Biological Physics · Cross-listed from cond-mat.soft
Near-field Hydrodynamics Disentangles Angular Correlations in Confined Active Suspensions
Changle Liao, Haruki Hayano, Yuto Uesugi et al. (+3 more)
Spatial confinement profoundly impacts the transport and self-organization of active matter across diverse biological systems. While the collective orders in confined active matter have been extensively characterized, how
geometric constraints reshape near-field flows and the resulting inter-particle correlations remains largely unexplored. In this study, we combine experiments and hydrodynamic simulations to investigate inter-particle correlations within quasi-two-dimensional Chlamydomonas reinhardtii suspensions. We reveal two disentangled modes characterizing
cell pairs: a dipolar mode and an entrainment mode, which exhibit a density- and distance-dependent competition. Combining single-
cell flow field analysis, hydrodynamic simulations, and active-passive mixtures, we link these two modes to singular hydrodynamics and lubrication-induced entrainment. Our results demonstrate that spatiotemporal correlations in confined active matter are fundamentally rooted in the interplay of these two hydrodynamic mechanisms.
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All authors Changle Liao, Haruki Hayano, Yuto Uesugi, Akira Furukawa, Daiki Nishiguchi, Kazumasa A. Takeuchi
Optics
Transverse quantum-state characterization of programmable electron optics
Shengbo You, Paolo Rosi, Enzo Rotunno et al. (+6 more)
Programmable electron optics – electronically controlled phase plates – underpin proposals from dose-efficient phase imaging to shaped-electron X-ray sources, nearly all assuming a pure, fully coherent delivered wave whose purity has never been measured. Here we reconstruct the transverse density
matrix of a microelectromechanical electrostatic spiral phase plate by mixed-state ptychography, from one four-dimensional STEM scan per state and without added hardware. The delivered beam is substantially mixed: its purity falls from approximately 0.47 to approximately 0.24 as the applied bias grows, inconsistent with a fixed lateral source-blur model, while the real-space coherence width stays near 1 nm. The same scans calibrate the device in situ, allow virtual orbital-angular-momentum sorting and, through a partial-coherence-aware transfer theory, indicate that purifying the output could improve dose efficiency roughly threefold. One acquisition thus becomes a
quantum-state acceptance test for programmable electron optics, supplying the purity and coherence that emerging phase-plate and diffractive-imaging schemes assume but leave unquantified.
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All authors Shengbo You, Paolo Rosi, Enzo Rotunno, Alberto Roncaglia, Luca Belsito, Amir H. Tavabi, Rafal E. Dunin-Borkowski, Vincenzo Grillo, Philipp M. Pelz
Optics · Cross-listed from cs.CV
Engram-E2VID: Reference-Based Event-to-Video Reconstruction via Generative Activation of Appearance Engrams
Feiyu Ji, Xiang Li, Hao Ma et al. (+6 more)
Reference-based event-to-
video reconstruction aims to recover target RGB frames from a reference frame and the event stream captured over the reference-to-target interval. Although events provide fine-grained temporal cues, they encode sparse and asynchronous log-intensity changes rather than absolute appearance, making faithful reconstruction intrinsically challenging. The central challenge lies in associating event-derived target-time structures with relevant appearance information from the reference frame, especially under complex motion and long temporal intervals. In this work, we propose Engram-E2VID, a structure-guided framework that reconstructs target frames through the generative activation of appearance engrams. Specifically, the reference frame is encoded into
token-space appearance engrams, while the event stream and reference context are transformed into a target-time motion-structure scaffold that captures motion boundaries and event-induced structural changes. Within a one-step
diffusion backbone, scaffold-derived structural
tokens progressively interact with and activate relevant appearance engrams across layers. This
token-space association allows target structures to access reference appearance without relying on direct pixel-wise correspondence, while the
diffusion prior complements uncertain or newly revealed regions. Across three
benchmarks, Engram-E2VID improves PSNR by up to 3.29 dB and reduces LPIPS by up to 0.08 over the strongest same-input baseline, while degrading more slowly as the reconstruction interval increases.
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All authors Feiyu Ji, Xiang Li, Hao Ma, Tianxiang Huang, Qingxin Lu, Mengqi Ji, Lei Han, Xiaokang Yang, Xiaoyun Yuan
Accelerator Physics · Cross-listed from hep-ph
Net electron spin rotation in a plane-wave pulse: Holonomy set by the anomalous magnetic moment
N. S. Akintsov, A. P. Nevecheria, S. N. Andreev et al. (+1 more)
We compute the
spin rotation that survives after a relativistic electron has crossed a plane-wave
laser pulse of finite duration. In the interaction picture built on the exact $g=2$
evolution, the Thomas-Bargmann-Michel-Telegdi equation becomes parallel transport by a connection with constant coefficients on the polarization plane, and the pulse enters only through the closed curve that the transverse vector potential traces there. The net rotation is the holonomy of that connection: an angle $-\frac{1}{2}a_e^2\mathcal{A}$ about the propagation direction, with $a_e=(g-2)/2$ the anomaly and $\mathcal{A}$ twice the signed area enclosed by the curve. That area is the
spin angular momentum the pulse carries per unit area, so the rotation measures the helicity of the light. Reduction of the residual dynamics to a rotation coupled through the anomaly alone is an exact result of the 1960s [Ternov, Bagrov, and Klimenko, Sov. Phys. J. 11, 29 (1968); Bagrov and Gitman, The Dirac Equation and its Solutions (De Gruyter, Berlin, 2014), Sec. 5.3], which yields two closed-form cases; the area law is the general second order that those two cases bound. The same area governs the orientation
memory of a neutral
magnetic dipole [Oblak and Seraj, Phys. Rev. D 109, 044037 (2024)] with a coupling of order unity. For a charged electron on a Volkov orbit the coupling $g/2$ cancels identically, which suppresses the rotation by $1.3\times10^{-6}$ and leaves a channel with no $g$-independent part. We verify the cancellation at $g=2$ over 180 pulse configurations and the area law over 89 more. Finite focusing restores that part at second order in $1/kw_0$, and it exceeds the anomalous signal unless $w_0\gtrsim16\lambda$ at $\gamma=10$, or $270\lambda$ at $\gamma=1$.
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All authors N. S. Akintsov, A. P. Nevecheria, S. N. Andreev, Qing-Hua Qin
Chemical Physics · Cross-listed from math.OC
A Damped Subspace Splitting Algorithm for Constrained Density Functional Theory
Yuanming Su, Yukuan Hu, Xin Liu et al. (+1 more)
Constrained density functional theory (CDFT) provides a powerful framework for describing electronically excited and charge-localized states, which underlie a broad range of physical and chemical phenomena. However, the discretized optimization problems arising from CDFT calculations remain challenging, owing to the presence of both the Stiefel
manifold constraint and additional nonconvex quadratic constraints. Existing
algorithms either fail to enforce the quadratic constraints with high accuracy or face convergence issues due to double-loop iterative structures. In this paper, we first derive a subspace-splitting reformulation that decouples the two groups of constraints, by exploiting the inherent rotation invariance and introducing a nonlinear subspace
alignment constraint. Based on this reformulation, we propose a single-loop damped alternating direction method of multipliers, called DASSP. To the best of our knowledge, DASSP is the first
algorithm for CDFT calculations with rigorous convergence guarantees. Each iteration of DASSP comprises a spectral minimization step, a projected gradient step, and a damped dual ascent step, all of which admit efficient implementations. Numerical results on synthetic and realistic CDFT problems demonstrate that DASSP attains high feasibility accuracy and exhibits favorable efficiency without compromising robustness. We expect that this work will pave the way toward reliable and efficient large-scale CDFT applications.
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All authors Yuanming Su, Yukuan Hu, Xin Liu, Guanghui Hu
Plasma Physics
SafeDivertor: Faithful Divertor Heat Flux Reconstruction from Macroscopic Plasma State Signals via Time-Frequency Prior Exploitation
Hao Si, Zehua Chen, Qingquan Yang et al. (+8 more)
Divertor heat-flux analysis is essential for understanding
plasma-wall interactions and protecting
plasma-facing components in
magnetic-confinement fusion devices, while conventional infrared-based inversion is usually performed after discharge and requires heat-conduction modeling with device-specific material properties, divertor geometry, and boundary conditions. Rather than accelerating this conventional infrared-based inversion paradigm, we introduce a new online-oriented signal-based reconstruction paradigm that directly reconstructs time-resolved radial heat-flux profiles from multi-source macroscopic
plasma-state signals available during discharge. To enable systematic study of this task, we construct DivMPS2HF, a multi-source discharge
dataset that provides the data foundation and
benchmark for signal-based divertor heat-flux reconstruction. We further propose SafeDivertor, a task-driven framework designed to address the key challenges of signal-based heat-flux reconstruction. It employs physical prior-aware initialization to provide radial-distribution guidance for target channels, input perturbation to reduce over-reliance on specific heterogeneous signals, spectral-aware reconstruction optimization to exploit time-frequency priors and preserve transient dynamics, and progressive training to stabilize the optimization of these complementary objectives. Experiments on DivMPS2HF demonstrate that SafeDivertor achieves the best overall performance among the evaluated time-series baselines across all five metrics, establishing a new performance
benchmark for signal-based divertor heat-flux reconstruction. The source code will be released on https://github.com/Event-AHU/OpenFusion
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All authors Hao Si, Zehua Chen, Qingquan Yang, Xiao Wang, Dengdi Sun, Wanli Lyu, Gaoting Chen, Guosheng Xu, Hang Su, Jin Tang, Jun Zhu
Plasma Physics
BORAY-3D: A ray tracing code for three-dimensional magnetized plasma configurations
Yuxuan Wang and Huasheng Xie
Ray tracing codes are useful tools for studying electromagnetic wave propagation and absorption using the geometrical-optics approximation. Existing codes commonly provide either broad
radio-frequency coverage in axisymmetric
equilibria or three-dimensional capability specialized for electron-cyclotron (EC) applications. BORAY-3D integrates three desirable features in a single version. First, it has a broad frequency range of validity regime from ion-cyclotron, helicon and lower-hybrid waves to EC waves and emission. Second, it provides a unified treatment of arbitrary two- and three-dimensional
magnetic-
plasma configurations, including both closed and open field-line regions. Third, it incorporates fully relativistic Maxwellian EC absorption. The code extends the axisymmetric BORAY formulation by solving the ray equations in cylindrical coordinates $(r,\phi,z)$ while allowing the toroidal mode number $n_\phi$ to vary.
Magnetic-field, density and temperature data are directly described in $(r,\phi,z)$ coordinates without the restriction of flux functions, so that numerical
equilibria and analytic field models can be handled in the same form. The non-relativistic hot-
plasma model inherited from BORAY is used for lower-hybrid, ion-cyclotron and helicon absorption, whereas the relativistic model is coupled to reciprocal radiative transfer for electron cyclotron emission (ECE). Practical applications include 13.56 MHz helicon and 50 MHz fast waves, a 3.7 GHz lower-hybrid wave, and 115–220 GHz EC emission. BORAY-3D has been systematically benchmarked against GENRAY for tokamak toroidal-field ripple, Raytrax and TRAVIS for W7-X, as well as public HSX heating and W7-X ECE results.
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Medical Physics
The Virtual Hearing Clinic (VHC)- a modular online platform for hearing research and hearing health care
Lena Schell-Majoor, Kim M. Rullmann, Tobias Bruns et al. (+4 more)
Objective: The aim is to introduce the concept of the Virtual Hearing Clinic (VHC), give an overview of the current status and exemplify its feasibility with data from a diagnostics module obtaining hearing thresholds. Design: The architecture of the VHC is described and an overview of functional modules that have been developed and tested in respective studies is given. As a functional example data from an experiment is presented. Hearing thresholds were obtained from 20 subjects with hearing loss with the VHC using the Graded Response Bracketing (GraBr) procedure and compared to reference thresholds obtained with a clinical audiometer. Results: Median VHC-based hearing thresholds over all frequencies did not differ significantly from the reference with values of 57.4 dB SPL (VHC) and 55.5 dB SPL (reference). The shape of the frequency-dependent thresholds was also found to be very similar for 250 Hz to 4 kHz. Results for 6 kHz showed larger differences. Conclusion: The VHC is suitable as a mobile hearing health application and to collect data for audiological research. By offering flexibility in time and location it can lower barriers for hearing health care and enable collecting large
datasets that are needed for the advancement of data-driven audiology.
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All authors Lena Schell-Majoor, Kim M. Rullmann, Tobias Bruns, Theresa Jansen, Volker Hohmann, Hendrik Kayser, Birger Kollmeier
Optics
Spectrally flat and broadband doublepumped fiber optical parametric amplifiers
J. M. Chavez Boggio, J. D. Marconi, S. R. Bickham et al. (+1 more)
We study theoretically and experimentally spectrally flat and broadband double-pumped fiber-optical parametric amplifiers (2P-FOPAs). Closed formulas are derived for the gain ripple in 2P-FOPAs as a function of the pump wavelength separation and power, and the fiber non-linearity and fourth order dispersion coefficients. The impact of longitudinal random variations of the zero dispersion wavelength $\lambda_0$ on the gain flatness is investigated. Our theoretical findings are substantiated with experiments using conventional dispersion shifted fibers and highly nonlinear fibers (HNLFs). By using a HNLF having a low variation of $\lambda_0$ we demonstrate high gain and flat spectrum ($25 \pm 1.5\text{ dB}$) over $115\text{ nm}$.
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All authors J. M. Chavez Boggio, J. D. Marconi, S. R. Bickham, H. L. Fragnito
Optics
Dual-polarization control of broadband nonreciprocal thermal radiation by combining local and nonlocal metasurfaces
Shuang Xia, Mengqi Liu, Wenjian Wan et al. (+10 more)
Nonreciprocal thermal radiation offers a route to decouple spectral directional absorptivity and emissivity, thereby enabling new paradigms in thermal-photonic systems. However, in magneto-optical platforms, the intrinsic gyroelectric response generally confines observable nonreciprocity to transverse-
magnetic (TM) polarization, while the transverse-electric (TE) response is absent. In this work, we experimentally demonstrate, for the first time, a local thermal metasurface strategy to activate TE-polarized nonreciprocity by creating artificial gyromagnetic response in a gyroelectric
semiconductor platform. We further extend this mechanism to broadband dual-polarization operation employing a nonlocal thermal metasurface, which combines a resonator supercell with gradient-doped epsilon-near-zero magneto-optical multilayers. Pronounced absorptivity contrast is maintained over 22-27 {\mu}m for TE polarization and 19-27 {\mu}m for TM polarization. This platform provides a mechanism-based route to achieve broadband and dual-polarization nonreciprocal thermal absorption, opening new opportunities for advancing radiative energy-conversion devices.
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All authors Shuang Xia, Mengqi Liu, Wenjian Wan, Jialong Wang, Weihao Yang, Chaoran Wang, Huiqin Ma, Jun Qin, Hua Li, Yuan Wang, Lei Bi, Chengwei Qiu, Xiaobo Yin
Fluid Dynamics
Area and Perimeter Rules of Velocity Circulation in Two-Dimensional Turbulence with Large-scale Absolute Equilibrium
Zi-Ang Zhang and Jin-Han Xie
We demonstrate that the area rule of velocity circulation – traditionally associated with the turbulent inertial range but shown not to be exact – is strictly satisfied in the large-scale absolute
equilibrium of two-dimensional (2D) homogeneous isotropic
turbulence under enstrophy equipartition. We also derive a novel perimeter rule from the 2D inviscid loop equation, which posits that the probability distribution function (PDF) of velocity circulation depends solely on the loop perimeter rather than its area. This perimeter rule holds strictly in the large-scale absolute
equilibrium characterized by energy equipartition. At the intermediate states determined by both enstrophy and energy, these two regimes are separated by a characteristic
equilibrium scale $l_\text{eq}$: the area rule governs loop statistics when $l\ll l_\text{eq}$, while the perimeter rule emerges for $l\gg l_\text{eq}$. These statistical laws remain robust even for loops with extreme aspect ratios as low as $0.03$, a value that inertial-range studies never achieved. Our findings provide a new steady-state solution to the 2D loop equation and suggest additional solutions, paving the way for exploring previously undiscovered
geometric invariants of
turbulence.
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Instrumentation and Detectors
Nonproportional Response of a GAGG Scintillator to Beta and Gamma Radiation over a Wide Energy Range in PIKACHU
Takumi Omori, Takashi Iida, Yosuke Suga et al. (+12 more)
Nonproportional response of scintillation light yield for sub-MeV radiations is a well-known characteristic of inorganic scintillators. In the PIKACHU experiment, a precise understanding of the nonproportional response of the GAGG ($\mathrm{Ce:Gd_3Al_2Ga_3O_{12}}$) scintillator is essential for background modeling. In this study, the nonproportional response of the GAGG scintillator was evaluated for both $\beta$ and $\gamma$ rays. The response for $\beta$ rays was measured using the Compton coincidence technique with a germanium detector, while that for $\gamma$ rays was evaluated using several monoenergetic $\gamma$-ray sources. The measurement results showed different responses for $\beta$ and $\gamma$ rays, with a stronger nonproportional response for $\gamma$ rays than for $\beta$ rays over the energy range of 50–2614~keV. The background model incorporating the measured nonproportional responses reproduced the measured background spectra more accurately compared with the model without the nonproportional response correction. These results demonstrate the importance of precise evaluation of the nonproportional response of the GAGG scintillator which is essential not only for background modeling in the PIKACHU experiment but also for accurate energy calibration in scintillator-based experiments.
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All authors Takumi Omori, Takashi Iida, Yosuke Suga, Masao Yoshino, Ken-Ichi Fushimi, Azusa Gando, Nobuo Hinohara, Keishi Hosokawa, Motonao Ishigami, Kei Kamada, Tadafumi Kishimoto, Keita Mizukoshi, Takuya Sako, Yasuhiro Shoji, Shota Sugi
Fluid Dynamics
Effect of Discharge on the Nonlinear Bar Growth: A Flume Experiment
Shohei Seki, Daichi Moteki and Hiroyasu Yasuda
Alternate bars are ubiquitous bedforms in alluvial rivers, and excessive bar-height growth can increase flood risk and disrupt ecosystems. Predicting bar-height variability requires quantifying the dependence of bar growth rate on water discharge, yet this has rarely been achieved because conventional flume measurements interrupt the flow and cannot continuously capture bar
evolution. Here we conducted laboratory experiments under four discharges and four channel slopes (16 conditions) and continuously mapped bed topography using Stream
Tomography, a nonintrusive, flow-through measurement technique. Bar height exhibits sigmoidal growth and is well described by the Landau equation, allowing robust estimation of the growth rate and
equilibrium height. The inferred dimensionless growth rate tends to increase as discharge decreases, but its sensitivity is weaker than that predicted by stability theory for a single alternate-bar mode. This discrepancy becomes more pronounced at lower discharge, indicating limitations of linearization and the influence of interactions among multiple bar modes. Furthermore, numerical flow simulations over the measured bed topography reveal that, during bar development, lower-discharge conditions produce a relatively larger bar height-to-depth ratio, making the flow more prone to deflection. In such cases, sediment transport is restricted downstream of depositional areas, thereby limiting bar migration. Consequently, flow and sediment transport become concentrated in the scour zones, enhancing local scour and promoting the growth of bar height. These results provide
benchmark constraints for bar stability theories and help improve predictions of how bar height responds to changes in discharge.
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Chemical Physics
X-ray Driven Trihydrogen Formation on Silica Nanosurfaces
Samuel Sahel-Schackis, Adam Summers, Ritika Dagar et al. (+29 more)
The trihydrogen cation ($\mathrm{H_3^+}$) initiates the ion-molecule reactions that build molecular complexity in interstellar space. Whether its canonical formation reaction, $\mathrm{H_2^+ + H_2 \rightarrow H_3^+ + H}$, proceeds on inorganic surfaces under radiation-driven ionization has remained untested. Here we drive $\mathrm{H_3^+}$ formation on hydrated silica nanoparticles using intense 1.88 keV X-ray pulses, combining ion velocity map imaging, electron time-of-flight spectroscopy, and single-particle coherent diffractive imaging to resolve this chemistry on individual particles. The self-induced surface electric field on the V/nm scale drives interfacial charge transfer and water fragmentation. This field is the dominant parameter governing the relative yields of $\mathrm{H^+}$, $\mathrm{H_2^+}$, and $\mathrm{H_3^+}$ across particle size, composition, and aggregation. Density functional theory and nonadiabatic
quantum molecular dynamics simulations trace this field-driven charge transfer, directly analogous to band bending at
semiconductor photoelectrodes. These results establish surface-field-driven charge transfer as a unifying mechanism between radiation dominated astrophysical environments and field-driven surface catalysis.
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All authors Samuel Sahel-Schackis, Adam Summers, Ritika Dagar, Alexandra Feinberg, Martin Grassl, Simon Dold, Rebecca Boll, Yevheniy Ovcharenko, Chris Aikens, Cesar Costa Vera, Alberto De Fanis, Avijit Duley, Felix Gerke, Daniel Jost, Regina Leiner, Michael Meyer, Ilana J. P. Molesky, Razib Obaid, Jeffrey Powell, Nils Rennhack, Björn Senfftleben, Hendrik Tackenberg, Paul Tuemmler, Sergey Usenko, Christian Peltz, Thomas Fennel, Markus Gallei, Eckart Rühl, Artem Rudenko, Daniel Rolles, Thomas Linker, Matthias F. Kling
Computational Physics · Cross-listed from cs.CE
A hybrid s-version isogeometric strategy for dynamic crack propagation in 2D and 3D problems
Tianyu He, Kosei Kurosaki, Naoki Morita et al. (+2 more)
A hybrid s-version of isogeometric analysis (hS-IGA) strategy is proposed for accurate and efficient evaluation of near-crack fracture quantities in dynamic crack propagation analysis. The strategy retains the global-local superposition framework of the conventional s-method, while introducing B-spline basis functions only into the global discretisation and preserving a Lagrange-based local mesh in the crack domain. This hybrid formulation is motivated by the continuity-related bottleneck in the global-local coupling integration of the conventional Lagrange-based s-method, and by the need to retain a Lagrange-based local mesh for crack representation and post-processing of the dynamic stress intensity factor (DSIF) and local stress. The resulting formulation removes discontinuities in the coupling integrands caused by the global approximation and enables accurate coupling integration by standard Gauss quadrature without recursive subdivision. The proposed strategy is verified using two-dimensional stationary and dynamic straight-crack problems against the standard finite element method and the conventional s-method, and is further assessed using three-dimensional stationary and dynamically propagating circular-crack problems against the conventional s-method. Results show that the proposed hS-IGA strategy accurately evaluates the DSIF and local stress while retaining the global-local modelling advantages of the s-method. It also substantially reduces the number of integration points required for coupling integration, by approximately 81% in the two-dimensional dynamic
benchmark and 95.6% in the three-dimensional dynamic
benchmark relative to the conventional s-method. These results demonstrate that the proposed hS-IGA framework provides an accurate and efficient global-local strategy for dynamic crack propagation analyses requiring reliable evaluation of near-crack fracture quantities.
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All authors Tianyu He, Kosei Kurosaki, Naoki Morita, Naoto Mitsume, Kazuki Shibanuma
Plasma Physics
Millisecond-Scale Neural Operator Surrogates for Double-Null Free-Boundary Grad-Shafranov Equilibria
Plamen G. Krastev
The Grad-Shafranov (GS) equation governs ideal magnetohydrodynamic
equilibrium in tokamak
plasmas. Free-boundary GS solvers are central to diverted-
equilibrium modeling, but nonlinear Picard iteration introduces computational cost and sample-dependent latency that can become prohibitive in optimization, modeling, and control-oriented loops. Here we train a geometrically conditioned
Fourier Neural Operator (FNO) to learn a constrained forward map from spatial coordinates, scalar operating parameters $(P_{\mathrm{axis}}, I_p, f_{\mathrm{vac}})$, and prescribed X-point locations to the poloidal-flux field $\psi(R,Z)$. The model is trained on a controlled family of constrained double-null free-boundary
equilibria generated with FreeGS for a single fixed machine geometry and prescribed
topology. The best model achieves a mean relative $L^2$ error of $0.05\%$, with test error following an empirical $N^{-0.68}$ power law over $N_{\mathrm{train}}\in\{500,1000,2000,5000\}$. It recovers both X-points to within $0.2$ cm and localizes the O-point to $0.03$ cm. As a physics-consistency diagnostic, the predicted fields satisfy an external finite-difference GS residual evaluation at the same level as the ground-truth fields, with mean normalized residual $2.29$, indistinguishable from the $2.29\pm0.06$ FreeGS baseline using the same diagnostic. The trained FNO evaluates one
equilibrium in $2.77$ ms on GPU and $25.6$ ms on CPU, corresponding to speedups of ${\sim}640\times$ and ${\sim}69\times$ relative to FreeGS as configured here, with near-deterministic latency (p95/median $=1.01$). These results show that neural-operator surrogates can provide accurate, geometrically precise, millisecond-scale
equilibrium evaluations for
magnetic-confinement fusion workflows within a prescribed
topology and machine geometry.
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Classical Physics · Cross-listed from math-ph
On the synthesis of complete two-dimensional second-gradient continua: Tri-pantographic fabrics
Casey Rodriguez, Emilio Barchiesi, Simon R. Eugster et al. (+2 more)
We introduce a notion of completeness for two-dimensional second-gradient elastic continua and propose a microstructural route toward its synthesis. A continuum is said to be complete if the Hessian of the stored energy with respect to the second-gradient variable is locally positive definite, so that every nonzero admissible increment of the placement second gradient is quadratically controlled in the highest-order part of the energy about each configuration. Starting from the Principle of Virtual Work, we derive the constitutive relations,
equilibrium equations, and admissible boundary interactions for a broad class of fibrous second-gradient continua whose stored energies depend on fiber stretch, stretch gradients, and
curvature. The theory is then applied to several continua motivated by pantographic microstructures. Classical pantographic sheets are shown to be incomplete, while bi-pantographic fabrics enlarge the class of components of the second gradient detected by the energy but remain incomplete. Finally, we formulate a tri-pantographic continuum associated with a proposed three-family architecture and prove that it is complete. The examples illustrate how microstructural architecture influences both the completeness properties of an effective continuum and the pointwise form of its higher-order boundary interactions.
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All authors Casey Rodriguez, Emilio Barchiesi, Simon R. Eugster, Ivan Giorgio, Francesco dell'Isola
Data Analysis and Statistics · Cross-listed from nlin.CD
Equation-Free Period-Aware Forecast-Error Contraction for Estimating Negative Largest Lyapunov Exponents from Short Trajectory Ensembles
Andrei Velichko, N'Gbo N'Gbo and Viet-Thanh Pham
Estimating positive largest Lyapunov exponents from data is comparatively natural because neighboring trajectories separate, whereas stable dynamics require resolving contraction before measurement noise or finite precision erases the signal. We introduce a period-aware forecast-error contraction procedure for estimating a dominant negative Lyapunov exponent from ensembles of short scalar trajectories without using governing equations or an analytical Jacobian. A k-nearest-neighbor predictor is trained on trajectory histories, the
geometric-mean absolute forecast error is evaluated at phase-consistent horizons, and the exponent is obtained from the slope of the logarithmic error profile. Unlike data-driven approaches that reconstruct local
evolution matrices or differentiate a learned surrogate, the proposed method extracts the contraction rate directly from out-of-sample forecast errors. Two adaptations are essential: the forecast step is synchronized with the detected orbit period, and candidate slopes are accepted only when they form a stable consensus across several transient lengths. On the logistic map, the method recovers 92 of 112 negative-exponent parameter values with a mean absolute error of 0.0253 and $R^2=0.886$. On a two-dimensional map without fixed points, independent scalar pipelines based on the three observables $x_n$, $y_n$, and $z_n$ give mean absolute errors of 0.00879–0.01145 and $R^2=0.983$–$0.986$. Because the estimation stage uses only observed trajectories, the framework provides a basis for repeated-relaxation experiments in which short sensor responses are available but the governing equations and analytical Jacobian are unknown. Experimental validation remains a subject of future work.
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Fluid Dynamics · Cross-listed from cond-mat.soft
A floor and a ceiling for the advancing contact angle
Yong Sung Park
Reported maxima of the advancing contact angle scatter from $87^\circ$ to $147^\circ$ in a single systematic study, and
liquids on surfaces with static angles as low as $5^\circ$ reach dynamic maxima near $90^\circ$. We show that both observations follow from the hinged motion of the free surface near a moving contact line. The local Stokes solution for a wedge rotating about its contact line has two singular angles of opposite character: at $90^\circ$ the hinged motion generates no wall shear and the rotation is free, and at $\theta_h = 128.73^\circ$, where $\tan 2\alpha = 2\alpha$, a resonance with the $r^2$ eigensolution arrests the rotation through an $r^2 \ln r$ term. Between the two angles lies a band that a transient advancing angle cannot leave while the interface near the contact line remains a quasi-steady wedge. A compilation of 68
liquid-solid systems from nine sources and five configurations confirms the band and its two exits: systems not limited by the apparatus, with $\theta_s \le 40^\circ$, reach $87^\circ$ to $119^\circ$ regardless of chemistry, and every exceedance of $\theta_h$ occurs either where chemistry places the static angle above the band or where the flow leaves the quasi-steady regime. The record of a waterline on a vertical wall exhibits the band within a single unsteady experiment, together with a distinct quieting of the local contact angle at the crossing of $90^\circ$.
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Atomic Physics
Large anomalous shifts of potassium-39 Feshbach resonances
Ali Zaheer, Mohammed Bouras, Krzysztof Giergiel et al. (+3 more)
We report the observation of large anomalous shifts, up to +7.5 G, of the positions of the 33.6 G and 39.9 G Feshbach resonances in potassium-39 atoms confined in a 1063.9 nm optical dipole trap (ODT) at temperatures up to around 35 {\mu}K and trap depths up to about 136 {\mu}K. When the atom cloud is cooled to lower temperatures, by reducing the trap depth of the ODT, the shifts decrease proportionally with trap depth and approach zero at zero depth. We show that the large observed shifts originate from a large differential ac Stark shift between the incoming pair of potassium-39 atoms and the weakly bound Feshbach molecule, which in turn originates from an unexpectedly large dynamic polarizability of the Feshbach molecule. The polarizabilities of the Feshbach molecules extracted from the measured shifts of the 33.6 G and 39.9 G resonances are about four to seven times the sum of the polarizabilities of the two incoming potassium-39 atoms, that is, about four to seven times larger than the usual polarizability of weakly bound Feshbach molecules. The large polarizabilities of the Feshbach molecules are attributed to a near-coincidence between the frequency of the 1063.9 nm ODT
laser and the frequency of a molecular transition from the last vibrational level of the lowest triplet a3{\Sigma}+u potential to a vibrational level of the excited b3{\Sigma}+g potential. Other potassium-39 Feshbach resonances we have studied exhibit a zero or very small shift, corresponding to molecular polarizabilities close to the sum of the polarizabilities of the two incoming potassium-39 atoms.
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All authors Ali Zaheer, Mohammed Bouras, Krzysztof Giergiel, Rudolf Grimm, Andrei Sidorov, Peter Hannaford
Optics · Cross-listed from quant-ph
Generating two-mechanical mode entangled cat states, and steady-state entanglement, in cavity optomechanics in the presence of dissipation
Sanket Das and Jason Twamley
We investigate a dissipation-engineering approach to produce a phase-dependent collective-mode Schrödinger cat state involving two modes. Our model features a single cavity mode that interacts with two spectrally identical mechanical oscillators. Both oscillators are coupled through a phase-dependent hopping interaction. We demonstrate that by adjusting the phase of the
phonon-hopping interaction, one can control the bipartite
entanglement of the phase-dependent two-mode cat state during its generation. Additionally, our study reveals that
phonon interactions act as a tunable parameter, enabling the manipulation of steady-state
entanglement between the bare mechanical modes, even in the presence of environmental effects and thermal excitations. Our scheme provides a feasible approach for the phase-dependent multi mode non-Gaussian states preparation.
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Biological Physics · Cross-listed from cs.ET
A Quantum Circuit Framework for Protein Ensemble-Level Energetics
Pratik Patil, Bhushan Bonde and Bhaskar Choubey
Proteins occupy heterogeneous free-energy landscapes in which high-
entropy ensembles converge toward compact, low-energy basins with multiple sub-states. Molecular dynamics can access these landscapes at atomic resolution, but exhaustive sampling remains computationally demanding. Meanwhile, most
quantum approaches target only single optimal structures, leaving full ensemble energetic heterogeneity unexplored. We introduce a residue-level, gate-based
quantum circuit framework for coarse-graining
protein thermodynamics. Each amino acid is represented as a two-state
qubit (stabilised vs. excited solvation state) based on residue solvation energetics. A structure-informed
entanglement block then encodes covalent and non-covalent contacts using parameterised controlled gates,
embedding correlations across the residue-interaction network. Sampling the
circuit ($\sim 10^6$ measurements) yields binary thermodynamic microstates used to compute
protein energy distributions, residue-level statistical couplings, energetic sensitivities, and information gains relative to total free energy. We showcase the framework on the
benchmark Trp-cage miniprotein 1L2Y (TC5b) and 9GDL, a disulfide-stabilised Trp-cage-fortified exenatide chimera. For 1L2Y, the
circuit reproduces a structured, folding-funnel-like energy distribution. Comparative analysis with 9GDL reveals shifts in global energy distributions and residue-level stability profiles. Coupling and information-theoretic analyses localise residues associated with ensemble reorganisation, while multi-body couplings show the
circuit resolves both direct and indirect statistical correlations. This framework expands
quantum protein modelling beyond single-structure optimisation toward ensemble-level characterisation, capturing key features of rugged energy landscapes to guide
protein design, mutation mapping, and allosteric pathway identification.
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Optics
Inverse mask design for interference lithography using automatic differentiable wave propagation
Chuntian Cao, Jangwoon Sung, Jack Griffiths et al. (+9 more)
Interference lithography (IL) is powerful for fabricating high-resolution periodic nanostructures, but designing masks to produce non-periodic patterns remains challenging. We introduce a gradient-based optimization framework for binary IL mask design using automatic differentiation. The forward model is implemented using the differentiable angular spectrum method (ASM). The inverse mask design is formulated as an optimization problem, where the mask logits are updated through backpropagation of the loss between the simulated field amplitude and the target pattern. We optimize a mask that reproduces a target pattern with only 0.1% isolated pixel-level defects, resolving features at half the mask pixel pitch. To scale mask optimization, we employ the shifted ASM, which partitions the mask into patches that are propagated independently and summed at the image plane. For a 3.84 mm$\times$3.84 mm mask, shifted ASM with 16 patches reduces peak GPU
memory by 3.8$\times$ at only 1.3$\times$ runtime cost relative to standard ASM. With gradient checkpointing, peak
memory is reduced by 7.4$\times$ at 2$\times$ runtime. Distributing across multiple GPUs further accelerates the optimization. This work establishes a physics-informed, machine learning-driven approach for IL mask design, moving a step further towards complex, non-periodic patterns. The source code is available at https://github.com/chuntian236/holography-optimization.git .
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All authors Chuntian Cao, Jangwoon Sung, Jack Griffiths, Yuan Gao, Xi Yu, Paul Baity, Nikhil Tiwale, Zhitian Shi, Juhong Ahn, Shinjae Yoo, Yong S. Chu, Chang-Yong Nam