Fluid Dynamics
An investigation into the combined effect of steady and pulsatile flow within a wavy channel filled with an anisotropic porous medium
Sanchita Pramanik and Timir Karmakar
We provide an analytical solution to examine the impact of steady and pulsatile flow in a symmetric wavy channel filled with an anisotropic porous medium. The flow inside the wavy channel with a porous substrate is governed by the Darcy-Brinkman equation. We used the perturbation approach to ascertain the solution to the problem, assuming that the ratio between the channel width and the wavelength is very small (i.e., $\delta^2 \ll 1$). We solved the problem up to $O(\delta^2)$ by assuming $\lambda^2 \delta^2 \ll 1$, where $\lambda$ is the ratio of anisotropic permeability. Our primary objective is to investigate how the anisotropic permeability ratio influences flow reversal near the crest and trough of a wavy wall under both steady flow conditions and when a pulsatile component is superimposed on the steady flow. In the case of steady flow, flow separation occurs near the crest region of the wavy wall, leading to the formation of recirculating zones where fluid becomes trapped. In contrast, for pulsatile flow as well as combined effects of steady and pulsatile flow,
vortices form transiently at certain phases of the pulsation cycle. Subsequently, these
vortices bulge into the mainstream, resulting in a complete backflow. We explored the approximate flow reversal zone using Darcy's approximation theory far from the wavy wall. The flow recirculation associated with steady flow is critical for mass transport and enhances convective mixing. On the other hand, flow reversal at different time instances can optimize oxygen transfer in devices such as membrane oxygenators.
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Computational Physics
Theoretical Analysis of Topotomography Using Small Intragranular Strain Approximations
Zheheng Liu, Nicola Vigano, Henry Proudhon et al. (+1 more)
Topo-
Tomography (TT) is a synchrotron-based X-ray diffraction imaging technique used to characterize grain shape and
crystal orientation in polycrystalline samples. This work aims to provide a decisive and fundamental understanding of 3D grain shape and orientation field reconstruction from TT diffraction data. We derive mathematical expressions for the TT projection geometry, considering grain shape, intragranular
lattice rotations, and elastic strains, under the assumption of kinematical diffraction. These expressions are simplified using approximations for small strain variations and grain size. The simplified expressions show that integrated TT projection images correspond to projections of a "pseudo" distorted grain volume. Its
Fourier analysis provides insights into the feasibility of orientation field reconstruction from TT scans. We propose methods to expand data coverage, including using opposite scattering vectors and varying detector distance. A lower bound for orientation sampling resolution is derived and validated through simulations.
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All authors Zheheng Liu, Nicola Vigano, Henry Proudhon, Wolfgang Ludwig
Atomic Physics · Cross-listed from quant-ph
Single-shot conditional displacement gate between a trapped atom and traveling light
Seigo Kikura, Hayato Goto, Fumiya Hanamura et al. (+1 more)
We propose a single-shot conditional displacement gate between a trapped atom as the control
qubit and a traveling light pulse as the target oscillator, mediated by an optical cavity. Classical driving of the atom synchronized with the light reflection off the cavity realizes the single-shot implementation of the crucial gate for the universal control of hybrid systems. We further derive a concise gate model incorporating cavity loss and atomic decay, facilitating the evaluation and optimization of the gate performance. This proposal establishes a key practical tool for coherently linking stationary atoms with itinerant light, a capability essential for realizing hybrid
quantum information processing.
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All authors Seigo Kikura, Hayato Goto, Fumiya Hanamura, Takao Aoki
Fluid Dynamics
Understanding the Influence of Rheological Properties of Shear-Thinning Liquids on Segmented Flow in Microchannel using CLSVOF Based CFD Model
Somasekhara Goud Sontti, Pankaj G. Pallewar, Amritendu Bhuson Ghosh et al. (+1 more)
In this study, two phase gas-shear-thinning
liquid flow in a square microchannel is numerically investigated using the coupled level set and volume of fluid (CLSVOF) methods. A systematic investigation is carried out to explore the influence of polyacrylamide (PAM) concentration, surface tension, velocity ratios, and contact angle on the gas slug length, volume, unit
cell length, and pressure drop. Three different concentrations of PAM solutions, which exhibit shear-thinning behaviour are considered as the continuous phase. Gas slug length, volume, and unit
cell length decreased with increasing the PAM concentration. Velocity and non-homogeneous viscosity distributions in the
liquid slug for three different PAM concentration solutions are reported. Gas slug length decreases with an increase of the contact angle and the bubble shape change from convex to concave. This numerical work provides the fundamental insights in segmented flow formation and two-phase flow characteristics comprising shear-thinning
liquids.
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All authors Somasekhara Goud Sontti, Pankaj G. Pallewar, Amritendu Bhuson Ghosh, Arnab Atta
Atomic Physics · Cross-listed from quant-ph
Sujay Kazi and Iman Marvian
We study coherence
distillation under time-translation-invariant operations: given many copies of a
quantum state containing coherence in the energy eigenbasis, the aim is to produce a purer coherent state while respecting the time-translation
symmetry. This
symmetry ensures that the output remains synchronized with the input and that the process can be realized by energy-conserving
unitaries coupling the system to a reservoir initially in an energy eigenstate, thereby modeling thermal operations supplemented by a work reservoir or battery. For
qubit systems, we determine the optimal asymptotic fidelity and show that it is governed by the purity of coherence, a measure of asymmetry derived from the right logarithmic derivative (RLD) Fisher information. In particular, we find that the lowest achievable infidelity (one minus fidelity) scales as $1/N$ times the reciprocal of the purity of coherence of each input
qubit, where $N$ is the number of copies, giving this quantity a clear operational meaning. We additionally study many other interesting aspects of the coherence
distillation problem for
qubits, including computing higher-order corrections to the lowest achievable infidelity up to $O(1/N^3)$, and expressing the optimal channel as a boundary value problem that can be solved numerically.
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Geophysics
Diffusion-Based Probabilistic Modeling for Hourly Streamflow Prediction and Assimilation
Wencong Yang, Haoyu Ji, Leo Lonzarich et al. (+2 more)
Hourly predictions are critical for issuing flood warnings as the flood peaks on the hourly scale can be distinctly higher than the corresponding daily ones. Currently a popular hourly data-driven prediction scheme is multi-time-scale long short-term
memory (MTS-LSTM), yet such models face challenges in probabilistic forecasts or integrating observations when available.
Diffusion artificial intelligence (AI) models represent a promising method to predict high-resolution information, e.g., hourly streamflow. Here we develop a denoising
diffusion probabilistic model (h-
Diffusion) for hourly streamflow prediction that conditions on either observed or simulated daily discharge from hydrologic models to generate hourly hydrographs. The model is benchmarked on the CAMELS hourly
dataset against record-holding MTS-LSTM and multi-frequency LSTM (MF-LSTM) baselines. Results show that h-
Diffusion outperforms baselines in terms of general performance and extreme metrics. Furthermore, the h-
Diffusion model can utilize the inpainting technique and recent observations to accomplish data assimilation that largely improves flood
forecasting performance. These advances can greatly reduce flood
forecasting uncertainty and provide a unified probabilistic framework for downscaling, prediction, and data assimilation at the hourly scale, representing risks where daily models cannot.
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All authors Wencong Yang, Haoyu Ji, Leo Lonzarich, Yalan Song, Chaopeng Shen
Chemical Physics · Cross-listed from cond-mat.soft
Anomalous Diffusion in Driven Electrolytes due to Hydrodynamic Fluctuations
Ramin Golestanian
The
stochastic dynamics of tracers arising from hydrodynamic fluctuations in a driven electrolyte is studied using a self-consistent field-theory framework in all dimensions. A plethora of scaling behaviour that includes two distinct regimes of anomalous
diffusion is found, and the crossovers between them are characterized in terms of the different tuning parameters. A short-time ballistic regime is found to be accessible beyond two dimensions, whereas a long-time diffusive regime is found to be present only at four dimensions and above. The results showcase how long-ranged hydrodynamic interactions can dominate the dynamics of non-
equilibrium steady states in ionic suspensions and produce strong fluctuations despite the presence of Debye screening.
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Instrumentation and Detectors
Silicon Wafer Fracture Stress for Tracking Sensors in Particle Physics Experiments
Haider Abidi, Vitaliy Fadeyev, Tim Jones et al. (+6 more)
For the construction of the ATLAS Inner Tracker strip detector, silicon strip sensor modules are glued directly onto carbon fibre support structures using a soft silicone gel. During tests at temperatures below \unit[-35]{$^{\circ}$C}, several of the sensors were found to crack due to a mismatch in coefficients of thermal expansion between polyimide
circuit boards with copper metal layers (glued onto the sensor) and the silicon sensor itself. While module assembly procedures were developed to minimise variations between modules, cold tests showed a wide range of temperatures at which supposedly comparable modules failed. The observed variance (fracture temperatures between \unit[-35]{\textcelsius} and \unit[-70]{\textcelsius}) for supposedly comparable modules suggests an undetected variation between modules suspected to be intrinsic to the silicon wafer itself. Therefore, a test programme was developed to investigate the fracture stress of representative sensor wafer cutoffs. This paper presents results for the fracture stress of silicon sensors used in detector modules.
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All authors Haider Abidi, Vitaliy Fadeyev, Tim Jones, Akhil Kumar, Tom Lee, Luise Poley, Craig Sawyer, Giorgio Vallone, Sven Wonsak
Atomic Physics · Cross-listed from nucl-ex
Spectrometry of Captured Highly Charged Ions Produced Following Antiproton Annihilations
F. P. Gustafsson, M. Volponi, J. Zielinski et al. (+61 more)
We report a proof-of-principle study demonstrating the first capture and time-of-flight spectrometry of highly charged ions (HCIs) produced following antiproton annihilations in a Penning-Malmberg trap. A multi-step nested-trap technique was developed using the \aegis\ experiment to identify annihilation-linked captured ions. The trapping and spectrometry of helium and argon ions demonstrates the approach. This work establishes a foundation for the in-trap synthesis of radioactive HCIs and the study of cold
nuclear annihilation fragments, with the long-term goal of enabling a sensitive tool for probing the outer
nuclear periphery.
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All authors F. P. Gustafsson, M. Volponi, J. Zielinski, A. Asare, I. Hwang, S. Alfaro Campos, M. Auzins, D. Bhanushali, A. Bhartia, M. Berghold, R. S. Brusa, K. Calik, A. Camper, R. Caravita, F. Castelli, G. Cerchiari, S. Chandran, A. Chehaimi, S. Choudapurkar, R. Ciuryło, P. Conte, G. Consolati, M. Doser, R. Ferguson, M. Germann, A. Giszczak, L. T. Glöggler, Ł. Graczykowski, M. Grosbart, F. Guatieri, N. Gusakova, S. Haider, S. Huck, C. Hugenschmidt, M. Jakubowska, M. A. Janik, G. Kasprowicz, K. Kempny, G. Khatri, A. Kisiel, Ł. Kłosowski, G. Kornakov, V. Krumins, L. Lappo, A. Linek, S. Mariazzi, P. Moskal, M. Münster, P. Pandey, L. Penasa, M. Piwiński, F. Prelz, T. Rauschendorfer, B. S. Rawat, B. Rienäcker, V. Rodin, H. Sandaker, S. Sharma, T. Sowiński, E. Tēberga, M. Tockner, C. P. Welsch, M. Zawada, N. Zurlo
Computational Physics · Cross-listed from quant-ph
When Less is More: Approximating the Quantum Geometric Tensor with Block Structures
Ahmedeo Shokry, Alessandro Santini and Filippo Vicentini
The natural gradient is central in neural
quantum states optimizations but it is limited by the cost of computing and inverting the
quantum geometric tensor, the
quantum analogue of the Fisher information
matrix. We introduce a block-diagonal
quantum geometric tensor that partitions the metric by network layers, analogous to block-structured Fisher methods such as K-FAC. This layer-wise approximation preserves essential
curvature while removing noisy cross-layer correlations, improving conditioning and scalability. Experiments on Heisenberg and frustrated $J_1$-$J_2$ models show faster convergence, lower energy, and improved stability.
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Optics
Circular Dichroism without absorption in isolated chiral dielectric Mie particles
Rafael S. Dutra, Felipe A. Pinheiro, Diney S. Ether Jr et al. (+3 more)
We demonstrate that an effect phenomenologically analogous to circular dichroism can arise even for dielectric and isotropic
chiral spherical particles. By analyzing the polarimetry of light scattered from a
chiral, lossless microsphere illuminated with linearly polarized light, we show that the scattered light becomes nearly circularly polarized, exhibiting large, nonresonant values of the Stokes parameter $S_3$ for a broad range of visible frequencies. This phenomenon occurs only in the Mie regime, with the microsphere radius comparable to the wavelength, and provided that the scattered light is collected by a high-NA objective lens, including non-paraxial
Fourier components. Altogether, our findings offer a theoretical framework and motivation for an experimental demonstration of a novel chiroptical effect with isolated dielectric particles, with potential applications in enantioselection and characterization of single microparticles, each and every one with its own
chiral response.
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All authors Rafael S. Dutra, Felipe A. Pinheiro, Diney S. Ether Jr, Cyriaque Genet, Nathan B. Viana, Paulo A. Maia Neto
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Enhanced thermal stability of inverted perovskite solar cells by bulky passivation with pyridine-functionalized triphenylamine
Ekaterina A. Ilicheva, Irina A. Chuyko, Lev O. Luchnikov et al. (+11 more)
Despite competitive efficiency compared to Si
solar cells and relevant stability at near room temperatures the rapid degradation at elevated temperatures remains the critical obstacle for exploitation of perovskite photovoltaics. In this work, a 4-(pyridin-4-yl)triphenylamine (TPA-Py) with pyridine anchor group was employed for inter-grain bulk modification of double-cation CsCH(NH2)2PbI3 perovskite absorbers to enhance thermal stability. Through coordination and dipole-dipole interactions, nitrogen-containing fragments (diphenylamine and pyridine) of TPA-Py passivate uncoordinated cations and improve the phase resilience of perovskite films against segregation. This resulted in a power conversion efficiency of 21.3% with a high open-
circuit voltage of 1.14 V. Notable impact of self-assembled monolayer incorporated into the bulk of perovskite film manifested in huge improvement of thermal stability at 85{\deg}C (ISOS-D-2). TPA-Py modification improved extended the T80 lifetime to ~600 h compared to only 200 h for the reference under harsh heating stress in ambient conditions. In-depth analysis using photoinduced voltage transients and admittance spectroscopy after different stress periods revealed the screening of ion migration (0.45 eV) for devices with TPA-Py. This work offers an important understanding of the bulk modification of microcrystalline perovskite absorbers and guide for robust design of bulk and buried interfaces in highly efficient perovskite
solar cells.
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All authors Ekaterina A. Ilicheva, Irina A. Chuyko, Lev O. Luchnikov, Polina K. Sukhorukova, Nikita S. Saratovsky, Anton A. Vasilev, Luiza Alexanyan, Anna A. Zarudnyaya, Dmitri Yu. Dorofeev, Sergey S. Kozlov, Andrey P. Morozov, Dmitry S. Muratov, Yuriy N. Luponosov, Danila S. Saranin
Atomic Physics · Cross-listed from quant-ph
Entanglement of mechanical oscillators mediated by a Rydberg tweezer chain
Cedric Wind, Chris Nill, Julia Gamper et al. (+5 more)
Mechanical systems provide a unique test bed for studying
quantum phenomena at macroscopic length scales. However, realizing
quantum states that feature
quantum correlations among macroscopic mechanical objects remains an experimental challenge. Here, we propose a
quantum system in which two micro-electromechanical oscillators interact through a chain of Rydberg atoms confined in optical tweezers. We demonstrate that the coherent dynamics of the system generate
entanglement between the oscillators. Furthermore, we utilize the tunability of the radiative decay of the Rydberg atoms for dissipative
entanglement generation. Our results highlight the potential to exploit the flexibility and tunability of Rydberg atom chains to generate nonclassical correlations between distant mechanical oscillators.
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All authors Cedric Wind, Chris Nill, Julia Gamper, Samuel Germer, Valerie Mauth, Wolfgang Alt, Igor Lesanovsky, Sebastian Hofferberth
Atomic Physics · Cross-listed from quant-ph
Selective high-order topological states and tunable chiral emission in atomic metasurfaces
Yi-Xin Wang, Yan Zhang, Lei Du et al. (+2 more)
Atomic metasurfaces (AMs) provide a powerful nanophotonic platform for integrating topological effects into
quantum many-body systems. In this Letter, we investigate the
quantum optical and topological properties of a two-dimensional Kagome AM, going beyond the tight-binding approximation and incorporating all-to-all interactions. We reveal selective higher-order topological states with a unique dynamical “chasing" behavior, protected by a generalized
chiral symmetry and enabling efficient topological directional transfer. By introducing an
impurity atom – a
giant atom – coupled to all array atoms, we observe
chiral emission patterns strongly dependent on the atomic polarization. This nonlocal coupling structure allows exploration of self-interference effects at subwavelength scales. Our findings establish AMs as a versatile platform for engineering tunable topological states and
chiral quantum optical phenomena, with potential applications in customized light sources and photonic devices.
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All authors Yi-Xin Wang, Yan Zhang, Lei Du, Lingzhen Guo, Jin-Hui Wu
Optics · Cross-listed from cond-mat.mes-hall
Topological surface magnon-polariton in an insulating canted antiferromagnet
Weixin Li, Rundong Yuan, Fenglin Zhong et al. (+3 more)
Excitation and control of
antiferromagnetic magnon modes lie at the heart of coherent
antiferromagnetic spintronics. Here, we propose a topological surface
magnon-polariton as a new approach in the prototypical magnonic material hematite. We show that in an insulating canted antiferromagnet, where strong-coupled
magnon-
photon modes can be achieved using electrical on-chip layouts, a surface
magnon-polariton mode exists in the gap of the bulk
magnon-
photon bands. The emergence of surface
magnon-polariton mode is further attributed to the nontrivial
topology of bulk
magnon-
photon bands.
Magnon-
photon coupling enhances the Berry
curvature near the anticrossing points, leading to a topological bulk Chern band associated with the surface
magnon-polaritons. Our work provides a general principle for the utilization of optomagnetic properties in antiferromagnets, with an illustration of its experimental feasibility and wide generality as manifested in hematite.
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All authors Weixin Li, Rundong Yuan, Fenglin Zhong, Bo Peng, Jean-Philippe Ansermet, Haiming Yu
Applied Physics
A Simultaneous Synergistic Protection Mechanism in Hybrid Perovskite-Organic Multi-junctions Enables Long-Term Stable and Efficient Tandem Solar Cells
Chao Liu, Kaicheng Zhang, Xin Zhou et al. (+22 more)
Perovskite-organic tandem
solar cells (P-O TSCs) hold great promise for next-generation thin-film photovoltaics, with steadily improving power conversion efficiency (PCE). However, the development of optimal interconnecting layers (ICLs) remains one major challenge for further efficiency gains, and progress in understanding the improved long-term stability of P-O tandem configuration has been lagging. In this study, we experimentally investigate the enhanced stability of p-i-n P-O TSCs employing a simplified C60/atomic-layer-deposition (ALD) SnOx/PEDOT: PSS ICL without an additional charge recombination layer (CRL), which achieve an averaged efficiency of 25.12% and a hero efficiency of 25.5%. Our finding discovers that the recrystallization of C60, a widely used electron transport layer in perovskite photovoltaics, leads to the formation of grain boundaries during operation, which act as migration channels for the interdiffusion of halide and Ag ions. Critically, we demonstrate for the first time that the tandem device architecture, incorporating organic
semiconductor layers, effectively suppresses the bi-directional ion
diffusion and mitigates electrode corrosion. Thus, the P-O TSC establishes a mutual protection system: the organic layers stabilize the perovskite sub-
cell by suppressing ion
diffusion-induced degradation, and the perovskite layer shields the organic sub-
cell from spectrally induced degradation. The simultaneous synergistic protection mechanism enables P-O TSCs to achieve exceptional long-term operational stability, retaining over 91% of their initial efficiency after 1000 hours of continuous metal-halide lamp illumination, and to exhibit minimal fatigue after 86 cycles (2067 hours) of long-term diurnal (12/12-hour) testing. These results demonstrate that tandem
cells significantly outperform their single-junction counterparts in both efficiency and stability.
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All authors Chao Liu, Kaicheng Zhang, Xin Zhou, Mingjian Wu, Paul Weitz, Shudi Qiu, Andrej Vincze, Yuchen Bai, Michael A. Anderson, Johannes Frisch, Regan G. Wilks, Marcus Bar, Zijian Peng, Chaohui Li, Jingjing Tian, Jiyun Zhang, Jianchang Wu, Jonas Englhard, Thomas Heumuller, Jens Hauch, Yixing Huang, Ning Li, Julien Bachmann, Erdmann Spiecker, Christoph J. Brabec
Biological Physics · Cross-listed from cond-mat.soft
Dynamics of individual active elastic filaments with chiral self-propulsion
Chanania Steinbock and Daniel A. Beller
We study the over-damped dynamics of individual one-dimensional elastic filaments subjected to a
chiral active force which propels each point of the filament at a fixed angle relative to the tangent vector of the filament at that point. Such a model is a reasonable starting point for describing the behavior of
polymers such as microtubules in gliding assay experiments. We derive sixth-order nonlinear coupled partial differential equations for the intrinsic properties of the filament, namely, its
curvature and metric, and show that these equations are capable of supporting multiple different stationary solutions in a co-moving frame, i.e.\ that
chiral active elastic filaments exhibit dynamic multi-stability in their shapes. A linear stability analysis of these solutions is carried out to determine which solutions are stable and a brief analysis of the time-dependent approach to stationary shape is considered. Finally, simulations are presented which confirm many of our predictions while also revealing additional complexity.
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Computational Physics
Iterated Agent for Symbolic Regression
Zhuo-Yang Song, Zeyu Cai, Shutao Zhang et al. (+8 more)
Symbolic regression (SR), the automated discovery of mathematical expressions from data, is a cornerstone of scientific inquiry. However, it is often hindered by the combinatorial explosion of the search space and a tendency to overfit. Popular methods, rooted in genetic programming, explore this space syntactically, often yielding overly complex, uninterpretable models. This paper introduces IdeaSearchFitter, a framework that employs Large
Language Models (LLMs) as semantic operators within an evolutionary search. By generating candidate expressions guided by natural-
language rationales, our method biases discovery towards models that are not only accurate but also conceptually coherent and interpretable. We demonstrate IdeaSearchFitter's efficacy across diverse challenges: it achieves competitive, noise-robust performance on the Feynman Symbolic Regression Database (FSReD), outperforming several strong baselines; discovers mechanistically aligned models with good accuracy-complexity trade-offs on real-world data; and derives compact, physically-motivated parametrizations for Parton Distribution Functions in a frontier high-energy physics application. IdeaSearchFitter is a specialized module within our broader iterated
agent framework, IdeaSearch, which is publicly available at https://www.ideasearch.cn/.
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All authors Zhuo-Yang Song, Zeyu Cai, Shutao Zhang, Jiashen Wei, Jichen Pan, Shi Qiu, Qing-Hong Cao, Tie-Jiun Hou, Xiaohui Liu, Ming-xing Luo, Hua Xing Zhu
Accelerator Physics
Simulation of the thermoelectric effect in a multi-metallic superconducting cavity
N. K. Raut, N. Stilin, J. Vennekate et al. (+2 more)
Superconducting
radio frequency accelerating cavities made with different material layers, such as copper, Nb or Nb3Sn, are susceptible to thermoelectric effects due to differences in Seebeck coefficients between the metals. A temperature gradient across the surfaces can drive thermoelectric currents, which may impact the cavity performance. A layered Cu/Nb/Nb3Sn single
cell cavity was tested with cryocoolers in 2022. Three heaters were mounted on the cavity surface at different locations and three single axis cryogenic fluxgate magnetometers were attached close to the cavity equator. A linear increase in the
magnetic field was measured while increasing the heaters power. The cavity setup was analysed with COMSOL and the results showed a trend similar to that observed in the experiment. This contribution details the approach chosen for the simulation and some of the challenges encountered.
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All authors N. K. Raut, N. Stilin, J. Vennekate, S. Wang, G. Ciovati
Computational Physics · Cross-listed from cond-mat.dis-nn
Non-Hermitian many-body localization in asymmetric chains with long-range interaction
Wen Wang, Han-Ze Li and Jian-Xin Zhong
Understanding the relationship between many-body localization and spectra in non-Hermitian many-body systems is crucial. In a one-dimensional clean, long-range interaction-induced non-Hermitian many-body localization system, we have discovered the coexistence of static and dynamic spectral real-complex phase transitions, along with many-body ergodic-localized phase transitions. The phase diagrams of these two types of transitions show similar non-monotonic boundary trends but do not overlap, highlighting properties distinct from conventional disorder-induced non-Hermitian many-body localization. We also propose a potential experimental realization of this model in cold-atom systems. Our findings provide valuable insights for further understanding the relationship between non-Hermitian many-body localization and non-Hermitian spectra in long-range interacting systems.
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Physics and Society
Effectiveness of Quota Policies Across STEM, Biological, and Humanities Programs
Ricardo D. Matheus, Elmer M. Gennaro and Marcelo T. Yamashita
We examine more than a decade of quota policy at Unesp, analyzing Physics, Biology, and Pedagogy as representative programs of distinct assessment styles. Quotas show little impact in Physics, where the admission barrier is low, and in Pedagogy, where high pass rates make it difficult to differentiate students, but they reveal systematic differences in Biology. Focusing the analysis on Calculus I - an introductory course in Physics and other Science, Technology, Engineering, and Mathematics (STEM) programs - for which much larger statistics are available, a clear hierarchy emerges: students admitted through open competition perform best, those from public schools achieve intermediate results, and students from racial quotas perform worst. When students are divided directly by the admittance exam grade, the performance difference is even clearer. Statistical analysis also shows that, contrary to expectation, the probability of passing decreases as the number of attempts increases, indicating that initial educational gaps are difficult to overcome within higher education.
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Physics and Society
Modelling and evaluating travel information during disruptions: An illustrative example from Swedish railways
Abderrahman Ait-Ali and Anders Peterson
Accurate and timely travel information is an asset for enhancing passenger travel experience during normal traffic, and for mitigating the discomforts during disruptions. With longer and more frequent disruptions as well as increasing ridership, traffic delays can incur substantial costs for passengers and other transport stakeholders, e.g., operators and infrastructure managers. Such costs can, however, be reduced thanks to effective travel information strategies during traffic disruptions. In this paper, we introduce an evaluation model to assess the value of travel information under different scenarios. Focusing on real-time travel information to train passengers, accessibility benefits are quantified in monetary terms based on historical delay distributions, timing of travel information (pre/on-trip) and ridership. Using a case study from the Swedish railways, the model is showcased and applied to a commuter line in Stockholm. The experimental results indicate individual valuations that are higher than references and savings at the system level of at least 23% of the delay costs. Further testing of the model, e.g., on larger-scale scenarios, and including transfer trips, is a possible direction for future works.
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Applied Physics · Cross-listed from cond-mat.mes-hall
Dominant scattering mechanisms in the low/high electric field transport in cryogenic 2D confinement in Silicon (110) with high-$\kappa$ oxides
Hsin-Wen Huang, Xi-Jun Fang, Edward Chen et al. (+1 more)
The performance of silicon nano-devices at cryogenic temperatures is critical for
quantum qubit control
circuits and space applications. Using multi-valley Monte Carlo simulations, we investigate electron transport in Si~(110) systems. At low electric fields,
phonon absorption becomes negligible, and mobility is governed by competition between remote Coulomb scattering~(RCS) at low inversion charge density and surface roughness scattering~(SRS) at high density, leading to a mobility peak. High-$\kappa$ dielectrics such as $\mathrm{HfO_2}$ introduce remote
phonon scattering~(RPS), which suppresses mobility. Under high electric fields,
phonon emission dominates at 4~K, limiting velocity enhancement and resulting in limited current improvement
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All authors Hsin-Wen Huang, Xi-Jun Fang, Edward Chen, Yuh-Renn Wu
Fluid Dynamics
Generalised actuator disk theory: wake development with turbulent entrainment
Majid Bastankhah, Peter E. Hydon, Carl Shapiro et al. (+2 more)
Classical actuator disk theory, developed more than a century ago, provides an idealised description of turbine rotor performance. It treats a rotor as an infinitesimally-thin permeable disk and applies the governing flow equations over a streamtube encompassing the disk. A well-known limitation of the theory is its assumption of ideal flow downstream of the disk, which restricts its applicability to short downwind distances before
turbulence and mixing processes governing the wake
evolution take hold. The classical theory also leads to unphysical predictions of thrust and power coefficients for highly-loaded rotors. Turbulent axisymmetric wakes, by contrast, represent an extensively-studied canonical free shear flow with much of the progress and its applications to wind turbines limited to the far-wake dynamics. In this work, we introduce a generalised actuator disk theory based on a hybrid stream-tube and wake control volume, that seamlessly integrates classical actuator disk analysis with wake
turbulence modelling at arbitrary distances from the rotor. The resulting model, while still idealised, can be used to predict variations in velocity, pressure, and cross-sectional flow area as function of position, both upstream and downstream of the rotor disk. Furthermore, by accounting for turbulent entrainment in the wake development, it provides more realistic predictions of thrust and power coefficients for highly-loaded disks.
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All authors Majid Bastankhah, Peter E. Hydon, Carl Shapiro, Dennice F. Gayme, Charles Meneveau
Atomic Physics
Electronic phase-locking for three-color, two-pathway coherent control
Jonah A. Quirk, Carol E. Tanner and D. S. Elliott
We report a new method of two-pathway coherent control using three narrow-band cw
laser sources, phase locked in an optical phase-lock loop, to maintain the high degree of optical coherence required for the coherent control process. In addition, we derive expressions for two-
photon transition amplitudes and demonstrate their dependence on the polarization of the field components. This phase-locking technique expands the set of interactions to which coherent control techniques may be applied. It also allows for a constant low-frequency offset between the optical interactions, producing a continuous and constant phase ramp between the interactions, facilitating phase-sensitive detection of the modulating atomic signal. We illustrate this technique with two-
photon vs.~one-
photon excitation of a $\Delta F = 1$ component, and alternatively a $\Delta F = 0$ component, of the $6s \: ^2S_{1/2} \rightarrow 7s \: ^2S_{1/2}$ transition of atomic cesium.
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Physics and Society
Pursuing decarbonization and competitiveness: a narrow corridor for European green industrial transformation
Alice Di Bella, Toni Seibold, Tom Brown et al. (+1 more)
This study analyzes how Europe can decarbonize its industrial sector while remaining competitive. Using the open-source model PyPSA-Eur, it examines key energy- and emission-intensive industries, including steel, cement, methanol, ammonia, and high-value chemicals. Two development paths are explored: a continued decline in industrial activity and a reindustrialization driven by competitiveness policies. The analysis assesses cost gaps between European green products and lower-cost imports, and evaluates strategies such as intra-European relocation, selective imports of green intermediates, and targeted subsidies. Results show that deep industrial decarbonization is technically feasible, led by electrification, but competitiveness depends strongly on policy choices. Imports of green intermediates can lower costs while preserving jobs and production, whereas broad subsidies are economically unsustainable. Effective policy should focus support on sectors like ammonia and steel finishing while maintaining current production levels.
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All authors Alice Di Bella, Toni Seibold, Tom Brown, Massimo Tavoni
Optics
Hänsch-Couillaud locking of a large Sagnac interferometer: advancing below the flicker floor
Jannik Zenner, Karl Ulrich Schreiber and Simon Stellmer
Large Sagnac interferometers in the form of active ring
lasers have emerged as unique rotation sensors in the geosciences, where their sensitivity allows to detect geodetic and seismological signals. The passive
laser gyroscope variant, however, is still at a stage of development, and thus far, only the Pound-Drever-
Hall frequency stabilization technique has been explored, a method limited by residual amplitude modulation. Here, as an alternative method, we present the first Hänsch-Couillaud locked passive
laser gyroscope. We find that this method is limited by flicker noise, and we introduce a cost-effective lock-in scheme to overcome this limitation. We achieve a sensitivity of 3.1 nrad/s, corresponding to a fraction of $7.7\cdot 10^{-5}$ in the Earth's rotation rate.
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Optics
Proposal for Forward Brillouin Inter-Modal Scattering in Non-suspended Lithium Niobate Waveguides at Visible Wavelengths
Jia-Lin Chen, Yuan-Hao Yang, Zheng-Xu Zhu et al. (+7 more)
Thin-film lithium niobate on sapphire provides an excellent platform for simultaneously confining acoustic and optical modes without suspended structures, enabling efficient acousto-optic modulation through strong piezoelectric coupling. Here, we identify the challenges in realizing the forward Brillouin interaction at visible wavelengths, and overcome the limitation by introducing a quasi-phase-matching scheme through periodic waveguide width modulation. We predict a complete inter-modal optical conversion over 1.1 mm using only 1 mW acoustic power. Our study paves the way for high-performance visible-wavelength acousto-optic devices on integrated platforms.
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All authors Jia-Lin Chen, Yuan-Hao Yang, Zheng-Xu Zhu, Jia-Qi Wang, Xin-Biao Xu, Ming Li, Zheng-Fu Han, Guang-Can Guo, Wei Chen, Chang-Ling Zou
Chemical Physics
The Effect of Chlorine Substitution on Rotational Speed and Light Absorption of Second Generation Molecular Motors
Ivan Tambovtsev, Óskar Kristinsson and Hannes Jónsson
The effect of substituting a hydrogen atom by a chlorine atom or a methyl group by a trichloromethyl (CCl3) group at the stereogenic center of light-driven second generation molecular motors is calculated in order to assess the effect on rotational speed and the separation of the absorption peaks of the isomers. While experimental and theoretical studies have previously been carried out for fluorine substitution, this is the first study of chlorine substitution. Five well-characterized base molecules are studied and the trends are compared with the effect of fluorine substitution. The trichloromethyl substitution is found to accelerate the rotation more than a trifluoromethyl (CF3) substitution by reducing the life-time of the metastable state, due to larger steric hindrance in the metastable state than in the transition state for the thermal helix inversion (THI). A larger increase in the separation of the absorption peaks of the two isomers is also obtained. The Cl atom substitution, however, changes the energy landscape significantly, making the M isomer lower in energy than the P isomer, and raising the energy barrier for THI beyond that of the back transition, thus quenching the rotation.
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Optics
Kirigami-based Flexible Metasurface with Reconfigurable Intrinsic Chirality from Zero to Near-unity
Yiyi Yao, Shijie Kang, Aoning Luo et al. (+7 more)
Chiral responses in electromagnetic metasurfaces are typically categorized as extrinsic, resulting from asymmetric interactions between the structure and incident waves, and intrinsic, arising from three-dimensional
symmetry breaking of the unit
cell. However, most existing metasurface designs target only one type of chirality and lack a unified, continuously tunable platform for broader chiroptical control. To address this limitation, the designed kirigami-based flexible metasurface is proposed for dynamic, continuous modulation of chirality, which expands the control scope to both extrinsic and intrinsic
chiral responses within a single, reconfigurable platform. Initially, the unfolded metasurface exhibits extrinsic chirality under oblique incidence. By introducing well-designed kirigami-based cuts and folds, the metasurface transitions from a planar and achiral configuration to a three-dimensional
chiral geometry that breaks the mirror
symmetry, thereby exhibiting tunable intrinsic chirality and asymmetric extrinsic chirality. As the folding angle increases, the resulting deformation enables continuous tuning of the
chiral response, with circular dichroism and its asymmetry under oblique incidences progressively increasing and reaching pronounced levels across the X-band. Our work provides a lightweight, easy-fabricated, and mechanically reconfigurable metasurface, which offers strong potential for future development in adaptive photonic systems and advanced chiroptical technologies.
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All authors Yiyi Yao, Shijie Kang, Aoning Luo, Jiusi Yu, Ken Qin, Xiexuan Zhang, Jiayu Fan, Xusheng Xia, Haitao Li, Xiaoxiao Wu