High Energy Physics (Phenomenology)
Finite-$t$ and target mass corrections for the short-distance expansion of quasi(pseudo) GPDs
Vladimir M. Braun and Hua-Yu Jiang
We calculate the “kinematic” corrections $t/P_z^2$ and $m_N^2/P_z^2$ to the short distance expansion of gauge-invariant nonlocal
quark-antiquark operators sandwiched between nucleon states with different momenta. Here $t$ is the momentum transfer, $m_N$ is the nucleon mass and $P_z$ is the momentum component in the direction of the
quark-antiquark separation, which is assumed to be large. These
matrix elements can be calculated in
lattice QCD and, at leading twist, expressed in terms of moments of the generalized parton distrubutions (GPDs). Our results allow one to control one of principal uncertainties in such calculations and extend their region of applicability to larger momentum transfers, which is important in the quest to access the three-dimension image of the
proton. The calculated corrections turn out to be significant for a realistic
lattice QCD setup.
Read the full abstract ▾
Quantum Physics
Quantum Cut Sparsifiers
Arpon Basu, Joshua Brakensiek, Pravesh K. Kothari et al. (+1 more)
In this paper, we continue a line of research initiated by Basu, Brakensiek, and Putterman [2026] studying the sparsifiability of
Hamiltonians. We focus particularly on the sparsifiability of the widely-studied
Quantum Cut (QC)
Hamiltonians. Our main result is that in an $n$-
qubit system, any $n$-
qubit QC
Hamiltonian can be sparsified to $\widetilde{O}(n /\varepsilon^2)$ many terms while preserving the energy of every state up to a factor of $1 \pm \varepsilon$. Our result can be interpreted as giving an importance sampling scheme for the edges of an arbitrary graph $G$ such that the Kikuchi graph at level $\ell$ of the sampled graph is a spectral approximation to the Kikuchi graph of $G$. Importantly, the same sampling scheme works simultaneously for all $\ell$. The natural approach of leverage score sampling, analyzed via
matrix concentration inequalities, yields a polynomially worse bound in our setting because the underlying
matrices have dimension $\sim 2^n$. Instead, our approach relies on decomposing the action of these
matrices into invariant subspaces. Then, by using an operator-valued inequality of Alon and Kozma [Ann. Henri Poincaré, 2020], itself building on an octopus inequality of Caputo, Liggett, and Richthammer [J. AMS, 2010], we extend our sparsification technique to all expander graphs. We then invoke expander decomposition to extend our sparsifier to all graphs.
Read the full abstract ▾
All authors Arpon Basu, Joshua Brakensiek, Pravesh K. Kothari, Aaron Putterman
Quantum Physics
Sambe Approach to Floquet-Lindblad Open Quantum Systems
Andriani Keliri and Marco Schirò
We study driven and open
quantum systems described by a time-periodic Lindblad master equation. In closed systems, the stroboscopic dynamics can always be described by an effective time-independent Floquet
Hamiltonian; this idea is the basis of Floquet engineering. However, in the presence of dissipation, the existence of an effective time-independent Floquet Lindbladian is not guaranteed due to the non-
unitary nature of the
evolution. Using Floquet theory, we construct a well-defined time-independent Floquet Lindbladian in an extended Sambe-Liouville space, transforming the initial time-dependent problem to a static and non-Hermitian
eigenvalue problem. For harmonic driving, we introduce a
matrix continued fraction method to nonperturbatively resum multiphoton processes and construct an effective Floquet Lindbladian acting only on the physical Liouville space. Compared to other high-frequency expansions, this method has the advantage of providing the whole infinite series expansion at once. Using a resolvent formalism, we show how to obtain a spectral Floquet representation of correlation functions of an open
quantum system. As an application, we consider a dissipating two-level system in a linearly polarized field and calculate its resonance fluorescence spectrum. Furthermore, we consider a parametrically driven
quantum dot with pump and loss for which we calculate its spectral function and current-voltage characteristics.
Read the full abstract ▾
Astrophysics of Galaxies
ATLAS. I. A Scaling Relation of LRDs between Broad H$\alpha$ and Bolometric Luminosities: Enhanced Broad H$\alpha$ Emission Relative to Low-$z$ Type 1 AGN
Hiroto Yanagisawa, Masami Ouchi, Tomokazu Kiyota et al. (+6 more)
We investigate the demography of little red dots (LRDs) using 37 objects at $z\sim3$-$7$ with JWST/NIRSpec PRISM and grating spectra compiled from various JWST programs. We focus on spectroscopic quantities of the broad H$\alpha$ luminosity $L_\mathrm{H\alpha,broad}$ (and the broad H$\beta$ luminosity $L_\mathrm{H\beta,broad}$ where available) and the bolometric luminosity $L_\mathrm{bol}$ represented by modified blackbody emission, avoiding quantities contaminated by host-
galaxy emission (e.g., total H$\alpha$ luminosity). We identifiy a tight scaling relation between $L_\mathrm{H\alpha,broad}$ and $L_\mathrm{bol}$, supporting the interpretation that these emissions are primarily powered by the central engine. Interestingly, the $L_\mathrm{H\alpha,broad}$-$L_\mathrm{bol}$ scaling relation of LRDs is enhanced by a factor of $\sim40$ in $L_\mathrm{H\alpha,broad}$ relative to that of low-$z$ Type 1 AGN. A similar trend is found in the $L_\mathrm{H\beta,broad}$-$L_\mathrm{bol}$ relation, although the enhancement in $L_\mathrm{H\beta,broad}$ is smaller, only by a factor of $\sim10$. We explore the physical origin of these enhancements and find that Cloudy photoionization modeling within the classic locally optimally-emitting cloud (LOC) framework can explain them through an increase in the covering factor from $\sim20$% (Type 1 AGN) to $\sim100$% (LRDs), together with an increase in the hydrogen column density from $N_\mathrm{H}\sim10^{23}\,\mathrm{cm}^{-2}$ to $\gtrsim10^{24}\,\mathrm{cm}^{-2}$, with a preferred gas density of $\sim10^{10}\,\mathrm{cm}^{-3}$, successfully reproducing the modified blackbody emission. Such a nearly unity covering factor without requiring a gas density increase may result from a significant increase in the BLR filling factor or size, corresponding to a “stuffed BLR" or “
giant BLR," respectively.
Read the full abstract ▾
All authors Hiroto Yanagisawa, Masami Ouchi, Tomokazu Kiyota, Yuta Kageura, Makoto Ando, Yuichi Harikane, Minami Nakane, Yoshiaki Ono, Yui Takeda
Quantum Physics
A Bell-State Extension of Loop-Back Quantum Key Distribution
Luis Adrián Lizama-Pérez
Bidirectional
quantum key distribution (QKD) protocols face persistent challenges related to classical disclosure, confinement of the signal space to predictable subspaces, and limited detectability under substitution or
entanglement-swapping attacks. In this work, we present a Bell-state extension of the Loop-Back QKD architecture that improves efficiency and detectability while preserving its defining feature of a simplified, measurement-free remote terminal. The protocol employs entangled Bell states together with deterministic local Pauli encoding at the remote node. A central element is that Alice privately prepares and knows the initial Bell state, which serves as a hidden reference enabling her to interpret the Bell-state transition induced by Bob, while preventing an adversary from reconstructing the encoding without access to this reference. By exploiting both intra- and inter-family Bell transitions, the scheme expands the effective signal space beyond the subspace restrictions of earlier two-way protocols. Alice performs a Bell-state measurement to deterministically infer Bob's operation without any basis sifting. Although the traveling subsystem remains locally maximally mixed, concealing the initial Bell family amplifies disturbance under separable substitution strategies, yielding an intrinsic detection probability of approximately 3/4 per round. From an efficiency perspective, the protocol lifts the intrinsic post-selection limitation of single-
qubit Loop-Back schemes: the effective throughput is bounded only by the Bell-state measurement success probability, reaching up to 50% in linear-optical implementations. These features make the proposed scheme particularly suitable for mobile or edge-based QKD scenarios, where passive remote nodes must operate under high loss and limited interaction times.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Frequency-resolved decoherence spectroscopy of a semiconductor charge qubit coupled to a high-impedance resonator
Ekaterina Al-Tavil, Wonjin Jang, David J. van Woerkom et al. (+10 more)
Superconducting resonators coupled to
semiconductor quantum dots provide a powerful platform to investigate light-matter interaction and decoherence mechanisms in solid-state
quantum systems. Here we study a hybrid
circuit quantum electrodynamics architecture consisting of a GaAs double-
quantum-dot charge
qubit capacitively coupled to a high-impedance, frequency-tunable SQUID-array resonator. By tuning the
qubit transition frequency over the range $\omega_\mathrm{q}/2\pi \sim 3$-$6$ GHz, we perform frequency-resolved decoherence spectroscopy of the charge
qubit across a broad energy window. Time-resolved measurements enable us to disentangle relaxation and pure dephasing processes and to identify distinct decoherence regimes as a function of
qubit frequency. We find that at lower frequencies ($\leq 4.5$ GHz) dephasing dominates the
qubit linewidth, whereas at higher frequencies energy relaxation becomes the leading contribution. The measured frequency dependence of the relaxation rate exhibits a cubic scaling, consistent with charge-
qubit decay dominated by coupling to a piezoelectric
phonon bath and providing frequency-resolved access to the corresponding
phonon-induced spectral density. Our results show that hybrid
semiconductor–superconducting
circuits can serve as sensitive spectroscopic tools to probe microscopic decoherence mechanisms relevant for a wide range of hybrid
quantum devices.
Read the full abstract ▾
All authors Ekaterina Al-Tavil, Wonjin Jang, David J. van Woerkom, Ville Maisi, Stefano Bosco, Jan A. Krzywda, Jeroen Danon, Christian Reichl, Werner Wegscheider, Thomas Ihn, Klaus Ensslin, Andreas Wallraff, Pasquale Scarlino
Astrophysics of Galaxies
NEXUS: Abundance, Environments, and Spectral Diversity of Little Red Dots from the NIRSpec MSA Sample
Zhiwei Pan, Ming-Yang Zhuang, Yue Shen et al. (+6 more)
We present a comprehensive study of Little Red Dots (LRDs) at 2.3 < z < 7.4 using NIRCam photometry and NIRSpec MSA/PRISM spectra from the ongoing NEXUS program. Photometric selection combining several commonly adopted methods yields a high completeness of about 85% for LRD selection over this
redshift range and for a flux limit of F444W < 26. The overall purity is about 60%, with contamination from emission-line
galaxies and normal active
galactic nuclei (AGNs), as well as
dwarf stars. Most (>90%) of the spectroscopically confirmed LRDs have robust broad-line detection. Our spectroscopic sample of 36 LRDs displays the full range of spectral diversity of LRDs. It includes objects with extreme Balmer breaks similar to the LRD "Cliff", as well as objects with moderately reddened rest-optical continua that can be fit with low-temperature blackbody components in the recent BH* model framework. The broad H$\alpha$ emission is correlated with the continuum emission at 5100 Angstrom, suggesting common origins for these emission components; the narrow [O III] emission, however, is poorly correlated with the optical continuum. We do not find evidence of
redshift evolution in these spectral properties. The space density of LRDs declines toward z about 2, opposite to the trend for normal AGNs, although low-luminosity LRDs at z about 2-4 may be more abundant than currently probed by ground-based searches. The clustering of LRDs suggests that they live in dark matter
halos of several times $10^{11}\ h^{-1}$
solar masses, albeit with large uncertainties. Overall, these results are consistent with recent observations of LRDs and with the emerging picture of accreting SMBHs enshrouded in dense gas envelopes as the origin of LRDs.
Read the full abstract ▾
All authors Zhiwei Pan, Ming-Yang Zhuang, Yue Shen, Feige Wang, Jenny E. Greene, Adam J. Burgasser, Junyao Li, Zachary Stone, Padmavathi Venkatraman
Atomic Physics
Long-term laser frequency stabilization with an FPGA-controlled scanning cavity
R. Forti, R. Panza, A. Muzi Falconi et al. (+5 more)
We present an FPGA-based implementation of a scanning transfer cavity lock (STCL) for
laser frequency stabilization, allowing for the simultaneous stabilization of multiple
laser sources with respect to a single reference
laser by means of a continuously scanned Fabry-Perot cavity. By exploiting the FPGA architecture to simultaneously perform cavity scanning, peak detection, and feedback actuation, we minimize latency and allow independent control loops for several
lasers within a single device, offering direct scalability. The system performance is analyzed through heterodyne measurements from short ($<1\,$s) to long ($\sim20\,$hours) timescales. The end-to-end locking performance is validated through atomic spectroscopy of ytterbium atoms in a magneto-optical trap, demonstrating sub-MHz absolute frequency stability over several hours for the stability transfer across $\sim 150\,$nm in the visible-wavelength range. Importantly, we demonstrate a novel fast-scanning approach based on acousto-optic modulator (AOM) frequency modulation, enabled by the low detection latency of our FPGA implementation. This increases significantly the effective locking bandwidth and reduces the intrinsic noise of the system with respect to standard piezo-actuated scanning of the cavity length, allowing to reach sub-$100\,$kHz long-term stability and offering perspectives for
laser-line narrowing. Owing to its modularity, low cost and ease of implementation within the open-source PyRPL firmware package for the STEMlab Red Pitaya platform, our architecture offers a compact and flexible alternative to existing STCL and locked-cavity implementations, providing a practical approach to the operation of a state-of-the-art cold-atom experiment without relying on any atomic references for
laser stabilization.
Read the full abstract ▾
All authors R. Forti, R. Panza, A. Muzi Falconi, S. Sbernardori, A. Vardé, M. Marinelli, A. Carini, F. Scazza
Quantum Physics
Optomechanically controlled response amplification for enhanced quantum sensing
Javid Naikoo
We show that strongly amplified dynamical responses in cavity optomechanical systems can be harnessed for enhanced
quantum sensing. By tuning the optomechanical interaction to a regime of enhanced susceptibility, weak perturbations produce disproportionately large changes in the system response, leading to substantially improved estimation precision. Using Gaussian estimation theory, we demonstrate that the
quantum Fisher information exhibits a divergent scaling as the perturbation strength decreases, implying a corresponding suppression of the estimation error. We further show that heterodyne detection of the output cavity field yields the classical Fisher information with the same asymptotic scaling as the
quantum Fisher information, demonstrating that the enhanced sensitivity is accessible with a standard measurement protocol. These results identify amplified optomechanical dynamics as a controllable resource for
quantum enhanced sensing and metrology.
Read the full abstract ▾
High Energy Physics (Phenomenology)
Finite Massless Pentaboxes
Gustavo Figueiredo, David A. Kosower and Pavel P. Novichkov
We characterize the integrand numerators that give rise to locally finite or evanescent Feynman integrals for the massless pentabox. We provide compact expressions for the generators of the corresponding ideal in terms of an adapted momentum basis and also in terms of Gram determinants. We also compute the integrals corresponding to the lowest-rank numerators in terms of polylogarithms using the HyperInt package, and in terms of pentagon functions.
Read the full abstract ▾
High Energy Physics (Experiment)
Atmospheric Neutrino Oscillations: the Full Picture
Philipp Eller
We present the first combined oscillation analysis of recent atmospheric
neutrino datasets, featuring data from Super-Kamiokande, IceCube-DeepCore, and KM3NeT/ORCA together with reactor data from Daya Bay. Such combinations have long been considered infeasible outside experimental collaborations; we demonstrate that a unified physics model can simultaneously describe all
datasets with no significant parameter tensions. Fitting 839\,048 events across 1536 ins with 91 parameters, our combined analysis yields competitive measurements of the
neutrino mixing parameters, and prefers the Normal over the Inverted Mass Ordering at $3\sigma$ significance.
Read the full abstract ▾
High Energy Physics (Phenomenology)
PTA-Compatible Domain Walls at LISA and Taiji: Bayesian Reconstruction and Multiband Inference
Satyabrata Datta and Rome Samanta
Domain walls provide an excellent fit to
Pulsar Timing Array (PTA) data. A distinctive feature of the associated gravitational-wave (GW) spectrum is its ultraviolet (UV) tail, which can extend into the mHz band and thereby make cross-detection with space-based interferometers such as LISA and Taiji possible. In this work, we explore the PTA-compatible parameter space of domain-wall models and study both the reconstruction prospects at LISA and Taiji and the information gain achievable through joint PTA–LISA and PTA–Taiji analyses. We find that LISA and Taiji can probe an extended region of parameter space yielding an ultraviolet tail in the milli-Hz band, even in the presence of astrophysical foregrounds. Within the PTA-supported region, however, the genuinely informative regime is more restricted and concentrated toward the high-signal edge. In the space-based-detector-only analysis, the posterior is strongly degenerate in the underlying model parameters, although one principal parameter combination can be reconstructed with high precision where the signal is sufficiently strong. When PTA-informed priors are incorporated, the additional information gain is localized to the same high-signal region: there the space-based data produce a non-negligible posterior update and strongly suppress the catastrophic LISA(Taiji)-only degeneracy, while the final posterior often retains an axis ratio comparable to that of PTA alone. Our analysis is based on a 10-dimensional
Bayesian inference with two domain-wall signal parameters and eight nuisance parameters describing instrumental noise and astrophysical foregrounds. We use 49 grid injections for the LISA-only and Taiji-only analyses and 65 injections from the PTA-supported region for the joint analyses, with Clough–Tocher interpolation used to construct posterior heat maps.
Read the full abstract ▾
Quantum Gases
Analog quantum simulation of chiral magnetic dynamics using optical superlattices
Sabhyata Gupta and Luis Santos
We propose an analog
quantum simulation of
chiral magnetic dynamics using ultracold atoms in an optical superlattice. The massive Schwinger model in the zero gauge coupling limit maps onto the Rice-Mele model, with the
fermion mass and topological angle encoded in the superlattice parameters. We study the real-time dynamics of the vector current following two quench protocols that drive continuous chirality injection and chirality relaxation. Simulations with realistic superlattice parameters and experimental noise demonstrates clear mass dependence of the current dynamics in both protocols, robust against experimental imperfections. The vector current may be directly measurable via single-bond-resolved detection, establishing cold atom superlattices as a viable platform for probing non-
equilibrium chiral phenomena.
Read the full abstract ▾
Quantum Physics
Leveraging Landau-Zener-Stückelberg interference for accelerating diabatic quantum annealing
Matthias Werner, Matías Jonsson, Artur García-Sáez et al. (+2 more)
Diabatic
quantum annealing with variationally optimized schedules can exhibit exponential speedups over conventional adiabatic
quantum annealing, as was demonstrated numerically for a frustrated Ising ring model by Côté et al. Here we identify Landau-Zener-Stückelberg interference as the underlying mechanism for this speedup, and based on this insight we propose a variational schedule ansatz with far fewer parameters. This simplified ansatz allows us to show analytically that the classical optimization of the schedule parameters can be done in
polynomial time and discuss conditions when we expect this type of mechanism to provide speedups over adiabatic annealing. Furthermore, we provide an analytical argument that coherence is an essential resource for this mechanism, which we verify numerically. We perform extensive numerical tests of the proposed ansatz and observe substantial improvements over adiabatic annealing and competitive performance in particularly challenging problem instances, including a well-studied MAXCUT instance commonly used for benchmarking. Our work shows that explicitly leveraging physical mechanisms can lead to more effective designs of variational annealing
algorithms.
Read the full abstract ▾
All authors Matthias Werner, Matías Jonsson, Artur García-Sáez, Arnau Riera, Tameem Albash
Statistical Mechanics · Cross-listed from cs.LG
When Do Local Score Models Extrapolate Across Size? A Diagnostic Theory and Benchmark
Wenjie Xi
Scientific generative modeling often requires size transfer, where models trained on small systems are evaluated on larger ones. While translation-invariant architectures enable this evaluation, we show that architectural locality alone does not guarantee stable size extrapolation. Instead, stable extrapolation is governed by the quasi-locality of the Gaussian-smoothed score. Through Tweedie's formula, far-away perturbations can influence local score components via posterior covariance, meaning a local model succeeds only if its receptive field covers the smoothed score's response range. We formalize this mechanism, proving a size-uniform comparison
theorem for local marginals under reverse
diffusion. We also introduce Finite-Depth Local Flow (FDLF), a white-box diagnostic
benchmark with exact scores, densities, and controllable response ranges. Empirically, we validate the interplay between spatial mixing, smoothed-score quasi-locality, and model receptive fields. Under spatial mixing, the smoothed score remains quasi-local relative to the receptive field, enabling stable extrapolation. Conversely, when spatial mixing weakens, the score's locality rapidly degrades, causing size transfer to fail.
Read the full abstract ▾
Materials Science
Bi-S network origin of cation-disorder stability and dispersive band edges in AgBiS2
Han-Pu Liang, Songyuan Geng, Heng Kang et al. (+9 more)
Cation-disordered AgBiS2 is a promising lead-free optoelectronic material, but both its ordered structure and the microscopic origin of its favorable electronic properties remain debated. Theory has proposed a mixed-coordination tendency with tetrahedral AgS4 and octahedral BiS6 units, whereas experiments mainly report octahedrally coordinated ordered and cation-disordered phases, together with local cation off-centering. Here, we combine a machine-learning interatomic potential with a deep-learning
Hamiltonian to resolve the coupled structural and electronic
evolution of AgBiS2 at large length scales. We identify the three-dimensional Bi-S network as the central structural motif governing both disorder stability and band-edge electronic states. At weak disorder, Ag/Bi exchange competes with the off-centering tendency of the Ag sublattice, producing strongly distorted local environments and convoluted diffraction signatures that hinder the identification of the ordered phase. With increasing disorder, BiS6-like units connect into a continuous Bi-S network, which stabilizes the rocksalt-like disordered phase. Despite strong cation disorder, AgBiS2 retains clear
semiconductor-like band dispersion and develops a direct band gap. The connected Bi:p-S:p states supported by the Bi-S network preserve a dispersive conduction-band edge and a small electron effective mass. In contrast, mobile Ag disrupts the long-range periodicity of Ag-S bonding, leading to strongly localized valence states. These results clarify the structural controversy in ordered AgBiS2 and establish a unified physical picture of disorder stability and optoelectronic response in nonisovalent
semiconductor alloys.
Read the full abstract ▾
All authors Han-Pu Liang, Songyuan Geng, Heng Kang, Chen Qiu, Xiao-Ping Yao, Qing'an Li, Bozhao Zhang, Lechuan Sun, Yuxuan Chen, Shan Zhang, Su-Huai Wei, Peng-Fei Guan
Soft Condensed Matter
Elastoinertial effects govern dynamic response of soft hair beds
Jonas Smucker, Naiesa Freeman, Eric Caballero et al. (+2 more)
Fluid-immersed hair beds are ubiquitous in biology-from the endothelial glycocalyx and primary cilia to intestinal microvilli-where they serve as mechanosensors that transduce dynamic flow signals into biochemical regulatory responses. Despite the inherently dynamic nature of physiological flows, the dynamic mechanical properties of fluid-immersed hair beds under time-varying conditions remain poorly characterized. Here we investigate the transient rheological response of elastic hair beds to large-amplitude oscillatory shear flows at low to intermediate Reynolds number. While the hairs and fluid themselves obey linear constitutive laws, their coupled interaction produces a dynamic nonlinear response that depends sensitively on driving frequency and amplitude. We identify a crossover from a stress-lagging regime to a stress-leading regime, which is governed by an interplay between fluid viscosity, fluid inertia, and hair elasticity. A simplified rigid-beam model qualitatively captures the crossover behavior. Characterizing the dynamic flow response of soft hair beds has direct biological implications, since the lag time sensitively determines the stability of mechanosensory signaling in the feedback loops underlying essential biological processes such as vasodilation, ciliary remodeling, and tubular reabsorption. Our results establish a framework for understanding how the physical properties of biological hair beds optimize dynamic information transmission during mechanotransduction.
Read the full abstract ▾
All authors Jonas Smucker, Naiesa Freeman, Eric Caballero, Philip J. Morrison, José Alvarado
Mathematical Physics
Engineering classical waves with quantized energy spectra in periodic media
Arnaud Lazarus, Georgi Gary Rozenman and John W. M. Bush
Field quantization is a central feature of modern physics, that underpins the concept of
photons and forms the foundation of
quantum electrodynamics as well as much of solid-state theory. Classical linear wave equations are not generally expected to reproduce the quantization arising in
quantum systems without introducing additional ingredients such as ad hoc nonlinear constraints, resonant particle-wave couplings or
stochastic background fields. Here, we show that appropriately engineered linear wave media can recover fundamental features evocative of energy quantization in
quantum mechanics. The key is to tailor periodic media in which wave propagation is strongly suppressed, except over a discrete set of narrow pass bands. In this regime, stationary wave solutions exhibit discrete energy and frequency spectra analogous to those arising in
quantum mechanics despite the underlying dynamics remaining linear. Owing to the universality of the proposed mechanism, these effects may be realized experimentally using mechanical, electrical, or electromagnetic waves in appropriately designed periodic media. This work opens new avenues for designing metamaterials that enable control over discrete wave states while strengthening the conceptual bridge between classical and
quantum wave physics.
Read the full abstract ▾
General Relativity and Quantum Cosmology
Stationary scalar clouds around a rotating Kalb-Ramond BTZ black hole
Rui Ding, Fangli Quan, Zhong-Wu Xia et al. (+2 more)
We investigate the scalar clouds around a rotating Kalb-Ramond (KR) BTZ black hole under Robin boundary conditions. The clouds are obtained as stationary bound states at the superradiant threshold $\omega=m\Omega_H$, where the KR parameter, the rotation and the Robin boundary jointly determine their existence. It is shown that the KR parameter qualitatively changes the existence lines of clouds. For a nonpositive KR parameter, the lines remain monotonic, whereas for a positive KR parameter they can become nonmonotonic, so that a fixed boundary condition may admit clouds in disconnected regions of parameter space. Quasinormal modes (QNMs) and horizon fluxes are further used as consistency checks, confirming that the cloud solutions correspond to non-damping modes at the superradiant threshold where the energy flux changes sign. The KR parameter also shifts the critical Robin parameter at which the clouds exist. These results establish stationary scalar clouds as sensitive probes of the interplay between the Robin boundary conditions and KR
gravity.
Read the full abstract ▾
All authors Rui Ding, Fangli Quan, Zhong-Wu Xia, Qiyuan Pan, Jiliang Jing
Cosmology and Nongalactic Astrophysics
Stochastic constant-roll inflation beyond the hilltop with the spectral method
Eemeli Tomberg
Stochastic inflation can be used to study large inflationary perturbations. This paper presents such a study for a quadratic hilltop potential, corresponding to constant-roll inflation. I solve the perturbation distribution using the spectral method, with detailed solutions of the
eigenvalues and eigenfunctions of the Fokker-Planck operator. Contrary to previous studies of
stochastic constant-roll inflation, the solution allows trajectories that cross the hilltop and get stuck near a reflecting boundary on the other side, tunneling out slowly in a way dictated by the lowest eigensolution. Despite their rarity, these trajectories turn out to dominate the mean first-passage time. For this reason, I argue the mean does not properly describe the inflationary background. Using the median instead, I compute the distribution of the coarse-grained $\Delta N$ distribution and show that its well-known exponential tail first flattens out and then forms a peak near a maximal $\Delta N$ value. I argue similar intricacies arise in
primordial black hole models.
Read the full abstract ▾
Materials Science
Crystallography of periodic nanotextures in a strained Mott insulator
Benjamin Z. Gregory, Yorick A. Birkhölzer, Noah Schnitzer et al. (+9 more)
Here we investigate stripes of alternating structural phases spontaneously forming in epitaxially strained $Ca_2RuO_4$ thin films below the metal-
insulator transition. Using large-volume X-ray reciprocal-space mapping, we show that satellite-pattern intensities across 24
symmetry-inequivalent Bragg reflections collapse onto a single parameter-free curve. The collapse identifies a coherent martensitic laminate of few-nm-wide domains separated by ${012}$ interfaces, with displacements along $\left\langle01\bar{2}\right\rangle$. Satellite-extinction analysis demonstrates that both coexisting phases retain the bulk orthorhombic space group despite the pseudocubic $LaAlO_3$ substrate, biaxial epitaxial strain, and intrinsic strain at the interfaces. Classical invariant-plane-strain crystallography thus governs the nanoscale domain geometry of a Mott
insulator with intertwined
magnetic, electronic, and
lattice order.
Read the full abstract ▾
All authors Benjamin Z. Gregory, Yorick A. Birkhölzer, Noah Schnitzer, Ziming Shao, Jeff Hodgson, Suchismita Sarker, Jacob P. Ruff, Berit H. Goodge, David A. Muller, Kyle M. Shen, Darrell G. Schlom, Andrej Singer
Statistical Mechanics
Geometric Dissipation Constraints in Stochastic Reaction Dynamics: A Variational Observable for Hidden Kinetic Structure in Energy Landscapes
Shlomo Segal
We propose a
geometric framework for characterizing hidden kinetic constraints in
stochastic reaction dynamics. While free-energy barriers and
entropy production provide global descriptors of thermodynamic behavior, they are largely insensitive to local
geometric structure in configuration space that governs pathway selection. Starting from overdamped Langevin dynamics formulated as a gradient flow in Wasserstein space, we derive a variational functional whose leading-order asymptotic structure defines a local dissipation-geometry coupling observable. This quantity combines force-drift
alignment with phase-space contraction induced by the divergence of the drift field, yielding a scalar field that reflects second-order
geometric features of the underlying energy landscape. We demonstrate that this observable distinguishes kinetically distinct reaction channels that are degenerate under conventional free-energy analysis, as shown through numerical experiments on
benchmark systems including the Muller-Brown potential, corrugated periodic landscapes, and the conformational transitions of Alanine Dipeptide. These experiments demonstrate robust separation of pathways and are consistent with a quadratic scaling behavior in the high-frequency homogenization regime. Our results suggest that
stochastic reaction dynamics contain an additional
geometric layer of kinetic control in molecular motion not captured by standard thermodynamic or reaction-coordinate descriptions.
Read the full abstract ▾
Quantum Physics
The dynamic 4.8.8 Floquet code
Aliki A. Capatos
Fault-tolerant
quantum memories depend on the syndrome extraction
circuit as much as on the underlying code. Ancilla-free or dynamic
circuits are an effective way to improve this
circuit layer. For the 6.6.6 honeycomb Floquet code, making the
circuit dynamic raises the threshold and lowers the
qubit overhead, but at the cost of halving the spatial code distance. A dynamic construction for the 4.8.8
lattice layout was conjectured to preserve full distance. I confirm this and give a dynamic measurement
circuit for the CSS 4.8.8 Floquet code. To
benchmark it, I construct and compare four
circuit-level implementations on a
torus, including two dynamic variants (with and without mid-
circuit resets), the standard ancilla-based
circuit, and a pipelined ancilla-based
circuit. Under
circuit-level depolarising noise, the reset dynamic
circuit reaches a per-round threshold of $0.463\%$ $(0.490\%)$ with MWPM (BP+matching), while the no-reset variant reaches the highest threshold of all four
circuits at $0.512\%$ $(0.574\%)$. The standard ancilla-based
circuit only achieves $0.228\%$ $(0.240\%)$, but the pipelined schedule reaches $0.478\%$ $(0.489\%)$. The reset dynamic
circuit also has a faster-growing timelike distance, with $2\le d_t/n_{\mathrm{qec}}\le 3$ asymptotically against a tight $3/2$ for the other three, and running it for fewer rounds gives the smallest spacetime volume in the fast-reset regime, while the no-reset variant is smallest in the slow-reset regime. The 4.8.8 dynamic
circuits therefore see the expected threshold gain and overhead reduction without the spatial-distance cost, demonstrating the advantage of dynamic syndrome extraction in Floquet codes.
Read the full abstract ▾
Astrophysics of Galaxies
A Meta-Learning Framework for Multitask Reverberation Mapping in Active Galactic Nuclei
Aman N. Raju, Andjelka B. Kovačević, Dragana Ilić et al. (+8 more)
The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to observe active
galactic nuclei (AGN) at sky densities of approximately 1000-4000 per sq. deg, enabling photometric reverberation mapping on an unprecedented scale. We present a meta-learning framework for AGN photometric reverberation mapping based on Attentive Latent Neural Processes (ALNP), developed by the SER-SAG-S1 directable software in-kind team for LSST. The framework clusters AGN light curves with similar
topologies using Self-Organizing Maps and combines ALNPs with Mixture Density Models to learn light-curve structure, supermassive black hole (SMBH) properties, and
accretion-disk transfer functions in an unsupervised manner. We evaluate the framework on simulated AGN light curves spanning a range of cadences and transfer functions, as well as on real data from the Zwicky Transient Facility. The learned latent representations encode information on both transfer functions and SMBH parameters. Relative to ensemble-trained baseline regressors, including Gaussian-process models, the framework improves light-curve reconstruction by 60-70%. The transfer function recovery improves by approximately 35% relative to the training prior in a low-variability cluster, while recovery of intrinsic SMBH and red-noise parameters improves by approximately 34%. We further demonstrate that models trained on simulated data can be applied to real AGN light curves. These results indicate that ALNP-based representations provide a flexible and scalable approach to photometric reverberation mapping and are well suited to the diverse AGN population expected from LSST and future time-domain surveys.
Read the full abstract ▾
All authors Aman N. Raju, Andjelka B. Kovačević, Dragana Ilić, Francesco Tombesi, Luka Č. Popović, Eric Slezak, Paula Sanchez-Saez, Marina Pavlović, Iva Čvorović-Hajdinjak, Saša Simić, {\DJ}or{\dj}e Savić
Nuclear Theory
Angular and Kinetic Properties of Scission Neutrons within Time-dependent Density Functional Theory
Antonio Bjelčić, Ibrahim Abdurrahman and Kyle Godbey
Scission-
neutron emission is investigated in $^{235}\mathrm{U}(\mathrm{n}_{\mathrm{th}},\mathrm{f})$, $^{239}\mathrm{Pu}(\mathrm{n}_{\mathrm{th}},\mathrm{f})$ and $^{252}\mathrm{Cf}(\mathrm{sf})$ within time-dependent density functional theory. Using a substantially larger simulation domain than in previous studies, the angular and energy distributions of emitted scission
neutrons are extracted over a specific range of emission angles. At these angles, scission
neutrons are absent below a threshold energy of roughly $1.5$–$2\,\mathrm{MeV}$, and instead contribute predominantly to the higher energy part of the
prompt fission
neutron spectrum. Combining the calculated scission-
neutron spectrum with a Maxwellian model for the evaporated component, constrained by low-energy experimental data, reproduces the measured high-energy
prompt-fission-
neutron yield in both $^{239}\mathrm{Pu}(\mathrm{n}_{\mathrm{th}},\mathrm{f})$ and $^{252}\mathrm{Cf}(\mathrm{sf})$, whereas the evaporation-only model systematically underestimates it. This identifies a signature of scission
neutrons already present in existing high-energy
prompt fission
neutron spectra and constitutes direct evidence for a non-negligible scission-
neutron component in
prompt fission
neutron emission.
Read the full abstract ▾
Astrophysics of Galaxies
Star Formation Drives Production of Low Energy Cosmic Rays
Ningyu Tang, Jiahao Liu, Di Li et al. (+18 more)
For over a century, the origin of low-energy
cosmic rays (LECRs), the dominant heaters and ionizers of dense interstellar gas, remains elusive owing to
solar modulation and uncertain transport processes. In this study, we introduce a new astrophysical approach based on HI Narrow Self-Absorption (HINSA) to obtain spatially resolved measurements of LECR ionization rates using high-fidelity HI observations toward the Orion region from the FAST
telescope. The LECR ionization rate is found to scale with local
star formation rate (SFR) as $log_{10}\zeta = (1.4\pm 0.70)log_{10}\mathrm{SFR} + (-10.5\pm 2.9)$. Moreover, it increases with visual extinction, and is found to exceed, toward active
star-forming regions, the value predicted for diffuse regions based on Voyager measurements and an external propagation model. These findings demonstrate that LECRs are generated in situ by
star-forming activities rather than penetrating from the broader
Galactic cosmic-ray population. This is further supported by
Fermi-LAT gamma-ray observations toward the Orion region. Together, these results resolve a key uncertainty in
cosmic-ray origin and establish a new avenue for quantifying the energetic feedback that regulates the interstellar medium.
Read the full abstract ▾
All authors Ningyu Tang, Jiahao Liu, Di Li, Ruizhi Yang, Thomas G. Bisbas, Bing Liu, Marko Krco, Paul Goldsmith, Paola Caselli, Sihan Jiao, Yan Gong, Gan Luo, Xinwen Shu, Liangchong Zhu, Xiaohui Sun, Chen Wang, Tao-Chung Ching, Donghui Quan, Junzhi Wang, Xuejian Jiang, Pei Zuo
Cosmology and Nongalactic Astrophysics
Pantheon+ supernovae corrected for progenitor age indicate the universe is decelerating
Animesh Sah, Mohamed Rameez and Subir Sarkar
We examine the impact of progenitor age-dependent luminosity
evolution of Type Ia
supernovae on a cosmographic measurement of the deceleration parameter $q_0$. Our recent
redshift tomographic analysis showed that locally $q_0$ has a strong dipole anisotropy aligned approximately with the bulk flow, and only a small monopole component remains at distances exceeding a few hundred Mpc. Applying
redshift-dependent corrections for progenitor age to the Pantheon+ catalogue, we find that this shifts the monopole component of $q_0$ to positive values (i.e. deceleration), while leaving the local dipole component essentially unchanged.
Read the full abstract ▾
Quantum Physics
Parahydrogen Cooling of Nuclear Spin Chains at Hypogeomagnetic Fields
Alexey Kiryutin, Danil Markelov, Ivan Zhukov et al. (+3 more)
Solution-state molecular
nuclear spin networks are promising
quantum simulators because their scalar-coupling
Hamiltonians are chemically programmable, precisely measurable, and coherent at room temperature. Their main limitation for
quantum information science is initialization: thermal Boltzmann polarization produces highly mixed, high-
entropy states. Here, we use parahydrogen-based Signal Amplification by Reversible Exchange (SABRE) at hypogeomagnetic fields (i.e.,
magnetic fields below Earth field) to hyperpolarize the chemically engineered 12-
spin chain [U-13C,15N]-butyronitrile. SABRE generates percent-level 13C and 15N polarization and prepares non-
equilibrium multi-
spin orders across the network. A von Neumann
entropy analysis of such a hyperpolarized system shows that, at the optimal transfer field of 0.52 uT, the full
spin system could reach S/k = 8.274, compared with S/k = 8.318 for the unpolarized reference, giving (S-Sth)/k = -0.043. Experimentally,
nuclear spin temperatures of 52 mK and 257 mK are achieved for 15N and 13C subensembles, respectively. The larger
entropy deficit of the full network than of individual subsystems indicates correlated multi-
spin order beyond single-
spin polarizations. Rapid field cycling to 9.4 T enables site-resolved NMR readout, while the precisely determined coupling network provides an experimentally benchmarked
Hamiltonian for testing
quantum-simulation,
quantum-control, and
Hamiltonian-learning protocols.
Read the full abstract ▾
All authors Alexey Kiryutin, Danil Markelov, Ivan Zhukov, Erik Van Dyke, Alexandra Yurkovskaya, Danila Barskiy
Materials Science
Ab initio parametrization of distributed polarizable force fields
Felix Post, Jean-Philip Filling, Toulik Maitra et al. (+3 more)
Polarizable force fields offer superior transferability and accuracy compared to classical force fields, enabling access to electronic response properties such as refractive index and electronic density of states. Here, we demonstrate two key improvements that significantly enhance their accuracy: (1) assigning atomic polarizability to individual atoms rather than atom types, and (2) employing atomic polarizability tensors instead of scalar values. These modifications extend the applicability of polarizable force fields to cations, anions, and excited states, while also providing more accurate descriptions of neutral molecules. We propose a first-principles-based parameterization procedure for atomic polarizability tensors and scalars, validated on a set of small organic molecules with conjugated building blocks. To overcome the computational cost of ab initio calculations, we train a message-passing graph neural network to predict polarizability parameters, enabling efficient and scalable parameterization. Crucially, this approach imposes no additional computational cost during simulations and provides a clear diagnostic criterion for identifying cases where polarizable force field models fail to accurately describe molecular polarizability.
Read the full abstract ▾
All authors Felix Post, Jean-Philip Filling, Toulik Maitra, Falk May, Michael Wand, Denis Andrienko
Mathematical Physics · Cross-listed from cs.LG
Data-driven discovery of governing differential equations across physical systems
Siyu Lou, Hao Xu, Wenguan Wang et al. (+6 more)
Differential equations play a critical role in scientific discovery because they provide a mathematical framework to describe the behaviour of physical phenomena. As a promising alternative to traditional first principles, data-driven differential equation discovery has attracted increasing
attention for its ability to infer governing laws directly from experimental or simulated data, especially when the underlying physics is unclear. However, the field has expanded rapidly along diverse methodological directions, particularly with the emergence of AI-based approaches, and still lacks a clear organizing perspective. In this Review, we propose a problem-oriented perspective on data-driven differential equation discovery. We first introduce a two-dimensional phase diagram of equation discoverability, where discovery problems are organized according to structural complexity and coefficient complexity. This phase diagram shows how the field has moved from the discovery of sparse equations with simple coefficients toward more complex governing laws with richer structures and more flexible parameterizations. It also clarifies why different methodological families succeed or fail in different problem settings. We then present the representation-evaluation-optimization (REO) framework as a fundamental abstraction of the discovery process. By identifying the core problems of equation discovery that persist across algorithmic variations, REO shifts the discussion from individual
algorithms to the fundamental principles that determine discoverability. We connect these perspectives to applications across physics and adjacent sciences, and argue that the next challenge is not merely recovering equations, but using them to revise existing theories, distil mechanisms and form new scientific concepts.
Read the full abstract ▾
All authors Siyu Lou, Hao Xu, Wenguan Wang, Lu Lu, Hao Sun, Yang Liu, Linfeng Zhang, Dongxiao Zhang, Yuntian Chen