Quantum Physics
Phase-accumulating hyperfine strain sensing with rare-earth-ion phase memories
Mustafa Gündoğan
Long-lived hyperfine coherences in rare-earth-ion
crystals provide controlled phase
evolution windows for metrology. We use this resource to propose an experimental protocol for accessing strain shifts of ground state hyperfine transitions in non-Kramers rare-earth-ion doped (REID) materials, a quantity that is difficult to access directly with conventional spectroscopic methods. Starting from the
crystal field
Hamiltonian, we relate the response to strain-dependent effective quadrupole and Zeeman tensors, including changes in electronic wave functions, virtual electronic admixtures, and the bare
nuclear quadrupole interaction. The protocol optically prepares a selected hyperfine class, uses a phase-controlled rf $\pi/2$ pulse to create the sensing coherence, and applies synchronized dynamical decoupling pulses during the phase
evolution interval so that a coherent ac strain drive accumulates phase rather than averaging away. The accumulated phase is then retrieved by Raman heterodyne readout. The resulting framework provides a route to understanding strain-induced hyperfine couplings in non-Kramers REID systems.
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Quantum Gases
Rydberg-Atom-Mediated Strong Antisymmetric Spin Exchange in Molecular Arrays
Yunqing Jiao, Jin-Zhu Jiang, Bo-Wen Guan et al. (+6 more)
Ultracold molecular systems have recently emerged as a versatile platform for
quantum computation and simulation.
Spin-exchange interactions arising from direct molecular dipolar interactions constitute the key mechanism for generating
quantum entanglement and simulating
quantum spin models. However, the relatively small electric dipole moments result in weak
spin-exchange couplings, fundamentally limiting the speed of
quantum information processing and interaction cycle of many-body dynamics. Here, we introduce a framework that employs Rydberg atoms with large electric dipole moments to mediate strong interactions between molecules in optical tweezer arrays that enables individually
laser addressing both the Rydberg atom and molecules. Our result reveals that the mediated coupling can realize an effective molecular
spin-exchange interaction with an intrinsic Dzyaloshinskii-Moriya character, with the Rydberg atoms dynamically decoupled from the molecular degrees of freedom, and the effective interaction strength enhanced by up to three orders of magnitude. We further demonstrate its versatility through rapid
entanglement generation, high-fidelity two-
qubit gate operations, and the realization of non-
equilibrium symmetry-protected topological phase with long-lived edge coherence. Our work establishes a route toward strong molecular
spin interactions and opens opportunities for fast, scalable
quantum information processing and
quantum simulation of long-time non-
equilibrium quantum many-body physics in optical tweezer arrays of ultracold molecules.
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All authors Yunqing Jiao, Jin-Zhu Jiang, Bo-Wen Guan, Jie Ma, Liantuan Xiao, Chi Zhang, Weibin Li, Feng Mei, Suotang Jia
General Relativity and Quantum Cosmology
Thermodynamic geometry as the missing link: toward a unified framework for black hole first-order phase transitions
Shi-Hao Zhang, Jing-Fei Zhang and Xin Zhang
Black hole first-order phase transitions have been described by several seemingly independent frameworks, including local geometry, global
topology, complex analysis, and thermodynamic geometry. While the first three have been unified, thermodynamic geometry has remained outside. We prove that the divergence points of the normalized Ruppeiner
curvature scalar $R_N$ coincide exactly with the solutions of $T'(r_h)=0$, where $r_h$ is the horizon radius. These solutions include extremal points (spinodal points) and stationary inflection points (thermodynamic critical points). Thus, the divergence of $R_N$ is a necessary but not sufficient condition for a first-order phase transition. This clarifies the mathematical origin of
curvature divergence and why thermodynamic geometry can reliably indicate but not alone confirm phase transitions. Using the local
geometric framework as a central framework, we incorporate Ruppeiner geometry into this unified picture; a similar analysis also applies to Weinhold geometry. Consequently, the four frameworks are unified within a single structure based on the local folding of the temperature function. This advances our understanding of the mathematical structure of black hole first-order phase transitions and provides clues for possible extensions to other types of phase transitions.
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Soft Condensed Matter
S. Biswas, W. S. Fall and H. H. Wensink
Weakly flexible, directed
polymers can adopt a potentially infinite variety of conformations, some of them
chiral. We develop a second-virial theory for semi-rigid
polymers embedded in a nematic environment based on the assumption that the chains possess no intrinsic molecular chirality but can take on weakly helical conformations of either handedness. We demonstrate how these transient helical fluctuations can be exploited to predict the degree of chain stiffening induced by molecular crowding. The theoretical predictions are in good agreement with large-scale molecular dynamics simulations of bead-spring
polymers with tunable backbone flexibility. Although both theory and simulations rule out spontaneous global
chiral symmetry breaking imparted by chain conformations alone, they do reveal that
polymers can develop pronounced enantiomeric shapes. Nematic fluids of semi-rigid
polymers can be viewed as compensated cholesterics composed of transiently helical
polymers with zero enantiomeric excess. By quantifying the degree of compensated
chiral order developed over a broad range of concentrations and persistence lengths, two distinct regimes of weak and strong enantiomerism can be identified. A crossover between the two occurs when the chain persistence length drops below roughly three times the contour length.
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Optics
High-gain vortex transfer via activated forbidden transitions in molecular magnets
Fan Meng, Hao Zhu, Xin-Yao Huang et al. (+1 more)
Vortex light has garnered considerable interest in recent years owing to its distinctive properties and broad application potential. In this paper, we employ a conventional three-level ladder-type configuration in molecular magnets to realize high-gain
vortex light transfer by enabling otherwise forbidden transitions. We demonstrate that the intensity and phase of the generated
vortex signal field are governed by the detuning of the probe field and the strength of the control field, and that the topological charges of the incident and generated fields obey a well-defined algebraic relation during the
vortex transfer process. Furthermore, we show that, in molecular magnets, the Autler-Townes splitting (ATS) effect yields a larger
vortex signal field gain than electromagnetically induced transparency (EIT) over a broad parameter range in nonlinear three-wave mixing. This result suggests that the widely accepted view of EIT as the dominant enhancer of nonlinear optical effects may not hold universally. In addition, we revisit previous studies and re-examine the characterization of
vortex beam transfer efficiency, emphasizing the need for a more careful interpretation in multi-beam interaction systems. Leveraging the long
spin coherence and microwave transitions of molecular magnets, our results may enable
quantum information transfer, storage, computing, and radar imaging in solid-state platforms.
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All authors Fan Meng, Hao Zhu, Xin-Yao Huang, Guo-Feng Zhang
Materials Science · Cross-listed from cs.AI
AtomWorld-Mem: Memory-Restored World States for Long-Horizon Atomistic Evolution
Tian Luo, Ruge Zhang, Haozhi Han et al. (+5 more)
High-fidelity atomistic
evolution over long timescales requires more than observing the current
crystal configuration. Instantaneous atomistic snapshots are often incomplete: locally similar configurations can correspond to different hidden dynamical contexts, future event preferences, and waiting-time scales. We argue that this snapshot ambiguity makes long-horizon atomistic
evolution fundamentally a
memory-based world-state restoration problem. To address this, we introduce AtomWorld-Mem, a
memory-restored atomistic world model that recovers the latent world state missing from instantaneous
crystal snapshots. AtomWorld-Mem treats the evolving
alloy as an AtomWorld: spatial encoders write multi-scale atomistic keyframes from dense local
topology and sparse long-range defect context, while short-term event
memory and long-term structural
memory integrate these keyframes across time to restore a future-predictive evolutionary state. The restored state is used to prioritize legal vacancy-mediated events under single-event Kinetic Monte Carlo (KMC) constraints, while event legality, physical execution, and residence-time updates remain governed by the underlying simulator. Empirically, AtomWorld-Mem improves long-horizon atomistic progress under fixed microscopic event budgets while maintaining high-fidelity
evolution across energetic, structural, and vacancy-transport observables. It further transfers zero-shot across diverse unseen
alloy-temperature AtomWorlds, suggesting that the learned
memory-restoration mechanism captures reusable principles of hidden-state inference rather than a system-specific local energy heuristic. These results position
memory-restored world-state modeling as a promising route toward efficient, physically grounded, and transferable atomistic
evolution.
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All authors Tian Luo, Ruge Zhang, Haozhi Han, Yifeng Chen, Yunquan Zhang, Yunxin Liu, Ting Cao, Kun Li
Optics
Distributed laser energy deposition enables fog-resilient optical communications
Malte C. Schroeder, Victor Moreno, Christophe Coreixas et al. (+2 more)
Fog and clouds remain major obstacles to free-space optical (FSO) communications because micron-sized droplets can impose tens of decibels of attenuation. Ultrashort
laser filamentation can transiently clear fog in laboratory-scale experiments, but its extension to atmospheric-scale propagation has remained uncertain. Here we demonstrate
laser-assisted fog clearing under atmospheric-scale propagation conditions over a 140-m optical path using a high-energy, high-average-power picosecond
laser and weak focusing to sustain extended multifilamentation. A steady-state transparent channel approximately 2 cm in diameter restores up to 12 dB of transmission for an independent optical beam. Increasing the clearing-
laser pulse energy primarily extends the multifilament region while maintaining a nearly constant longitudinally averaged deposited energy per unit length of ~2 mJ/m over the measured bundle length. This low average deposition, together with self-sustained filament propagation through dense fog, provides a favorable scaling route toward weather-resilient optical links.
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All authors Malte C. Schroeder, Victor Moreno, Christophe Coreixas, Jonas Latt, Jean-Pierre Wolf
Physics Education
Multiple harmonics from a hand-struck tube: a simple and precise measurement of the speed of sound
Francisco Echegorri, Martin Monteiro, Cecilia Stari et al. (+1 more)
The speed of sound in air can be determined from the resonance frequencies of the harmonic waves inside a thin cylindrical tube. A pressure wave is generated in the tube by striking several times one of its ends with an open hand and keeping the hand in place. In this way pulses of short duration are produced which propagate along the tube and decompose into a superposition of harmonic waves whose frequencies are determined by the harmonics present in a tube open at one end and closed at the other. The tube thus acts as a filter that reinforces those harmonic waves exhibiting an antinode of acoustic pressure at the closed end and a node at the open end. Their frequencies are determined by these boundary conditions, while waves with different frequencies cancel out by destructive interference. Recording the sound with a microphone connected to a computer and analyzing its spectrum with freely available software, the resonance frequencies are obtained and the speed of sound is determined with an accuracy better than $0.5\%$. The whole experiment requires nothing but a tube, a microphone and free software, so it is inexpensive, takes a few minutes to set up and is well suited to introductory physics laboratories.
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All authors Francisco Echegorri, Martin Monteiro, Cecilia Stari, Arturo C Marti
Mathematical Physics
Unifying non-Markovian Dynamics and Agent Heterogeneity in Scalable Stochastic Networks
Aurelien Pelissier, Miroslav Phan, Didier Le Bail et al. (+2 more)
Stochastic processes underpin dynamics across biology, physics, epidemiology, and finance, yet accurately simulating them remains a major challenge. Classical approaches such as the Gillespie
algorithm are exact for Markovian, time-independent systems, where propensities depend only on the current state and
agents of a given type are statistically identical. While efficient, this framework misses a defining feature of many real systems: heterogeneity and
memory at the level of individual
agents.
Cells may divide or differentiate on distinct intrinsic timescales, individuals may preferentially interact with specific partners, and inter-event-time distributions can deviate strongly from the exponential. We introduce MOSAIC (Modeling of
Stochastic Agents with Individual Complexity), a general and scalable framework that embeds
agent-specific properties directly into the dynamics. MOSAIC unifies heterogeneous rates, dynamic interaction preferences, and both Markovian and non-Markovian waiting-time distributions within a single
stochastic formalism, while retaining Gillespie-like computational cost.
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All authors Aurelien Pelissier, Miroslav Phan, Didier Le Bail, Niko Beerenwinkel, Maria Rodriguez Martinez
General Relativity and Quantum Cosmology
Global variables and dynamics of emergent cosmology in loop gravity
Iñaki Garay, Luis J. Garay, Diego H. Gugliotta et al. (+2 more)
Deriving emergent cosmology from the discrete geometry of Loop
Quantum Gravity remains an open challenge. We solve the two-vertex model exactly, including general non-symmetric configurations, by introducing macroscopic global variables that form a closed Poisson subalgebra. This yields an intrinsic minimal area gap from the Casimir invariants of the subalgebra. In the semiclassical limit, a generalized Friedmann equation emerges incorporating graph anisotropies and
quantum geometry corrections, which lead to a Big Bounce. This global formulation opens a coarse-graining route toward statistical descriptions of
quantum spacetime.
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All authors Iñaki Garay, Luis J. Garay, Diego H. Gugliotta, Sergio Rodríguez-González, Raül Vera
High Energy Physics (Phenomenology)
Probing the Validity of EFT Approaches in Higgs + Jet Production at $\sqrt{s}=13$ TeV
Shubham Yadav and Prashant Shukla
The production of a
Higgs boson with a jet is one of the most important processes studied at the LHC. It serves as a sensitive probe of high-energy dynamics and provides a powerful testing ground for the Standard Model, while also offering sensitivity to possible new physics effects. In this work, we perform a phenomenological study of
Higgs + jet production in
proton-
proton collisions at 13 TeV center of mass energy, using the MadGraph5_aMC@NLO framework. We compare predictions obtained from the full loop induced Standard Model with those derived within the HEFT and SMEFT frameworks. Taking the
Higgs transverse momentum as a probe, we study normalized distributions and ratio spectra to test the effective field theories. Our results show that effective approaches successfully reproduce the Standard Model behavior in the low transverse-momentum region. However, sizable deviations emerge at high pT, signaling the breakdown of the effective approximation. These findings highlight the importance of carefully accounting for kinematic effects when applying EFT-based methods to precision
Higgs studies and provide a quantitative estimate of their range of validity.
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General Relativity and Quantum Cosmology
Architecture Acceleration of Machine Learning Gravitational Waveform Surrogate Models
Adriano Frattale Mascioli, Lorenzo Piccari, Saulo Albuquerque et al. (+9 more)
Accurate and computationally efficient waveform models of compact binary coalescences are a fundamental requirement for gravitational wave data analysis. This work presents differentiable and hardware-accelerated implementations of the machine-learning surrogate models mlgw and mlgw-bns within the JAX ecosystem. The proposed framework enables JIT compilation, vector paralellization, native GPU acceleration, and automatic differentiation, while preserving the original surrogate training infrastructure and its applicability to arbitrary non-precessing waveform approximants.
Benchmarks are performed in the binary black hole case with a newly trained surrogate of the SEOBNRv5HM approximant; on CPU, they show speed-ups in waveform evaluation time with respect to the original mlgw implementation that exceed one order of magnitude; further, when exploiting GPU acceleration and large-batch vectorization these reach approximately two orders of magnitude. The
benchmarks performed in the case of binary
neutron stars with a TEOBResumSPA surrogate model achieve similar gains on GPU. Our JAX-based surrogate modeling framework can be integrated into
Bayesian parameter estimation pipelines through GWgpu-jax, an open-source package that connects JAX-compatible gravitational waveform generators to JAX-native sampling
algorithms. We demonstrate this capability with a nested-sampling pipeline built upon BlackJax-NS, performing parameter estimation analyses of the GW150914 and GW170817 events with mlgw and mlgw-bns. The analyses require approximately twelve and seventeen minutes, respectively, on a single GPU and yield posterior distributions consistent with those reported by the LIGO-Virgo-KAGRA Collaboration. Beyond nested sampling, JAX automatic differentiation provides efficient gradient and Hessian evaluations of the waveform models, enabling integration with gradient-based
Bayesian inference methods.
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All authors Adriano Frattale Mascioli, Lorenzo Piccari, Saulo Albuquerque, Gabriele Demasi, Giulia Capurri, Massimo Lenti, Angelo Ricciardone, Barbara Patricelli, Gianluca M. Guidi, Giulia Stratta, Walter Del Pozzo, Francesco Pannarale
Optics
From OpenSPIM to FlowSPIM: Enhancing the versatility of a light sheet microscope through an iterative design process
Endre Joachim Lerheim Mossige, Sergey Ponomartsev, Natalia Smirnova et al. (+12 more)
Light sheet microscopy is ideal for the 3D imaging of large biological specimens, yet systematic documentation on adapting microscope designs to diverse experimental requirements remains limited. We present the iterative process used to design and build a modular light-sheet microscope and adapt it to different sample types and experimental conditions. Starting from a stripped-down OpenSPIM platform, we gradually make our microscope more versatile by implementing new hardware, such as additional
laser channels and optical filters, and new protocols for sample handling. In its final iteration, FlowSPIM is a new flow-based incubation technique for 3D tissue culture.
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All authors Endre Joachim Lerheim Mossige, Sergey Ponomartsev, Natalia Smirnova, Wietske van der Ent, Siri Andresen, Xian Hu, Felix Margadant, Rainer Heintzmann, Roland Kádár, Kesavan Sekar, Helene Knævelsrud, Camila Vicencio Esguerra, Stefan Krauss, Dag Kristian Dysthe, Alexander Refsum Jensenius
Cosmology and Nongalactic Astrophysics
Observational constraints on scalar-vector-tensor dark energy with phantom-divide crossing
Nandan Roy, Shinji Tsujikawa, Ying-li Zhang et al. (+1 more)
We constrain a scalar-vector-tensor (SVT) dark-energy model in which the vector sector drives the dark-energy equation of state below $-1$ at earlier times, while a canonical scalar field subsequently drives it across $-1$ toward a present-day value above $-1$. We confront the model with DES Year 5
supernovae, DESI DR2
baryon acoustic oscillations, and compressed
cosmic microwave background information, and then include Gold-2017
redshift-space-distortion (RSD) measurements to probe structure growth. The background posterior assigns substantial weight to crossing histories and gives a better best fit than the flat $\Lambda$-cold-dark-matter ($\Lambda$CDM) model. The RSD analysis preserves this qualitative background
evolution, constrains the clustering amplitude, and increases the posterior support for the directional crossing criterion. Since the growth analysis also imposes additional perturbative support conditions, this increase cannot be attributed to the RSD likelihood alone. Matched PolyChord calculations give Bayes factors larger than unity for SVT relative to $\Lambda$CDM under both prior-volume conventions considered here. The quantitative Bayes factor depends on the prior normalization assigned to the regular radiation-era branch and is larger in the RSD analysis under either convention. Overall, current expansion and structure-growth data are consistent with a stable dynamical crossing of the phantom divide in the SVT model.
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All authors Nandan Roy, Shinji Tsujikawa, Ying-li Zhang, Zejun Zhang
General Relativity and Quantum Cosmology
Energy extraction from a Kerr-Bardeen-Letelier black hole by Comisso-Asenjo Mechanism
Bijendra Kumar Vishvakarma, Dharm Veer Singh and Sanjay Siwach
We explore the energy extraction from a Kerr-like regular black hole coupled with a cloud of strings (CoS) via the Comisso-Asenjo mechanism. We study the effects of the black hole
spin (a), black hole charge (g) and CoS parameter (b) on the ergo-region of the black hole and the
magnetic reconnection process, which is governed by the Comisso-Asenjo mechanism. We also analyze the phase space involving negative energy density of the relativistic magnetized
plasma at infinity. The rate of energy extraction in the
magnetic reconnection process is also computed and compared with that of the Blandford-Znajek mechanism.
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Solar and Stellar Astrophysics
The NEMESIS general YSO catalogue - I. Supervised classification with deep learning methods
G. Marton, M. Madarász, J. Roquette et al. (+4 more)
In modern large-scale surveys, young
stellar objects (YSOs) are mostly identified by the infrared excess in their spectral energy distributions (SEDs). To this end, YSO identification and classification were mostly based on certain colours, resulting in wavelength-specific methods. Using all available data allows us to construct a uniformly classified YSO catalogue by applying the same identification method to heterogeneous samples, reducing systematic differences and enabling more consistent studies of YSO populations and
star formation. Our goal is to develop a method that takes advantage of the heterogeneous data available in the VizieR database and to provide a tool that can be used to identify YSOs with high accuracy. We also aim to create the largest homogeneous catalogue of YSOs. We use the CDS VizieR and NASA/IPAC IRSA to collect data for a large number of objects of various types. The data collected included SEDs, light curves, and direct imaging and were used to build different image representations. These were used to teach deep learning
algorithms to differentiate between YSOs and all other types of sources. Architectures from the PyTorch library and custom-built convolutional neural networks were applied to create an ensemble of binary classifiers specialised at identifying YSOs. The resulting method is able to automatically identify YSO candidates with an accuracy higher than 90% while contamination is identified with an accuracy higher than 99%. We applied our classifier to numerous YSO catalogues to confirm the youth of the
stars and to create the largest catalogue of homogeneously identified potential YSOs ever – the NEMESIS General YSO catalogue contains 274\,408 unique, high reliability YSOs. Their positions on the colour-magnitude diagrams, and their distribution relative to the local
Galactic structures, were also used to test their young nature.
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All authors G. Marton, M. Madarász, J. Roquette, M. Audard, I. Gezer, D. Hernandez, O. Dionatos
Cosmology and Nongalactic Astrophysics
Probing the cosmic web with fast radio bursts: II. Scintillation
Sharon Lapiner, Nir Mandelker, Paz Beniamini et al. (+1 more)
We consider the formation of multiphase gas in
cosmic web objects (CWOs) through cooling and fragmentation within the shock-heated medium of
cosmic sheets and filaments, and the circumgalactic medium (CGM) of
haloes. This leads to dense, cool ($\sim10^{4}\,\mathrm{K}$), small-scale cloudlets in pressure
equilibrium with their surroundings. Such ionized overdensities can affect the propagation of
radio waves emitted by fast
radio bursts (FRBs), allowing us to probe the small-scale structure in CWOs by examining their impact on the scintillation pattern of the observed FRB flux. While we find that the probability of encountering a high-temperature filament or sheet with cold cloudlets is rather small and usually confined to high
redshifts, the expected high rates of FRBs may still permit detection through scintillation along rare sightlines. We suggest scintillation from the Milky Way (MW) interstellar medium as a promising probe: CWO
plasma screens can suppress it, placing constraints on their cold-gas properties. Filaments and sheets can suppress MW scintillation from sources at $z_\mathrm{S}\gtrsim2$ and $3$, respectively, while cold and turbulent cloudlets in the CGM can be probed by sources at
redshifts as low as $z_\mathrm{S}\sim0.5$, constraining remarkably low volume-filling fractions, $f_\mathrm{v}$ (e.g. $f_\mathrm{v}\gtrsim10^{-5}$ for $z_\mathrm{S}\gtrsim2$). To provide testable predictions, we estimate the fraction of FRBs expected to encounter CWOs that may suppress MW scintillation below a given frequency, and express this as a function of the average extragalactic dispersion measure. Future FRB samples could map these constraints onto bounds on the existence and properties of cloudlets in CWOs, such as their density, size, $f_\mathrm{v}$, and
turbulence.
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All authors Sharon Lapiner, Nir Mandelker, Paz Beniamini, S. Peng Oh
Disordered Systems and Neural Networks
A Flatness-Generalization Relation in the Teacher-Student Tree-Committee Machine
Brandon Livio Annesi, Davide Straziota and Enrico Maria Malatesta
The flatness of the loss landscape at a minimizer is a widely used heuristic for
reasoning about neural-network generalization, yet evidence for this relation is mostly empirical and controversial. We study this relation in a teacher-student tree committee machine, where both the ERM
estimator and the Hessian spectrum are analytically tractable in the proportional high-dimensional limit. First, we use a zero-temperature Gibbs formulation to obtain predictions for the observables of the typical minimizers of the empirical loss. Secondly, we use Edwards-Jones formalism to derive the limiting Hessian resolvent around these typical minimizers. All predictions agree with finite-size gradient-descent simulations. Finally, we study three measures of flatness, namely the left and right edges and the spectral mean, and check if a decrease in generalization error as the
dataset size is increased corresponds to an increase in flatness. We find that the answer strongly depends on the learning task and on the ratio of the number of parameters to the number of data points. In regression, the spectral mean and right edge correlate with the generalization error, while the left edge does so only in the overparametrized regime. In classification this correlation reliably holds only in the highly overparametrized phase, while for underparametrized networks it can even reverse.
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Quantum Physics
Supporting functionals and singular boundary geometry of two-qubit entanglement of formation
Wei Song and Xiao-Lan Zong
We give a criterion for the existence of a global supporting affine functional for the
entanglement of formation at an entangled two-
qubit state. It exists if and only if the
spin-flip bilinear form is nondegenerate on the support of the state, or equivalently, if the last concurrence root associated with the support is nonzero. In this case the
entanglement of formation satisfies a two-sided Lipschitz bound relative to the reference state. In the degenerate case the state has rank two or three, and its projective support is tangent to the product-state quadric. By suitably choosing a perturbation outside the original support space, the decrease in the
entanglement of formation is, to leading order, proportional to the square root of the mixing parameter. We give an explicit expression for the leading coefficient. Such a square-root decrease violates the one-sided Lipschitz bound, and therefore no globally supported affine functional exists at this state.
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Statistical Mechanics
Thermodynamics of the $q$-deformed Kittel–Shore model for spin-1 particles
V. Mariscal and J. J. Relancio
Quantum algebras ($q$-
algebras) have been used in the literature to deform
spin-chain models. In particular, in previous works by the present authors, the Kittel–Shore
Hamiltonian was deformed using $\mathfrak{su}_q(2)$
algebra. The deformed
Hamiltonian was presented for a general
spin, and the thermodynamic properties were studied for
spin-1/2 particles. In this paper, we focus on the $q$-deformation of the Kittel–Shore model for
spin-1 systems. We analyse the impact of this deformation on the thermodynamic properties and phase transitions of the system as a function of the deformation parameter $q$. Specifically, we study the specific heat,
magnetic susceptibility, and magnetisation, including a detailed analysis of the Curie temperature characterising the
ferromagnetic phase. Furthermore, a finite-size scaling analysis is conducted for both the
ferromagnetic and
antiferromagnetic cases. Results are systematically compared with those of the undeformed model to reveal the physical effects of the $q$-deformation.
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Statistical Mechanics
2D target search with boundary-induced resetting
Kevin Chen and Paul C. Bressloff
Most studies of
stochastic search processes with resetting focus on spontaneous resetting events that occur at a random sequence of times typically generated by a Poisson process. One of the major consequences of spontaneous resetting is that it yields a finite mean first passage time (MFPT) in unbounded domains, resulting in an optimal resetting rate that minimises the MFPT. An optimal resetting rate can also occur in bounded domains provided that the reset point is not too far from the target. Recently, there has been growing interest in event-based rather than spontaneous resetting, where resetting is triggered when a specific threshold is reached. Identifying the threshold with a physical non-target boundary then leads to so-called boundary-induced resetting. In this paper, we explore the effects of boundary-induced resetting on single-particle diffusive search in a two-dimensional (2D) bounded domain $\Omega$ containing one or more small interior targets. The interior target boundaries are totally absorbing, whereas the exterior boundary $\partial \Omega$ is sticky. That is, whenever the particle reaches a point on $\partial \Omega$ it remains attached for a random waiting time $\tau$ after which it immediately resets to a fixed interior point $\x_0\in \Omega$. Using renewal theory, matched asymptotic analysis and Green's functions we calculate the unconditional MFPT for absorption by any of the targets and compare this with the corresponding MFPT of a search process on the same domain with a reflecting surface $\partial \Omega$ and no resetting. We show that boundary-induced resetting only reduces the MFPT relative to the no resetting case if the searcher's reset point $\x_0$ is sufficiently close to one of the targets.
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Computational Physics
Trajectory Paradox is a Boundary Layer!
Kush Kumar, Sovan Lal Das and Shakti S. Gupta
This study derives the asymptotic conditions under which the massless stretched string formulation is valid for the equivalent dynamics of the inertial string carrying a moving point mass. Consequently, the governing equation under such conditions can be written as a singularly perturbed partial differential equation when the inertia of the string is included. When the inertia of the string is ignored, the governing equation reduces to a non-homogeneous hypergeometric ordinary differential equation governing the transverse motion of the moving mass. This hypergeometric equation has a discontinuous solution at the terminating boundary known as the trajectory paradox. However, numerically solving the actual equation yields a continuous solution with a rapid variation near the boundary. The complete solution resembles the inner solution as well, whereas the hypergeometric ordinary differential equation leads to an outer solution, revealing that the trajectory paradox is a boundary layer.
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Astrophysics of Galaxies
Simulating tidal disruption events in nuclear star clusters
Philip Cho, Kai Wu, Francesco Flammini Dotti et al. (+5 more)
Context.
Nuclear star clusters (NSCs) and supermassive black holes (SMBHs) often coexist at the centers of
galaxies, engaging in complex dynamical interactions that influence SMBH growth.
Stars that approach the SMBH too closely are tidally disrupted, and a fraction of their debris is accreted onto the black hole. Such events may contribute to SMBH growth in gas-deficient
galaxies. Aims. Our work aims to improve the theoretical framework for understanding the mass
accretion of
stellar debris following
tidal disruption events (TDEs) through numerical simulations. We perform direct N-body simulations of an NSC with a central SMBH embedded in a fully self-consistent dynamical model to test a new TDE
accretion prescription in a set of pilot simulations. Methods. The previous TDE prescription used a fixed
accretion radius and assumed that the entire
stellar mass was accreted after disruption. In the new partial-mass
accretion model, the mass added to the SMBH depends on the orbital eccentricity and penetration factor of the disrupted
star. Results. We find that most TDEs involving main-sequence
stars are marginally eccentric or marginally
hyperbolic and contribute approximately half of the
stellar mass to SMBH growth, consistent with recent hydrodynamical simulations. In all simulated models, the TDE-driven mass
accretion rate exhibits an early peak followed by a rapid decline. Models with higher initial SMBH masses exhibit a faster decline in the
accretion rate, consistent with more rapid loss-cone depletion and inefficient replenishment
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All authors Philip Cho, Kai Wu, Francesco Flammini Dotti, Taras Panamarev, Shuo Li, Shiyan Zhong, Klaus Reuter, Rainer Spurzem
Nuclear Theory
Set Transformer inference of the neutron star equation of state from stellar observations
Márcio Ferreira, Valéria Carvalho, Michał Bejger et al. (+1 more)
We develop a permutation-invariant Set
Transformer to reconstruct the equation of state (EoS) of dense matter from variable-size, unordered sets of
neutron star (NS) observations. The model takes
stellar masses together with radii,
tidal deformabilities, or both, and predicts either the pressure $P(n)$ or the sound speed $c_s^2(n)$ on a fixed density grid, along with density-dependent uncertainties. Nothing in the architecture prescribes which
star informs which density: self-
attention couples all observations nonlinearly, and each density point reads the full set through its own learnable query, so the
star-to-density mapping is learned from the data. Trained on independent piecewise-polytropic and Gaussian-process EoS ensembles, the model provides well-calibrated predictions whose uncertainty increases in density regions that stable
stars cannot probe. Reconstruction errors decrease with the number of observations, while
tidal deformability generally improves accuracy at a fixed observation count, even when it carries its own measurement noise. Sensitivity analysis reveals a density-local mapping: in the pressure models, predictions at density $n$ depend most strongly on
stars whose central densities are near $n$. We also show that the sensitivity of the model to the inferred
stellar compactness provides information on the minimum central density. These results demonstrate that set-based neural inference, in which the
star-to-density mapping is learned rather than assumed, can extract physically interpretable EoS information with calibrated uncertainties.
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All authors Márcio Ferreira, Valéria Carvalho, Michał Bejger, Constança Providência
Astrophysics of Galaxies
AKARI near-infrared spectroscopy of circumstellar hydrocarbon dust associated with young stellar objects
Yuki Kuroda, Hidehiro Kaneda, Natsuko Izumi et al. (+2 more)
We investigate the processing of the circumstellar polycyclic aromatic hydrocarbons (PAHs) associated with young
stellar objects (YSOs) through their
stellar activities. We analyze the AKARI near-infrared (2.6$-$4.4 $\mu$m) long-slit spectral data of 10 YSOs, focusing on the aromatic feature at a wavelength of 3.3 $\mu$m and the aliphatic features at 3.4$-$3.6 $\mu$m. The spectral fitting results show large variations from target to target in the flux ratio of the aliphatic to aromatic features, the shape of the aliphatic feature profile, and the central wavelength of the aromatic feature. In particular, HD 97048 and Elias 1 show strong aliphatic features at wavelengths longer than 3.5 $\mu$m, which is consistent with the hydrogenated nanodiamond features reported in previous studies. We find that the properties of the hydrocarbon
dust vary under the influence of the YSO activity, where the degree of
dust processing is likely to be related to the age of the YSO and the amount of the circumstellar
dust. In addition, correlation is observed between the variations of the H$_2$O and CO$_2$ ice features and the aliphatic feature profiles, suggesting connection between the formation of CO$_2$ ice and the processing of aliphatic hydrocarbons. Finally, we find a significant correlation between the variations in the central wavelength of the aromatic feature and the shape of the aliphatic feature profile. These findings may be consistent with a tentative scenario in which circumstellar PAHs are converted to nanodiamonds through irradiation by high-energy particles produced by YSO activity.
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All authors Yuki Kuroda, Hidehiro Kaneda, Natsuko Izumi, Takuma Kokusho, Shinki Oyabu
Materials Science
Unraveling the electronic structure and the oxygen $K$-edge x-ray absorption near-edge structure spectrum of DyFeO$_3$
G. Gebreyesus, Eric Macke, Pietro Delugas et al. (+5 more)
Rare-earth orthoferrites such as DyFeO$_3$ exhibit a rich interplay between localized rare-earth and transition-metal moments, giving rise to complex
magnetic phases and magnetoelectric phenomena. Understanding their electronic and spectroscopic properties from first principles requires an accurate description of the localized Fe-$3d$ and Dy-$4f$ states and their hybridization with O-$2p$ states. Here, we combine first-principles calculations and x-ray absorption near-edge structure (XANES) measurements to investigate the electronic structure and the O $K$-edge spectrum of DyFeO$_3$. We employ density-functional theory (DFT) with Hubbard $U$ corrections (DFT+$U$) determined from first principles using density-functional perturbation theory, the HSE06 hybrid functional, and orbital-resolved DFT+$U$ with Hubbard parameters calibrated to reproduce the electronic structure computed using HSE06. We find that standard DFT+$U$, despite improving the band gap, substantially underestimates the
crystal-field splitting of the unoccupied Fe-$3d$ states and consequently fails to accurately reproduce the separation of the two lowest-energy features in the O $K$-edge spectrum. HSE06 provides a more balanced description of the relevant electronic states, including the Fe-$3d$
crystal-field splitting. Mapping the corresponding electronic structure onto orbital-resolved DFT+$U$ yields a spectrum that remarkably reproduces the two lowest-energy experimental features and captures the main characteristics of the spectrum at higher energies. These results establish the low-energy O $K$-edge features as a sensitive probe of the Fe-$3d$
crystal-field splitting, while showing that the localized Dy-$4f$ states leave no distinct spectral fingerprints despite their importance for the
magnetic properties.
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All authors G. Gebreyesus, Eric Macke, Pietro Delugas, Weiguo Jing, Banani Biswas, Carlos A. F. Vaz, Christof W. Schneider, Iurii Timrov
Quantum Physics
Quantum Approximate Optimisation Algorithm for Protein Sidechain Packing
Sebastian O. M. Stewart, Nick Chancellor, Jonte R Hance et al. (+1 more)
Sidechain packing is a critical stage in
protein folding, with direct implications for structure-based drug discovery. Google DeepMind's tool, AlphaFold2, predicts
protein backbone reliably but sidechain positioning less accurately. Recovering the lowest-energy rotamer assignment over a fixed backbone is NP-hard. We present a hybrid
quantum-classical pipeline that repacks sidechains on the AlphaFold backbone using the
Quantum Approximate Optimisation
Algorithm (QAOA), encoding the one- and two-body energies as a quadratic unconstrained binary optimisation (QUBO) problem. We introduce a constraint-preserving ansatz, pairing a W-state initialisation with a cyclic XY ring mixer, that enforces one-hot rotamer validity without penalty terms while keeping two-
qubit gate scaling linear in the rotamer count. We also define an asymptotic shot-scaling metric, measured against the experimentally resolved conformation, that fixes optimiser quality independently of the baseline; its fitted growth stays below the classical exhaustive-search rate at moderate rotamer flexibility. Evaluated on bovine pancreatic trypsin inhibitor (5PTI) across high- and moderate AlphaFold-confidence regions, the pipeline lowers conformational energy against the AlphaFold baseline.
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All authors Sebastian O. M. Stewart, Nick Chancellor, Jonte R Hance, Ittoop Vergheese Puthoor
Quantum Physics
On the applicability of Kolmogorov's theory of probability to the description of quantum phenomena. Part II: Bell inequalities
Maik Reddiger
Among the various "no-go
theorems" in the foundations of
quantum mechanics, Bell inequalities are among the few, which do not implicitly rely on the mathematical structure of
quantum mechanics. Instead, Bell inequalities are commonly understood to rest on Kolmogorov's theory of probability and a "locality" assumption. Physical evidence supporting their violation is hence taken as evidence against at least one of these two assumptions. This work provides a comprehensive analysis of the physical debate on Bell inequalities from the point of view of Kolmogorov's theory of probability, focusing on the Bell-Clauser-Horn-Shimony-Holt inequality (BCHSH inequality). The central contribution is the motivation and mathematical study of the notion of contextuality in Bell experiments: in so-called contextual Bell models the detectors themselves behave randomly and the distribution of the random detector parameters depends on the chosen detector settings. It is shown how even "classical" Bell experiments motivate such a description. The need to account for contextuality was pointed out before by de la Peña, Cetto, Brody, Lochak, Bohm, Hiley and others. A broad class of contextual models is proven to satisfy the BCHSH inequality, thereby generalizing a previous result by Gill and Lambare. Nonetheless, even under strong locality requirements, contextual Bell models may violate the BCHSH inequality: based on work by Popescu and Rohrlich, we consider a "proof of concept" example exhibiting the maximum possible violation. Contrary to the much debated "loopholes" in empirical tests of Bell inequalities, contextuality thus reveals a conceptual misunderstanding in the physical conclusions commonly drawn from Bell inequality violations.
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Geophysics
Data-driven analysis of muon flux variations in muography time series at the Sos Enattos Mine
M. Tramontini, J.-C. Ianigro and J. Marteau
Muon flux variations in muography time series can provide information on density-related changes in geological targets. A common approach is to define regions of interest before constructing flux time series, but this choice may dilute coherent signals or mask localized variations. We present a data-driven analysis of two
muon data acquisitions at the Sos Enattos Mine in Sardinia, Italy. The method aggregates lines of sight into overlapping spatial blocks, computes standardized flux deviations, and applies principal component analysis through singular value decomposition. The leading components reveal spatially coherent structures and distinct temporal evolutions. In each run, the first mode explains more than 20% of the variance, while the first eight modes explain approximately 80%. Regions selected from the spatial modes show anticorrelated and delayed flux variations. These results show that the proposed approach can identify candidate regions of coherent
muon-flux variability without imposing them a priori.
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Mathematical Physics
A Kinetic Theory Approach To Ordered Fluids: Direct Simulation Monte Carlo Methods
José A. Carrillo, Patrick E. Farrell, Andrea Medaglia et al. (+1 more)
We present a direct simulation Monte Carlo (DSMC) method for the kinetic theory of ordered fluids recently introduced by the authors. The microscopic constituents of these fluids carry an order parameter belonging to a
manifold. The method applies Strang splitting to couple a Monte Carlo treatment of the binary collisions with a
symplectic integration of the mean-field Vlasov transport on the order-parameter
manifold. We use the Nanbu-Babovsky approach for Maxwellian collision kernels, and Bird's acceptance-rejection method for general ones. The mean-field Vlasov force is reconstructed from the particle ensemble at each time step. We also include a Bhatnagar-Gross-Krook (BGK) / Andersen thermostat to control the system temperature. We formulate the method for a generic order-parameter
manifold, and specialize it to two-dimensional calamitic (rod-like) molecules. Numerical tests validate the method. We confirm the relaxation to the Maxwellian distribution predicted by the H-
theorem, and simulate the mean-field
alignment driven by quadratic, Kuramoto, and Onsager interaction potentials. With the Onsager potential we successfully capture the isotropic-nematic phase transition at the correct critical temperature.
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All authors José A. Carrillo, Patrick E. Farrell, Andrea Medaglia, Umberto Zerbinati