Quantum Physics
Applications of quantum annealing to magnetic dipole hyperfine structure constants: First results beyond energies for atoms
Boni Paul, Subimal Deb, Per Jönsson et al. (+2 more)
We report the first results of the
magnetic dipole hyperfine structure (HFS) constants of neutral $\mathrm{Li}$, Li-like $\mathrm{Be}$, neutral $\mathrm{Na}$, and Na-like $\mathrm{Mg}$ using a modified version of the
Quantum Annealer Eigensolver (QAE)
algorithm on D-Wave's
quantum hardware. The results are benchmarked against relativistic configuration interaction with multiconfiguration Dirac Hartree-Fock (MCDHF) calculations using the General-purpose Relativistic Atomic Structure Package (GRASP), and simulated annealing. In our modified QAE, a zooming-and-sigma-annealing approach with a floating-point encoding scheme is adopted to estimate the ground-state
eigenvalue and eigenvector of the relativistic Dirac-Coulomb
Hamiltonian matrices ($H_{\mathrm{DC}}$) constructed from 11 or fewer configuration state functions (CSFs). For calculations with extended correlation orbital sets, we applied a CSF truncation scheme, retaining only CSFs (up to 12) that make significant contributions to the ground-state wavefunction. Our modified QAE precision is kept limited to three decimal places (up to 10
qubits). Hardware demonstrations on the D-Wave
quantum processing unit (QPU) yielded results that were completely consistent with GRASP (at the chosen precision) in determining the
magnetic dipole HFS constants, with accuracy varying across systems and $H_{\mathrm{DC}}$
matrix dimensions.
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All authors Boni Paul, Subimal Deb, Per Jönsson, Jörgen Ekman, Bhanu Pratap Das
Atmospheric and Oceanic Physics
PRecover 1.0: Process Rate Recovery with Machine Learning
Miriam Simm, Tom Beucler and Corinna Hoose
Comprehensive information on cloud microphysical process rates from numerical simulations allows for better understanding of precipitation formation pathways and aerosol-cloud interactions. However, resource limitations often make it impractical to include all microphysical process rates in the model output, limiting in-depth analyses. To address this shortcoming, we introduce PRecover, a data-driven post-processing approach to recover microphysical process rates that are not stored during runtime from standard output of a numerical weather prediction model. In particular, we train random forests, gradient boosting models, and feed-forward neural networks to recover microphysical process rates from a two-moment bulk microphysics scheme in the ICOsahedral Nonhydrostatic (ICON) model. We use cloud variables as input, obtained from high-resolution simulations in a limited-area setup over Europe. Warm-rain and ice microphysical process rates are recovered with a two-step classification-regression approach for both instantaneous and accumulated process rates. As a physics-based baseline, we assess whether process rates can be directly recalculated from stored ICON output variables. Accurate recalculation is possible for process rates such as
accretion and self-collection but not for the autoconversion, rain melting or heterogeneous ice nucleation rate. Using PRecover, we successfully recover most of the process rates that are accumulated over output time steps of 10 minutes or less, but the values are increasingly difficult to recover for rates accumulated over longer accumulation intervals. To quantify predictive uncertainty, we provide calibrated prediction intervals through conformalized
quantile regression. We demonstrate spatial transferability of the models with two case studies over different regional domains and simulation settings unseen during training.
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Quantum Physics
Multi-objective design of photon blockade for bright single-photon sources
Sunkyu Yu, Xianji Piao and Namkyoo Park
High-quality single-
photon sources, realized through saturable emitters,
photon blockade, or heralded pair generation, are indispensable building blocks for photonic
quantum platforms. Although these mechanisms suppress multiphoton emission through distinct principles typically captured by analytical models, their practical implementation is constrained by conflicting requirements for purity, brightness, and indistinguishability, which must be balanced within high-dimensional design landscapes. Here, we propose a computational framework for optimizing competing metrics of single-
photon sources. Building on a Liouville-space adjoint formulation that efficiently evaluates multiple objectives in Markovian open
quantum systems, we develop a Jacobian-based update, which ensures first-order monotonic reduction of multi-objective costs. By incorporating simulated annealing to escape gradient-vanishing plateaus, our framework achieves a design success rate of nearly 60 % for
photon blockade with g2(0) smaller than 0.1 and theoretically bounded brightness across a broad parameter space, without any analytical guidance. This framework provides a general recipe for multi-objective design of open
quantum systems.
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Mesoscale and Nanoscale Physics
Electric-field-driven magnetic switching and tightly bound interlayer excitons in bilayer CrSBr
Xiubin Li, Yu Sun, Xuanji Wang et al. (+8 more)
Electric field control of
magnetic order in two-dimensional (2D) van der Waals magnets is a central goal for low-power
spin-based technologies. In the ambient-stable antiferromagnet CrSBr, strong
magnetic anisotropy and robust
exciton-
spin coupling provide a favorable platform, yet deterministic electric field control of its
magnetic phases has not been achieved. Here we demonstrate electric-field-driven reversible switching between
antiferromagnetic and
ferromagnetic states in dual-gated
bilayer CrSBr without intentional carrier doping. In parallel, photoluminescence measurements resolve a tightly bound interlayer
exciton with an intrinsic dipole moment of only ~1 e angstrom. The electric field dependence of the
magnetic phase transition reveals two coexisting mechanisms: a linear magnetoelectric effect in the
antiferromagnetic state and an electric-field-modulated interlayer exchange coupling. Their interplay accounts for the asymmetric
evolution of the critical
magnetic field. Our results establish
bilayer CrSBr as a promising 2D material for electrically controlled
spin-optoelectronic functionalities.
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All authors Xiubin Li, Yu Sun, Xuanji Wang, Chunyan Wang, Kenji Watanabe, Takashi Taniguchi, Sheng Liu, Ting Yu, Liang Li, Tao Zhang, Jing Li
Superconductivity
Direct Observation of Channelised Supercurrents in a Kagome Superconductor
Matthijs Rog, Tycho J. Blom, Reinier Q. Regter et al. (+9 more)
Superconductors are many-body
quantum states in which current flows without dissipation. Theory predicts that supercurrents follow a relatively simple spatial pattern in both conventional and unconventional
superconductors. Recent studies into the AV3Sb5 (A = Cs, K, Rb) family of Kagome
superconductors indicate that CsV3Sb5 has unconventional transport properties that cannot be accounted for with these simple theories, including reports of intrinsic Josephson junctions, higher order Cooper pairing and the zero field diode effect. Attempts to interpret these findings have focused on the interplay of superconductivity with the unconventional charge density wave (CDW) order in these materials, with which superconductivity competes. A current roadblock to understanding how these kagome
superconductors give rise to their intriguing properties is the lack of spatially resolved information about transport. Here we show, using a recently developed superconducting
quantum interference device (SQUID) microscope, that flakes of CsV3Sb5-xSnx host a network of narrow supercurrent channels. These supercurrent channels emerge at the critical temperature and remain stable for all temperatures and currents. Their non-linear behaviour is consistent with a network of Josephson junctions linked by narrow supercurrent filaments, which naturally leads to the observed transport anomalies. Intriguingly, these observations are much weaker in undoped samples, which suggests links to the physics of charge density waves, disorder, and electronic correlations, all of which are greatly influenced by the doping strength. These results establish new frontiers for the local investigation of charge transport and competing orders in strongly correlated electron systems, and shine a new light on the anomalous transport properties of the AV3Sb5 kagome
superconductors.
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All authors Matthijs Rog, Tycho J. Blom, Reinier Q. Regter, Andrea Capa Salinas, Dalal Benali, Jinwon Lee, Daan B. Boltje, Mark H. Fischer, Titus Neupert, Stephen D. Wilson, Milan P. Allan, Kaveh Lahabi
Quantum Physics
Optimizing resource allocation for accuracy in noisy variational quantum algorithms
Harshit Verma, Thomas Ayral, Alexia Auffèves et al. (+1 more)
For
quantum algorithms to achieve their full potential, we need methodologies to optimize them, such as reaching a given output accuracy with minimal resource costs. Here, we develop such a methodology for a class of Noisy Intermediate-Scale
Quantum (NISQ)
algorithms. We leverage simulations of a Variational
Quantum Eigensolver (VQE) to propose a phenomenological model of such
algorithms that captures the complex relationship between algorithmic accuracy, algorithmic resource costs, and the noise that exists in realistic
quantum hardware. For this, we take the algorithmic resource cost to be the total number of
quantum gate-operations in the
algorithm; minimizing this cost typically makes the
algorithm faster and more energy-efficient. We consider the subtle trade-off between
quantum circuit size (small
circuits are too imprecise, but large ones are too noisy), and the number of iterations of that
quantum circuit for the full
algorithm to sufficiently converge. Using a noise-metric-resource methodology, we identify the sweet spot (of
circuit size versus iterations) that minimizes the algorithmic resource costs for a desired
algorithm accuracy. It also gives the
circuit size that maximizes
algorithm accuracy for a fixed resource cost. Our methodology provides a practical guideline for near-term deployment of variational
algorithms on realistic noisy hardware, including hardware that uses error mitigation.
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All authors Harshit Verma, Thomas Ayral, Alexia Auffèves, Robert Whitney
Optics
High-Power Laser Drives Motion in Ultra-thin Photonic Crystal Lightsails via Radiation Pressure
Lucas Norder, Ata Keşkekler and Richard A. Norte
Laser-driven lightsails have emerged as a promising route for accelerating ultralight spacecraft to high speeds using beamed optical energy. Realizing this concept pushes the limits of light-matter interaction, materials science, structural engineering, and nanomechanical design. A central challenge is to create nanophotonic reflectors that combine ultralow mass, large illuminated area, and survival under high optical power densities. No previous experiment has combined these constraints in a single structure sufficient to produce measurable radiation-pressure displacement. Here, we report the largest subwavelength tethered lightsails to date: nanoscale-thickness, millimeter-wide silicon nitride membranes patterned with billions of holes. Despite their subwavelength thickness, they achieve 99% reflection through resonant photonic modes, combining ultralow areal density with high reflectivity. Their compliance enables radiation-pressure displacements of up to 1.75 micrometer, a 50,000-fold increase over previous lightsail optomechanical responses. These thin mirrors are shown to withstand and maintain high reflectivity under directed
laser intensities comparable to optical intensities at the surface of the Sun. Together, these results establish a testbed for high-power nanophotonics, directed-energy systems, and light-driven propulsion, defining the practical limits of ultrathin photonic materials under intense optical loading.
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Statistical Mechanics · Cross-listed from q-fin.ST
Trends, Volatility, Correlations, and Critical Phenomena in Financial Markets
Sara A. Safari and Christoph Schmidhuber
We forecast future
volatilities and correlations of financial
markets based on the current trends in these
markets. This complements previous work that models future expected returns by a cubic
polynomial of the current trend strength. Empirically, we observe that
volatilities and correlations tend to increase day after day in times of strong up- or down-trends. This effect is particularly pronounced in down-trends. It can be accurately quantified by quadratic
polynomials of today's trend strengths, which refine common mean-reversion models of
volatilities and correlations. Our results improve the prediction of
market risk by accounting for
market trends. They also support a recent proposal to model financial
markets by a
lattice gas near its critical point.
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Nuclear Experiment
Precision mass measurements of multistrange baryons and their antiparticles
ALICE Collaboration
The $\Omega^-$
baryon, composed of three strange
quarks (sss), was predicted by the
quark model and discovered in 1964, playing a pivotal role in establishing
quarks as fundamental constituents of matter. Despite its importance, experimental knowledge of its mass remains limited, with the current world average relying on measurements performed more than four decades ago and lacking robust estimates of systematic uncertainties. This is notable given the central role of the $\Omega^-$ mass, and alternatively that of the $\Xi^-$(dss), in
lattice QCD calculations, where it is widely used to set the overall physical scale. Precise scale setting is essential for first-principles studies of
quark confinement,
chiral symmetry breaking, and stringent tests of the Standard Model. Here we report high-precision measurements of the masses of the $\Omega^-$ and $\Xi^-$
baryons and their antiparticles, determined from invariant-mass reconstruction of their decay products in
proton$-$
proton collisions at the LHC. The analysis exploits the excellent tracking and particle-identification capabilities of the ALICE experiment, enabling accurate reconstruction of the displaced decay vertices characteristic of these short-lived particles. Each mass is measured with a fractional uncertainty of about 60 parts per million, for example $M_{\bar{\Omega}^+}=1672.558\,\pm\,0.034\,({\rm stat.})\,\pm\,0.102\,({\rm syst.})$ MeV/$c^2$. The precisely known K$^0_{\rm S}$ and $\Lambda$ masses are used for calibration. These results establish new precision
benchmarks in strange-
baryon spectroscopy and enable stringent tests of Charge-Parity-Time invariance in the multistrange-
hadron sector. Our measurement reduces the scale uncertainty in
lattice QCD calculations, enabling for instance sub per mille precision for the hadronic
vacuum-polarization contribution to the
muon anomalous
magnetic moment.
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Fluid Dynamics
A high-fidelity numerical database for free-stream-turbulence-induced transition under varying pressure gradients
Louenas Zemmour, Xavier Gloerfelt and Paola Cinnella
Free-stream-
turbulence-induced transition under streamwise-varying pressure gradients, as encountered on turbine blades, has received much less
attention in high-fidelity simulations than its zero-pressure-gradient counterpart. The ERCOFTAC T3 experiments provide a carefully documented reference for this problem and remain central to transition-model calibration. Complementing them with full-field, three-dimensional data opens new opportunities for the development of physics-based and machine-learning transition models. To this end, wall-resolved implicit large-eddy simulations of the T3A, T3B, and T3C2–C5 flat-plate cases are performed with a high-order compressible solver, using an upstream slip-wall block that lets the synthetic free-stream
turbulence develop up to the leading edge. The simulations reproduce well the measured transition locations, integral quantities, and velocity profiles, and predict a separation bubble near the end of the plate for the lowest-Reynolds-number case T3C4. As the Reynolds number decreases and transition moves into the adverse-pressure-gradient region, the mechanism evolves continuously from classical bypass transition to transition governed by the tendency of the laminar boundary layer to separate, up to separation-induced transition. Intermittency, conditioned statistics, and Reynolds-stress budgets document this
evolution and the associated non-
equilibrium effects, which challenge current RANS transition models.
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Computational Physics
A Social Force Model of the Evacuation from a Big Box Store
Gavin A. Buxton
We include elliptical cross-sections to physically represent people, and irregular polygons to represent wheelchair users, in an anisotropic social force model whose velocity and angular dependence also captures the social tendency for people to avoid walking into one another. Physical interactions are included that depend on the area of overlap between people, or obstacles, to capture normal forces that resist compression and tangential forces that resist sliding motion. The model is further extended to include decision making capabilities, small social groups, the spread of panic, and herding behavior. A large box store is simulated during an evacuation where people move through the store, along the shortest path, to their desired exits. The effects of exit choice, or the perceived availability of exits, on exit times is elucidated. It is found that ignoring 'staff only' exits, and only exiting from the main entrances, can significantly increase average egress times.
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Physics and Society
The Moving Target of Urban Equity: Spatiotemporal Demand and Double Disadvantage in Hefei, China
Shirui Zhou, Matteo Bruno, Mattia Mazzoli et al. (+5 more)
Equitable access to essential urban services is a pillar of modern planning, yet most accessibility models rely strictly on static residential locations, ignoring how demand shifts throughout the daily loop. This study introduces a population-based, temporally differentiated framework to examine the resulting "moving target" of urban equity, focusing on medical facilities and green spaces in Hefei, China. Utilising large-scale mobile phone GPS data, we construct dynamic residential and workplace population exposure surfaces to capture shifting hourly demand. We then evaluate accessibility via network-based travel times paired with a novel per-capita provision metric that accounts for real-time demand competition. We define double disadvantage as the co-occurrence of poor spatial accessibility and insufficient per-capita service availability. Counterintuitively, the results reveal that double-disadvantaged areas cluster primarily along the inner suburban belt rather than the remote periphery, where per-capita service provision remains relatively sufficient. Furthermore, temporal shifts drastically alter equity landscapes: daytime workplace concentrations intensely exacerbate demand competition in urban job centres. These findings demonstrate that urban inequality depends heavily on spatiotemporal population flows rather than just the fixed location of services. Ultimately, achieving true urban equity requires dynamic planning interventions that address time-varying demand rather than focusing solely on static, home-based metrics.
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All authors Shirui Zhou, Matteo Bruno, Mattia Mazzoli, Junfang Tian, Rui Jiang, Enwan Zhang, Zheng Li, Vittorio Loreto
Optics
Caustic-Driven Fluidic Microlenses for Enhanced Nonlinear and High-Energy-Density Physics
Sourabh Singh, S. Sree Harsha, Tamanna et al. (+1 more)
We demonstrate that caustic microlensing occurring in a
liquid jet efficiently drives linear, nonlinear, and high-energy-density phenomena. In the linear regime, caustics provide localized focusing, distinct from external high-NA optics. In the nonlinear regime, they enhance the input field at the
liquid-air interface and boost surface-sensitive processes. In the high-energy-density domain, caustic-driven localized
laser absorption generates gigapascal shocks using microjoule femtosecond pulses, with scalability up to repetition rates of 0.2 MHz. Caustic-driven fluidic microlensing offers opportunities for surface nonlinear optics, ultrafast science, and high-energy-density physics.
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All authors Sourabh Singh, S. Sree Harsha, Tamanna, Prashant Kumar Singh
Computational Physics
Advancing Threshold-Inception Modeling for Predictive Simulation of Ionic Wind Fan Performance
Siim Heering, Juri Volodin, Vootele Mets et al. (+5 more)
This study investigates the predictive capability of a threshold inception-based multiphysics modeling approach for ionic wind fans by direct comparison with experimental measurements. A wire-to-cylinder electroaerodynamic (EAD) fan with variable electrode spacing is used as a reference system to assess the model's ability to reproduce airflow characteristics, discharge current, and performance trends under atmospheric conditions. Numerical simulations show good qualitative agreement with experimental results across all tested configurations; however, systematic deviations emerge at higher voltages and larger electrode gaps. Analysis of these discrepancies indicates that the commonly adopted assumption of perfectly smooth emitter surfaces can limit model accuracy. Experimental characterization of the emitter wire reveals micro-scale surface protrusions, which locally enhance the electric field and alter corona inception behavior. Incorporating representative surface roughness into the numerical model improves quantitative agreement with measured airflow velocities. The results demonstrate that while the threshold inception model provides a robust foundation for EAD fan simulations, electrode surface morphology is a critical factor for reliable prediction. This work advances the validation and refinement of ionic wind fan modeling methodologies and identifies key considerations for the development of more accurate engineering-oriented simulation tools.
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All authors Siim Heering, Juri Volodin, Vootele Mets, Rasmus Talviste, Jüri Raud, Karl-Eerik Unt, Indrek Jõgi, Veronika Zadin
Quantum Physics
QPU-scale randomized benchmarking via Bell-pair injection
Haripriya Pettugani, María Aguado-Yáñez, Astryd Park et al. (+2 more)
Mirror randomized benchmarking (MRB) is an established technique that provides a global error metric at the scale of a whole QPU. To expand upon this we introduce Mirror
Quantum Awesomeness (MQA), a hybrid protocol that adds a structured entangling layer to MRB
circuits. This enables per-edge correlation dynamics to be tracked via mutual information while preserving the MRB infidelity estimate. The resulting analysis of the injected entangled pairs locates a critical
circuit depth, beyond which rudimentary error mitigation techniques can be expected to fail. A topological variant, Topological MQA, supplies a second critical depth via a decoder based on the surface-code decoding problem. Both are validated in simulation and demonstrated on the 156-
qubit ibm\_fez and ibm\_kingston processors, where MQA closely agrees with MRB on the
entanglement infidelity and the critical depth for ibm\_fez is found to be $\sim 50$.
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All authors Haripriya Pettugani, María Aguado-Yáñez, Astryd Park, Daniel Bultrini, James R. Wootton
High Energy Physics (Phenomenology)
The Simplest Dirac Scoto-Seesaw Realization
Sin Kyu Kang, Ranjeet Kumar and Hemant Kumar Prajapati
We present a simple Dirac scoto-seesaw framework based on the anomaly-free $U(1)_{B-L}$ charge assignment $(-4,-4,5)$ for $\nu_R$. This
chiral charge assignment naturally accounts for the observed
neutrino mass-squared differences, with $\Delta m^2_{\rm atm}$ generated at tree level and $\Delta m^2_{\rm sol}$ arising radiatively. After the spontaneous breaking of gauged $U(1)_{B-L}$, a residual $Z_6$
symmetry stabilizes the dark matter candidate. We investigate two minimal realizations of the framework, finding that both normal and inverted orderings are viable in one case, whereas only normal ordering survives in the other, with distinctive features for
neutrino observables. Moreover, the
chiral nature of the $U(1)_{B-L}$ charges suppresses the dilepton branching fraction of $Z'$, resulting in weaker ATLAS mass bounds than in the conventional vector $B-L$ scenario, thereby easing constraints on the dark sector. We explore the dark matter phenomenology of the singlet scalar and fermionic dark matter candidates. While singlet scalar DM is often severely constrained, the presence of the $Z'$ portal together with annihilation and co-annihilation channels substantially broadens the allowed parameter space. Thus, the framework offers a predictive scenario for
neutrino and dark matter phenomenology that can be probed in future experiments.
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Materials Science
Hartree-Fock Limit for Energies in Solids
Jānis Užulis and Andris Gulans
This study establishes a route to the Hartree–Fock (HF) limit for molecules and solids within the linearized augmented plane wave (LAPW) framework. We remove current limitations of the standard LAPW approach to nonlocal exchange by constructing radial basis functions and core orbitals consistently with the HF
Hamiltonian. The presented method yields total energies of molecules and solids with a precision of a few $\mu$Ha, and we use it to provide reference data for 14
semiconductors and
insulators. For the systems considered in this study, the standard approach based on (semi)local potentials for constructing radial basis functions and core orbitals remains highly precise for practical relative energies, including molecular and solid-state formation energies and Si self-interstitial defect formation energies. More broadly, the results provide stringent all-electron
benchmarks for basis-set and pseudopotential assessment, improve error control in hybrid-functional calculations within LAPW, and open the way to X-ray spectroscopy simulations within LAPW based directly on hybrid-functional core orbitals.
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Nuclear Theory
Hybrid stars with hyperons: structure based on QCD sum rule coupling constants
F. Moradi Jangal, H. R. Moshfegh and K. Azizi
We present a comprehensive study of hybrid
stars composed of
hadrons,
leptons, and
quarks within a relativistic mean-field framework. Using coupling constants derived from QCD sum rules (QCDSR), we first determine the bulk properties of
nuclear matter and evaluate the single-particle potentials of nucleons and hyperons to constrain the hadronic sector. The equation of state (EOS) under beta
equilibrium is then constructed employing the $\sigma-\omega-\rho$ model for the hadronic phase, while the
quark phase is described using both the MIT bag model and the Nambu-Jona-Lasinio (NJL) model. The
hadron-
quark phase transition is analyzed through both Gibbs and Maxwell constructions. Based on resulting EOSs, we obtain the mass-radius relations of hybrid
stars, investigate particle fractions and their radial distributions, and calculate the
tidal Love number ($\mathcal{K}_{2}$) and the dimensionless
tidal deformability ($\varLambda$). Our results provide quantitative predictions relevant for comparison with current multimessenger astrophysical observations.
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General Relativity and Quantum Cosmology
Regular Black Holes from Anisotropic Source with Hydrodynamic Equation of State
Hassan Firouzjahi
We study regular black hole solutions sourced by an anisotropic energy momentum tensor. It is well known that the geometry of the interior of a spherically symmetric regular black hole approaches the dS metric. Having decomposed the energy momentum tensor into its isotropic and anisotropic components, we assume a hydrodynamic equation of state, $P= P(\rho)$, for the pressure, and look for spherically symmetric, regular black hole solutions. We consider different forms of $ P(\rho)$ which yield the previously known regular black hole solutions, as well as various new metrics. We show that the profile of $ P(\rho)$ has a root and a maximum as it approaches $0^+$ at large distances. Consequently, the square of the sound speed of perturbations, $c_s^2$, changes sign at the point where $P$ reaches its maximum, indicating a potential hydrodynamic instability. In addition, imposing the subluminal bound on $c_s$ puts strong constraints on the model parameters, excluding models in which the energy density has an exponential fall off. We establish a universal hierarchy among the relative positions at which the strong energy condition is violated, at which $P$ has its root, and at which $P$ attains its maximum.
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Chemical Physics
Can DFT-trained neural network potentials reproduce structure, solvation, and water-exchange properties in aqueous magnesium solutions?
Sebastian Falkner, Pablo Montero de Hijes, Christoph Dellago et al. (+1 more)
Magnesium ions play an essential role in many biological processes but remain challenging to model in biomolecular simulations. Despite considerable scientific effort, classical force fields fail to simultaneously reproduce key structural, thermodynamic and kinetic solution properties, likely due to their inability to explicitly account for
quantum many-body effects. Here, we develop and systematically
benchmark MACE neural network potentials (NNPs) for aqueous MgCl$_2$ solutions trained on revPBE-D3/zd and revPBE0-D3/zd density functional theory reference data and assess their ability to reproduce a broad range of experimental solution properties including the structure of the first hydration shell,
diffusion coefficient, activity derivative, water-exchange rate and mechanism as well as solvation free energy. Both NNPs accurately reproduce the octahedral structure of the first hydration shell, ion pairing properties and
diffusion coefficients. Combining the NNPs with transition path sampling and other enhanced sampling techniques allows us to capture the rare event of water exchange in the first hydration shell of Mg$^{2+}$ revealing a dissociative exchange mechanism. Transition interface sampling yields exchange rates within one order of magnitude of experiment, representing a substantial improvement over classical dissociative force fields. In contrast, the NNP-derived solvation free energy significantly underestimates the experimental value, revealing a limitation of the present local NNP architectures for describing ion solvation thermodynamics. Our results demonstrate that DFT-trained NNPs can accurately describe Mg$^{2+}$ hydration structure,
diffusion, ion pairing, and exchange kinetics, while highlighting the need for explicit long-range electrostatic treatments to achieve quantitative agreement with experimental ion solvation free energies.
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All authors Sebastian Falkner, Pablo Montero de Hijes, Christoph Dellago, Nadine Schwierz
Lattice Field Theory
Hamiltonian-based dimensional reduction and spectral reconstruction with Wilson-Dirac fermions
P. V. Buividovich and B. Hind
Motivated by the process of reconstructing real-time spectral functions from Euclidean correlators in
lattice QCD, we derive explicit expressions for the fermionic determinant and the propagator of the four-dimensional clover-improved Wilson-Dirac
fermions on anisotropic
lattices in terms of the three-dimensional Wilson-Dirac
Hamiltonian operator. We derive an effective
Hamiltonian that governs Euclidean time
evolution at finite temporal
lattice spacing, and demonstrate its hermiticity and particle-anti-particle
symmetry. Our results allow to quantify
lattice artifacts of the numerical spectral reconstruction based on Euclidean fermionic correlators at finite temporal
lattice spacing.
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High Energy Astrophysical Phenomena
On the impact of the carbon fusion rate over the properties of superbursts – Numerical simulations of superbursts with MESA
Martin Nava-Callejas, Stéphane Goriely and Nicolas Chamel
Context: Superbursts are very energetic explosions in the crust of
neutron stars in Low-Mass X-ray Binaries (LMXBs). These are triggered by unstable carbon burning at $T\leq 10^{9}$ K. In recent years, there has been a re-examination of the carbon fusion rate, finding that at these temperatures it might be either smaller or higher with respect to the standard rate from Caughlan & Fowler (1988). Aims: We explore the consequences changing the carbon fusion rate has over the physics of superbursts. Methods: For simulating superbursts, we employ the public code \mesa\ v.24.08.1, as well as four versions of the carbon fusion reaction rate. Results: A significant enhancement of the reaction rate at $T\leq 10^9$~K would reduce the recurrence and decay times of the superburst, as well as the column depth at ignition. The opposite behavior is observed when the carbon fusion rate is reduced. The maximum temperature reached during the explosion is also sensitive to a change in the carbon fusion rate, leading to either an enhancement or a reduction in the synthesis of $\alpha$-nuclides. These changes are comparable to the effect of reducing the amount of base heating at the bottom of the envelope. Conclusions: The modelling of X-ray superburst is sensitive to the adopted carbon fusion rate at $T\leq 10^{9}$ K. Given its role for determining the ignition conditions, this rate needs to be better experimentally constrained to reduce the uncertainty in
nuclear physics when modeling the superburst light curve and the nucleosynthesis of the explosion. At the same time, multizone simulations of superburst also requires improvement in the description of the initially accreted material and
stellar conditions prior to the explosion.
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High Energy Astrophysical Phenomena
A FAST search for radio pulsations during the dormant state of the AMSPs IGR J00291+5934 and MAXI J1957+032
A. Marino, E. Parent, F. Coti Zelati et al. (+15 more)
Accreting millisecond
pulsars (AMSPs) and transitional millisecond
pulsars (tMSPs) are
neutron star low-mass X-ray binaries which can evolve into "recycled"
radio millisecond
pulsars. In both types of systems, X-ray pulsations have been detected during phases of X-ray activity when matter
accretion through a disc is turned on. On the other hand, when
accretion stops, and these systems enter the quiescent, low-luminosity X-ray state, only tMSPs become visible as
radio pulsars. Despite several attempts,
radio pulsations have never been detected in quiescent AMSPs, except for IGR J18245$-$2452. In this manuscript, we present the results of two observational campaigns performed on the AMSPs IGR J00291+5934 and MAXI J1957+032 with the Five-hundred-meter Aperture Spherical
Telescope ($\it{FAST}$) in L-band (1-1.5 GHz). Both sources have most likely been observed in quiescence, as suggested by the upper limits on their X-ray and optical flux obtained with Swift and the Las Cumbres Observatory, respectively. We have performed a deep search for coherent periodicities in
radio but found no significant candidate signal, either at the known
spin frequency of those sources or at other frequencies. Assuming a pulse duty cycle of 10%, we derive upper limits on the pulsed
radio flux density of 3.3 $\mu$Jy and 5.6 $\mu$Jy for IGR J00291+5934 and MAXI J1957+032, respectively, which are the most stringent limits so far for any known persistent AMSP.
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All authors A. Marino, E. Parent, F. Coti Zelati, M. C. Baglio, A. Papitto, A. Sanna, A. Anitra, C. Kazantsev, N. Rea, A. Borghese, L. Burderi, T. Di Salvo, C. Espinoza, X. Hou, R. Iaria, G. Illiano, D. M. Russell, R. Sathyaprakash
Optics
Time- and frequency-domain study for electron beams penetrating dielectric nanospheres: fingerprints of Cherenkov and transition radiation
Wenhua Zhao, Christos Tserkezis, N. Asger Mortensen et al. (+1 more)
We present a theoretical study of Cherenkov and transition radiation for swift electron beams penetrating dielectric nanospheres using material models of different sophistication. Specifically, we perform a combined time-domain (numerically, via the discontinuous Galerkin time-domain method) and frequency-domain (numerically and analytically, via Mie-based theory) study, including the induced-field distribution, cathodoluminescence (CL) multipole/directional decomposition, as well as the time-dependent angular power flow. For low velocities below the Cherenkov threshold, we show that transition radiation is dominant in the far-field CL, and the near-fields at the transition points are primarily responsible for the main features observed in the far-field. For higher velocities far beyond the Cherenkov threshold, we identify the fingerprints of the observable Cherenkov front. Specifically, a constant-permittivity model allows us to isolate the respective contributions of CR and TR to the far-field radiation, thereby facilitating the interpretation of the results for a more realistic material model that includes material resonances. Our combined time- and frequency-domain framework provides a direct view of radiative excitation channels for swift electron beams penetrating dielectric nanoparticles, thereby revealing their interplay beyond the conventional frequency-domain analyses.
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All authors Wenhua Zhao, Christos Tserkezis, N. Asger Mortensen, Kurt Busch
Materials Science
Terahertz frequency upconversion by coherently driving charge dynamics in the InSb/CdTe heterostructure
Pai Peng, Mingxiang Pan, Jiuming Liu et al. (+10 more)
We investigate terahertz (THz) harmonic generation in the InSb/CdTe
heterostructure, demonstrating, for the first time, efficient in-plane
magnetic field-induced second-harmonic generation (SHG). We also achieve significant third-harmonic generation (THG), rivalling Dirac materials such as
graphene and Cd3As2. Our theoretical analysis identifies the primary SHG mechanism as the orbital-Zeeman correction to Drude conductivity, while the dominant THG contribution also shows Drude-like behavior. The results provide a general route to efficient THz harmonic generation in high mobility materials.
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All authors Pai Peng, Mingxiang Pan, Jiuming Liu, Yi Yang, Lei Wang, Hao Lin, Zehao Hu, Jianlin Luo, Tao Dong, Xufeng Kou, Xinbo Wang, Huaqing Huang, Luyi Yang
Applied Physics
Temperature-Dependent Charge Transport in USD-Grown High-Purity Germanium: Interplay Between Freeze-Out and Multi-Scattering Mechanisms
Narayan Budhathoki, Dongming Mei, Abhinna Rajbanshi et al. (+1 more)
We report temperature-dependent charge transport measurements in p-type high-resistivity germanium
crystals grown at the University of South Dakota.
Hall-effect and four-probe resistivity measurements were performed on five planar samples over the temperature range of 2-300 K. The apparent
Hall mobility exceeds 10$^6$ cm$^2$ V$^{-1}$ s${^-1}$ at cryogenic temperatures and decreases systematically with increasing temperature, while the effective
Hall carrier concentration exhibits strong carrier freeze-out behavior at low temperatures. The combined
evolution of
Hall mobility, effective
Hall carrier concentration, and resistivity reveals distinct transport regimes associated with carrier freeze-out, extrinsic conduction, and
phonon-limited scattering. The transport behavior is interpreted using a Matthiessens-rule-inspired phenomenological mobility model motivated by the combined influence of ionized
impurity, neutral
impurity, and acoustic
phonon scattering. Variations among samples are correlated with differences in effective
Hall carrier concentration and transport behavior. These measurements establish a transport baseline for USD-grown high-resistivity germanium
crystals and provide guidance for future material optimization toward detector-grade high-purity germanium for low-background rare-event detector applications.
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All authors Narayan Budhathoki, Dongming Mei, Abhinna Rajbanshi, Rongying Jin
Soft Condensed Matter
E. coli bacterium near corrugated surfaces: near-surface swimming, escape, and hydrodynamic trapping
Pierre Martin, Gonçalo C. Antunes and Holger Stark
Bacteria often swim in complex environments where surfaces are ubiquitous and rarely flat. Surface topography and
curvature can strongly affect bacterial motility, with important consequences for surface exploration, adhesion, and biofilm formation. Here, we investigate the swimming of a non-tumbling Escherichia coli bacterium near an undulating no-slip surface using hydrodynamic simulations of a detailed model bacterium. The latter is described by a rigid spherocylindrical
cell body and flexible flagella modeled with the Kirchhoff rod theory, while the surrounding fluid is simulated using the method of multi-particle collision dynamics. At low
curvatures of the sinusoidal surface modulations, the bacterium exhibits persistent near-surface swimming and clockwise trajectories, consistent with the known behavior near flat no-slip walls. As the
curvature increases, bacteria swimming toward a ridge can escape from the surface, which we use to estimate a critical
curvature where surface detachment is more likely. At larger
curvatures, we find that the surface geometry promotes oscillatory swimming along the groove direction, which reduces escape opportunities and, therefore, enhances bacterial trapping. Indeed, the confinement around the groove reverses the swimming of the bacterium from clockwise to counter-clockwise, as we demonstrate by two minimal models. Thus our work highlights the importance of the three-dimensional surface topography in bacterial surface exploration.
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Instrumentation and Methods for Astrophysics
VASTER: The ASKAP real-time fast-imaging pipeline – overview and discovery of two long period transients
Yuanming Wang, Dougal Dobie, Tara Murphy et al. (+22 more)
Recent developments in widefield
radio telescopes have enabled searches of a new region of parameter space in the time domain: timescales of seconds to minutes, that have been overlooked in traditional surveys. These searches have revealed a new population of sources: long period transients, which typically show periodic behaviour of minutes to hours. In addition they have detected phenomena ranging from extreme scintillation to
stellar radio bursts. However, almost all searches to date have involved archival data that has been processed in offline, batch mode. In this context, we present VASTER, the first short-timescale imaging and transient detection pipeline running in real time on a widefield
radio telescope. VASTER has been running on the Australian SKA Pathfinder (ASKAP) since July 2025, and images most of the ASKAP survey project data on timescales of 15 minutes. In this paper we describe the VASTER system, and present the results from the first two weeks of operation, including the discovery of two long period transients: ASKAP~J165130.3$-$450520 with a period of 6.48 hours and ASKAP~J170036.6$-$445758 with a period of 4.69 hours. The detection of these two sources adds to the small, but growing, population of long period transients, as well as demonstrating the potential of VASTER to explore this region of transient parameter space.
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All authors Yuanming Wang, Dougal Dobie, Tara Murphy, Emil Lenc, David L. Kaplan, Joshua Pritchard, Daniel Mitchell, Wasim Raja, Matthew Whiting, Owen Cole, Paul J. Hancock, Jiting Hu, Yu Wing Joshua Lee, Alex Massen-Hane, Shibli Saleheen, Raymond Shao, Lei Zhang, Adarsh Bathula, Manisha Caleb, Raghav Girgaonkar, Ashna Gulati, Natasha Hurley-Walker, Iris de Ruiter, Ryan M. Shannon, Gregory R. Sivakoff
High Energy Physics (Theory)
Quantization of Brane-Skyrmions via Physics-Informed Neural Networks
Jose A. R. Cembranos, Alberto García Martín-Caro and Sergio S. Rentero
In this work, we investigate the canonical quantization of topological
solitons appearing in braneworld scenarios. In particular, we focus on Brane-Skyrmions, topological field configurations analogous to standard Skyrmions, which emerge as solutions of the Dirac-Nambu-Goto action supplemented by an induced
curvature term. By quantizing the (iso)
spin collective coordinates of the Brane-Skyrmion, we obtain a
Hamiltonian that we solve perturbatively via an expansion in powers of $J^2$, in contrast to the standard Skyrme model. Furthermore, we implement a Physics-Informed Neural Network (PINN) to determine the
soliton profile that minimizes the energy, consistently incorporating the backreaction from the quantized
spin degrees of freedom. We conclude with a discussion of the potential applications of this framework to the description of hadronic spectra. Our results highlight both the theoretical potential of brane-defect models and the growing role of neural network methods in theoretical physics.
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High Energy Physics (Phenomenology)
Toward Precision Fragmentation of $\Omega_{3Q}$ Baryons: The OMG3Q1.1 Framework
Francesco Giovanni Celiberto
Recent experimental advances in the
baryon sector, including the observation of doubly charmed states, have renewed interest in the production mechanisms of increasingly heavy hadronic systems, calling for precision and uncertainty-controlled descriptions. We present the OMG3Q1.1 framework for the fragmentation of same-
flavor all-heavy $\Omega_{3Q}$
baryons in high-energy hadronic collisions. The construction combines diquark-inspired inputs for constituent-heavy-
quark and
gluon channels with threshold-aware DGLAP
evolution within the HF-NRevo scheme. A replica-based strategy consistently quantifies perturbative missing-higher-order effects (F-MHOUs) and nonperturbative wave-function uncertainties (F-NPWFs), yielding the first uncertainty-resolved fragmentation-function set for the $\Omega_{3Q}$ sector. The resulting LHAPDF6 grids are employed to investigate semi-inclusive $\Omega_{3Q}$ plus jet production at the HL-LHC and future FCC within the (sym)JETHAD environment. The OMG3Q1.1 framework establishes a precision-oriented baseline for rare triply heavy
baryons and provides a foundation for future studies of the heavy-
flavor baryon landscape.
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