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Physics Physics

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Thursday 19 March

Fluid Dynamics

The Role of Drop Shape in Impact Force

Yang Zeng, Zhen Chen and Lei Xu

Drop impacts are ubiquitous in natural and industrial processes, yet the influence of drop shape on impact force remains a fundamental open question. Combining experiments with theoretical analysis, we show that drop shape plays a critical role, with impact force varying by more than an order of magnitude solely due to changes in shape. By uncovering self-similarity in time and cross-shape similarity across diverse drop profiles, we develop a universal cylinder model that accurately predicts both the magnitude and timing of the impact force. This study establishes a comprehensive framework for understanding impact forces across a wide range of drop shapes. Given the prevalence of drop impacts with varying shapes in real-world scenarios, our findings hold fundamental significance and have broad potential applications across industries such as soil erosion prevention, jet cutting, spray coating, and design of windshields and wind turbines.
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Applied Physics

Programmatically Generated Microparticles Using SUEX Dry-Film Epoxy Resist

Jason P. Beech and Jonas O. Tegenfeldt

We present a lithographic method for fabricating free-standing microparticles directly from SUEX dry-film epoxy resist. Unlike conventional SU-8 particle fabrication, which requires patterning on solid substrates followed by sacrificial-layer release, our approach eliminates substrate use entirely and produces particles with near 100% yields. The process supports a wide design space of in-plane geometries, including high-aspect-ratio and highly complex shapes. To enable large-scale particle libraries, we integrate the method with the Nazca Python library, allowing programmatic generation of tens of thousands of parametrically defined particle designs. This combination of substrate-free fabrication and automated design provides a scalable route to custom microparticles for materials science, microfluidics, and soft-matter applications.
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Physics and Society

Beyond the Main Mode: The contribution of access and egress trips in door-to-door travel

Nejc Geržinič, Mark van Hagen, Hussein Al-Tamimi et al. (+2 more)

Access and egress trips constitute a substantial part of a train trip in minds of travellers, often being the deciding factor whether to travel by train at all. Despite a host of studies analysing individual legs within a multimodal trip chain, the full chain within a multimodal trip - including access, main and egress - has seen very limited attention. To understand the importance of all these choices, we use travel diaries from the Dutch Mobility Panel to estimate a nested logit discrete choice model. Our results suggest that as a main mode, train and bus/tram/metro (BTM) seem to be associated with an inherent disutility compared to walking, cycling or car. The in-vehicle time in train and BTM, however, seems to be perceived significantly less negatively (60% lower) than in private modes, making them comparatively more attractive for longer journeys. These results imply that, given the strong preference for walking for both access and egress, train stations should be sufficiently dense to allow most people to walk to a station. This, however, should not come at the expense of additional transfers, as they inflict substantial disutility. Operators need to find a balance between accessibility and directness. Given the strong dispreference of travelling by car to dense urban areas, these trips should be the primary target of policymakers and operators for attracting additional travellers to take the train. Future studies could further enhance our understanding of multimodal trips by including additional attributes in the data, account for respondent heterogeneity and study how individuals build their consideration set when making multimodal trips.
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All authors Nejc Geržinič, Mark van Hagen, Hussein Al-Tamimi, Niels van Oort, Dorine Duives

Accelerator Physics

Design and implementation of a high-density sub-nanosecond timing system for a C-band photocathode electron gun test platform

Peng Zhu, Kangjia Xue, Lin Wang et al. (+8 more)

This paper presents the design and implementation of a high-density, deterministic trigger distribution system tailored for the C-band photocathode electron gun test platform at the Southern Advanced Photon Source (SAPS). Implemented within a scalable 6U VME modular architecture, the system achieves high-density integration by consolidating a master controller, clock distribution network, and 80 heterogeneous output channels into a single chassis. This design leverages a high-performance FPGA core combined with custom backplane interconnections to establish a master-slave topology, significantly reducing the system footprint compared to stacked standalone generators. To guarantee timing determinism in high-noise environments, precise placement and timing constraints are applied to the FPGA logic, while optical isolation is employed to mitigate electromagnetic interference. Furthermore, a dual-channel SFP optical signaling architecture enables seamless expansion to 160 synchronized channels. A remote control framework based on a serial server and a virtual machine Input/Output Controller (IOC) facilitates flexible configuration. Performance tests demonstrate adjustable trigger frequencies from 1 Hz to 100 Hz, with delays and pulse widths tunable from 0 to 10 ms at a resolution of 10 ns (or the RF period). The local electrical output exhibits an ultra-low RMS jitter of 6.55 ps (60 ps peak-to-peak). For remote optical distribution, the system maintains a sub-nanosecond RMS jitter of 119.5 ps, with peak-to-peak variation confined to 1 ns due to the combined effects of transceiver optoelectronic conversion (utilizing HFBR-1414T/2412T modules) and fiber transmission. The system has been successfully commissioned and is currently in reliable routine operation, verifying the architecture as a robust, highly integrated, and cost-effective solution for compact accelerator facilities.
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All authors Peng Zhu, Kangjia Xue, Lin Wang, Yuliang Zhang, Yongcheng Hea, Xuan Wu, Mingtao Li, Sinong Cheng, Xiaohan Lu, Shiming Jiang, Xiao Li

Instrumentation and Detectors

Stability of Charge Collection Efficiency and Time Resolution in 4H-SiC PIN Diodes Under X-ray Irradiation

Jiaqi Zhou, Sen Zhao, Xiyuan Zhang et al. (+6 more)

This study evaluates the radiation tolerance of a 4H-SiC PIN detector under X-ray irradiation up to \SI{2}{MGy} (Si) at \SI{160}{keV}. The detector features a fully epitaxial vertical PIN structure with mesa terminations and field plates. Comprehensive pre- and post-irradiation characterization includes I-V/C-V measurements, charge collection efficiency (CCE) and timing resolution tests using $\beta$-particles ($^{90}$Sr). After \SI{2}{MGy} irradiation, the reverse leakage current remains at an ultralow level of $\sim 10^{-11}$ \si{A/cm^2} at \SI{-300}{V} with negligible degradation. C-V characteristics are basically consistent, with full depletion at \SI{~130}{V}. CCE for $\beta$-particles decreases by less than 5%. The detector maintains good timing resolution: \SI{21}{ps} before and \SI{31}{ps} after irradiation, with jitter increasing moderately. These results demonstrate stable performance under extreme X-ray exposure, highlighting the detector's potential for radiation-hard applications in high-energy physics, space missions, and nuclear reactor monitoring.
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All authors Jiaqi Zhou, Sen Zhao, Xiyuan Zhang, Suyu Xiao, Chenxi Fu, Congcong Wang, Yanpeng Li, Weimin Song, Xin Shi

Optics

Laser-Scrawled Random Plasmonic Metasurface in Nanoseconds for Physical Unclonable Functions

Haining Xu, Yang Zhang, Shenqi Yang et al. (+10 more)

Randomness in optical systems emerges as a powerful resource for generating complex, non-deterministic light-matter interactions. In particular, random plasmonic metasurfaces harness nanoscale disorder to produce unique and irreproducible optical responses, positioning them as an ideal platform for physical unclonable function in secure optical authentication. However, realizing such random metasurfaces in a rapid, scalable, and chemical-free manner for optical PUFs remains challenging. Here, we introduce a nanosecond pulsed laser scribing method for one-step fabrication of a robust random plasmonic metasurface physical unclonable function. By delivering spatially localized, ultrafast energy bursts, this technique harnesses naturally occurring instability to generate stochastic plasmonic nanostructures in nanoseconds. The unique plasmonic metasurfaces are effectively transformed into a macroscopic, non-replicable optical fingerprint via morphology-dependent resonance at the nanoscale, enabling low-cost and fast readout. Leveraging the wavelength-selective plasmonic response, we present a multidimensional multiplexing strategy that expands the challenge response pairs space and encoding capacity by 5-fold via topography and RGB multiplexing. The resulting plasmonic keys exhibit good bit uniformity (average: 0.500), high uniqueness (inter-Hamming distance: 0.499), and large capacity (~28000 bits per PUF), with strong environmental stability and resistance to reverse nanofabrication. This work demonstrates how fast laser induced stochasticity can be rationally harnessed and engineered for optical PUFs, opening pathways toward disorder-enabled photonic devices.
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All authors Haining Xu, Yang Zhang, Shenqi Yang, Zhiwei Yuan, Jiahui Jin, Kaili Kuang, Mingze Liu, Qiao Wang, Yannan Tan, Zhenguo Jing, Changyu Shen, Yurui Fang, Wei Peng

Fluid Dynamics

The Effect of Corneal Topography and Mucins on Tear Film Rupture

Deepak Kumar and S Pushpavanam

Tear film rupture on the corneal surface plays a critical role in ocular health and visual comfort. Conventional theoretical approaches often idealize the cornea as a perfectly smooth surface, ignoring the surface roughness that are characteristic of healthy as well as diseased eyes. In this study, we develop a comprehensive mathematical model to investigate tear film dynamics over the corneal surface incorporating the effects of surface roughness, slip, van der Waals forces, and lipid transport at the film-air interface. The corneal surface is represented by a small-amplitude periodic modulation. Steady-state solutions obtained using asymptotics reveal nonlinear corrections to the base profile at $O(\eta^2)$, which are confirmed numerically. Linear stability analysis performed using the Floquet theory demonstrates that an increase in the amplitude of roughness destabilizes the film. Specifically, both the dominant growth rate and the most unstable wavenumber increase with the roughness amplitude. Nonlinear simulations show that surface roughness significantly accelerates tear-film rupture. The slip coefficient, amplitude of roughness of the corneal surface and the initial film profile are found to significantly influence the rupture time. Moreover, the location of the rupture is sensitive to the initial disturbance. These results highlight the crucial role of surface topography and slip in determining tear film stability. The predicted rupture times are consistent with the experimental observations. The proposed model provides a realistic and accurate prediction of tear film dynamics and rupture over the corneal surface. This study offers a new perspective on tear film instability and will help address challenges such as contact lens failure which is related to tear film behavior.
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Biological Physics

Robust Near-Critical Dynamics in Heavy-Tailed Neural Networks

Ryota Kojima

The criticality hypothesis posits that biological neural networks operate near a phase transition, yet within standard Gaussian mean-field theories this regime appears fragile and requires fine tuning. Here we show that heavy-tailed synaptic connectivity provides a robust alternative mechanism. By developing a dynamical mean-field theory for Cauchy-distributed couplings, we reduce the macroscopic dynamics to a one-dimensional gradient flow with a global Lyapunov potential. The resulting theory exhibits a continuous phase transition in which collective activity grows with the square root of the distance to criticality, and static susceptibility diverges only as the square root rather than linearly as in Gaussian mean-field theories. This structure gives rise to an emergent automatic gain control: activity-dependent noise fluctuations suppress the effective gain at high activity levels while preserving high susceptibility near the critical point. Extending this mechanism to general symmetric $\alpha$-stable inputs, we identify heavy-tailed synapses as a key microscopic origin of robust near-critical dynamics in disordered neural circuits.
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Atomic Physics · Cross-listed from quant-ph

Inhomogeneous mass trap for dark-state polaritons in atomic media

Ding-An Chen, Kai-You Huang, Chun-Yen Hsu et al. (+3 more)

The generation of a trapping potential for dark-state polaritons in a two-dimensional electromagnetically induced transparency system is theoretically studied. We show that such a trap can arise from a spatially inhomogeneous effective mass of the dark-state polariton. Because this mass inhomogeneity can be engineered by tuning the parameters of the control fields, the motion, spatial profile, and coherent behavior of bound dark-state polaritons can be tailored accordingly. Our results enable spatial controls of optical information and provide a possible route toward realizing Bose-Einstein condensation of dark-state polaritons in a trapping potential.
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All authors Ding-An Chen, Kai-You Huang, Chun-Yen Hsu, Meng-Cheng Xie, Ite A. Yu, Wen-Te Liao

Computational Physics · Cross-listed from math.NA

Wavelet-based grid adaptation with consistent treatment of high-order sharp immersed geometries

Changxiao Nigel Shen and Wim M. van Rees

Wavelet-based grid adaptation methods use multiresolution analysis for error estimation, offering a mathematically rigorous approach to adaptive grid refinement when solving Partial Differential Equations (PDEs). However, applying these methods to PDE discretizations with immersed geometries is challenging, as standard interpolating wavelet transforms lose consistency near non-grid-aligned boundary intersections. To address this, we propose a high-order interpolating wavelet transform adaptation strategy compatible with sharp immersed boundary and interface discretizations. The approach performs consistent high-order wavelet transforms on narrow intervals using a 1D polynomial extrapolation technique. To maintain high order, the technique incorporates boundary values and derivatives, which are evaluated from multivariate interpolating polynomials similar to those used in high order immersed finite difference discretizations. Consequently, the proposed approach maintains the wavelet order on any arbitrary smooth multidimensional domain, including near concave geometry sections. This approach enables grid adaptation in complex domains while robustly bounding the numerical error via a manually set refinement threshold. The algorithm's performance is validated on both static and dynamic problems, including the Navier-Stokes equations with moving boundaries and temporally adapting grid resolutions. The results demonstrate that the proposed method enables effective grid adaptation, establishing a robust, predictable relationship between a user-defined refinement threshold and the overall solution error, even for problems with complex, moving boundaries.
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Chemical Physics

An SO(3)-equivariant reciprocal-space neural potential for long-range interactions

Lingfeng Zhang, Taoyong Cui, Dongzhan Zhou et al. (+6 more)

Long-range electrostatic and polarization interactions play a central role in molecular and condensed-phase systems, yet remain fundamentally incompatible with locality-based machine-learning interatomic potentials. Although modern SO(3)-equivariant neural potentials achieve high accuracy for short-range chemistry, they cannot represent the anisotropic, slowly decaying multipolar correlations governing realistic materials, while existing long-range extensions either break SO(3) equivariance or fail to maintain energy-force consistency. Here we introduce EquiEwald, a unified neural interatomic potential that embeds an Ewald-inspired reciprocal-space formulation within an irreducible SO(3)-equivariant framework. By performing equivariant message passing in reciprocal space through learned equivariant k-space filters and an equivariant inverse transform, EquiEwald captures anisotropic, tensorial long-range correlations without sacrificing physical consistency. Across periodic and aperiodic benchmarks, EquiEwald captures long-range electrostatic behavior consistent with ab initio reference data and consistently improves energy and force accuracy, data efficiency, and long-range extrapolation. These results establish EquiEwald as a physically principled paradigm for long-range-capable machine-learning interatomic potentials.
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All authors Lingfeng Zhang, Taoyong Cui, Dongzhan Zhou, Lei Bai, Sufei Zhang, Luca Rossi, Mao Su, Wanli Ouyang, Pheng-Ann Heng

Atomic Physics · Cross-listed from quant-ph

Alice and Bob through a quantum mirror

M. Uria, C. Hermann-Avigliano, P. Solano et al. (+1 more)

A quantum mirror is a device whose optical response, that is, transmission and reflection, can be controlled by a single qubit. Here, we propose the use of quantum mirrors as nodes in quantum networks. Propagating coherent states mediate the interaction between the control qubits of each quantum mirror. This allows implementing quantum teleportation, quantum state transfer, and entanglement swapping with success probability and average fidelity exponentially approaching unity as the average photon number increases. Furthermore, we show that quantum teleportation exhibits robustness against known sources of error, such as optical path phase difference, photon loss, and reduced quantum mirror reflectivity, presenting a promising alternative towards long-distance quantum communication.
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All authors M. Uria, C. Hermann-Avigliano, P. Solano, A. Delgado

Optics

Enhancement of vacuum-ultraviolet dispersive-wave emission using gas-filled tapered hollow-core fibers

Yinuo Zhao, Donghan Liu, Baoqi Shi et al. (+12 more)

The recent breakthroughs in laser-driving 229Th nuclear transition have created an urgent demand for coherent vacuum-ultraviolet (VUV) sources delivering high spectral brightness at the critical 148.38 nm isomer energy. However, generating sufficient photon flux to overcome the low nuclear excitation probability remains a challenge for compact setups. While resonant dispersive wave emission in gas-filled hollow-core fibers offers a promising route, standard capillaries face a fundamental trade-off: maximizing input coupling requires large core diameters, whereas efficient nonlinear VUV conversion demands the high intensities using small cores. Here, we resolve this conflict using a gas-filled tapered capillary fiber. This architecture utilizes a longitudinally decreasing core diameter to combine a large input aperture with adiabatic field concentration, thereby continuously enhancing the nonlinear interaction. Experimentally, we demonstrate a widely tunable source (135-240 nm) that achieves a twofold efficiency enhancement specifically at the 148.38 nm wavelength compared to uniform geometries. By providing a scalable route to high-flux VUV generation, this work establishes a critical tabletop tool for advancing solid-state nuclear clocks and time-resolved spectroscopy.
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All authors Yinuo Zhao, Donghan Liu, Baoqi Shi, Zhiyuan Huang, Tiandao Chen, Jinyu Pan, Zhengzheng Liu, Xinglin Zeng, Wenbin He, Jiapeng Huang, Jinxin Zhan, Xin Jiang, Yuxin Leng, Junqiu Liu, Meng Pang

Optics

Asynchronous-spectral fusion fluorescence microscopy for microsecond-scale behavioral dynamics

Richard G. Baird, Boyden Myers, Erik M. Jorgensen et al. (+1 more)

Event-based image sensors provide microsecond temporal resolution but lack spectral discrimination, whereas diffractive spectral imagers encode wavelength information at conventional frame rates. We introduce a fluorescence microscopy architecture that fuses asynchronous event streams with diffraction-encoded CMOS measurements to decouple temporal and spectral sampling. The system achieves ~3.9 um spatial resolution over a 0.5 mm field of view, effective temporal resolution down to 100 us, and differentiates fluorophores whose emission peaks are separated by only 23 nm. By synchronizing and computationally merging both sensing modalities, we enable spectrally resolved tracking at 100,000 frames/s without scanning or filter switching.
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All authors Richard G. Baird, Boyden Myers, Erik M. Jorgensen, Rajesh Menon

Wednesday 18 March

Physics and Society

Planning for climate neutrality in the Nordic power sector: Insights from a non-harmonised comparison of eight energy system models

Emir Fejzić, Will Usher, Ida Græsted Jensen et al. (+12 more)

The Nordic countries have adopted ambitious climate targets that require far-reaching power-sector transformations, making energy system modelling an important input to long-term planning. However, model-based evidence is produced using different model structures, assumptions, scopes, and scenario designs. This paper examines what can be learned from comparing such independently developed scenarios by assessing Nordic power-sector climate-neutrality pathways across eight structurally diverse energy system models. The comparison covers Denmark, Finland, Norway, and Sweden for 2030, 2040, and 2050, and focuses on electricity demand, generation capacity, CCS deployment, and power-sector CO2 emissions. Inputs are not harmonised; instead, outputs are compared using a common reporting basis reflecting how modelling evidence is encountered in applied policy contexts. The results show broad agreement on the direction of transition. Wind power, mainly onshore but complemented by offshore wind in some countries, is the clearest cross-model finding and forms the backbone of the Nordic power system by 2050. At the same time, installed capacities, CCS deployment, nuclear outcomes, and emissions levels vary substantially. These differences are interpreted considering renewable-resource potentials, technology availability, policy constraints, sectoral and geographical scope, emissions-accounting boundaries, and different implementations of climate-neutrality targets. The study shows that non-harmonised model comparisons can support policy analysis by identifying where models point in the same direction, such as wind expansion, and where outcomes depend more strongly on model and scenario assumptions, such as CCS, nuclear, and net-negative emissions. For policy use, the findings underline the need to report model scope, technology representation, policy constraints, and emissions-accounting boundaries..
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All authors Emir Fejzić, Will Usher, Ida Græsted Jensen, Marianne Zeyringer, Oskar Vågerö, Maximilian Roithner, Guillermo Valenzuela-Venegas, Rasmus Bramstoft, Marie Münster, Jean-Nicolas Louis, Pernille Seljom, Miguel Chang, Eirik Ogner Jåstad, Dmitrii Bogdanov, Christian Breyer

Geophysics

Spatio-temporal evolution of low-magnitude seismicity before the May 24, 2013, Sea of Okhotsk earthquake recovered by waveform cross correlation. Is it an earthquake prediction case?

Ivan Kitov

According to the International Data Centre (IDC), the Sea of Okhotsk earthquake occurred at 05:44:49.7 on May 24, 2013, had coordinates 54.89{\deg}N,153.31{\deg}E, mb=6.27, and depth of 604 km. The USGS moment magnitude is 8.3. The previous event detected by the IDC in the surrounding volume 53{\deg}N-57{\deg}N, 151{\deg}E-155{\deg}E, depth from 400 to 700 km occurred on February 6, 2012. Using the same seismic data from the stations of the International Monitoring System together with detection and phase association methods based on waveform cross correlation, a series of low-magnitude earthquakes was recovered immediately before this major earthquake. More than 200 events obeying the Event Definition Criteria adapted by the IDC were found between May 13 and the mainshock, with a sudden increase in their occurrence rate starting on the afternoon May 19. The evolution of the numbers of these low-magnitude earthquakes in various ranges of statistical significance within the source volume demonstrates some features, which can be related to the approaching initiation of the Sea of Okhotsk earthquake.
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2603.26717 · 18 Mar · It was found that the results are significantly biased by the effect of side-sensitivity of the WCC detector to the high seismicity at regional distance from the studied volume. There was a M6 earthquake on July 19, 2013. The effect was studied after this paper had been published and revealed the bias. Okhotsk Sea earthquake occurred on May 24, 2013. This case is currently under investigation

Abstract PDF $EVO ×2

Fluid Dynamics · Cross-listed from math.AP

2D inviscid Boussinesq equations and 3D axisymmetric Euler equations: (1) A unification ($Em$), (2) Finite-time blow-up of two unified $(1+1)$D systems rigorously derived from ($Em$)

Yaoming Shi

We derive a unified polar $(1+2)$D subsystem $(Em)$, with $m=1,2$, from the 2D inviscid Boussinesq and 3D axisymmetric Euler equations. On the symmetry axes $\theta=0,\pm\pi/2,\pi$, ridge flatness closes the dynamics and gives two exact unified $(1+1)$D reductions: the horizontal-axis system $(R0)$ and the vertical-axis system $(Z0)$. Their common apex trace is a Constantin–Lax–Majda type ODE that yields finite-time blow-up at $x=0$. Subsection~\ref{seq:vorticity-strain} connects this pointwise mechanism with Euler continuation theory: for any compatible axisymmetric realization, explicit apex blow-up forces divergence of the time-integrated $L^\infty$ norm of $\nabla\boldsymbol v$, so the singularity is detected by the strain criterion. Section~\ref{sec:R0-SS} strengthens the reduced mechanism by constructing regular apex-only self-similar profiles for the convective horizontal-axis equation $(R0)$; the resulting solution is bounded away from $x=0$, blows up at the apex, and satisfies the same strain-divergence condition. Finally, we derive the exact background–remainder equations and state a conditional nonlinear stability framework: if a compatible full background, weighted elliptic/coercive estimates, and a spectral gap exponent are available, then the apex blow-up transfers to the full solution. Thus the rigorous components are the derivation of $(Em)$, $(R0)$, and $(Z0)$, the apex blow-up and strain verification, the apex-only $(R0)$ self-similar construction, and the perturbative framework; the remaining open step is the unconditional construction and control of the full background away from the apex.
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Space Physics

Trapped Proton Environment in Medium-Earth Orbit (2000-2010)

Yue Chen, Reinhard H.W. Friedel and Richard M. Kippen

This report describes the method used to derive fluxes of the trapped proton belt along the GPS orbit (i.e., a Medium-Earth Orbit) during 2000-2010, a period almost covering a solar cycle. This method utilizes a newly developed empirical proton radiation-belt model, with the model output scaled by GPS in-situ measurements, to generate proton fluxes that cover a wide range of energies (50keV- 6MeV) and keep temporal features as well. The new proton radiation-belt model is developed based upon CEPPAD proton measurements from the Polar mission (1996 - 2007). Comparing to the de-facto standard empirical model of AP8, this model is not only based upon a new data set representative of the proton belt during the same period covered by GPS, but can also provide statistical information of flux values such as worst cases and occurrence percentiles instead of solely the mean values. The comparison shows quite different results from the two models and suggests that the commonly accepted error factor of 2 on the AP8 flux output over-simplifies and thus underestimates variations of the proton belt. Output fluxes from this new model along the GPS orbit are further scaled by the ns41 insitu data so as to reflect the dynamic nature of protons in the outer radiation belt at geomagnetically active times. Derived daily proton fluxes along the GPS ns41 orbit, whose data files are delivered along with this report, are depicted to illustrate the trapped proton environment in the Medium-Earth Orbit. Uncertainties on those daily proton fluxes from two sources are evaluated: One is from the new proton-belt model that has error factors < ~3; the other is from the in-situ measurements and the error factors could be ~ 5.
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Accelerator Physics · Cross-listed from cond-mat.supr-con

Nb$_3$Sn Films Exhibiting Continuous Supercurrent Across a Diffusion Bonded Seam

Andre Juliao, Wenura Withanage, Nikolya Cadavid et al. (+2 more)

Multiple pairs of bronze pieces were joined along a common seam and then exposed to Nb vapor via sputter deposition during heating at $\sim$715 $^\circ$C to form a diffusion bond between the pieces. Polishing and alignment of the pieces created smooth surfaces normal to the Nb flux with seams perpendicular to the surface (i.e. parallel to the Nb flux). Conversion of Nb to Nb$_3$Sn took place simultaneously with diffusion bonding, resulting in Nb$_3$Sn thin films that coated bronze surfaces and spanned seams with uniform thickness. Characterization of superconducting properties via magneto-optical imaging suggests that supercurrent flows freely across the seam in several examples when cooled to 9 K and shielding or trapping low magnetic field. Modification of the process to coat the pieces with Nb prior to diffusion bonding and Nb$_3$Sn formation resulted in varying degrees of seam coverage by the resultant Nb$_3$Sn films. The pre-coating method did not produce any example with quality comparable to the examples obtained by the hot bronze approach. This work could enable new approaches to joining Nb$_3$Sn materials in magnet conductor and RF cavity applications.
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All authors Andre Juliao, Wenura Withanage, Nikolya Cadavid, Anatolii Polyanskii, Lance D Cooley

Chemical Physics

Elucidating Norrish Type-I reactive pathways by ultrafast X-ray absorption spectroscopy

Martin Graßl, Pablo Unzueta, Andreas E. Hillers-Bendtsen et al. (+20 more)

Norrish type I reactions selectively cleave carbon-carbon bonds directly adjacent to carbonyl groups. Despite their broad use in combination with aromatic carbonyls for additive manufacturing and dental UV curing applications, the nature of the photochemically active state and its population mechanism remain insufficiently understood. Detailed mechanistic insight requires mapping of the photoexcited population flow involving internal conversion and intersystem crossing. We present a time-domain study of gas phase acetophenone as a prototypical aromatic carbonyl combining soft X-ray time-resolved near-edge X-ray absorption fine structure (TR-NEXAFS) spectroscopy at the oxygen K-edge with ab initio multiple spawning (AIMS) simulations. Exploiting the specific sensitivity of TR-NEXAFS spectroscopy to states with $n\pi^*$ character, we observe population transfer from the initially excited $^1\pi\pi^*$ state to the $^1n\pi^*$ state with a time constant of $(0.13 \pm 0.02)$ ps after an initial induction period of $(0.12 \pm 0.02)$ ps without population transfer, in quantitative agreement with the AIMS simulations. The population in the $^1n\pi^*$ state subsequently decays via intersystem crossing, likely mediated by a $^3\pi\pi^*$ state, within $(3.17 \pm 0.66)$ ps to a long-lived $^3n\pi^*$ state, which is presumed to be active towards Norrish type I chemistry.
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All authors Martin Graßl, Pablo Unzueta, Andreas E. Hillers-Bendtsen, Yusong Liu, Diptarka Hait, Alice E. Green, Xinxin Cheng, Felix Allum, Taran Driver, Ruaridh Forbes, James. M. Glownia, Erik Isele, Kirk A. Larsen, Xiang Li, Ming-Fu Lin, Razib Obaid, Adam Summers, Emily Thierstein, Jun Wang, James P. Cryan, Matthias F. Kling, Todd J. Martinez, Thomas J. A. Wolf

General Physics

Photometric and Astrometric Information for Sources around HD~163296 Revealed by JWST/NIRCam Coronagraphy

Taichi Uyama, Luca Ricci, Marie Ygouf et al. (+1 more)

Background stars observed through a circumstellar disk provide valuable benchmarks for investigating the disk's extinction properties. The HD~163296 system is an excellent case study due to its large disk, the clearly visible extinction effects in JWST/NIRCam data, and the presence of numerous background sources within or around its disk. We present the measured contrasts and astrometry of sources surrounding HD~163296 from Cycle~1 JWST/NIRCam coronagraphic observations, which will serve as a useful reference for future studies of the disk's extinction characteristics.
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All authors Taichi Uyama, Luca Ricci, Marie Ygouf, Massimo Robberto

Atmospheric and Oceanic Physics

Marine Heatwaves in the Arabian Sea: Drivers and Impacts on Atmospheric Circulation and Extreme Precipitation

D. L. Suhas, Weiqing Han, Toshiaki Shinoda et al. (+4 more)

Marine heatwaves (MHWs) threaten marine ecosystems and significantly impact weather patterns. In the Arabian Sea, summer MHWs are of particular concern due to their potential impacts on the Indian summer monsoon, a lifeline for nearly a billion people. However, the drivers of these MHWs and their influence on atmospheric circulation and monsoon rainfall remain poorly understood. Using satellite observations, reanalysis datasets, and numerical model experiments, we investigate the key drivers of MHW events and assess their impacts. When SST warming trends are retained, the eastern and northern Arabian Sea emerge as MHW hotspots, showing rapid increases during 1982-2023, largely due to anthropogenic warming. On detrending the SSTs to remove the influence of anthropogenic warming on individual MHWs, we find that most MHWs are short-lived (lasting <= 20 days) and are initiated by enhanced surface shortwave radiation and reduced latent heat loss associated with the suppressed convection phase of the Boreal Summer Intraseasonal Oscillations (BSISOs). Interannual SST anomalies, including ENSO and Indian Ocean Dipole (IOD), further modulate the year-to-year MHW variability. Conversely, the warm SSTs during MHWs exert strong atmospheric feedbacks. MHWs in the eastern Arabian Sea drive cyclonic winds, intensify moisture convergence and increase the risk of extreme precipitation along the southwest coast of India. In the northern Arabian Sea, MHW-induced cyclones trigger intense rainfall over northwestern India and Pakistan, contributing to extreme events like the 2022 Pakistan floods. These findings improve our capacity to predict Arabian Sea MHWs and assess their risks, offering significant socio-economic and ecological benefits.
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All authors D. L. Suhas, Weiqing Han, Toshiaki Shinoda, Rui Sun, Aneesh Subramanian, Mark Bourassa, Michael Alexander

Computational Physics · Cross-listed from quant-ph

Multi-Outcome Circuit Optimization for Enhanced Non-Gaussian State Generation

S. Ismailzadeh and B. Abedi Ravan

Photonic quantum computing has gained significant interest in recent years due to its potential for scaling to large numbers of qubits. A critical requirement for fault-tolerant quantum computation is the reliable generation of non-Gaussian quantum states, typically achieved using Gaussian operations and photon-number-resolving detectors. However, the probabilistic nature of quantum measurement typically results in low success rates for state preparation. Conventionally, these circuits are optimized to herald a single specific target outcome, thereby disregarding the potential utility of alternative measurement patterns generated by the same physical setup. In this work, we propose and demonstrate a multi-outcome optimization strategy that increases the overall acceptance probability by allowing a single circuit to produce useful quantum states across several measurement patterns. To evaluate this approach, we apply the framework to the generation of Gottesman-Kitaev-Preskill core states, Schrodinger cat states, binomial codes, and cubic phase states using both two-mode and three-mode Gaussian circuits. We demonstrate that the success probability can be enhanced through two distinct mechanisms: first, by simultaneously targeting a diverse set of useful resource states, and second, by aggregating degenerate outcomes to maximize the production rate of a single target state.
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Fluid Dynamics

Sub-Yield Dynamics in Yield-Stress Materials

Alice Woodbridge, Kasra Amini, Fredrik Lundell et al. (+4 more)

The mechanical response of yield-stress materials below the yield point remains a subject of debate. Two of the most widely used constitutive models for these materials offer fundamentally conflicting views: one permits plastic flow at all stress levels, the other assumes entirely recoverable viscoelasticity below yield. Using parallel superposition rheometry, we test the sub-yield behaviour of a microgel and an emulsion. When residual slip effects are properly accounted for, both fluids exhibit bounded, periodic strain responses, offering compelling evidence that they do not flow in the studied regime. Our results indicate that the sub-yield regime is underpinned by nonlinear viscoelasticity and underscore the need for improved constitutive relations that capture such effects without treating yielding as a precursor for nonlinearity.
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All authors Alice Woodbridge, Kasra Amini, Fredrik Lundell, Outi Tammisola, Anne Juel, Robert J. Poole, Cláudio P. Fonte

Atomic Physics

Electron Emission in Antiproton-Hydrogen Interactions Studied with the One-Centre Basis Generator Method

Jay Jay Tsui and Tom Kirchner

Electron emission from hydrogen atoms induced by antiproton impact at intermediate energies is investigated using the one-centre Basis Generator Method within a semi-classical impact-parameter framework. The formulation employs a single-centre expansion of the time-dependent Schrödinger equation with a pseudostate basis consisting of hydrogenic orbitals acted upon by powers of a Yukawa-regularized potential, providing a compact and effective representation of the electronic continuum. Ionization probabilities are obtained by projecting the time-evolved wavefunction onto Coulomb continuum states, from which energy-differential cross sections (EDCS) are extracted. Exponential piecewise functions are constructed to interpolate between the pseudostate eigenenergies, yielding smooth EDCS profiles for each partial wave. The total EDCS, reconstructed by summing over all partial-wave contributions, exhibits good agreement with results from other pseudostate-based approaches.
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Biological Physics

Mechanical cues for totipotency and the preneural state: embryo and cancer expanding the frontiers of developmental physics

Jaime Cofre

In this article, I advance the idea that physics plays a central role in cell differentiation and makes fundamental contributions to morphogenesis, revealing the totipotent nature of the zygote. Totipotency is a persistent mechanical memory that preserves the biomechanical records of animal morphogenesis. I examine the mechanical and biophysical pathways underlying cell differentiation in embryonic development and cancer, treating them as closely related biological and mechanical processes. Drawing inspiration from evolutionary history, I also propose a biophysical mechanism for the emergence of the animal nervous system. By linking physical principles to cellular differentiation, this review positions mechanobiology as a pillar of innovation with high-impact clinical implications for diseases such as cancer.
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Chemical Physics

Visualization-Based Approach to Condensed-Phase Line Broadening Using Polyene Chains

Saba Mahmoodpour and Andrew M. Moran

Condensed-phase spectral line shapes encode the strength and timescale of interactions between molecules and their environments, yet these ideas are often difficult to introduce at the undergraduate level due to their reliance on formal theoretical treatments. We present a visualization-based approach that combines analytic results with numerical simulations to illustrate the physical origins of spectral line broadening in conjugated molecular systems. Using a time-dependent Hückel Hamiltonian, we derive closed-form expressions for coherent electronic motion in finite polyene chains and show how these results provide direct insight into the role of molecular orbital structure in light absorption. Environmental effects are introduced through stochastic fluctuations of the Hamiltonian matrix elements, allowing students to observe how system–environment interactions disrupt coherent motion and produce scattering-like features in electronic trajectories. Real-space animations and simulated absorption spectra provide an intuitive link between microscopic dynamics and measured line shapes. The MATLAB code provided with this work offers an accessible platform for integrating computation and visualization into undergraduate instruction while introducing key concepts in condensed-phase spectroscopy.
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Physics and Society · Cross-listed from math.CO

Counting Strict Gridlock on Graphs

Matthew I. Jones and Zachary Winkeler

Graph colorings have been of interest to mathematicians for a long time, but relatively recently, social scientists have also found them to be interesting tools for studying group behavior. In the last 20 years, scientists have begun to study how coloring problems can be solved by groups of individuals on a graph, which has led to new insights into network structure, group dynamics, and individual human behavior. Despite this newfound utility, the exact nature of these distributed coloring problems is not well-understood, and established mathematical tools like the chromatic polynomial miss the unique challenges that arise in these social problem-solving situations with limited information. In this paper, we provide a new framework for understanding these distributed problems by defining a new kind of graph coloring with particular relevance to consensus formation on networks, in which all vertices are trying to agree on a common color. These strict gridlock colorings represent roadblocks to consensus where the group will not reach a uniform coloring using natural update processes. We describe a recurrence relation that provides an algorithm for counting these gridlocked colorings, which establishes a mathematical measure of how much a given graph hinders consensus in a group.
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Chemical Physics

Isotope Effects in 2D correlation infrared Spectra of Water: HEOM Analysis of Molecular Dynamics-Based Machine Learning Models

Kwanghee Park, Ryotaro Hoshino and Yoshitaka Tanimura

We model, simulate, and analyze the intramolecular modes of liquid H2O and D2O to elucidate how energy excitation, relaxation, and vibrational dephasing interplay through anharmonic mode-mode coupling. Our analysis employs two-dimensional (2D) correlation spectra, a representative observable in nonlinear infrared vibrational spectroscopy. Accurate reproduction of these 2D spectral profiles requires not only a precise dynamical description of intramolecular vibrations but also an appropriate treatment of thermal environmental effects arising from strong interactions with surrounding molecules, which act as thermal baths. Capturing the essential features of the 2D spectra further demands a non-Markovian, non-perturbative, and nonlinear description of the interactions between intramolecular modes and their baths. To this end, we adopt a hierarchical equations of motion (HEOM) framework to compute the 2D spectra. By comparing the resulting spectra of H2O and D2O, we explore the underlying mechanisms governing their complex energy and phase relaxation dynamics.
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Chemical Physics

sbml4md: A computational platform for System-Bath Modeling via Molecular Dynamics powered by Machine Learning

Kwanghee Park, Seiji Ueno and Yoshitaka Tanimura

We introduce sbml4md, a newly developed algorithm implemented as a software package to extract parameters of multimode anharmonic Brownian (MAB) models from molecular dynamics (MD) trajectories for simulating nonlinear vibrational spectra of intramolecular modes of molecular liquids. By leveraging machine learning (ML) techniques to capture vibrational anharmonicity, intermolecular couplings, and bath correlation functions for each mode, sbml4md obviates empirical fitting and enables the modeling of environments with spatial and temporal heterogeneity. This work provides a set of parameters specifically tailored for the Hierarchical Equations of Motion (HEOM) framework, enabling numerically "exact" simulations of nonlinear vibrational spectra. Building upon our previous implementation for intramolecular vibrational modes [Park, Jo, and Tanimura, J. Chem. Phys. 163, 214104 (2025)], the present code enhances optimization efficiency by explicitly accounting for intermolecular vibrational contributions. This extension enables sbml4md to broaden the applicability of HEOM-based dynamical modeling by seamlessly integrating classical MD approaches, thereby providing a flexible and scalable framework for simulating both linear and nonlinear spectra under realistic conditions with minimal empirical input. The accompanying ML code, written in Python, is provided as supporting material.
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