Chemical Physics
How Accurate Are DFT Forces? Unexpectedly Large Uncertainties in Molecular Datasets
Domantas Kuryla, Fabian Berger, Gábor Csányi et al. (+1 more)
Training of general-purpose machine learning interatomic potentials (MLIPs) relies on large
datasets with properties usually computed with density functional theory (DFT). A pre-requisite for accurate MLIPs is that the DFT data are well converged to minimize numerical errors. A possible symptom of errors in DFT force components is nonzero net force. Here, we consider net forces in
datasets including SPICE, Transition1x, ANI-1x, ANI-1xbb, AIMNet2, QCML, and OMol25. Several of these
datasets suffer from significant nonzero DFT net forces. We also quantify individual force component errors by comparison to recomputed forces using more reliable DFT settings at the same level of theory, and we find significant discrepancies in force components averaging from 1.7 meV/Å in the SPICE
dataset to 33.2 meV/Å in the ANI-1x
dataset. These findings underscore the importance of well converged DFT data as increasingly accurate MLIP architectures become available.
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All authors Domantas Kuryla, Fabian Berger, Gábor Csányi, Angelos Michaelides
Plasma Physics · Cross-listed from astro-ph.HE
Coupling of neutrino beam-driven MHD waves and resonant instabilities in rotating magnetoplasmas with neutrino two-flavor oscillations
Jyoti Turi and Amar P. Misra
We present an analysis of
neutrino-driven magnetohydrodynamic (MHD) waves and instabilities in a rotating magnetoplasma with weak
neutrino interactions. We show that
neutrino-driven shear Alfvén and oblique magnetosonic waves can be coupled by the Coriolis force, forming new wave modes affected by this force, as well as
neutrino beam and two
neutrino flavor oscillations. Our work extends previous theories by demonstrating that shear Alfvén waves are influenced by
neutrino effects and by identifying instabilities resulting from resonant interactions with both a streaming
neutrino beam and
flavor oscillations. We find that the Coriolis force,
plasma density, and
magnetic field strength significantly affect the profiles of instability growth rates. Such a growth rate for magnetosonic waves appears much higher than the Alfvén wave, implying that magnetosonic waves provide a superior mechanism for energy extraction from the
neutrino beam. For typical parameters relevant to the protoneutron
star surface, the instability time for magnetosonic waves may vary in the range 0.09-0.14 s, which is within the predicted time of the
neutrino-driven explosion (0.3 s after bounce) reported in the recent three-dimensional MHD simulations of core-collapse
supernovae. Our findings may shed new light on the physical mechanisms underlying core-collapse
supernovae.
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Instrumentation and Detectors
Afterpulse prediction for SUBMET experiment
Claudio Campagnari, Sungwoong Cho, Suyong Choi et al. (+26 more)
The SUB-Millicharge ExperimenT (SUBMET) investigates an unexplored parameter space of millicharged particles with mass $m_\chi < $ 1.6 GeV/c$^2$ and charge $Q_\chi < 10^{-3}e$. The detector consists of an Eljen-200 plastic scintillator coupled to a Hamamatsu Photonics R7725 photomultiplier tube (PMT). PMT afterpulses, delayed pulses produced after an energetic pulse, have been observed in the SUBMET readout system, especially following primary pulses with a large area. We present a prediction method for afterpulse rates based on measurable parameters, which reproduces the observed rate with approximately 20% precision. This approach enables a better understanding of afterpulse contributions and, consequently, improves the reliability of background predictions.
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All authors Claudio Campagnari, Sungwoong Cho, Suyong Choi, Seokju Chung, Matthew Citron, Ryan De Los Santos, Albert De Roeck, Martin Gastal, Seungkyu Ha, Andy Haas, Christopher Scott Hill, Byeong Jin Hong, Haeyun Hwang, Insung Hwang, Hoyong Jeong, Minseo Kim, Hyunki Moon, Jayashri Padmanaban, Ryan Schmitz, Changhyun Seo, David Stuart, Juan Salvador Tafoya Vargas, Eunil Won, Jae Hyeok Yoo, Jinseok Yoo, Ayman Youssef, Ahmad Zaraket, Haitham Zaraket, Collin Zheng
Optics · Cross-listed from cond-mat.str-el
Temperature-invariant magneto-optical Kerr effect in a noncollinear antiferromagnet
Camron Farhang, Weihang Lu, Yuchuan Yao et al. (+6 more)
Noncollinear antiferromagnets exhibit anomalous
Hall and magneto-optical Kerr effects driven by Berry
curvature despite negligible net magnetization, promising ultrafast spintronic applications. While both effects are theoretically expected to reveal the intrinsic Berry
curvature that serves as a spintronic
memory bit, their quantitative interpretation is complicated by additional temperature-dependent contributions superimposed on the
magnetic order parameter: extrinsic skew scattering in dc
Hall transport, and optical-resonance effects in visible-wavelength Kerr measurements. Here we perform polar Kerr measurements at the infrared telecommunication wavelength (1550 nm) on epitaxial, stoichiometric Mn3NiN single
crystal films, revealing for the first time a spontaneous Kerr signal that remains stable within a few percent over a 200 K range below the Néel temperature. This temperature-invariant intrinsic Kerr response contrasts with the strongly temperature-dependent anomalous
Hall effect in the same sample dominated by extrinsic skew scattering. Our findings establish infrared Kerr effect as a robust, local probe of Berry
curvature in noncollinear antiferromagnets, enabling quantitative characterization and advancing
antiferromagnetic spintronic technologies.
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All authors Camron Farhang, Weihang Lu, Yuchuan Yao, Pratap Pal, Shaofeng Han, Jian-Guo Zheng, Hua Chen, Chang-Beom Eom, Jing Xia
Optics
High Uniformity GaN Micro-pyramids and Platelets by Selective Area Growth
Changhao Li, Vitaly Z. Zubialevich, Peter J. Parbrook et al. (+2 more)
The development of uniform GaN micro-pyramids and platelets via selective area growth is a critical step toward advancing III-nitride device technologies, particularly for micro-light-emitting diode applications. This work investigates the origins of morphological non-uniformity in micro-pyramids and micro-platelets grown by metal-organic chemical vapor deposition (MOCVD). We observe that a direct one-step growth approach leads to significant growth rate inhomogeneity across arrays. To shed light on this issue, we examine the mechanisms driving non-uniformity and explore process modifications aimed at mitigating these effects. Building on these insights, we propose a controlled multi-step growth strategy that combines sequen-tial growth and thermal treatment phases. This approach is demonstrated to enhance surface morphology and structural regularity. The work contributes to the broader objective of enabling scalable, high-precision GaN microstructure fabrication for next-generation optoelectronic applications.
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All authors Changhao Li, Vitaly Z. Zubialevich, Peter J. Parbrook, Brian Corbett, Zhi Li
Plasma Physics
Modification of ion-temperature-gradient turbulence by impurities in stellarator plasmas
Ivan Calvo, Felix I. Parra, Hanne Thienpondt et al. (+1 more)
Recent nonlinear gyrokinetic simulations have shown that
impurities can strongly modify the turbulent heat flux in stellarator
plasmas. Here, the ion-temperature-gradient (ITG) dispersion relation in a
plasma containing
impurities is analytically solved in certain limits and an expression for the modification of the ITG growth rate by
impurities is derived. The analytical expression is the sum of three terms corresponding to three different physical causes (
impurity density gradient,
impurity temperature gradient and dilution) of the change in the growth rate. The scalings predicted analytically for the modification of the growth rate are shown to be reproduced by linear gyrokinetic simulations. The conditions for reduction or increase of the ITG growth by
impurities are also correctly predicted by the analytical solution to the dispersion relation. Finally, a remarkable correlation is found between the analytical expression for the modification of the growth rate and the modification of the turbulent heat flux obtained from nonlinear gyrokinetic simulations.
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All authors Ivan Calvo, Felix I. Parra, Hanne Thienpondt, Jose Manuel Garcia-Regaña
Fluid Dynamics · Cross-listed from math.AP
Classical Euler flows generate the strong Guderley imploding shock wave
Giorgio Cialdea, Steve Shkoller and Vlad Vicol
We prove that Guderley's self-similar imploding shock solution for the compressible Euler equations with ideal–gas law ($\gamma>1$) arises from classical, radially symmetric, shock–free data. For such data prescribed at initial time $\mathrm{T_{in}} < 0$, we prove that the flow remains smooth up to a first singular time $t=\mathrm{T}_* \in (\mathrm{T_{in}}, 0)$, where a preshock forms with a $C^{1/3}$ cusp in the fast acoustic variable. From this preshock a unique, initially weak, regular shock is born, whose strength can be made arbitrarily large on a controlled time interval; the front then deforms onto the Guderley shock and implodes at the origin at the collapse time $t=0$. There exists a matching time $t=\mathrm{T_{fin}} \in (\mathrm{T}_*,0)$ such that on $[\mathrm{T_{fin}},0)$ the solution coincides exactly with the classical Guderley self–similar profile, and at $t=\mathrm{T_{fin}}$ the shock trajectory matches the self–similar front to all orders. As $t \to 0^-$, the Euler solution implodes at the center, and continues for $t>0$ as a reflected blast wave, providing a global-in-time unique Euler solution which evolves from regular initial conditions.
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Chemical Physics · Cross-listed from astro-ph.SR
Collisional Excitation in Space: Recent Advances and Future Challenges in the JWST Era
Francesca Tonolo
This perspective offers a viewpoint on how the challenges of molecular scattering investigations of astrophysical interest have evolved in recent years. Computational progress has steadily expanded collisional databases and provided essential tools for modeling non-LTE astronomical regions. However, the observational leap enabled by the JWST and new observational facilities has revealed critical gaps in these databases. In this framework, two major frontiers emerge: the characterization of collisional processes involving heavy projectiles, and the treatment of ro-vibrational excitation. The significant computational effort of these investigations emphasizes the need to test and develop robust theoretical methods and approximations, capable of extending the census of collisional coefficients required for reliable astrophysical modeling. Recent developments in these directions are outlined, with particular
attention to their application and their potential to broaden the coverage of molecular systems and physical environments.
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Applied Physics · Cross-listed from quant-ph
Addressing spins at the clock transitions with a frequency- and bandwidth-tunable superconducting resonator
Yutian Wen, V. Ranjan, T. Lorriaux et al. (+5 more)
Solid-state
spin ensembles addressed via superconducting
circuits are promising candidates for
quantum memory applications, offering
multimodal storage capability and second-long coherence times at their clock transition. Implementing practical
memory schemes requires dynamic control over both the resonator frequency and bandwidth. In this letter, we report measurements of a superconducting resonator whose frequency can be tuned by passing a DC current through the high-kinetic-inductance thin film, and whose bandwidth can be tuned by parametric coupling to a low-Q buffer resonator. Using this resonator, we address an ensemble of bismuth donors at their clock transition, measuring a Hahn-echo coherence time of 450 ms. We demonstrate RF driving of the bismuth donor hyperfine transitions, as well as dynamic bandwidth control of the resonator.
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All authors Yutian Wen, V. Ranjan, T. Lorriaux, D. Vion, B. Huard, A. Bienfait, E. Flurin, P. Bertet
Applied Physics
T2 mapping at 0.55 T using Ultra-Fast Spin Echo MRI
Margaux Roulet, Hamza Kebiri, Busra Bulut et al. (+9 more)
Low-field T2 mapping MRI can democratize neuropediatric imaging by improving accessibility and providing quantitative biomarkers of
brain development. Purpose: To evaluate the feasibility of high-resolution T2 mapping using a single-shot fast
spin-echo (SS-FSE) sequence at 0.55~T in a healthy control cohort. Study Type: Prospective single-center study. Population: In vivo: ten healthy adults (18–43~years, 5 females/5 males). In vitro: NIST Phantom. Field strength/sequence: Multi-echo ultra-fast
spin-echo at 0.55~T and 1.5~T. Assessment: Feasibility was first assessed in vitro using the NIST Phantom, comparing T2 relaxation times to spectrometer references at 0.55~T. Acquisition and T2-fitting parameters optimized in vitro were applied in vivo. Repeatability was evaluated by atlas-based analysis of white matter (WM) and cortical grey matter (GM) regions. Coefficients of variation (CoV) were computed across runs, sessions, and subjects. Statistical Tests: Wilcoxon signed-rank test with Bonferroni correction ($\alpha = 0.05/n_{ROI}$) assessed CoV differences. Pearson correlation coefficients quantified T2 associations. Results: In vitro, mono-exponential fitting under Gaussian–Rician noise yielded deviations $<12\%$ from reference values. In vivo, inter-subject CoV was 5.2% (WM) and 17.7% (GM), comparable to 1.5~T. Mean T2 times were 118~ms (WM) and 188~ms (GM) at 0.55~T, with a 16.5-minute acquisition. Conclusion: A rapid, robust high-resolution T2 mapping protocol at 0.55~T for HASTE MRI is presented, employing Gaussian noise-based fitting. We report the first normative T2 values for healthy adult
brains at 0.55~T, demonstrating technical feasibility and reliability.
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All authors Margaux Roulet, Hamza Kebiri, Busra Bulut, Vladyslav Zalevskyi, Thomas Sanchez, Jean-Baptiste Ledoux, Vincent Dunet, Mériam Koob, Tom Hilbert, Tobias Kober, Erick J Canales-Rodriguez, Meritxell Bach Cuadra
Data Analysis and Statistics · Cross-listed from cond-mat.mtrl-sci
Dara: Automated multiple-hypothesis phase identification and refinement from powder X-ray diffraction
Yuxing Fei, Matthew J. McDermott, Christopher L. Rom et al. (+2 more)
Powder X-ray diffraction (XRD) is a foundational technique for characterizing crystalline materials. However, the reliable interpretation of XRD patterns, particularly in multiphase systems, remains a manual and expertise-demanding task. As a characterization method that only provides structural information, multiple reference phases can often be fit to a single pattern, leading to potential misinterpretation when alternative solutions are overlooked. To ease humans' efforts and address the challenge, we introduce Dara (Data-driven Automated Rietveld Analysis), a framework designed to automate the robust identification and refinement of multiple phases from powder XRD data. Dara performs an exhaustive tree search over all plausible phase combinations within a given chemical space and validates each hypothesis using a robust Rietveld refinement routine (BGMN). Key features include structural database filtering, automatic clustering of isostructural phases during tree expansion, peak-matching-based scoring to identify promising phases for refinement. When ambiguity exists, Dara generates multiple hypothesis which can then be decided between by human experts or with further characteriztion tools. By enhancing the reliability and accuracy of phase identification, Dara enables scalable analysis of realistic complex XRD patterns and provides a foundation for integration into
multimodal characterization workflows, moving toward fully self-driving materials discovery.
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All authors Yuxing Fei, Matthew J. McDermott, Christopher L. Rom, Shilong Wang, Gerbrand Ceder
Fluid Dynamics
Exact results for dissipation and steady creeping flow in three-dimensional chiral active fluids
Laura Meissner-Oszer, Bogdan Cichocki and Jeffrey C. Everts
Chiral active fluids consist of self-spinning particles that rotate due to continuous energy injection at the microscopic scale (e.g. by activity or an external field). The hydrodynamics of such fluids is described by antisymmetric contributions in the viscosity tensor - called odd viscosity - which are allowed by
symmetry due to the presence of a non-trivial
spin angular momentum density. By generalising the Helmholtz minimum dissipation
theorem to systems with odd viscosity, we show that incompressible three-dimensional odd fluids in the presence of sources that induce flow (e.g. surfaces that impose boundary conditions) admit a unique solution for their steady flow fields at low Reynolds number. Furthermore, we prove that such flows dissipate more energy than ordinary Stokes flow, provided that the flow field is affected by odd viscosity. As an example, we consider a model fluid described by one shear viscosity and one odd viscosity in the creeping flow regime. We explicitly compute the stress tensor for a fluid subjected to a point-force density. Finally, we compute exact results for the pressure and flow fields around a translating and rotating spherical particle from their singularity representations. From these solutions and our extended Helmholtz
theorem, we explain why a translating sphere dissipates more energy when odd viscosity is present, whereas a rotating sphere does not.
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Optics
Detuning Tunable OAM Generation via Double-$\Lambda$ Four-Wave Mixing in Hot Rubidium Vapor
Shahar Monsa, Michael Shulinder, Shmuel Sternklar et al. (+1 more)
We demonstrate detuning-tunable generation of orbital-angular-momentum (OAM) light using a double Lambda four-wave-mixing (FWM) process in Doppler broadened rubidium vapor. Two near-resonant pumps on the D1 line drive non degenerate FWM that produces bright probe conjugate beams whose transverse modes evolve with pump detuning. A paraxial density-
matrix model coupled to split-step propagation predicts detuning-dependent spatial gain shaping that sets the OAM content; experiments with a mode cleaned pump
laser and a 12-mm AR-coated vapor
cell validate these predictions. We quantify mode formation by imaging, spectroscopy, and power measurements, and verify OAM conservation between the generated beams. The results establish resonant atomic vapor as a compact, tunable platform for structured-light generation with applications to high-dimensional
quantum communications and imaging.
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All authors Shahar Monsa, Michael Shulinder, Shmuel Sternklar, Eliran Talker
Chemical Physics
Manning-type potential induced by kink scatterings with phonons in molecular chains with hyperbolic double-well substrates
Alain M. Dikande
A rescaled Manning potential is obtained in the analysis of scatterings of small- amplitude excitations with a kink defect. The generic model is a nonlinear Klein- Gordon
Hamiltonian describing a one-dimensional chain of identical molecules, sub- jected to an
hyperbolic single-particle substrate potential. To account for isotope effects that are likely to affect characteristic
equilibrium parameters of the molec- ular chain, including the
lattice spacing (i.e. the characteristic intermolecuar dis- tance) and/or the barrier height, the
hyperbolic substrate potential is endowed with a real parameter whose variation makes it suitable for the description of molecu- lar excitations in a broad range of systems with inversion
symmetry. These include hydrogen-bonded molecular
crystals, {\alpha}-helix
proteins, long
polymer chains and two- state
quantum-tunneling systems in general. Double-well models with deformable profiles are relevant in physical contexts where the
equilibrium configurations are sensitive to atomic or molecular substitutions, dilution, solvation and so on.
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Applied Physics · Cross-listed from quant-ph
Twisted Superconducting Quantum Diodes for High Fidelity Anharmonic Qubits
Han Zhong, Denis Kochan, Igor Zutic et al. (+1 more)
In superconducting
circuits, bidirectional signal propagation can cause back-reflections and back-action that couple environmental noise back to coherent elements, degrading fidelity. Nonreciprocal superconducting diodes provide an intrinsic route to suppress such backscattering at the
circuit level. However, their diode efficiency and
quantum integration remain limited. Here, we realize a
quantum diode in twisted NbSe2 under in-plane and out-of-plane
magnetic fields. A mere 1 degree twist yields an efficiency enhancement over pristine devices, reaching 27.6 percent.
Quantum simulations reveal that this intermediate efficiency, well below 100 percent ideal, is both experimentally practical and optimal for preserving
qubit anharmonicity and stabilizing two-level systems. These findings show that maximal rectification is not always beneficial for
quantum information, establishing a new principle for designing the fundamental properties of twisted
superconductors towards low-power, high-fidelity
quantum circuits.
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All authors Han Zhong, Denis Kochan, Igor Zutic, Yingying Wu
Fluid Dynamics
Generalized Gauss-Jacobi rules for discrete velocity method in Multiscale Flow Simulations
Lu Wang, Lingyun Deng, Guanqing Wang et al. (+2 more)
The discrete velocity method (DVM) is a powerful framework for simulating gas flows across continuum to rarefied regimes, yet its efficiency remains limited by existing quadrature rules. Conventional infinite-domain quadratures, such as Gauss-Hermite, distribute velocity nodes globally and perform well near
equilibrium but fail under strong nonequilibrium conditions. In contrast, finite-interval quadratures, such as Newton-Cotes, enable local refinement but lose efficiency near
equilibrium. To overcome these limitations, we propose a generalized Gauss-Jacobi quadrature (GGJQ) for DVM, built upon a new class of adjustable weight functions. This framework systematically constructs one- to three-dimensional quadratures and maps the velocity space into polar or spherical coordinates, enabling flexible and adaptive discretization. The GGJQ accurately captures both near-
equilibrium and highly rarefied regimes, as well as low- and high-Mach flows, achieving superior computational efficiency without compromising accuracy. Numerical experiments over a broad range of Knudsen numbers confirm that GGJQ consistently outperforms traditional Newton-Cotes and Gauss-Hermite schemes, offering a robust and efficient quadrature strategy for multiscale kinetic simulations.
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All authors Lu Wang, Lingyun Deng, Guanqing Wang, Hong Liang, Jiangrong Xu
Optics
The Eckhaus instability: from initial to final stages
Michael I. Tribelsky
A systematic analysis of the Eckhaus instability in the one-dimensional Ginzburg-Landau equation is presented. The analysis is based on numerical integration of the equation in a large (xt)-domain. The initial conditions correspond to a stationary, unstable spatially periodic solution perturbed by "noise." The latter consists of a set of spatially periodic modes with small amplitudes and random phases. The
evolution of the solution is examined by analyzing and comparing the dynamics of three key characteristics: the solution itself, its spatial spectrum, and the value of the Lyapunov functional. All calculations exhibit four distinct, mutually agreed, well-defined regimes: (i) rapid decay of stable perturbations; (ii) latent changes, when the solution and the Lyapunov functional undergo minimal alterations while the
Fourier spectrum concentrates around the most unstable perturbations; (iii) a phase-slip period, characterized by a sharp decrease in the Lyapunov functional; (iv) slow relaxation to a final stable state.
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Optics · Cross-listed from cond-mat.mes-hall
Universal valley filtering via uniform dissipation and velocity contrast
Sijie Yue, Wentao Xie, Kai Shao et al. (+6 more)
Valley, as a ubiquitous degree of freedom in
lattices, has found wide applications in both electronic and classical-wave devices in recent years. However, achieving valley-polarized states, a prerequisite for valley-based operations, still remains challenging. Here, we propose and experimentally demonstrate a universal non-Hermitian mechanism for valley filtering using only uniform background dissipation, which creates a propagation length contrast between valleys through their intrinsic group velocity differences. We implement this concept in an acoustic
crystal, observing switchable and robust valley polarization of sound through large-scale field mapping. Remarkably, our approach is solely based on uniform loss, without the need for any special
lattice structures, tailored excitations, or external fields. We further provide designs of our non-Hermitian valley filter on photonic and electronic platforms. Our results offer a simple and effective solution to valley-polarized state generation and may advance the development of novel valley-based devices in both classical and
quantum regimes.
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All authors Sijie Yue, Wentao Xie, Kai Shao, Hong-yu Zou, Bingbing Wang, Hong-xiang Sun, Y. X. Zhao, Wei Chen, Haoran Xue
Computational Physics · Cross-listed from cond-mat.stat-mech
Time crystalline solitons and their stochastic dynamics in a driven-dissipative \phi^4 model
Xingdong Luo and Zhizhen Chen
Periodically driven systems provide unique opportunities to investigate the dynamics of topological excitations far from
equilibrium. In this paper, we report a time-crystalline
soliton (TCS) state in a driven-dissipative $\phi^4$ model. This state exhibits spontaneous breaking of discrete time-translational
symmetry while simultaneously displaying spatial
soliton behavior. During time
evolution, the
soliton pattern periodically oscillates between kink and anti-kink configurations. We further study TCS dynamics under noise, demonstrating that
soliton random walk can induce a dynamical transition between two distinct $Z_2$
symmetry-breaking time-crystalline phases in time domain. Finally, we examine the annihilation of two spatially separated TCSs under noise. Importantly, in contrast to the confined behavior of time-crystalline monopoles reported in [Phys. Rev. Lett. 131, 056502 (2023)], the dynamics of time-crystalline
solitons is deconfined despite the nonequilibrium nature of our model: the statistically averaged annihilation time scales as a power law with the
solitons' initial separation.
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Fluid Dynamics
From Interface Dynamics to Darcy Scale Description of Multiphase Flow in Porous Media
Steffen Berg, Ryan T. Armstrong, Maja Rücker et al. (+3 more)
An outstanding characteristic of porous media, desired in many applications, is the large surface area, which facilitates solid-fluid interactions, making porous media an extreme case in colloid and interface science. In two-fluid systems, wetting and the balance of capillary and viscous forces control fluid displacement processes, leading to a wide range of complex flow regimes with rich spatio-temporal dynamics. Macroscopic two-phase flow is historically described through the phenomenological extensions of Darcy's law. Besides many other shortcomings and inconsistencies, it covers only connected pathway flow in the capillary-dominated flow regime in a rigorous manner while other flow regimes with moving interfaces and associated topological changes are entirely implicit. Given the lack of adequate descriptions, upscaling multiphase flow from pore to Darcy scale represents a long-standing challenge paving into the fields of thermodynamics, statistical mechanics and integral geometry. In this review, we compare novel concepts which have been largely motivated by experimental insights, enabled by significant advances in pore-scale imaging and modeling over the last decade.
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All authors Steffen Berg, Ryan T. Armstrong, Maja Rücker, Alex Hansen, Signe Kjelstrup, Dick Bedeaux
Fluid Dynamics
Statistical State Dynamics of Couette MHD Turbulence
Eojin Kim and Brian F. Farrell
The roll streak structure (RSS) is ubiquitous in shear flow
turbulence and is fundamental to the dynamics of the self-sustaining process (SSP) maintaining the turbulent state. The formation and maintenance of the RSS in wall-bounded shear flow suggest the presence of an underlying instability that has recently been identified using statistical state dynamics (SSD). Due to the parallelism between the Navier-Stokes equation and the induction equation, it is reasonable to inquire whether the RSS in wall-bounded shear flow has a counterpart in the MHD equations formulated as an SSD. In this work we show that this is the case and that an analytic solution for the composite velocitymagnetic field RSS in the MHD SSD also arises from an instability, that this instability equilibrates to either a fixed point or to a turbulent state, that these turbulent statistical
equilibria may be self sustaining, and that both the fixed point and the turbulent states may correspond to large scale coherent dynamos.
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Chemical Physics
Ab Initio Calculations of the Static and Dynamic Polarizability of BaOH
E. H. Prinsen, A. Borschevsky, S. Hoekstra et al. (+5 more)
We present high-precision ab initio calculations of the static and dynamic polarizability of the barium monohydroxide ($^{138}$BaOH) molecule, using relativistic coupled-cluster theory. By thoroughly investigating the dependence of the calculated polarizabilities on computational parameters (basis set size, treatment of relativity, level of treatment of electron correlation, and vibrational corrections), a procedure to determine uncertainties is constructed and applied. The dipole moment of BaOH is also calculated and compared to experiment, confirming the accuracy of the predicted polarizabilities. The static and dynamic ($\lambda=1064\;\text{nm}$) polarizability was calculated for both the ground state and the (010) vibrational bending mode, the latter state being particularly interesting for a wide range of
quantum experiments. The ground state static polarizabilities were calculated to be 200.8(24) a.u. and 297(5) a.u. for the parallel and perpendicular components respectively.
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All authors E. H. Prinsen, A. Borschevsky, S. Hoekstra, A. K. Dutta, S. Chakraborty, B. J. Schellenberg, L. F. Pašteka, I. A. Aucar
Chemical Physics
Unveiling chiral electron-photon correlation effects in circularly polarized optical devices
Yassir El Moutaoukal, Rosario R. Riso, Andrea Bianchi et al. (+1 more)
Strong coupling with circularly polarized
vacuum fluctuations offers a viable route to manipulate molecular chirality. While experiments are advancing toward the realization of
chiral cavities, a mean-field theoretical framework for describing electron-
photon interaction in this platform has been missing. Here, we present a mean-field theory that can be systematically improved to capture the
chiral correlation effects responsible for the enantioselective power of
chiral light. We use strong coupling Møller-Plesset perturbation theory for accessing the excitation
manifold of electrons and
chiral virtual
photons. We apply the developed methods to selected
chiral systems and show that the mean-field theory captures cavity frequency dispersion, but fails to describe the
chiral discrimination arising from coupled electron-
photon excitations.
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All authors Yassir El Moutaoukal, Rosario R. Riso, Andrea Bianchi, Henrik Koch
Optics
Observation of counterion binding in the inner Helmholtz layer at the ionic surfactant-water interface
Yuyang Peng, Feng Gu and Chuanshan Tian
Understanding specific ion adsorption within the inner Helmholtz layer remains central to electrochemistry yet experimentally elusive. Here we directly quantify counterion adsorption and extract the associated thermodynamic parameters within the inner Helmholtz layer using phase-sensitive sum-frequency vibrational spectroscopy (PS-SFVS). Using sodium dodecyl sulfate (SDS) as a model ionic surfactant, we determine the Na+ and DS- surface densities by simultaneously analyzing interfacial free OH response and the diffuse-layer SF signal, from which the adsorption thermodynamic parameters are derived. We then construct an adsorption phase diagram that maps the
evolution of Na+ and DS- species in the compact layer as functions of bulk NaCl and SDS concentrations, revealing a continuous increase in surface ion pairing. The DS-: Na+ pairing ratio gradually decreases with increasing NaCl and approaches 2.8 at the supersaturation state prior to surface nucleation. These results establish PS-SFVS as a quantitative probe of ion-headgroup correlations in charged interfaces and reveal the thermodynamic mechanism underlying counterion-mediated interfacial ordering, with broad implications for electrolyte design, biomembrane stability, and soft-matter assembly.
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Computational Physics · Cross-listed from cond-mat.dis-nn
Demonstrating Real Advantage of Machine-Learning-Enhanced Monte Carlo for Combinatorial Optimization
Luca Maria Del Bono, Federico Ricci-Tersenghi and Francesco Zamponi
Combinatorial optimization problems are central to both practical applications and the development of optimization methods. While classical and
quantum algorithms have been refined over decades, machine learning–assisted approaches are comparatively recent and have not yet consistently outperformed simple, state-of-the-art classical methods. Here, we focus on a class of Quadratic Unconstrained Binary Optimization (QUBO) problems, specifically the challenge of finding minimum energy configurations in three-dimensional Ising
spin glasses. We use a Global Annealing Monte Carlo
algorithm that integrates standard local moves with global moves proposed via machine learning. We show that local moves play a crucial role in achieving optimal performance. Benchmarking against Simulated Annealing and Population Annealing, we demonstrate that Global Annealing not only surpasses the performance of Simulated Annealing but also exhibits greater robustness than Population Annealing, maintaining effectiveness across problem hardness and system size without hyperparameter tuning. These results provide clear and robust evidence that a machine learning–assisted optimization method can exceed the capabilities of classical state-of-the-art techniques in a combinatorial optimization setting.
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Plasma Physics
Microtearing Turbulence and Its Role in High-Density-Gradient Plasmas in Wendelstein 7-X
H. Cu-Castillo, A. Bañón Navarro, G. Merlo et al. (+10 more)
Gyrokinetic simulations reveal that microtearing mode (MTM)
turbulence dominates transport in a Wendelstein 7-X (W7-X) discharge characterized by large density gradients, moderate temperature gradients, and low
plasma beta. This conclusion is supported by the close agreement between simulated and experimentally measured heat and particle fluxes. The emergence of MTMs is attributed to the absence of competing instabilities – such as ion temperature gradient modes and density-gradient-driven trapped-electron modes – under these
plasma conditions, together with the stabilizing influence of the W7-X max-J
magnetic configuration. Furthermore, moderate collisionality and low
magnetic shear are found to facilitate MTM onset. These findings advance the understanding of high-density-gradient regimes, which are essential for achieving high-performance operation in W7-X
plasmas.
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All authors H. Cu-Castillo, A. Bañón Navarro, G. Merlo, F. Reimold, T. Romba, O. Ford, S. Bannmann, L. Vanó, M. Wappl, J. Geiger, A. Zocco, F. Jenko, the W7-X team
Fluid Dynamics
Real-time identification of parametric sloshing-induced heat and mass transfer in a horizontally oriented cylindrical tank
Samuel Akatchi Ahizi, Francisco Monteiro, Ramon Abarca et al. (+1 more)
Vertical forcing of partially filled tanks can induce parametric sloshing. Under non-isothermal conditions, the resulting mixing can disrupt the thermal stratification between
liquid and vapor, leading to enhanced heat and mass transfer and large pressure fluctuations. This work presents an experimental investigation of sloshing-induced heat and mass transfer in a horizontally oriented cylindrical tank under vertical harmonic excitation. This configuration is particularly relevant for cryogenic fuel storage in aircraft and ground transportation, yet its thermodynamic response under parametric sloshing remains largely uncharacterized. The present study provides the first experimental characterization of the sloshing-induced pressure drop and associated heat and mass transfer in this geometry. Decoupled isothermal and non-isothermal experimental campaigns are carried out across multiple fill levels and forcing amplitudes, near resonance of the first longitudinal symmetric mode $(2,0)$, using a hydrofluoroether fluid (3M Novec HFE-7000). To quantify heat and mass transfer, a lumped thermodynamic model is combined with an Augmented-state Extended Kalman Filter (AEKF), enabling real-time, time-resolved inference of Nusselt numbers. A critical forcing threshold is identified: below it, the fluid remains quiescent and thermally stratified; above it, parametric resonance drives strong sloshing, complete thermal destratification, and a rapid pressure drop. At 50% fill, the dominant (2,0) response intermittently alternates with a planar $(1,0)$ mode, indicating subharmonic mode interaction. The inferred Nusselt numbers increase by several orders of magnitude after destratification, and pressure-rate analysis confirms that condensation governs the pressure
evolution.
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All authors Samuel Akatchi Ahizi, Francisco Monteiro, Ramon Abarca, Miguel Alfonso Mendez
Computational Physics · Cross-listed from cond-mat.quant-gas
Quantum Monte Carlo study of low-dimensional Fermi fluids of dipolar atoms
Clio Johnson, Neil D. Drummond, James P. Hague et al. (+1 more)
Fermionic cold atoms in optical traps provide viable
quantum simulators of correlation effects in electronic systems. For dressed Rydberg atoms in two-dimensional traps with out-of-plane dipole moments, a realistic model of the pairwise interaction is of repulsive dipolar $1/r^3$ form at long range, softened to a constant at short range. This study provides parameterizations of fixed-node
diffusion Monte Carlo energy data for
ferromagnetic (one-component) and paramagnetic (two-component) two-dimensional homogeneous
Fermi fluids of interacting dipolar atoms. We find itinerant ferromagnetism to be unstable within our parameter spaces for dipolar interactions both with and without softening. Our parameterization of the energy as a function of density will enable density functional theory to support experimental studies of inhomogeneous fermionic cold atom systems.
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All authors Clio Johnson, Neil D. Drummond, James P. Hague, Calum MacCormick
Optics
Acceleration gradients in dielectric laser accelerators with triangular-shaped gratings
O.O. Svystunov, I.V. Beznosenko, A.V. Vasyliev et al. (+2 more)
The study investigated transparent on-chip structures with a rectangular profile and triangular profiles with grating ridge base angles of $\alpha = 36^\circ$, $30^\circ$, and $20^\circ$. Each triangular structure had both left- and right-handed profile orientations. For all variants, a modified version with a reflective gold coating was additionally considered. The maximum energy gains and accelerating gradients were determined and quantified for all structure classes: transparent and reflective (with both rectangular and triangular profiles).
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All authors O.O. Svystunov, I.V. Beznosenko, A.V. Vasyliev, R.R. Kniaziev, G.V. Sotnikov
Chemical Physics
Mechanism of the electrochemical hydrogenation of graphene
Y.-C. Soong, H. Li, Y. Fu et al. (+17 more)
The electrochemical hydrogenation of
graphene induces a robust and reversible conductor-
insulator transition, of strong interest in logic-and-
memory applications. However, its mechanism remains unknown. Here we show that it proceeds as a reduction reaction in which
proton adsorption competes with the formation of H2 molecules via an Eley-Rideal process.
Graphene's electrochemical hydrogenation is up to $10^6$ times faster than alternative hydrogenation methods and is fully reversible via the oxidative desorption of
protons. We demonstrate that the
proton reduction rate in defect-free
graphene can be enhanced by an order of magnitude by the introduction of nanoscale corrugations in its
lattice, and that the substitution of
protons for deuterons results both in lower potentials for the hydrogenation process and in a more stable compound. Our results pave the way to investigating the chemisorption of ions in 2D materials at high electric fields, opening a new avenue to control these materials' electronic properties.
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All authors Y.-C. Soong, H. Li, Y. Fu, J. Tong, S. Huang, X. Zhang, E. Griffin, E. Hoenig, M. Alhashmi, Y. Li, D. Bahamon, J. Zhong, A. Summerfield, R. N. Costa Filho, C. Sevik, R. Gorbachev, E. C. Neyts, L. F. Vega, F. M. Peeters, M. Lozada-Hidalgo