-mode quadratic energy $G_M=\frac12 R^TMR-\frac12\sqrt{\det M}$, with $M>0$ and $u^T\Omega v=\pi$, we prove $4-\gamma_{G_M,E}(h)=\frac{u^TMu+v^TMv+2\pi\sqrt{\det M}}{4E}+O(E^{-2})$. The lower bound holds over all normal states satisfying the mean-energy constraint, and a localized Zak construction attains the same coefficient. For $G=d\Gamma(H_1)$ and witness directions $u,v\in\operatorname{dom}H_1^{1/2}$, the fixed-witness deficit is $\Theta(E^{-1})$ whenever at least one direction lies outside $\ker H_1$; if both directions are zero modes, the constrained supremum equals the endpoint at every positive threshold.
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Quantum Physics

Holomorphic Quantum Error Correction Codes

M.W. AlMasri

We develop a holomorphic representation of quantum error correction codes (QECCs) within the Segal–Bargmann space. By encoding qubits into Schwinger boson modes $(z_{a_j}, z_{b_j})$ subject to a degree-one homogeneity constraint, we derive closed-form differential operator representations for stabilizers, syndrome extraction, and recovery for fundamental codes (three-, five-, seven-, and nine-qubit codes). Quantum errors are characterized as holomorphic perturbations violating this constraint, while syndrome measurement projects onto eigenspaces of commuting differential operators. Restricting to unit-magnitude variables ($|z|=1$) reveals a toroidal space $\T^{2n}$ where error syndromes manifest as discrete translations in winding number space $\Z^{2n}$, and recovery acts as Hamiltonian flows restoring the winding configuration. In the full Segal–Bargmann space, the code space is a holomorphic submanifold of $\CP^{2^n-1}$, with correctable errors as transverse normal directions. Consequently, the Knill–Laflamme condition becomes a Fubini–Study orthogonality condition between the code submanifold and its error-translated images. Topological protection emerges from the $U(1)^n$ fiber bundle structure: global phase noise along fibers is unobservable, while base-space errors require active correction. Finally, we establish a path-integral formulation for semiclassical error correction dynamics and show that geometric entanglement via the Segre embedding naturally quantifies code distance. This framework unifies algebraic, geometric, and topological perspectives on fault-tolerant quantum protocols.
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Quantum Physics

Femtoscopic Correlation Functions in Density Operator Representation

Hao-Nan Liu, Duo-Lun Ge, Zhi-Wei Liu et al. (+2 more)

Femtoscopic correlation functions (CFs) have been increasingly used to extract strong interactions between pairs of unstable particles, but their physical soundness has recently been questioned. To answer this, we formulate CFs at the operator level, with the observed subsystem described by a reduced density operator and subsequent dynamics absorbed into an effective measurement operator. The Koonin-Pratt form is recovered under four well-motivated reductions. The formulation makes explicit that the source-side and interaction-side representations must be consistently matched, and motivates an operational convention in which a measured reference correlation establishes a compatible source–interaction pairing that can be extended to other pairs for CF-to-CF predictions.
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All authors Hao-Nan Liu, Duo-Lun Ge, Zhi-Wei Liu, Jun-Xu Lu, Li-Sheng Geng

Atmospheric and Oceanic Physics

A Station-Based Evaluation of Machine Learning-based Weather Forecasting Models in Northern Norway

Siyan Chen, Lars Uebbing, Eirik Mikal Samuelsen et al. (+5 more)

Recent machine learning weather prediction (MLWP) models have demonstrated remarkable forecasting skill on global reanalysis-based benchmarks. However, their performance remains unclear in challenging environments such as Northern Norway, where narrow fjords and rapidly changing weather result in highly variable local wind conditions. In this case study, we evaluate FourCastNet3 (FCN3), GraphCast, and ECMWF High Resolution Forecast (HRES) for wind speed forecasting using multi-year station observations from Northern Norway, focusing on their relative performance, generalization beyond the training period, and performance under high-wind conditions. Our results show that HRES slightly outperforms FCN3 and GraphCast, with an overall RMSE of 2.89 $\mathrm{m\,s^{-1}}$, compared to 2.96 $\mathrm{m\,s^{-1}}$ for FCN3 and 2.94 $\mathrm{m\,s^{-1}}$ for GraphCast. Notably, the MLWP models maintain comparable performance beyond their respective training periods, with no clear evidence of noticeable degradation. FCN3 performs best under high-wind conditions, although all models substantially underestimate strong winds. Our findings suggest that MLWP has become competitive with NWP for local wind, but further refinements are still needed to capture complex terrain better.
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All authors Siyan Chen, Lars Uebbing, Eirik Mikal Samuelsen, Georgios Leontidis, Arnt-Børre Salberg, Sébastien Lefèvre, Robert Jenssen, Kristoffer Wickstrøm

Fluid Dynamics

Remarks on Fixed- and Variable-Order Fractional-Laplacian Closures for TurbulentDissipation

José I.H López

Two independent attempts, separated by two decades, to encode turbulent dissipation with a fractional Laplacian both converge on the operator order as the signature of the fully developedinertial range: the additive, fixed order model, and the dynamically deforming operator of the Adaptive Fractional Navier Stokes. We show that, despite sharing this fixed point, the two constructions belongto distinct universality classes: Chen operator is a superposition of two fixed order kernels whose relative weight drifts with scale, while AFNS posits a single operator whose order itself flows continuously with the local Reynolds number. We derive a scale resolved observable, the effective spectral order, whose logarithmic anomaly term discriminates between these two mechanisms in principle, and then obtain a sharper, purely analytic verdict from the two dimensional, enstrophy conserving limit: the generative mechanism matching a stable process index to the empirical pair dispersion law has no solution once vortex stretching is kinematically switched off. Whether this dichotomy leaves a residual signature in real quasi two dimensional flows is left as an open experimental challenge.
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General Physics

Finite-domain inverse reconstruction of a Morris–Thorne-type wormhole candidate with a derivative-consistent $f(R)$ curvature sector

Murat Metehan Türkoğlu

We present a finite-domain inverse reconstruction of a Morris–Thorne-type wormhole candidate as a methodological benchmark for constrained numerical model building in modified gravity. The throat condition and local flare-out behaviour are embedded analytically in the shape-function parameterization, while the redshift profile is kept finite by construction. Rather than fitting $f(R)$, $f_R(R)$, and $f_{RR}(R)$ as independent numerical arrays, a positive analytic generator is assigned to $f_{RR}(R)$ and integrated to obtain a derivative-consistent reconstructed curvature sector. The frozen reconstruction is evaluated on 10,019 radial nodes over $r\in[1,10^{5}]$. The corresponding Ricci-scalar trajectory spans $-1.1317\times10^{-9}\leq R\leq1.999999998$ and is weakly non-monotonic, so no inversion $r=r(R)$ is required. On the same finite grid, the reconstructed source variables retain positive pointwise energy-condition margins, the coordinate-radial null-energy integrals are positive both globally and in the near-throat band, and the maximum normalized tidal-curvature ratio is $0.8666<1$. The reconstructed source-side closure diagnostic has a maximum absolute residual of $5.3246\times10^{-5}$. The source closure is phenomenological rather than derived from a unique microphysical matter Lagrangian or a uniquely specified curvature–matter coupling function. Accordingly, the result is not presented as a full field-equation solution of a specified nonminimally coupled $f(R)$ theory, a stability proof, an exterior-matched global spacetime, or an observer-dependent safe-traversal model. It instead provides a finite-domain computational benchmark for auditable inverse reconstruction of Morris–Thorne-type geometries in modified gravity.
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General Relativity and Quantum Cosmology

Crudely Estimated Maximum Mass for a Cosmological Black Hole

Don N. Page

$N$-body simulations by M.~Milosavljevic and D.~Merritt \cite{Milosavljevic:2001vi} suggest that for supermassive black hole binaries in their expected nearly circular orbits, before gravitational wave emission dominates, the inspiral rate causes the dimensionless orbital relative velocity squared, $(v/c)^2$, to increase nearly linearly with time at a rate that is approximately the inverse of 210 Gyr (about 15 times the present age of the universe), nearly independently of the mass of the binary. This by itself would not lead to coalescence by the present time, but when it is augmented by gravitational radiation, it can lead to coalescence for equal-mass black hole binaries up to about $1.4\times 10^{14} M_\odot$, which might then be conjectured to be a very crude upper limit to the mass of black holes in our universe at the present time. This also suggests that the gravitational wave strain from coalescing supermassive black hole binaries should decrease for wave periods greater than about 100\,000 years.
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Instrumentation and Methods for Astrophysics

Engineering of titanium transition edge sensor wafers for the BA4-90/150 receiver of BICEP Array

A.Patel, P. A. R. Ade, Z. Ahmed et al. (+83 more)

BA4-90/150, the fourth receiver to be deployed in the BICEP Array (BA) series, is a dichroic 90/150 GHz instrument targeting the frequency space where sensitivity to the CMB polarization is maximized. The receiver will be deployed in the 2026-2027 austral summer, and is set to position BA to achieve exceptionally precise measurements of cosmic microwave background (CMB) polarization and strengthen constraints on inflationary models. Recent measurements in existing BA receivers suggest that unexpectedly high loop gain in the titanium (Ti) transition edge sensors (TESs) produces excess high-frequency noise that is consequently aliased down into the science band through the time-division multiplexed readout. To reduce the loop gain, we fabricated and tested prototype Ti TES wafers containing 16 modified detector architectures designed to broaden the superconducting transition and reduce the transition steepness (alpha). We present detector performance results, which will directly inform the final integrated wafer now being designed for full receiver commissioning.
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All authors A.Patel, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Detectors · Cross-listed from cs.AI

Agentic AI for operating scientific instruments for nanoscale characterization

Zahra Ayar, Marcos Penedo, Mahdi Mehdikhani et al. (+3 more)

Operating a scientific instrument such as an atomic force microscope (AFM) requires continuous expert decision-making. A trained user defines the experimental intent, translates it into instrument commands, assesses incoming data, adjusts imaging parameters, and post-processes the final image. Existing automation usually addresses only parts of this workflow through hard-coded routines, task-specific controllers, or trained machine-learning models. Here we present an agentic-AI framework that operates the executable part of the AFM workflow using a general-purpose, tool-augmented large language model connected to instrument functions through the Model Context Protocol (MCP). The framework consists of 3 MCP-based agents: AFM Messenger converts natural-language instructions into checked instrument commands; AFM Pilot assesses image quality through a large language model (LLM) and, if necessary, adapts imaging parameters; and AFM Doctor diagnoses image artifacts and applies transparent post-processing from a pre-approved tool set. Because the language model performs image assessment rather than a fixed scalar objective or external optimizer, the same strategy can be applied across sample types and imaging modes without specific retraining. Safe hardware operation is enforced through an ambiguity check layer before execution. Benchmarking against fine-tuned and off-the-shelf tool-using models shows that this guarded execution layer, rather than model capability alone, reduces wrong-command execution to zero. In live experiments on different samples, AFM Pilot matched expert operators in image quality, iteration count, and tuning time, with no significant difference. These results demonstrate a safe route to agentic operation of scientific instruments, where experimental intent remains human-defined while command execution, image-based tuning, and post-processing are delegated to AI agents.
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All authors Zahra Ayar, Marcos Penedo, Mahdi Mehdikhani, Nahid Hosseini, Prabhu Prasad Swain, Georg E. Fantner

High Energy Physics (Theory)

Single-Minus Graviton Amplitudes from Matrix Theory

Alfredo Guevara, Alexandru Lupsasca, Juan Maldacena et al. (+1 more)

The $n$-point single-minus graviton amplitudes are nonzero in a special kinematic region that preserves some supersymmetry when embedded in supergravity. We compute these amplitudes within the BFSS matrix theory by relating them to an index problem considered by A. Sen. More precisely, the single-minus amplitudes are obtained from an index that counts BPS states in the Coulomb branch of four-dimensional ${\cal N}=4$ super Yang-Mills. We explicitly check this relation in a specific kinematic region by computing the index using BPS wall-crossing formulae and matching it to the gravity result. We further employ BPS wall-crossing to show that the index satisfies a tower of $w_{1+\infty}$ soft theorems in any kinematic regime, again matching gravity. Finally, we show that for certain kinematics, the single-minus amplitudes can be realized by scattering a graviton off a plane wave.
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All authors Alfredo Guevara, Alexandru Lupsasca, Juan Maldacena, Andrew Strominger

Mathematical Physics · Cross-listed from math.AG

Spin structures and measures on the moduli space of curves

Paul Norbury

This article arose out of notes for a CIME summer school mini-course in Cetraro. In it we develop differential-geometric constructions on the moduli space ${\cal M}_{g,n}^{\rm spin}$ of smooth spin curves, with particular emphasis on their interpretation in hyperbolic geometry. We relate the locally constant sheaf arising from a hyperbolic spin structure to the corresponding holomorphic sheaf, extending this known relationship to spin curves with Ramond marked points. We use the hyperbolic description to construct characteristic forms and spin measures on moduli spaces of hyperbolic surfaces with geodesic boundary, providing a framework for applying Teichmüller-theoretic methods to their volumes and volume recursions. Finally, we study separately the even and odd components of spin moduli space and find symmetries between their volume contributions which are not apparent from the contributions of individual boundary strata.
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Cosmology and Nongalactic Astrophysics

The optimal redshift for dark energy I: formalism and interpretation

Mustapha Ishak, Travis Seth Rippentrop and Kristian Gonzalez

We introduce the concept of the optimal redshift for dark energy, a statistically motivated redshift at which departures of the dark-energy equation of state (EOS) from the cosmological-constant value are tested most effectively. Within a generalized CPL parameterization, we derive an analytic expression for the optimal redshift by maximizing the separation of the EOS from $w=-1$ relative to the corresponding uncertainty. We establish the optimal redshift relationship to the phantom-crossing and pivot redshifts. As an illustration, we apply the formalism to the dataset combination of DESI DR2 BAO measurements, the DES Year-6 independent BAO measurement, and the recalibrated DES-Dovekie supernova sample. Adopting the null hypothesis $\mathcal{H}_0:w(a_{\rm opt})=-1$, we find a tension of ~$2.8\sigma$ with the cosmological-constant prediction at the optimal redshift, compared with ~$2.6\sigma$ at the pivot redshift, despite the latter having a smaller EOS uncertainty. This behavior reflects the specific design of the optimal redshift to maximize the statistical significance of a departure of the EOS from the -1 value of the $\Lambda$CDM model. We further provide statistical and geometrical interpretations of the optimum. In the CPL parameter space, the pivot corresponds to the projection that minimizes the variance of the equation of state, whereas the optimum maximizes its squared-distance from the cosmological-constant value over its variance. While the optimum is dataset and parameterization dependent, the underlying optimization principle and definition of the optimal redshift can be extended beyond the CPL framework. Future applications to DESI, Rubin LSST, Euclid, Roman Space Telescope, and other Stage-IV dark-energy surveys appear particularly promising.
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Mathematical Physics · Cross-listed from math.AG

From Spectral Curves to Variational Equations: Geometry and Differential Galois Theory of KdV Cnoidal Waves

Juan Jose Morales-Ruiz, Jean Pierre Ramis and Maria-Angeles Zurro

We provide a spectral geometric description of the KdV variational equation around cnoidal waves in terms of two interacting spectral curves.

Strongly Correlated Electrons

Dynamical splitting and a nodal Bose liquid in 2d chiral XYZ model

Tarun Grover

We study a class of Hamiltonians with a structure that we call "dynamical splitting": the Hamiltonian terms can be divided into two sets acting on the same degrees of freedom such that every term in one set commutes with every term in the other, although terms within either set do not all commute. This structure yields an algebraic duality to effective degrees of freedom on which the two parts of the Hamiltonian act disjointly, enabling exact diagonalization on lattices with approximately twice as many spins as usually accessible. We exploit it in the "chiral XYZ model", a geometrically frustrated spin-$1/2$ model on the triangular lattice which was previously introduced as a special limit of a Majorana-Hubbard model. This model also possesses anticommuting noncontractible line symmetries, which enforce an exact, topology-dependent degeneracy between locally indistinguishable states. We first study a $\mathbb{Z}_N$ clock generalization and find, at large $N$, a gapless ground state with three subsystem-symmetry-protected nodal lines. Exploiting dynamical splitting and the subsystem symmetries, we carry out exact diagonalization of the $N=2$ model on lattices up to $9\times9$ spins. The many-body gap and bipartite entanglement provide strong evidence for a gapless state consistent with the large-$N$ nodal structure: the entanglement scales as $L\log L$ and exhibits $1+1$-dimensional CFT-like chord scaling on cylinders. Finally, we study instabilities and proximate phases. In particular, we find evidence that a subsystem-symmetry-preserving deformation drives a finite coupling transition to a gapped phase with $\mathbb Z_2 \times \mathbb Z_2$ topological order.
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Quantum Physics

Multipair-resilient entanglement swapping with complementary linear-optical measurements

Siavash Mirzaei Ghormish and Ryan M. Camacho

Multipair emission is a principal source of false heralds in entanglement swapping with spontaneous parametric down-conversion sources. A conventional Bell-state measurement (BSM) cannot distinguish the desired arrival of one photon from each neighboring source from a mixed-polarization double emission by one source accompanied by vacuum from the other. We show that a cascaded network can resolve this ambiguity by allowing its successive swapping stations to perform different measurements. A direct-basis BSM rejects same-polarization double emissions, whereas a balanced equatorial analyzer, implemented by a four-mode Green Machine (GM), uses two-photon interference to reject mixed-polarization double emissions. At the same time, it recovers same-polarization inter-source events rejected by the BSM as resolved $\phi$-type Bell heralds. Their rejection sets jointly cover both single-source two-photon classes while retaining contributions from both useful inter-source classes. We classify the passive four-mode, number-resolving analyzers satisfying this condition and identify the BSM and GM as canonical balanced representatives. Using a Gaussian-state analysis exact to all orders of multipair emission, we evaluate three-source BSM–GM and four-source BSM–GM–BSM Pure Bell Pair sources under coupling, detector, and channel loss. The three-source network suppresses the leading infidelity, while the four-source network heralds an exact Bell state in the lossless limit, a property that holds for every alternating BSM–GM chain with four or more sources. The fidelity advantage over source-count-matched all-BSM networks persists at every loss level studied, a single-channel rate advantage appears without multiplexing, and spectral multiplexing raises the Bell-pair delivery probability toward the asymptotically deterministic limit.
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Materials Science

Origin of High-Temperature Antiferromagnetic Order in a van der Waals Material

Rabindra Basnet, Hari Paudyal, Gicela Saucedo Salas et al. (+3 more)

While Van der Waals (vdW) itinerant antiferromagnets with high Neel temperatures (TN) are highly desirable for spintronics, they remain relatively scarce. Here, we unravel the physical origin of the unusually high TN (= 250 K) in the newly identified vdW compound (Fe0.65Co0.35)4GeTe2. The substitution of Co in Fe4GeTe2 induces layer-selective Fe-Co ordering and stabilizes a robust antiferromagnetic (AFM) state primarily driven by Co moments. The AFM order is further strengthened by enhanced electronic correlations of quasi-localized Co 3d-states at the Fermi level, giving rise to an itinerant-localized duality of the 3d electrons. This interplay generates strong magnetic correlations well above TN and stabilizes low-temperature spin canting with a possible nontrivial Berry curvature. Our results establish (Fe0.65Co0.35)4GeTe2 as a rare material bridging fundamental magnetic interactions with potential applications in AFM spintronics.
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All authors Rabindra Basnet, Hari Paudyal, Gicela Saucedo Salas, Nicholas P. Butch, Durga Paudya, Ramesh C. Budhani

Earth and Planetary Astrophysics

Discovery and Characterization of the TOI-4468 Planetary System: A Transiting Hot Jupiter With a Lone Nearby Outer Companion

Joseph R. Livesey, Benjamin J. Hord, Juliette Becker et al. (+28 more)

We report the discovery of two planets, a hot Jupiter and a nearby outer sub-Neptune, orbiting the star TOI-4468. This system is unique among the current exoplanet census in that it features a close outer companion to a hot Jupiter without an accompanying inner companion. By jointly fitting radial velocity measurements taken with the NEID spectrograph and transit photometry from TESS and several ground-based observatories, we constrain the orbital periods, masses, and radii of these two planets. We confirm the planetary nature of the hot Jupiter TOI-4468 b ($R = 1.01 R_J$, $m = 0.54 M_J$, $P = 2.77$ days). We also validate the outer planet TOI-4468 c ($R = 0.28 R_J$, $P = 7.01$ days) statistically, incorporating constraints from ground-based observations. We also identify, but cannot confirm, an additional radial velocity signal which may be due to an outer giant in this system with an orbital period of 624 days. From the observed geometry of this system, we argue that it must never have encountered an early secular resonance that is thought to excite the mutual inclination of other hot Jupiter/outer companion systems. We discuss the possibility of an undetected inner companion, as well as potential implications for hot Jupiter formation.
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All authors Joseph R. Livesey, Benjamin J. Hord, Juliette Becker, Andrew Vanderburg, Joseph E. Rodriguez, Elise Koo, Chelsea X. Huang, Gudmundur Stefánsson, Karen A. Collins, Ivan A. Strakhov, Zijun He, Maxwell A. Kroft, Robert Aloisi, Khalid Barkaoui, Fabian Rodriguez Frustaglia, Alyssa Jankowski, Kinga Kasprzyk, Judith Korth, Coleman Nelson, Hannu Parviainen, Adam Popowicz, Manfred Raetz, Richard P. Schwarz, Eva Stafne, Keivan G. Stassun, Thomas G. Beatty, Paul Foster, Thomas MacLean, Devansh Mathur, Lizhou Sha, Melinda Soares-Furtado

Statistical Mechanics

Finite relaxation protocols with minimal dissipation

Ben Ansbacher, Harrison Hartle, Abhishek Yadav et al. (+2 more)

Work extraction from nonequilibrium systems is a major challenge across biological, chemical, physical, and engineering systems. Idealized protocols generally require a quasistatic relaxation stage in which the Hamiltonian is gradually adjusted through a continuum of intermediaries. Here, we consider protocols restricted to a finite number $N$ of intermediary Hamiltonians, consisting of a sequence of quench-relax steps. We determine the sequence of quenches that minimizes the dissipated work, which can be expressed in terms of a recurrence involving the Lambert function. The optimal sequence converges to the Fisher-Rao geodesic, saturating known leading-order dissipation bounds at large $N$. We obtain lower bounds on work extraction from a nonequilibrium distribution as a function of its Fisher-Rao distance to equilibrium. We extend and apply the framework in two simple models: (i) an optical trap experiment, showing that the optimal intermediary distribution can be bimodal even for unimodal initial and final distributions, and (ii) an enzyme-catalyzed reaction, showing that that accounting for relaxation time in addition to dissipation can favor barrier-lowering.
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All authors Ben Ansbacher, Harrison Hartle, Abhishek Yadav, Jan Korbel, David H. Wolpert

Fluid Dynamics · Cross-listed from cs.GR

Hamiltonian Two-Way Coupling of Nonlinear Waves and 3D Flows

Sinan Wang, Ruicheng Wang, Taiyuan Zhang et al. (+5 more)

Simulating large-scale free-surface water by coupling a localized 3D fluid solver to a cheaper 2D surface model has long faced a mismatch in wave dynamics: efficient 2D wave models used in graphics are typically either linear or non-dispersive. These models are fast, simple, and accurate for calm, small-amplitude seas, but coupling them with strongly nonlinear 3D solvers produces visible reflections and artifacts at the 2D–3D interface. We address this problem by introducing a nonlinear and dispersive 2D wave model based on the canonical Zakharov formulation. Its Hamiltonian structure, in which the surface elevation and surface potential form a canonical pair ($\eta$, $\psi$) governed by the wave energy, enables a canonically consistent two-way coupling scheme, allowing information to pass smoothly across the 2D–3D interface. Our 2D solver reduces mean wave-height error by 1.7–5$\times$ over SWE, BEM, and Airy baselines while running more than $10^3\times$ faster than BEM; it achieves greater nonlinear accuracy and coupling fidelity than SWE and Airy, with minor losses in speed and stability. Coupling it with a 3D Navier–Stokes solver yields a full system that suppresses visible seam artifacts across a range of experiments, including dispersion-matching and Kelvin-wake tests, and runs over 4$\times$ faster than a pure GPU NB-FLIP simulation on the same domain.
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All authors Sinan Wang, Ruicheng Wang, Taiyuan Zhang, Fan Feng, Jinjin He, Yuchen Sun, Zhiqi Li, Bo Zhu

Quantum Physics

Separating Quantum Indistinguishability Obfuscation from Falsifiable Assumptions

Mohammed Barhoush, Tomoyuki Morimae and Ramis Movassagh

Quantum indistinguishability obfuscation (qIO) aims to make a quantum circuit unintelligible while preserving its functionality. It serves as a foundational primitive for advanced applications, such as witness encryption (WE) for QMA, non-interactive zero-knowledge arguments for QMA, and attribute-based encryption for BQP. Despite its importance, constructing qIO from standard assumptions remains a major open problem. In this work, we prove that the security of WE for QMA cannot be based on any falsifiable cryptographic assumption via a restricted class of quantum black-box reductions. Because qIO for null quantum circuits implies WE for QMA, this also separates null-qIO from falsifiable assumptions. Since almost all standard cryptographic assumptions are falsifiable, our result presents a barrier to basing qIO on standard cryptographic assumptions. The reductions we rule out are restricted: the reduction must query the adversary classically, non-adaptively, at the same security parameter, and only on honestly generated ciphertexts. Moreover, our impossibility applies only to WE with classical ciphertexts, and therefore does not rule out qIO with obfuscators whose output is a quantum state. Ruling out more general reductions, as well as more general forms of WE and qIO, remains open. Our impossibility relies on the existence of a QMA-QCIP[2] gap problem, an average-case assumption postulating a QMA language that cannot be verified with two messages of classical communication.
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