Chemical Physics · Cross-listed from cond-mat.soft
SAFT-P: A plaquette level perturbation for self-assembly in patchy colloids
Hamza Coban and Alfredo Alexander-Katz
We introduce SAFT-P, a plaquette-level extension of Statistical Associating Fluid Theory for patchy particles. By treating local clusters as associating superparticles and contracting their free energy back to monomer densities, SAFT-P retains information about patch
topology that is lost in conventional SAFT. Grand-canonical Monte Carlo simulations of binary and ternary mixtures show that SAFT-P captures
topology-dependent critical points and coexistence curves and discriminates between particles with identical valence but different patch layouts. Beyond
topology, incorporating plaquette-scale correlations also improves predictions in regimes where patch specific interactions are absent. Results indicate that resolving correlations at the plaquette scale provides an analytical route to model complex condensates and self-assembly with
topology-sensitive local structure.
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Chemical Physics
Partial Information Decomposition of Electronic Observables Along a Reaction Coordinate
Kyunghoon Han and Miguel Gallegos
A reaction-coordinate–resolved information-theoretic analysis of chemical reactivity is developed using mutual information and partial information decomposition (PID). Along an intrinsic reaction coordinate (IRC), a local empirical distribution is constructed at each position $s$ that couples a coarse-grained
geometric progress variable (target) to two electronic readouts (sources), and the joint mutual information $I(T;X,Y)$ is decomposed into redundant, unique, and synergistic contributions using the Williams–Beer PID formalism. In the numerical demonstrations, the target is a binned bond-asymmetry coordinate $\xi=d_{\mathrm{C}\!-\!\mathrm{nuc}}-d_{\mathrm{C}\!-\!\mathrm{LG}}$, while the sources are DDEC6 net atomic charges on the nucleophile and leaving-group centres. Application to three prototypical S$_\mathrm{N}$2 reactions (identity exchange $\mathrm{F^-+CH_3F}$, halide substitution $\mathrm{F^-+CH_3Br}$, and hydroxide substitution $\mathrm{OH^-+CH_3CH_2Br}$) yields compact,
symmetry-sensitive signatures of bonding
evolution: the identity reaction exhibits mirror-related information profiles with exchange of unique-information contributions between equivalent centres, whereas asymmetric reactions show shifted, centre-specific redistribution among redundancy and synergy as C–X cleavage couples to C–Nu formation. This Supplementary Information provides the formal construction, chemically motivated limiting toy models, a solvable analytic symmetric-transfer model, and the computational protocol used to obtain IRC-resolved PID curves.
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Physics and Society · Cross-listed from cond-mat.stat-mech
Operational Emergence of a Global Phase under Time-Dependent Coupling in Oscillator Networks
Veronica Sanz
Time-dependent coupling is often interpreted as introducing competition between a protocol rate and an intrinsic synchronization rate. We show that this interpretation is unavailable in the identical, overdamped Kuramoto model when time dependence enters only through a scalar multiplier of a fixed coupling field. The accumulated coupling $S(t)=\int_0^tK(u)\mathrm{d} u$ is then an exact dynamical clock: equal-exposure protocols traverse the same autonomous orbit, and integrable decays produce finite-exposure arrest rather than deterministic loss of adiabatic tracking. This clock suggests a classification under time reparametrization. Deterministic orbit observables and winding sectors are invariant; an additive perturbation $\varepsilon G$ has a leading response that is a linear functional of the reciprocal schedule $w(s)=1/K(t(s))$ against a kernel fixed by the autonomous orbit; and inertia or noncommuting graph generators lie outside this reciprocal-weighted class. Laboratory-time white noise has the corresponding $w$-weighted covariance. We derive exact mode covariances, prove a universal terminal bang–bang optimum under bounded coupling and fixed exposure, and validate both results in nonlinear networks. We also separate information in the full phase sample from information retained by the order parameter. Conditional observation error of $\arg Z$ follows a $1/(NR^2)$ law with a configuration-dependent prefactor, whereas a known-template experiment has Fisher information $N/\sigma^2$ independently of $R$; the efficiency of $\arg Z$ is $R^2/q_2$. Finally, periodic rings exhibit stable winding sectors with strong local but vanishing global order.
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Medical Physics
Ultra-high frequency ultrasound imaging and quantification of microvascular flow in xenograft renal cell carcinoma in an avian chorioallantoic membrane model
Sara Mar, Emmanuel Cherin, Justin Xu et al. (+2 more)
Patient derived xenograft (PDX) tumor models initiated in avian chorioallantoic membranes (CAM) are under investigation to evaluate the effectiveness of therapeutic options with the objective of personalizing treatments. CAM PDXs paired with ultra-high frequency ultrasound (UHFUS) imaging could potentially constitute prospective high throughput assays that can rapidly assess tumor volume and vascular response to therapy. To date, little work has been conducted to adapt and validate UHFUS flow imaging methods to CAM tumor models. Here we report the development and evaluation of an imaging pipeline for UHFUS detection of microvascular flow in a CAM tumor model using interframe subtraction (IS) to suppress tissue clutter. The IS pipeline included a tissue motion compensation (MC) stage prior to clutter filtering and was compared to a singular value decomposition (SVD) clutter filter. The performance was evaluated using UHFUS data acquired in phantom and in vivo Sunitinib-treated renal
cell carcinoma. MC substantially reduced tissue motion effects. MC+IS was comparable to MC+SVD filtering at detecting flow within tumors. The results for both IS and SVD filters were dependent on the details of implementation. The UHFUS imaging methods detected a significant decrease in blood flow metrics in treated versus control tumors. An effective imaging pipeline was developed for the assessment of the treatment response of CAM PDX models in a clinically relevant timeframe. The MC+IS approach implemented on B-scan image derived data is less computationally intensive and can be used with widely available UHFUS systems.
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All authors Sara Mar, Emmanuel Cherin, Justin Xu, David E. Goertz Hon S. Leong, Christine E.M. Demore
Chemical Physics
Latent space design of interatomic potentials
Susan R. Atlas
The advent of neural-network-based deep learning techniques has led to the emergence of increasingly sophisticated numerical interatomic potentials, including graph neural networks and large
language-motivated foundation models. Parameterized to reproduce large, precomputed
quantum mechanical training
datasets for molecules and materials, models can be fine-tuned for greater accuracy on specific problems. Despite notable successes, machine learning (ML) models of potentials still face intrinsic challenges due to the combinatoric complexity of the underlying
quantum chemical interactions, the existence of as-yet-undiscovered but potentially relevant bonding motifs absent from training
datasets, and the need for post-prediction interpretability analysis. Drawing inspiration from autoencoder methods, we propose a constructive approach to interatomic potential design. In standard autoencoder architectures, a ML model self-organizes numerical training data in an unsupervised manner to discover underlying patterns and construct a compressed representation or latent space
embedding model of the data, which is then used for prediction and inference. In the present work, we describe how latent space patterns and associated
quantum embeddings can be constructed using first-principles methods based on
theorems of density functional theory (DFT) and known, analytic constraints. This enables a parsimonious, physics-based representation of energies and densities, formally coupling the electronic and atomic length scales through the electron density, and linking ground, excited, and charge-transfer states of the interacting atoms. We describe the complete set of latent space components providing the foundation for a recently-proposed ensemble charge-transfer potential, and discuss opportunities for synergy in the design and explainability of contemporary machine-learned interatomic potentials.
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Space Physics · Cross-listed from astro-ph.SR
Active regions and the large-scale magnetic field of solar cycle 24
Ismo Tähtinen, Timo Asikainen and Kalevi Mursula
Most of the intracyclic variability in the large-scale
solar magnetic field comes from the equatorial dipole component of the
solar magnetic field. The equatorial dipole component is highly sensitive to the longitude distribution of the active regions. We quantify the effect of individual active regions on the large-scale
solar magnetic field of the
solar cycle 24. We study the effect of the longitude distribution of active regions on the strength of the large-scale dipole component. We used a surface flux transport (SFT) model to simulate the
evolution of individual active regions and quantified their effect on the large-scale
magnetic field using the recently developed vector sum method. We took advantage of the longitudinal translational invariance of the SFT model and compared the observed
solar cycle 24 to the 10 000 simulations of the
solar cycle 24 using randomized longitudinal source locations, but otherwise identical flux emergence. We find that taking into account both the axial and equatorial components of the vector sum characterizing the global
solar magnetic field sets better constraints on the parameter space of the SFT model than, for example, using the axial dipole moment alone as an optimization metric. We studied the maximum of cycle 24 and identified the recurrent and localized flux emergence in the southern hemisphere as the main culprit behind the rapid strengthening of the large-scale
magnetic field in late 2014. We find that during the declining phase of the
solar cycle, the strength of the large-scale
magnetic field stayed above the median level of randomized simulations (p < 0.027) for 42 subsequent. This indicates that the longitudinal distribution of active regions is not random and, rather, that it demonstrates a tendency for some regions to emerge at longitudes where their equatorial components reinforce the large-scale equatorial field.
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Chemical Physics · Cross-listed from quant-ph
Ramsey correlation spectroscopy with phase cycling using a single quantum sensor
Inbar Zohar, Santiago Oviedo-Casado, Andrej Denisenko et al. (+2 more)
Magnetic spectroscopy at the nanoscale provides unique insights into material properties and dynamics, with
quantum sensors like nitrogen-vacancy (NV) centers being ideally suited for these scales. However, detecting low-frequency signals remains a challenge due to finite coherence times ($T_2^*$), as signals oscillating slower than $1/T_2^*$ decay before sufficient phase accumulation occurs. We present RESOLUTE (Ramsey corrElation SpectroscOpy puLse seqUence wiTh phasE cycling), a protocol that overcomes these limitations by combining Ramsey measurements with correlation spectroscopy. By storing accumulated phase as a population imbalance during a correlation period ($T_\mathrm{corr} < T_1$) between two sensing periods, RESOLUTE generates an effective coherence time $T_2^p > T_2^*$. This shifts the frequency-matching condition to the correlation time, enabling detection in the previously inaccessible spectral region between $1/T_1$ and $1/T_2^p$. We experimentally demonstrate an extension of the effective coherence time from $T_2^* = 0.38\,\mu s$ to $T_2^p = 5.1\,\mu s$, surpassing Hahn Echo measurements. The technique successfully detects $^{13}$C
nuclear spin Larmor precession at fields as low as 49$\,$G ($\sim$50$\,$kHz). We further provide theoretical insight using Fisher information to characterize RESOLUTE's frequency estimation capabilities compared to existing protocols. Finally, by integrating adiabatic pulses and phase cycling, we demonstrate robust
spin control and effective DC signal extraction. These advancements provide enhanced sensitivity to weak dipolar interactions, essential for single-molecule imaging and
quantum sensing applications.
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All authors Inbar Zohar, Santiago Oviedo-Casado, Andrej Denisenko, Rainer Stöhr, Amit Finkler
Optics
Paraxial beam propagation from Airy-type initial conditions via the Operator Method
I. Julían-Macías, M. A. Jácome-Silva, I. Ramos-Prieto et al. (+4 more)
We employ
quantum mechanical operator techniques to solve the equations of $(1+1)D$ and $(2+1)D$ for paraxial waves with initial conditions defined by Airy-type functions. In the first part, we find the expressions of $(1+1)D$ optical beams, considering initial conditions such as Airy, Airy-truncated, and Airy-Gaussian functions. Subsequently, we extended the analysis to $(2+1)D$ optical beams with initial conditions generated by the product of two Airy, two Airy-truncated and two Airy-Gaussian functions, providing a comprehensive study of multidimensional Airy beam propagation. To validate our theoretical derivations, we present both theoretical and experimental intensity profiles, showing excellent agreement between the two, illustrating the physical characteristics of these beams. Although these solutions have previously been obtained via the diffraction integral and thoroughly studied, the primary goal here is to demonstrate that the optical fields can be derived using
quantum mechanical operator methods. Finally, we remark that this alternative approach offers an elegant and powerful framework for analyzing paraxial wave propagation.
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All authors I. Julían-Macías, M. A. Jácome-Silva, I. Ramos-Prieto, U. Ruiz-Corona, F. Soto-Eguibar, D. Sánchez-de-la-Llave, H. M. Moya-Cessa
Applied Physics
Single-particle limit of a topological edge state in a locally resonant band gap
Garigipati Sai Srikanth, Kai Qian, Ian Frankel et al. (+3 more)
Topological metamaterials promise unprecedented wave control. Here, we theoretically and numerically investigate a one-dimensional Su-Schrieffer-Heeger (SSH)-inspired stiffness dimer modified with a local resonator, which imparts a frequency-dependent effective stiffness to the unit
cell. The resonator introduces an attenuation singularity: at a frequency at which the effective stiffness vanishes, the spatial attenuation of waves diverges. By tuning a dimerization parameter, we migrate this singularity from one band gap to the other via an intermediate flat-band state, transferring the dominant local-resonance character between the gaps without closing either gap and while preserving the underlying band
topology. Crucially, when the resulting topological edge state intersects the attenuation singularity, the edge state collapses onto a single boundary particle, forming a single-particle mode (SPM). This yields an inverse participation ratio of exactly unity, the theoretical limit for localization in a discrete system. Moreover, this extreme localization can be realized at low frequencies, below the first Bragg-type band gap. Further, we demonstrate that while random disorder detunes this mode, merely tuning the boundaries stabilizes the single-particle mode over a broad parameter range. Our findings provide a clear pathway to designing ultra-localized edge states in low-frequency regimes, where band
topology guarantees the edge mode and local resonance drives its single-particle confinement.
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All authors Garigipati Sai Srikanth, Kai Qian, Ian Frankel, Georgios Theocharis, Nicholas Boechler, Rajesh Chaunsali
Computational Physics · Cross-listed from cs.LG
On the Value of Tokeniser Pretraining in Physics Foundation Models
Hadi Sotoudeh, Payel Mukhopadhyay, Ruben Ohana et al. (+4 more)
We investigate the impact of tokeniser pretraining on the accuracy and efficiency of physics emulation. Modern high-resolution simulations produce vast volumes of data spanning diverse physical regimes and scales. Training foundation models to learn the dynamics underlying such data enables the modelling of complex multiphysics phenomena, especially in data-limited settings. The emerging class of physics foundation models typically aims to learn two tasks jointly: (i) extracting compact representations of high-resolution spatiotemporal data, and (ii) capturing governing physical dynamics. However, learning both tasks from scratch simultaneously can impede the effectiveness of either process. We show that pretraining the tokeniser with an autoencoding objective prior to training the dynamics model enhances computational efficiency for physics emulation. Notably, the magnitude of this benefit depends on domain
alignment: pretraining on the same physical system as the emulation task yields the largest improvements, while pretraining on other systems provides moderate gains. In-domain pretraining reduces VRMSE by 64% after 10,500 training steps compared to training from scratch. To our knowledge, this is the first systematic investigation of tokeniser pretraining for physics foundation models. We further introduce flexible spatiotemporal compression operations that extend causal convolutions to support runtime-adjustable compression ratios, enabling efficient adaptation to diverse downstream tasks. Our findings provide practical guidance for training efficient physics emulators and highlight the importance of strategic pretraining data selection.
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All authors Hadi Sotoudeh, Payel Mukhopadhyay, Ruben Ohana, Michael McCabe, Neil D. Lawrence, Shirley Ho, Miles Cranmer
Atomic Physics · Cross-listed from quant-ph
In-situ Characterization of Light-Matter Coupling in Multimode Circuit-QED Systems
Kellen O'Brien, Won Chan Lee, Alexandra Behne et al. (+5 more)
Multimode cavity-QED systems can be leveraged to explore a wide range of physical phenomena; however, a complex multimode environment makes systematic characterization of light-matter interactions challenging. Here we present a general measurement protocol, applicable to both atomic and synthetic cavity-QED systems, that enables the determination of coupling to individual photonic modes. The method leverages measurements of the AC-Stark and Kerr effects, along with known detuning dependencies, to eliminate the need for single-
photon resolution, independent
photon-number calibration, or insertion-loss calibration. We demonstrate the method using a superconducting transmon
qubit coupled to a one-dimensional microwave resonator
lattice. We validate the consistency of the extracted light-matter couplings $g$ determined at multiple
qubit detunings, and from the self-Kerr and cross-Kerr shifts for three
photon modes, which provide separate measurements of $g$ for each of the three modes.
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All authors Kellen O'Brien, Won Chan Lee, Alexandra Behne, Ali Fahimniya, Yu-Xin Wang, Maya Amouzegar, Alexey V. Gorshkov, Alicia J. Kollár
Plasma Physics · Cross-listed from astro-ph.IM
UK White Paper on Magnetohydrodynamic (MHD) seismology of solar and heliospheric plasmas
Valery M. Nakariakov, David B. Jess, Andrew N. Wright et al. (+6 more)
Magnetohydrodynamic (MHD) seismology uses naturally occurring MHD waves to infer
plasma properties that are otherwise hard to measure, especially
magnetic field strength and
topology, electric currents, fine structuring, transport coefficients, and energy release. Across the
solar atmosphere, heliosphere, and planetary magnetospheres, multi-wavelength remote sensing and in-situ observations of waves provide powerful diagnostics that can address major open problems including chromospheric and coronal heating,
flare and eruption physics,
solar wind acceleration, and space weather impacts. This White Paper sets out the case for a coordinated UK programme that couples high precision observations with advanced theory and numerical modelling, modern time-frequency methods for non-stationary signals, and machine learning approaches for detection, classification, and parameter inference from rapidly growing multi-instrument
datasets. It outlines priority needs such as robust mode identification, reliable density and temperature constraints, multi line-of-sight capability, and models that include partial ionisation and non-adiabatic/collisionless effects, alongside enabling instrumentation such as next-generation spectropolarimetry, integral field units, and
radio facilities including the Square Kilometre Array. The paper highlights the UK's strong track record and infrastructure, and argues that sustained investment will amplify UK scientific return through international partnerships and mission involvement, delivering transformative
plasma diagnostics and downstream benefits for space weather
forecasting and related applications.
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All authors Valery M. Nakariakov, David B. Jess, Andrew N. Wright, Timothy K. Yeoman, Thomas Elsden, James A. McLaughlin, Dmitrii Y. Kolotkov, Viktor Fedun, Robertus Erdélyi
Atmospheric and Oceanic Physics
Hybrid ensemble forecasting combining physics-based and machine-learning predictions through spectral nudging
Inna Polichtchouk, Simon Lang, Sarah-Jane Lock et al. (+2 more)
We present the first application of spectral nudging in a probabilistic ensemble
forecasting framework, combining the physics-based ECMWF Integrated
Forecasting System ensemble (IFS-ENS) with forecasts from the probabilistic machine-learned AIFS-ENS ensemble. Large scales of virtual temperature and vorticity are relaxed toward the machine-learned forecasts, while mesoscale structures remain governed by the physics-based model. This hybrid ensemble shows substantial improvements in large-scale forecast skill, with gains in predictive skill extended by up to two days in the tropics and by approximately half a day in the extra-tropics relative to IFS-ENS. Despite nudging being applied only to upper-air fields, improvements are also found in several near-surface parameters. Tropical cyclone track forecasts improve significantly, consistent with improved representation of the large-scale steering flow, without degrading storm intensity or ensemble spread. These results demonstrate that spectral nudging can be successfully extended to ensemble prediction and provide an attractive pathway for combining machine-learned and physics-based weather prediction systems.
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All authors Inna Polichtchouk, Simon Lang, Sarah-Jane Lock, Michael Maier-Gerber, Peter Dueben
Applied Physics · Cross-listed from cs.LG
Towards Efficient and Stable Ocean State Forecasting: A Continuous-Time Koopman Approach
Rares Grozavescu, Pengyu Zhang, Mark Girolami et al. (+1 more)
We investigate the Continuous-Time Koopman Autoencoder (CT-KAE) as a lightweight surrogate model for long-horizon ocean state
forecasting in a two-layer quasi-geostrophic (QG) system. By projecting nonlinear dynamics into a latent space governed by a linear ordinary differential equation, the model enforces structured and interpretable temporal
evolution while enabling temporally resolution-invariant
forecasting via a
matrix exponential formulation. Across 2083-day rollouts, CT-KAE exhibits bounded error growth and stable large-scale statistics, in contrast to autoregressive
Transformer baselines which exhibit gradual error amplification and energy drift over long rollouts. While fine-scale turbulent structures are partially dissipated, bulk energy spectra, enstrophy
evolution, and autocorrelation structure remain consistent over long horizons. The model achieves orders-of-magnitude faster inference compared to the numerical solver, suggesting that continuous-time Koopman surrogates offer a promising backbone for efficient and stable physical-machine learning
climate models.
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All authors Rares Grozavescu, Pengyu Zhang, Mark Girolami, Etienne Meunier
Optics · Cross-listed from cs.LG
Autocorrelation effects in a stochastic-process model for solving two-armed bandit problems
Tomoki Yamagami, Mikio Hasegawa, Takatomo Mihana et al. (+2 more)
Decision makers exploiting photonic chaotic dynamics obtained by
semiconductor lasers provide an ultrafast approach to solving multi-armed bandit problems by using a temporal optical signal as the driving source for sequential decisions. In such systems, the sampling interval of the chaotic waveform shapes the temporal correlation of the resulting time series, and experiments have reported that decision accuracy depends strongly on this autocorrelation property. However, it remains unclear whether the benefit of autocorrelation can be explained by a minimal mathematical model. Here, we analyze a
stochastic-process model for solving the two-armed bandit problem based on time series, where the threshold and a two-valued Markov signal evolve jointly. Numerical results reveal an environment-dependent structure: negative (positive) autocorrelation is optimal in reward-rich (reward-poor) environments. These findings show that negative autocorrelation of the time series is advantageous when the sum of the winning probabilities is more than one, whereas positive autocorrelation is useful when the sum of the winning probabilities is less than one. Moreover, the performance is independent of autocorrelation if the sum of the winning probabilities equals one, which is mathematically clarified. This study paves the way for solving the two-armed bandit problems for reinforcement learning applications in wireless communications and robotics.
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All authors Tomoki Yamagami, Mikio Hasegawa, Takatomo Mihana, Ryoichi Horisaki, Atsushi Uchida
Atomic Physics
Environmental Measurements in the Sedrun Access Shaft to the Gotthard Base Tunnel – a Promising Site for a Long-Baseline Atom Interferometer
M. Guinchard, O. Buchmüller, S. Calatroni et al. (+7 more)
Atom interferometer (AI) experiments offer interesting prospects for searches for the interactions of ultralight bosonic dark matter with Standard Model particles as well as detection of gravitational waves in a frequency band inaccessible to experiments that are operating or under construction. Ideal locations for the next generation of such experiments are provided by long vertical shafts, such as that providing access to the Gotthard base railway tunnel from the Sedrun locality in the Canton Grisons of Switzerland. We present the results of an exploratory environmental measurement campaign at this location to evaluate the ground motion activity and the background electromagnetic field quality. We find that the backgrounds due to both ground motion and electromagnetic fields, including those due to passing trains, are low enough for successful operation of a 800-m AI experiment.
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All authors M. Guinchard, O. Buchmüller, S. Calatroni, J. Ellis, S. Hoell, M. Jaussi, L. Lombriser, M. Pentella, D. Thuliez, D. Valuch
Fluid Dynamics · Cross-listed from gr-qc
Black hole analogues in two-dimensional flows with constant shear
Alessia Biondi, Scott Robertson and Germain Rousseaux
We investigate the gravitational analogy for shallow water waves propagating on a unidirectional background flow with constant shear. Generalizing the standard irrotational treatment, we demonstrate that a transverse background vorticity is perfectly compatible with the existence of an effective curved spacetime for longitudinal surface waves. We extract the modified acoustic metric and show that the conformal factor, which governs wave scattering, becomes strongly dependent on the vorticity. Consequently, we find that the presence of background shear significantly suppresses the scattering of modes over an inhomogeneous bathymetry, while mildly modifying the analogue surface
gravity at the transcritical horizon. These results highlight the nontrivial role of rotational dynamics in analogue
gravity experiments.
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Biological Physics
Shape-Independent Fluidity in Epithelial Cell Monolayers
Pradip K. Bera, Anh Q. Nguyen, Molly McCord et al. (+2 more)
Tissue fluidity regulates biological processes such as embryonic development, wound healing, and cancer metastasis. In confluent epithelia, where
cell packing fraction is effectively fixed, the prevailing paradigm postulates that fluidity is governed by a
geometric shape index determined by the balance of cortical tension and intercellular adhesion. Here, we report that reducing
cell-
cell adhesion triggers an increase in fluidity with no change in
cell shape index,
cell density, substrate traction, or junctional line tension. The observed decoupling of shape and fluidity reveals that current vertex models, which treat adhesion as contributing solely to interfacial tension, are incomplete. To reconcile these findings, we extend the theoretical framework to account for the dual nature of adhesion—its thermodynamic role in setting interfacial adhesion energy at the
cell-
cell junctions and its kinetic role in generating viscous drag due to relative motion between adjacent
cells. This generalized model quantitatively captures the experimental data, demonstrating that the interplay between adhesive energy and dissipative friction is essential for epithelial fluidity.
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All authors Pradip K. Bera, Anh Q. Nguyen, Molly McCord, Dapeng Bi, Jacob Notbohm
Atomic Physics · Cross-listed from cond-mat.quant-gas
Core-bound waves on a Gross-Pitaevskii vortex
Evan Papoutsis, Nathan Apfel and Nir Navon
We find the dispersion relations of two elusive families of core-bound excitations of the Gross-Pitaevskii (GP)
vortex, varicose (axisymmetric) and fluting (quadrupole) waves. For wavelengths of order the healing length, these two families – and the well-known Kelvin wave – possess an infinite sequence of core-bound,
vortex-specific branches whose energies lie below the Bogoliubov dispersion relation. In the short-wavelength limit, these excitations can be interpreted as particles radially bound to the
vortex, which acts as a waveguide. In the long-wavelength limit, the fluting waves unbind from the core, the varicose waves reduce to
phonons propagating along the
vortex, and the fundamental Kelvin wave is the only core-bound
vortex-specific excitation. Finally, we propose a realistic spectroscopic protocol for creating and detecting the varicose wave, which we test by direct numerical simulations of the GP equation.
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Atomic Physics · Cross-listed from cond-mat.quant-gas
Spin-resolved microscopy of $^{87}$Sr SU($N$) Fermi-Hubbard systems
Carlos Gas-Ferrer, Antonio Rubio-Abadal, Sandra Buob et al. (+3 more)
Quantum-gas microscopes provide direct access to the phases of the Hubbard model, bringing microscopic insight into the complex competition between interactions, SU(2) magnetism, and doping. Alkaline-earth(-like)
fermions extend this
spin-1/2 paradigm by realizing higher
symmetries and giving access to SU($N$) Hubbard models, with rich phase diagrams to be unveiled. Despite its fundamental interest, a microscopic exploration of SU($N$)
quantum systems has remained elusive. Here we report the realization of a
quantum-gas microscope for fermionic $^{87}$Sr. Our imaging scheme, based on cooling and fluorescence on the narrow intercombination line at 689 nm, enables
spin-resolved single-atom detection. By implementing a
spin-selective optical pumping protocol, we determine the occupation of each of the 10
spin states in a single experimental realization, a crucial capability for probing site-resolved
magnetic correlations. We
benchmark our method by observing single-particle Larmor precession across the full
spin-9/2 ground-state
manifold and use numerical simulations of SU($N$)
Fermi-Hubbard chains, incorporating the measured detection fidelities, to demonstrate its capability to resolve many-body
spin correlations. Our results establish $^{87}$Sr
quantum-gas microscopy as a powerful approach to study exotic magnetism in the SU($N$)
Fermi-Hubbard model, and provide a new detection tool for studies in
quantum simulation, computation, and metrology.
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All authors Carlos Gas-Ferrer, Antonio Rubio-Abadal, Sandra Buob, Leonardo Bezzo, Jonatan Höschele, Leticia Tarruell
Computational Physics · Cross-listed from math.NA
A Space-Time Galerkin Boundary Element Method for Aeroacoustic Scattering
Maks Groom and Beckett Zhou
Acoustic scattering by vehicle surfaces can have significant effects on overall noise levels. In this paper, we present a space-time Galerkin time-domain boundary element method (TDBEM) that offers several distinct advantages over contemporary scattering methods for prediction of acoustic scattering and shielding of complex aeroacoustic sources such as propellers and rotors. The time-domain approach allows efficient simulation of transient, rotating, and broadband noise sources, while the Galerkin formulation is robust and unconditionally stable without any tuned numerical parameters. The main challenge of the Galerkin approach, namely the numerically difficult double space-time integration, is resolved through an efficient decomposition-based quadrature procedure. We present three cases with analytical solutions to validate the method and study its numerical properties, demonstrating excellent agreement for scattering and shielding by a variety of different geometries. We then apply the TDBEM to a trailing edge-mounted propeller case, comparing the numerical predictions with experimental measurements. The results demonstrate good agreement between predicted and measured scattering and shielding in a practical application case.
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Fluid Dynamics · Cross-listed from math.AP
2D capillary liquid drops with constant vorticity: rotating waves existence and a conditional energetic stability result for rotating circles
Giuseppe La Scala
We consider a two-dimensional, pure capillary drop of nearly-circular shape, having constant vorticity. We write the Craig-Sulem equations on the unit circle, then on the flat
torus. We show their
Hamiltonian structure and we then observe
symmetries and we derive constants of motions. After showing linear stability for rotating circles, we prove the existence of rotating waves by combining a bifurcation-theoretical approach together with critical point theory. Finally, by exploiting the
Hamiltonian structure, we show that whenever volume and barycenter are fixed to be the same as those of rotating circle, this solution is also conditionally energetically stable. This holds in the irrotational case as well, in agreement with the stability analysis of rotating cylinder jets in Rayleigh [25].
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Chemical Physics
Neural Wavefunction Calculations of {\mu}SR Spectra with Quantum Muons and Protons
Jamie Carr, Mathias Volkai, W. M. C. Foulkes et al. (+1 more)
Accurate prediction of
muon hyperfine constants is useful for interpreting
muon spin spectroscopy data, yet standard methods such as density functional theory (DFT) compute
muon-electron pair density functions, and thus hyperfine constants, by treating the
muon as a fixed classical particle. This work uses the variational
quantum Monte Carlo method with neural-network trial wavefunctions, a highly accurate and flexible approach recently applied to other
quantum chemical problems. The
muon can be treated classically or included in the many-particle electron-
muon wavefunction, in which case the fully
quantum mechanical pair density is obtained directly. We calculate
muon hyperfine constants in muoniated methyl and ethyl radicals for both
quantum mechanical and fixed classical
muons. The hyperfine constants obtained from our fixed-
muon calculations in the methyl and ethyl radicals differ from the corresponding DFT results significantly, highlighting the limitations of DFT even when the
muon is treated classically. The results with
quantum muons are closer to experiment after accounting for environmental effects. These findings suggest that explicitly calculating the
quantum mechanical
muon-electron pair density improves the accuracy of
muon hyperfine constant predictions.
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All authors Jamie Carr, Mathias Volkai, W. M. C. Foulkes, Andres Perez Fadon
Atomic Physics · Cross-listed from cond-mat.quant-gas
Efficient simulation of Bose-Einstein condensates in nontrivial topologies
Abel Beregi, Jean-Baptiste Gerent and Nathan Lundblad
Bubble-shaped Bose-Einstein condensates (BECs) constitute a unique class of
quantum fluids with a hollow, thin-shell geometry that supports a wide variety of phenomena that are distinct from those of compact condensates. Numerical simulation of such systems is particularly challenging due to their inherently three-dimensional structure and extreme aspect ratios. We present an efficient finite-difference simulation framework designed for solving partial differential equations in such nontrivial
topologies with a focus on the static and dynamical modeling of bubble-shaped BECs. By employing selective spatial sampling on a semi-structured grid, our method substantially reduces
memory usage and achieves more than an order-of-magnitude improvement in computational performance compared to conventional split-step
Fourier solvers. The
algorithm is naturally extendable for highly parallel execution on GPUs, enabling large-scale, time-dependent simulations of thin-shell condensates. We apply this framework to simulate the formation of bubble BECs through a controlled hollowing-out protocol using ab initio trapping potentials relevant to the Cold Atom Laboratory aboard the International Space Station. From these simulations, we identify characteristic timescales and parameter ramps required to achieve adiabatic
evolution, thereby assessing the feasibility of experimentally realizing bubble-shaped condensates in microgravity environments.
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Optics
Technical design report of a complete and compact broadband high-harmonics femtosecond beamline based on a modular hollow waveguide for photons generation centered on the upper region of the extreme ultraviolet spectral range
Yohann Brelet, Arnaud Marquette, Nicolas Beyer et al. (+5 more)
We have successfully developed and implemented an entire and compact table-top high-order harmonics generation (HHG) setup from monochromatic and intense femtosecond ($10^{-15}$ s)
laser pulses launched in a target composed of a high-purity monoatomic noble gas specie, which can be Argon or Helium, distinctively. Its frequency arrangement is distributed both in the full eXtreme UltraViolet (XUV, $22-124$ eV) spectral region and in the bottom part of the Soft-X Ray range (SXR, $124-132$ eV), at once. Specifically, the core of this coherent secondary light source is based solely on a homemade, modular, affordable, though sturdy, design. We take advantage of this opportunity to present our design guidance of the XUV generation from a hollow capillary waveguide apparatus, and our simple recipe regarding the
alignment process of the latter, which is easily carried out thanks to our adjustable design. Then, a comprehensive description of our entire XUV beamline is described, and participate in adding essential contents to the existing literature. Concurrently, we conducted theoretical studies, in order to anticipate or explain our experimental results. Overall, we found very good consistency between the experimental and cost-effective time-consuming numerical results. Finally, our setup provides very good
vacuum performance under high gas load pressures, to a few atmospheres. All of these attributes fulfill the requirements regarding ultrafast time-resolved pump-probe configuration in table-top element-sensitive spectroscopy of complex and integrated optoelectronic devices made of
magnetic materials.
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All authors Yohann Brelet, Arnaud Marquette, Nicolas Beyer, Gilles Versini, Jacques Faerber, Mircea Vomir, Valerie Halte, Marie Barthelemy
Chemical Physics
Quantum Dynamical and isotopic effects for Hydrogen isotopes scattering at W(110) surface
Raúl Bombín, Oihana Galparsoro, Daniel Peláez et al. (+3 more)
We investigate the scattering of hydrogen isotopes at the W(110) surface using both classical and
quantum dynamics approaches to elucidate the role of
quantum effects in this system. To characterize the scattering process we focus on key observables, including the absorption probability and diffraction channels that we evaluate at the quasi-classical and
quantum levels. The
quantum dynamics reveal pronounced resonance structures in the absorption curve that we rationalize in terms of diffraction-mediated selective adsorption and focused sticking mechanisms. Diffraction probabilities for reflected trajectories exhibit strong
quantum effects at low incident energies, where classical dynamics underestimate the back scattering probability. These effects become less pronounced with increasing isotope mass, from hydrogen to tritium, however discrepancies between the classical and
quantum description persist at low incident energies.
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All authors Raúl Bombín, Oihana Galparsoro, Daniel Peláez, Jean Christophe Tremblay, Cédric Crespos, Pascal Larregaray
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Equilibrium Thermochemistry and Crystallographic Morphology of Manganese Sulfide Nanocrystals
Junchi Chen, Tamilarasan Subramani, Deep Mekan et al. (+8 more)
Manganese sulfide (MnS) is a p-type
magnetic semiconductor whose physicochemical properties are sensitive to nanocrystal (NC) morphology, yet the thermodynamic driving forces governing morphology across MnS polymorphs remain poorly understood. Here, we use density functional theory (DFT) to predict the
equilibrium morphologies of rock salt (RS), zinc blende (ZB), and wurtzite (WZ) MnS NCs as a function of the relative chemical potential of sulfur, $\Delta \mu_{S}$. Benchmarking against Heyd$\unicode{x2013}$Scuseria$\unicode{x2013}$Ernzerhof (HSE06) hybrid functional calculations reveals that the r$^2$SCAN meta-generalized gradient approximation reproduces experimental
lattice constants and thermochemical reaction energies but underestimates S-terminated polar surface energies by up to a factor of five; applying a Hubbard $U$ correction (r$^2$SCAN+$U$, $U = 2.7$ eV) to the Mn 3d states brings the results into close agreement with HSE06. Using the benchmarked r$^2$SCAN+$U$ framework with the Gibbs$\unicode{x2013}$Wulff
theorem, we predict that RS-MnS NCs favor nanocubes across nearly the entire stability window, ZB-MnS NCs transform from rhombic dodecahedra (Mn-rich) to polyhedra with 16 triangular faces (S-rich), and WZ-MnS NCs adopt rod-like morphologies with $\Delta \mu_{S}$-sensitive base truncation. Synthesized RS-MnS NCs confirm the predicted cubic morphology, and high-temperature oxidative solution calorimetry yields an apparent surface energy of 1.15 $\pm$ 0.38 J$\cdot$m$^{-2}$, higher than the theoretical
equilibrium value (0.42$\unicode{x2013}$0.43 J$\cdot$m$^{-2}$), which we attribute to high-index facet exposure, surface area uncertainty, and non-ideal surface configurations in real samples. This work establishes a framework for predicting the
equilibrium morphologies of metal chalcogenide NCs.
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All authors Junchi Chen, Tamilarasan Subramani, Deep Mekan, Danielle Gendler, Ray Yang, Manish Kumar, Megan Householder, Alexis Rosado Ortiz, Emil A. Hernandez-Pagan, Kristina Lilova, Robert B. Wexler
Chemical Physics · Cross-listed from quant-ph
Extending spin-lattice relaxation theory to three-phonon processes
Nilanjana Chanda and Alessandro Lunghi
Spin-
lattice relaxation theory has been developed over almost a century, but some cardinal assumptions on the nature of the interactions involved have never been fully verified. This includes the weak coupling approximation, which makes it possible to describe
spin dynamics perturbatively and leads to the canonical description of
spin relaxation in terms of one- and two-
phonon processes. Here, we extend the first-principles theory of
spin relaxation to three-
phonon processes and apply it to the vdW
crystal of a
spin-1/2 Chromium nitride complex. Results show that three-
phonon contributions to
spin relaxation only become relevant at temperatures inaccessible to experiments for this molecule, thus providing unprecedented evidence for the validity of the weak
spin-
phonon coupling assumption in
spin relaxation theory. At the same time, we numerically show that a relatively small increase in
spin-
phonon coupling would lead to a crossover between three- and two-
phonon processes' efficiency at room temperature, illustrating the possibility for three-
phonon effects in molecular materials as well as paving the way to a systematic exploration of strong coupling in
spin systems.
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Fluid Dynamics · Cross-listed from cond-mat.other
Evidence for Vortex Rings with Multiquantum Circulation in He II
Yiming Xing, Yousef Alihosseini, Sosuke Inui et al. (+1 more)
Quantized
vortex dynamics in superfluid $^4$He (He~II) are widely regarded as well established: circulation is quantized in units of $\kappa=h/m_4$,
vortices carrying more than one
quantum are expected to split into singly quantized filaments, and
vortex rings shrink while accelerating due to dissipation from thermal-quasiparticle scattering. Using particle tracking velocimetry with frozen deuterium tracers, we uncover rare
vortex-bound particle events that disrupt this canonical picture. In a class of events exhibiting the acceleration characteristic of shrinkage driven
vortex ring motion, the measured kinematics cannot be reconciled with a singly quantized ring. Instead, they require an effective circulation $n\kappa$ with $n>1$, directly challenging the standard expectation that multiquantum
vortices are short lived. A more prosaic possibility is that the inferred $n\kappa$ arises from a bundle of closely spaced singly quantized rings, which could generate similar large-scale motion. However, this scenario is disfavored by
vortex-filament simulations that show rapid bundle dispersion. Furthermore, the persistence of particle trapping at the observed high speeds suggests a much deeper core trapping potential, consistent only with a truly multiquantum core. Together, these results point to anomalously long-lived multiquantum rings, a striking puzzle that calls for dedicated scrutiny beyond the prevailing paradigm.
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All authors Yiming Xing, Yousef Alihosseini, Sosuke Inui, Wei Guo
Chemical Physics
MQED-QD: An Open-Source Package for Quantum Dynamics Simulation in Complex Dielectric Environments
Guangming Liu, Siwei Wang and Hsing-Ta Chen
Simulating the dynamics of molecular
excitons in complex nanophotonic environments requires integrating rigorous electromagnetic simulations with accurate treatments of open
quantum system dynamics. In this work, we develop MQED-QD (Macroscopic
Quantum Electrodynamics for
Quantum Dynamics), a robust computational package for simulating
exciton dynamics in arbitrary dielectric and plasmonic environments. Based on the MQED framework, the package offers a unified workflow for constructing the dyadic Green's functions from classical electromagnetic solvers, parametrizing
quantum master equations, and propagating the time
evolution to determine the molecular subsystem's dynamical properties. To demonstrate the package's capabilities, we simulate
exciton transport within a one-dimensional molecular chain near a silver nanostructure, including benchmarking against planar surfaces and exploring the influence of silver nanorods. Our results reveal that surface plasmon polaritons on nanorods dramatically enhance long-range dipole-dipole interactions, accelerating
exciton delocalization and yielding higher participation ratios compared to planar geometries. By elucidating accurate molecular
exciton dynamics in conjunction with nanophotonics and plasmonics, MQED-QD provides a powerful, open-source package that facilitates the rational design of nanoscale architectures.
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