Quantum Physics
Predicting electric-field noise in ion traps using fluctuation electrodynamics
Markus Teller, Da An, Alberto M. Alonso et al. (+4 more)
Electric-field noise in microfabricated surface ion traps contributes to gate errors in trapped-ion
quantum computers, but this noise has been challenging to predict. Here, we present a method to predict the electric-field noise arising from fluctuations in the bulk of dielectric and metallic materials. The method is valid for arbitrary trap geometries, and the only relevant material property is energy loss. We apply it to an ion trap with an electrically floating electrode and find the contribution from dielectrics to be dominant. Our model predicts the observed noise for this trap within a factor of four. In addition, we apply our model to typical surface trap designs and analyze how the electrode structures shield the noise.
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All authors Markus Teller, Da An, Alberto M. Alonso, Philip C. Holz, Philipp Schindler, Hartmut Häffner, Tracy E. Northup
Medical Physics
AnatomIQ: An Open-Source Toolkit for Automated Background Detection in Medical Imaging
Rafael Carballeira, Hayley A. Cash and Marthony L. Robins
Manual background selection for contrast-to-noise ratio (CNR) calculations in CT image quality assessment is time-consuming, operator-dependent, and compromises reproducibility. Advanced metrics such as Noise Power Spectrum (NPS) and Task Transfer Function (TTF) traditionally require dedicated phantom acquisitions, adding cost, radiation exposure, and workflow disruption. We developed AnatomIQ, an open-source Python toolkit that automates background detection and performs phantom-free NPS and TTF analysis directly on patient anatomy. Automated background detection uses tissue-specific Hounsfield unit thresholding and morphological filtering, paired with a web interface for click-to-select lesion identification from PACS screenshots. Reported metrics include CNR, signal-to-noise ratio, detectability indices, and dose-normalized figures of merit with automated optimization recommendations. NPS quantifies noise texture from automatically detected uniform tissue regions, while TTF leverages natural circular anatomical structures (e.g., trachea, vessels) as edge phantoms, together characterizing the resolution-noise trade-off without dedicated phantom scans. Analysis takes 2-3 minutes per case, with CNR computed in under 10 seconds and NPS/TTF available on demand. Automated detection reliably identified valid regions across anatomical sites, including head-and-neck scans, a near-worst-case test of uniform-region availability. Both NPS and TTF pipelines were validated against phantom-derived references, confirming that in vivo measurements reflect genuine anatomical texture and resolution rather than pipeline artifacts. By eliminating operator variability and phantom requirements, AnatomIQ enables practical continuous quality monitoring and evidence-based reconstruction optimization. The toolkit is open-source, with optional commercial licensing for academic and clinical use.
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Quantum Physics
Mentor-Initiated Asymmetric Bidirectional Quantum Teleportation Protocol for Arbitrary Qubit States
Sugata Adhya and Benchao Yang
In this paper, a mentor-initiated bidirectional asymmetric
quantum teleportation protocol is proposed. Unlike existing schemes that restrict the two-
qubit state transmitted from Bob to Alice to a Bell-like form $\alpha|00\rangle+\beta|11\rangle$, our protocol allows an arbitrary two-
qubit state to be teleported from Bob to Alice within the mentor-initiated framework. The required entangled resources are constructed using standard
quantum gates, and the protocol is illustrated through its
quantum-
circuit implementation in Qiskit. The proposed protocol is further simulated using Qiskit, and the simulation results show probability distributions very close to the theoretically expected values for the chosen input states.
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Quantum Physics
A Code-Agnostic Graph Neural Network Decoder from the Detection Error Model
Federico Alberto Astolfi and Guido Pupillo
We present POLYMECHANON, a graph neural network (GNN) decoder for
quantum error correction whose only input is the detection error model (DEM) of a
quantum code under a given noise model. We represent the DEM as a tripartite graph of detectors, error mechanisms and logical observables, where every input feature is computed by using the
quantum code as data rather than design choice. In this way, the same architecture decodes in principle any stabiliser code, under any noise model that can be expressed as a detection error model, once trained on the DEM. We test this approach along four directions. Firstly, on the rotated surface code the decoder outperforms correlated MWPM under both phenomenological and
circuit-level noise, with up to $25\%$ fewer logical failures. Secondly, on a family of high-rate qLDPC codes it matches BP+OSD on the smaller codes and surpasses it on the larger ones, with up to $16\%$ fewer logical failures on $[\![130,4,6]\!]$. Thirdly, its decoding time does not depend on the physical error rate, whereas that of BP+OSD grows with it: on $[\![130,4,6]\!]$ its effective cost per shot is of the order of a few ms on a single GPU against a few tens of milliseconds for BP+OSD on a single CPU core, and its fixed computational graph makes it a candidate for real-time decoding on neutral-atom processors. Finally, a single model trained across codes of different families outperforms uncorrelated MWPM on the graph-like codes seen during training and stays within $10\%$ of BP+OSD on the others, while it tends to fail to generalize to unseen codes, particularly larger ones. Its probabilistic output enables confidence-based post-selection, lowering the logical error rate by more than an order of magnitude on the surface code while keeping more than $90\%$ of the shots. Since only the DEM changes, new codes and noise models can be decoded without redesigning the decoder.
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Solar and Stellar Astrophysics
Ensemble pulsational characteristics of eclipsing binaries containing $\beta$ Cep stars observed by the TESS mission
C. I. Eze, G. Handler, M. Vanrespaille et al. (+4 more)
Massive pulsators in eclipsing binaries provide precise, model-independent
stellar parameters that, combined with asteroseismic constraints, provide powerful probes of interior properties and angular-momentum transport in massive
stars. This study investigates the pulsational characteristics and their impact on the structure and
evolution of $\beta$ Cep pulsators in eclipsing binaries. We analyse an ensemble of 65 $\beta$ Cep
stars in eclipsing binaries, identify rotationally split modes where possible, and statistically investigate the dependence of pulsational properties on binary orbital parameters. We derive their interior properties using MESA model grids and associated StORM pulsation frequencies, together with an asteroseismic routine that tracks
stellar age and rotation across the $\beta$ Cep instability region. Interior rotation rates are derived for 14 systems that exhibit rotational mode splitting. While differential rotation is tentatively inferred for HD 112485, the other systems, except CZ Vel, are consistent with quasi-rigid rotation. The seismic and evolutionary properties of HD 112485 and EK Cru are derived through detailed forward asteroseismic modelling. HD 112485 is one of the least evolved $\beta$ Cep
stars asteroseismically modelled to date, with a core hydrogen mass fraction $X_{c}= 0.501_{-0.013}^{+0.009}$. The two reproduced zonal modes in HD 112485 are the first radial-order dipole pressure mode and the second radial-order quadrupole
gravity mode, while the zonal modes in EK Cru are the second-order quadrupole mixed mode and the third order dipole pressure mode. A multivariate regression shows a negative correlation of the pulsation amplitude with pulsation frequency, and no statistically significant relationship with the orbital period. In addition, no significant relationship is observed between the pulsation frequency and the orbital period in this sample.
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All authors C. I. Eze, G. Handler, M. Vanrespaille, A. Kemp, A. Tkachenko, D. M. Bowman, C. Aerts
Chaotic Dynamics · Cross-listed from math.DS
From trends to optimized forecasts: Quantifying the skill and advancing the utility of dynamics-based early warnings for tipping events
Franco Du Plessis, Victoria Volodina, Chris A. Boulton et al. (+5 more)
In this paper we explore and extend the state of the art for understanding the skill and utility of early warnings of critical transitions (tipping points) in forced nonlinear systems. We highlight some of the challenges and opportunities of transforming estimates of a dynamics-based early warning system, based on trends in stability or resilience into forecasts with high skill. We highlight the importance of (a) quantifying consequences of possible actions in response to warnings that may be false negatives or positives (b) considering finite time horizon predictions to give verifiable predictions (c) assumptions necessary for valid extrapolations of trends. We evaluate approaches to improving the skill and utility of the forecast.
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All authors Franco Du Plessis, Victoria Volodina, Chris A. Boulton, Muhammed Fadera, Sneha Kachhara, Timothy M. Lenton, Paul D. L. Ritchie, Peter Ashwin
Solar and Stellar Astrophysics
Delayed, Line-dependent Reorganization of Pore Oscillations Following a Compact C8.2 Flare Observed by Sunrise III/SUSI
Shahin Jafarzadeh, David B. Jess, Marco Stangalini et al. (+34 more)
Magnetic oscillations permeating the
solar atmosphere can be altered by
flares. This could be due to changes in the atmospheric
magnetic waveguide, the thermodynamic stratification, or both. To investigate this, we examine oscillations in a
magnetic pore crossed in part by the ribbon of a C8.2
flare, using observations from the Sunrise Ultraviolet Spectropolarimeter and Imager (SUSI) aboard Sunrise III. We track the core intensities of eight spectral lines between 327-329 nm and show that oscillatory power in the 4.2-7.0 mHz range, measured around 30 minutes after the
flare peak, exceeds the pre-event value in all eight lines by factors of 1.60-8.71. Conversely, in the 7.0-11.5 mHz band, the post-event intensity power is lower - approximately 0.13-0.41 of the original power in seven of the observed lines. Line-center velocity measurements support the lower-frequency enhancement. This delayed, line-dependent shift toward the lower-frequency band is consistent with
flare-induced changes in wave transmission, reflection, or resonant response, although thermodynamic and
magnetic effects cannot yet be separated.
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All authors Shahin Jafarzadeh, David B. Jess, Marco Stangalini, Lyndsay Fletcher, Ryan O. Milligan, Paulo J. A. Simões, Peter H. Keys, Sami K. Solanki, H. N. Smitha, Andreas Lagg, Achim Gandorfer, Alex Feller, Francisco A. Iglesias, Tino L. Riethmüller, Bianca Grauf, Johannes Hoelken, José Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alberto Álvarez-Herrero, Masahito Kubo, David Orozco Suárez, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović
Statistical Mechanics
Scalar field theory for (chiral) active Brownian particles: bottom-up derivation revisited
Yuta Kuroda and Thomas Speck
The active Brownian particle (ABP) model is one of the most widely used particle-based models in studies of scalar active fluids. A collection of interacting ABPs is known to exhibit intriguing phenomena that are absent in
equilibrium counterparts. A prominent example is spontaneous phase separation, known as motility-induced phase separation (MIPS), which occurs even in the absence of explicit attractive interactions. In parallel, the large-scale behavior of scalar active fluids is often modeled using continuum descriptions, namely, scalar field theories. Such scalar active field theories are usually formulated in a top-down manner, and establishing their connections to particle-based models remains challenging, with these connections not yet fully understood. To advance the microscopic derivation of scalar active field theories, we revisit the connection between ABPs interacting via a two-body potential in two dimensions and scalar field theories that include all possible terms up to fourth order in spatial gradients. Our approach is based on a pressure expansion and the renormalization group (RG) method in the context of singular perturbation theory. The RG method provides a systematic way to eliminate fast variables and identify the dynamics on the slow invariant
manifold. Within this framework, scalar field theories can be obtained as RG flow equations. We also apply this method to a
chiral variant of the ABP model, the
chiral ABP (cABP) model, in which a constant torque biases particle rotation to the left or right. We show that the scalar field theory corresponding to the cABP model contains two “odd” terms in addition to those present in the scalar field theory for ABPs. The method developed here may also be useful for deriving hydrodynamic descriptions of other types of active matter systems.
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Quantum Physics
Dissipation-Enabled Operator-Norm Locality Bounds for Bose-Hubbard Hamiltonians
Marius Lemm and Tim Möbus
Closed bosonic
lattice systems do not generally admit operator norm Lieb–Robinson bounds uniformly in the initial state. The reason is that the information propagation velocity can grow with the local
boson occupancy, which can be macroscopically large. Here, we show that local dissipation restores an operator-norm Lieb–Robinson bound. We consider the dissipative Bose–Hubbard model described by a Lindbladian operator with on-site $\ell$-
photon loss, $\ell>2$ and, for our main result, we establish an almost-ballistic Lieb-Robinson bound. Dissipation rapidly depletes highly occupied sites, thus regularizing the state on the Sobolev-type scale of local particle moments. The resulting moment bounds diverge as time approaches zero but remain integrable near zero at sufficiently low orders. We extend these ideas to treat cat-code dissipation and, for initial states in the code space, we prove a local adiabatic approximation uniform in the total volume. Further consequences include local channel approximation, a thermodynamic limit, and efficient digital
quantum simulation. The point is that these applications are now available uniformly in the input state, as for
quantum spin systems, but in contrast to closed Bose–Hubbard systems.
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High Energy Physics (Theory)
Einstein-Gauss-Bonnet quintessential inflation: From super-inflation to emergent warm inflation
Omar Chahboun, Rachid Ahl Laamara and El Hassan Saidi
This work presents a unified inflationary and late-time cosmology, developed within Einstein-Gauss-Bonnet
gravity coupled to three scalar fields, governed by a single potential and coupling function throughout
cosmic history. Permitting the Gauss-Bonnet coupling to depend on the field content, rather than assigning it arbitrarily, produces a two-phase inflationary scenario: the higher-
curvature term initially drives expansion and later becomes a subdominant. The initial super-inflationary stage ends dynamically when the geometrically induced stabilization of the waterfall field fails, at a field value determined by the combination $(n-1)Q$. Coherent oscillations of the waterfall condensate serve as the initial radiation source, replacing conventional reheating and establishing the thermal bath necessary for the subsequent warm phase. Utilizing a two-stage dissipation mechanism with $\Gamma_\phi\propto T^3$, the scalar and tensor spectra are derived while retaining Gauss-Bonnet contributions, demonstrating that the growth of inflaton fluctuations is regulated by the shear viscosity of the bath, which is essential for model viability. A quartic potential, previously excluded in the cold scenario, becomes viable, with $n_s$ within the Planck $1\sigma$ band and $r$ suppressed. Agreement with the spectral index is generic, while internal consistency confines the model to a narrow band in $(n-1)Q$. Finally, the release of the third scalar near matter-radiation equality transforms a very small mass scale into a very large coupling by a logic inverse to the seesaw mechanism. At late times, the inflaton persists as dark energy.
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Statistical Mechanics
Optimal sampling strategies in event-chain Monte Carlo
James Gulliford, Gareth O. Roberts and Michael F. Faulkner
Event-chain Monte Carlo (ECMC) has revolutionised computational sampling over recent years, providing a powerful alternative to the molecular-dynamics (MD) and
Hamiltonian Monte Carlo (HMC)
algorithms. Each method outperforms the ubiquitous random-walk Metropolis
algorithm by advancing particles along deterministic trajectories, but ECMC achieves this without being constrained by Newtonian dynamics. Recent advances exploited this dynamical freedom to induce a collective particle dynamics that relax local density variations on fast timescales. In a foundational model of $N$ pairwise-interacting particles on the 1D
torus, this led to an $O(N^{3/4})$ improvement on the industry-leading computational efficiency of MD and HMC - but with an impractically small prefactor at low/high mean particle density for general attractive/repulsive interactions. Here we present a universal framework that generalises this high-efficiency sampling strategy to all translationally symmetric pairwise models on the
torus - creating the potential to surpass MD and HMC as the state of the art. We also numerically elucidate the collective particle dynamics and discuss broad impact across the physical sciences and computational statistics.
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High Energy Physics (Phenomenology)
Overlapping Subcritical Bubbles: Free Energy and Lifetime
Guangshang Chen, Yang Xiao, Jin Min Yang et al. (+1 more)
Subcritical bubbles can form an appreciable population during weak first-order phase transitions, but are usually treated as isolated fluctuations. This raises the question of whether spatial overlap between neighboring subcritical bubbles can modify their
evolution. We address this question by combining analytic free-energy calculations for composite Gaussian profiles with Langevin simulations of overlapping configurations. We find that the overlap lowers the free-energy cost and generally increases the lifetime of subcritical bubbles, with the enhanced persistence potentially feeding back on their abundance. Such overlap can therefore generate collective effects and should be incorporated into kinetic descriptions of subcritical-bubble populations.
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All authors Guangshang Chen, Yang Xiao, Jin Min Yang, Yang Zhang
Chemical Physics
Relativistic Hirshfeld atoms in a molecule: An information-theoretic view, with application to Drude oscillator dispersion models
Keegan Paice and John M. Herbert
Several ad hoc dispersion models for density-functional theory are based on the use of Hirshfeld (or "stockholder") partition of a molecular charge density, which provides an in situ definition of atomic size. We show that a recently introduced "optimized"
quantum Drude oscillator model for dispersion admits a closed-form solution in terms of the Lambert $W$ function, whose branches identify the compact and diffuse oscillator solutions. The compact solution determines the $C_8$ (dipole-quadrupole) dispersion coefficient analytically from the free-atom polarizability, $C_6$ coefficient, and van der Waals radius, without any reference $C_8$ data. Next, we provide a formal basis for a relativistic version of the atoms-in-molecule Hirshfeld partition. Using four-component Dirac-Hartree-Fock densities for isolated atoms defines a strictly positive deformation field that carries the relativistic changes in atomic density into the Hirshfeld partition. A uniqueness
theorem for the non-relativistic case is extended to relativistic Hirshfeld atoms and admits an asymptotic expansion through quadratic order in the fine-structure constant. Normalization requires the relativistic density correction to reshape the reference atom while preserving its population. Finally, four-component polarizabilities and C6 coefficients are reported for closed-shell atoms and ions, which supply the reference data required to extend atoms-in-molecules dispersion models into the heavy-element regime. Periodic trends are observable in a scalar contraction factor that measures relativistic effects.
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Mathematical Physics
The Buchholz Algebra from the Universal Resolvent Algebra–Particle Structure, Gibbs States, and Closed-Path Expansions without Fock Representations
Yoshitsugu Sekine
We construct the Buchholz
algebra without a Fock representation, as the bounded inverse limit of intrinsic particle-cutoff quotients of the gauge-fixed resolvent
algebra, with isometric particle-degree coordinates. Its finite
matrix corners carry canonical traces, KMS states, and trace-norm product formulas, together with closed-path expansions that lay the groundwork for path-integral representations. The known Fock-space description and a proper quasilocal subalgebra arise as realizations.
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Soft Condensed Matter
Learning to Classify Threading in Melts of Rings
Filippo Conforto, Roman Staňo, Jan Smrek et al. (+1 more)
Dense melts of nonconcatenated ring
polymers exhibit anomalous dynamics and nonlinear rheology, in some cases linked to long-lived inter-ring threading
entanglement. Detecting these
geometric constraints remains computationally demanding, with different methods being based on different
geometric features tuned to specific models. Here, we introduce a machine-learning framework that detects threading directly from the writhe of ring conformations and we demonstrate its broad generalisability. Trained on simulations of isolated, distance-constrained pairs of short rings, a one-dimensional convolutional neural network (CNN1D) operating on the writhe profile classifies threading states with over 98% accuracy on held-out ring pairs. Remarkably, this model generalises without retraining to
equilibrium dense melts spanning a wide range of densities and chain lengths (N = 100 to 1600), maintaining true-positive rates above 91% with false-positive rates near zero. Misclassified conformations are limited to physically ambiguous, shallow threading events which are arguably not impacting the dynamics of the rings. Effectively, writhe captures the interaction between the two rings, allowing writhe-based classifiers to improve the topological analysis of large ring-
polymer systems with a 3-fold speed-up over the state-of-the-art minimal-surface detection. These results establish the writhe-trained neural networks as an accurate, scalable tool for characterising
entanglement in ring
polymer melts.
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All authors Filippo Conforto, Roman Staňo, Jan Smrek, Davide Michieletto
High Energy Physics (Phenomenology)
From the LZ Event to Grand Unification: Heavy Higgsinos and Proton Decay
Shihwen Hor, Natsumi Nagata and Tsutomu T. Yanagida
The recently reported LUX-ZEPLIN (LZ) event has renewed interest in inelastic Higgsino dark matter. While a weak-scale Higgsino provides a simple interpretation of the event, such a scenario is in tension with the IceCube bound from dark-matter capture and annihilation in the Sun. This tension can be avoided for a much heavier Higgsino, with a mass of order $10^5$ GeV and a neutral-state mass splitting of $\simeq 400$ keV, which in turn points to gaugino masses around $10^7$ GeV. Such a heavy supersymmetric spectrum is often thought to be unfavorable for supersymmetric grand unified theories (GUTs), since it tends to worsen gauge coupling unification and lower the unification scale, potentially leading to excessively rapid
proton decay. In this work, we revisit this expectation in minimal supersymmetric SU(5), taking into account the GUT-scale threshold corrections. We show that the resulting unification conditions allow the SU(5) gauge
bosons to remain sufficiently heavy when the adjoint-
Higgs self-coupling is small, thereby suppressing dimension-six
proton decay. At the same time, the color-triplet
Higgs mass can remain near the conventional GUT scale, $M_{H_C}\sim 10^{16}$ GeV, particularly when the gluino is significantly heavier than the wino. Remarkably, in this region the dimension-five decay mode $p\to K^+\bar\nu$ can have a lifetime within the reach of next-generation
proton-decay searches, including Hyper-Kamiokande, JUNO, and DUNE. We also discuss supersymmetry-breaking scenarios that can give rise to the required supersymmetric mass spectrum.
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Quantum Physics
Electromagnetic Side-Channel Vulnerability in QKD Equipment
Mikio Fujiwara, Katsumi Fujii, Fumie Ono et al. (+2 more)
Actual
quantum key distribution network nodes may be vulnerable to side-channel attacks such as electromagnetic leakage. In this study, we measured electromagnetic emissions from a prototype
quantum key distribution device implementing a time-bin decoy-state BB84 protocol with Y and Z bases. We measured the electromagnetic spectra and waveforms at distances of 0 m and 3 m from the transmitter and receiver inside an anechoic chamber. The results showed that the transmitter was the primary source of electromagnetic leakage, and distinct differences were observed between the
quantum states generated at the third harmonic of the 1241.6 MHz clock.
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All authors Mikio Fujiwara, Katsumi Fujii, Fumie Ono, Masakazu Ono, Akihisa Tomita
Accelerator Physics
From Simulation to Fabrication: Realizing Silicon Crystalline Undulators with Silicon Nitride Stressor Layer Patterning
L. Malagutti, L. Bandiera, F. Bonafè et al. (+14 more)
A crystalline undulator is a
crystal exhibiting periodic deformations that cause channeled particles to oscillate, generating coherent electromagnetic waves. In this study, stressor layer patterning has been employed to induce the desired deformations on a silicon substrate. Finite element method simulations were performed to optimize the
geometric parameters of the undulator. The primary focus was on achieving sinusoidal deformation with sub-millimeter period and amplitude exceeding 1~nm, utilizing the silicon (110) plane for its superior channeling properties. Key parameters, such as substrate thickness and undulator period, were meticulously refined to ensure uniform deformation while minimizing the impact of higher harmonics, which could degrade performance. Based on the simulation results, a crystalline undulator, 160 $\mu$m thick and consisting of 10 periods with a period length of 334 $\mu$m, has been successfully fabricated. The final device demonstrates structural integrity and a uniform deformation extending up to 20 $\mu$m from the surface. Specifically designed for use with 5-30 GeV particle beams, the undulator is capable of generating gamma
photons in the 5-15 MeV range. This work effectively integrates advanced simulation techniques with precise fabrication methods, demonstrating the feasibility of crystalline undulators as high-performance devices for generating gamma radiation.
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All authors L. Malagutti, L. Bandiera, F. Bonafè, N. Canale, D. De Salvador, P. Fedeli, V. Guidi, A. V. Korol, F. Mancarella, R. Negrello, Gianfranco Paternò, M. Romagnoni, F. Sgarbossa, A.V. Solov'yov, A. Sytov, D. Valzani, A.Mazzolari
General Relativity and Quantum Cosmology
Where Chaos Pauses: Sliding-Window Frequency Ratios Reveal Transient Resonances in Relativistic Orbits
Wenfu Cao, Ying Wang and Hongsheng Zhang
A long-time Poincaré section flattens a chaotic orbit into one static blur, erasing the order in which the orbit visits its own local structures. We introduce the sliding-window frequency ratio (SWFR), built from nothing but radial and polar turning events, to recover that order along individual relativistic orbits. Each window spans a fixed number of radial cycles and simply counts the polar events inside it; because event times are kept, any candidate interval can be sliced out and replotted as its own Poincaré section. No spectrum, no reference center, no basis functions. Integrable Kerr
benchmarks recover the known frequency ratios, and for regular motion with uniformly bounded count deviations the counting-error bound falls off as $O(W^{-1})$. The same counts then pay off in chaos. In magnetized Kerr spacetime a single charged orbit dwells near $3/5$ and later near $4/7$, and exactly those intervals open into fivefold and sevenfold section structures; a second orbit dwells near $1/2$ with two lobes. In Schwarzschild–Melvin spacetime a
photon holds $4/5$ across a fivefold pattern. In every case the section covers exactly the interval SWFR selected: integer counts and phase-space geometry agree that a globally chaotic orbit is paying a temporary visit to a resonance.
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Strongly Correlated Electrons
Why polar excitons stay sharp: parity protection of the center-of-mass recoil channel in exciton-phonon scattering
Michael O. Atambo
In polar
semiconductors the Fröhlich interaction is the dominant electron–
phonon coupling, yet excitonic resonances in materials such as halide perovskites remain anomalously sharp. We show that standard frozen-center-of-mass treatments of the
exciton–
phonon problem miss the decisive kinematic degree of freedom: restoring the exact center-of-mass (COM)
recoil reveals a universally open, parameter-free $1s\to1s$ absorption channel at
recoil momentum $q_*=\sqrt{2M_{\rm ex}\hbar\omega_{\rm LO}}/\hbar$, whose rate scales as $N_{\rm LO}(T)$. We prove that this
recoil channel is controlled by destructive electron–hole interference: the
recoil linewidth vanishes with the mass asymmetry as $\gamma_{\rm LO}^{\rm recoil}\propto\mathcal{F}_{1s,1s}(q_*)^2$, and the elastic dressing obeys the exact suppression law $S_X/S_{\rm ind}=\eta^2(6-\eta^2)/5$ within the hydrogenic Fröhlich model. The theory establishes a hierarchy of scattering regimes. In mass-asymmetric materials (GaAs, $\eta=-0.74$) the
recoil channel is active ($\gamma_{\rm LO}^{\rm recoil}=2.2$~meV); in mass-symmetric materials (FAPbI$_3$, $\eta=0$; MAPbI$_3$, $\eta=-0.11$) it is killed by interference (0.00 and 0.12 meV), showing that the observed 27–40 meV perovskite linewidths cannot be accounted for by COM
recoil and therefore require internal-state-changing and other inelastic channels, of which the constructive, $\eta$-robust $1s\to np$ resonance is the leading candidate within the present model. The Fröhlich constant $\alpha$ alone is therefore insufficient as a figure of merit: after projection onto the correlated
exciton, the controlling parameters are $\eta$, $q_*a_X$, and the Rydberg detuning.
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Chemical Physics
Numerical integration of intracule pair densities with optimized multicenter grids
Markel Ylla, Jesus M. Ugalde, Eduard Matito et al. (+1 more)
Intracule pair densities provide insight into electron correlation, but their routine analysis in extended systems is limited by the cost of numerical integration and the restriction of analytical methods to Gaussian basis functions. We present an efficient multicenter integration scheme for intracule densities and their moments. By adapting the topological fuzzy Voronoi
cell formalism, we partition intracule space around interatomic displacement vectors, concentrating quadrature points near secondary density maxima that standard single-center grids poorly resolve.
Benchmarks on linear alkanes show improved convergence with increasing molecular size, achieving relative errors below 0.02% in electron-electron repulsion energies with fewer quadrature points than single-center methods. The partitioning also enables the decomposition of global two-electron properties into spatial contributions associated with short- and long-range electron-pair separations. Coupling the multicenter grid with kernel density estimation reconstructs smooth radial intracule distributions at large interelectronic distances without the dense angular grids required by conventional surface integration. Validation on the S22
dataset supports the reliability of the method across diverse molecular systems. These developments facilitate intracule analysis in polyatomic systems and the investigation of electron correlation and dispersion interactions.
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All authors Markel Ylla, Jesus M. Ugalde, Eduard Matito, Eloy Ramos-Cordoba
Fluid Dynamics
Femtosecond laser-induced cavitation seeds liquid-jet breakup beyond the Rayleigh-Plateau stability limit
Sourabh Singh, Tamanna, S. Sree Harsha et al. (+1 more)
The Rayleigh-Plateau instability predicts that infinitesimal perturbations of a
liquid jet grow only for kR < 1, with kR = 1 marking the classical stability boundary. Here, we show that femtosecond-
laser-induced cavitation generates a localized, impulsive
recoil perturbation on a flowing
liquid jet, enabling a two-dimensional map of jet breakup across the (kR, epsilon/R) plane. The perturbation's spacing (wavelength) and strength (amplitude) are set independently by the
laser repetition rate and pulse energy, respectively. At low amplitudes, tuning the repetition rate recovers the classical Rayleigh-Plateau dispersion relation and its kR = 1 cutoff, while increasing the wavelength enables controlled generation of monodisperse droplet trains, bidisperse droplet populations, and ultimately isolated single droplets. Along the amplitude axis, low pulse energies produce a seed that amplifies only the imposed wavenumber, whereas above a critical energy Ec, the seed broadens to excite many wavenumbers simultaneously. At still higher amplitudes, we demonstrate deterministic breakup for kR > 1, extending to kR = 1.9, with
laser-synchronized droplet production rates up to 0.2 MHz. These results establish localized femtosecond-
laser-induced cavitation as a route to controlled Rayleigh-Plateau breakup both within and beyond the classical linear-stability boundary.
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All authors Sourabh Singh, Tamanna, S. Sree Harsha, Prashant Kumar Singh
Strongly Correlated Electrons
Mass-asymmetry-controlled exciton dressing and dissociation in a quantum lattice model
Michael O. Atambo
In a polar material, a neutral
exciton couples to
phonons through the sum of the electron and hole deformation potentials. Because the total source vanishes by charge neutrality, the elastic
exciton-
phonon vertex is regularized by electron-hole interference. Here we determine the non-perturbative fate of this interference by exact diagonalization of a Holstein-
exciton model. By parameterizing the mass asymmetry to decouple it from the small-polaron atomic limit, we map a regime map comprising an internal dressing crossover and a dissociation boundary. We prove analytically and verify numerically that for equal masses, the symmetric
exciton ground state is protected from
phonon dressing by an exact exchange selection rule, provided the
phonon source is odd under electron-hole exchange (the neutral case). As mass asymmetry increases, this selection rule is broken and the
exciton acquires a strong local polaronic cloud. We show that the dissociation boundary, conversely, is set by a global energy balance between Coulomb binding and polaronic stabilization, and is nearly independent of the internal dressing. Paradoxically, the very
symmetry that protects the
exciton from dressing denies it polaronic stabilization, driving it toward dissociation at strong coupling. We discuss these results in the context of
lattice exciton-polaron models and their implications for sharp versus broad excitonic lines in mass-symmetric versus mass-asymmetric polar
semiconductors.
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Fluid Dynamics
An unstructured finite-volume Helmholtz method with perfectly matched layers for heterogeneous two-phase acoustics
Chuanchao Xu, Jun Liu, Jan Helge Dörsam et al. (+3 more)
This paper presents a
cell-centred unstructured finite-volume method for time-harmonic two-phase acoustics. A volume-fraction representation supplies density and acoustic compressibility. Face fractions average available neighbouring planar interface cuts independently of velocity direction, retaining the established one-field face-density closure. Cartesian complex-coordinate stretching provides perfectly matched layers (PMLs). Real-imaginary splitting yields a real-valued block system, discretized with corrected non-orthogonal fluxes and consistent boundary contributions. Verification covers homogeneous waves, layered gas-
liquid transmission with PML truncation, baffled-piston radiation with Kirchhoff far-field reconstruction, and resolved rigid-sphere radiation forces. Homogeneous-wave pressure converges at approximately second order on orthogonal meshes and on meshes with non-orthogonal interiors and orthogonal boundary
cells. Reconstructed velocity converges at approximately second order on orthogonal meshes and with an observed order of about 1.7 on the latter mesh family. Under aligned refinement, the layered case's relative whole-domain complex-pressure $L_2$ error decreases to $2.657\times10^{-4}$. The resolved-sphere force differs from the Gorkov prediction by at most 1.5% over the tested Rayleigh size range. The results quantify the accuracy and current limitations of the heterogeneous Helmholtz-PML formulation.
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All authors Chuanchao Xu, Jun Liu, Jan Helge Dörsam, Mario Kupnik, Tomislav Maric, Dieter Bothe
Fluid Dynamics
Total Collision Energy model for surface processes in the DSMC method
Yevgeniy A. Bondar and Alexandra N. Molchanova
The total collision energy (TCE) approach originally developed for taking into account gas-phase chemistry in the direct simulation Monte Carlo method is applied to surface chemistry modeling. In the proposed surface TCE (sTCE) model probability of the impact process as a function of the translational energy of the molecule is found analytically from the finite-rate Arrhenius data. This probability function lacks some mathematical drawbacks typical of previous models. Effects of surface temperature, incident angle and internal energy can be taken into account in the sTCE model. Additionally the model is generalized to the specified reaction efficiency formulation.
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Disordered Systems and Neural Networks · Cross-listed from stat.ML
The hidden advantage of mask resampling: a theory of masked autoencoders
Jorge Medina Moreira, Lorenzo Bardone and Lenka Zdeborová
Why can masked prediction learn useful representations that unmasked reconstruction misses? We study this question in a high-dimensional model of a masked autoencoder (MAE) trained on data with shared latent structure and heterogeneous noise. We prove that masked linear reconstruction can recover the latent feature at linear sample complexity in regimes where unmasked linear reconstruction, equivalent to PCA, fails. The analysis also quantifies the statistical advantage of mask resampling, an established ingredient of masked pretraining. By introducing a fixed collection of $K$ masks per sample, we characterize its effect on feature recovery and downstream performance, identifying regimes where greater mask diversity lowers sample complexity. Guided by this prediction, we find that random cropping and flipping in standard image-training pipelines can obscure the advantage of mask resampling by renewing the prediction task even when the patch mask is fixed. Removing these transformations reveals a downstream advantage for dynamic over static masking in CNN autoencoders and
vision transformers. A complementary BERT pilot finds benefits from greater mask diversity on downstream
language tasks. Our results separate the benefit of the masked prediction objective from that of mask diversity, and show how a tractable theory can guide experiments that uncover advantages hidden by standard training practices.
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Nuclear Theory
Properties of rapidly rotating hot neutron stars within Brueckner theory
Hong-Ming Liu, Bo-Xiu Zhou, Zeng-Hua Li et al. (+2 more)
We study the properties of hot rapidly rotating
neutron stars using various equations of state based on the Brueckner-Hartree-Fock approach at finite temperature. The temperature dependence of gravitational mass, equatorial radius, Kepler frequency, moment of inertia are analysed in detail and universal relations are examined.
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All authors Hong-Ming Liu, Bo-Xiu Zhou, Zeng-Hua Li, Jin-Biao Wei, H.-J. Schulze
Soft Condensed Matter
Characterization and Quantification of Immiscible Polymer Blend Compatibilization by Phyllosilicate Clays
Ankit Patidar and Gaurav Goel
Phyllosilicate clays are widely used in
polymer nanocomposites owing to their high anisotropy and tunable surface polarity. Their distribution and interface localization in
polymer blends can be used to tune the properties of
polymer-clay nanocomposites (PCNCs). A coarse-grained (CG) force field for clays can aid molecular simulations in PCNC development. Here, we developed MARTINI-3 parameters, a CG force field with high chemical specificity, for phyllosilicate clays with diverse surface polarities. Initial interactions for the clay functional groups were determined from hydration free energies, obtained by applying the Lifshitz theory to experimental surface tension data. These were fine-tuned using the structural, thermodynamic, and dynamic properties of thermoplastic starch (TPS)-clay composites from all-atom (AA) molecular dynamics (MD) simulations. The radial distribution function and two-body excess
entropy of TPS components, not used in CG parameterization, were accurately estimated, establishing the robustness of the parameters. We investigated the effect of clay surface polarity on
polymer segmental dynamics and structure-property relationships. The CG parameters were then used to study the effect of dodecyltrimethylammonium (C12TAB)-modified montmorillonite (MMT), an organically-modified MMT, on TPS-polyethylene (PE) blend morphology using large time- and length-scale MD simulations. We observed compatibilization of the TPS-PE interphase by the amphiphilic clay particle, reducing the TPS-PE interfacial tension from 45 mN/m to 13.06 mN/m. We found good agreement between MARTINI-3 estimates for properties of model MMT-based PCNCs and those from AA simulations and experimental data, establishing grounds for the transferability of the parameters to other systems.
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Optics
Digitally enhanced Multi-wavelength Stabilization using a Passive Fiber Frequency Reference
Hilma Karlsson, Vaishali Adya, Robert L. Ward et al. (+1 more)
High-stability frequency stabilization between
lasers is essential for applications such as precision metrology, frequency dissemination, and
quantum communications. We demonstrate the use of code-based multiplexing of a passive fiber-based interferometer for frequency stabilization and transfer between
lasers separated by 85 GHz in frequency using a single shared passive reference. Out-of-loop characterization places an upper bound of sub-kHz/$\sqrt{\text{Hz}}$ on the transferred frequency noise at
Fourier frequencies above 40 mHz, with a differential fractional stability of $7\times10^{-13}$ at 1 second. We also demonstrate continuous
laser tunability and characterize the residual length noise coupling. Finally, we provide a framework for scaling the architecture to higher
laser counts, offering a pathway to scalable, frequency agile stabilization of multiple light sources without the overhead of an optical frequency comb.
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All authors Hilma Karlsson, Vaishali Adya, Robert L. Ward, Chathura P. Bandutunga
Quantum Physics
Marc Maußner and Volker Reers
This paper investigates the performance scalability and
adversarial robustness of
Quantum Machine Learning (QML) models deployed on noise-model-based fake simulators. We conduct a dual-phased study, first benchmarking the computational throughput of Qiskit's Aer simulation engine across varying hardware architectures, and second, evaluating the effectiveness of Projected Gradient Descent (PGD) attacks and
adversarial retraining strategies under realistic noise conditions. Our results quantify the runtime tradeoffs and scaling behavior for medium-scale simulations (projected up to 8
qubits) and demonstrate that high
adversarial-to-benign retraining ratios (50/50) are essential for achieving practical model robustness for 4-
qubit classifiers under realistic noise conditions.
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