Fluid Dynamics
Temperature transformation recovering the compressible law of the wall for turbulent channel flow
Youjie Xu, Steffen J. Schmidt and Nikolaus A. Adams
Velocity and temperature distributions are both crucial for modeling compressible wall-bounded turbulent flows. The compressible law of the wall for velocity has been extensively examined through velocity transformations. However, a well-established temperature transformation remains an open issue. We propose new Van Driest type (VD-type) and semi-local type (SL-type) temperature transformation for compressible turbulent channel flow. Our approach is based on an analysis of the momentum and energy balance equations in the overlap layer. It accounts for the influences of mixing length model, the work of the body force, and the turbulent kinetic energy (TKE) flux. The proposed transformations are evaluated using data from direct numerical simulations and wall-resolved large eddy simulations of compressible turbulent channel flow. The SL-type transformation provides better data collapse than the VD-type in the viscous sublayer and buffer layer. With a suitable mixing length model, the SL-type transformed temperature agrees well with the incompressible temperature profile or the extended law of the wall. For the isothermal wall, the integral mean error over the entire boundary layer remains below 2% for most cases, with root mean square value of about 1.7%. The results highlight the importance of mitigating the energy imbalance in the transformation. This work identifies the multi-layer structure of the turbulent TKE flux, which in turn enables approximate models and corresponding simplified yet effective temperature transformations. Applications of the proposed approach in near-wall modeling and inverse transformation, as well as its potential extension to more general configurations, are also discussed.
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Optics
Ultrafast Topological Transitions Driven by Permittivity Modulation in Non-Hermitian Multilayers
Giuseppina Simone
Ultrafast permittivity modulation in epsilon-near-zero (ENZ) media provides a pathway for real-time control of non-Hermitian photonic
topology. We model ultrafast topological dynamics in an ITO/SiO$_2$/Ag multilayer supporting hybrid epsilon-near-zero (ENZ)-plasmon modes. Using a time-dependent Drude-Lorentz permittivity for ITO and rigorous coupled-wave analysis, it is found that carrier relaxation with a 10-ps time constant
redshifts the ENZ resonance from 490 to 525~nm and shifts the reflection-phase singularities across the angle–wavelength plane. The motion of these singularities corresponds to the displacement of exceptional points and a discrete change in the cumulative winding number. The transient Floquet-like band structure exhibits avoided crossings and Dirac-type dispersions driven by ENZ modulation. The results directly link picosecond-scale permittivity dynamics to quantized topological transitions in non-Hermitian photonic systems.
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Plasma Physics
Reduced kinetic model for ion temperature gradient instability in tokamaks with reversed magnetic shear
B. Jia, Q. Zhong, Y. Li et al. (+1 more)
Using the averaged
magnetic drift model and a first-order finite Larmor radius (FLR) expansion, the
eigenvalue equation for the ion temperature gradient (ITG) mode in tokamak
plasmas is reduced to a Schrödinger-type differential equation. By invoking generalized translational invariance, the model is extended to reversed
magnetic shear (RMS) configurations and benchmarked against global gyrokinetic simulations from GTC, showing good quantitative agreement. The analysis reveals a characteristic double-well potential unique to RMS profiles, which gives rise to the degeneracy between the lowest-order even and first-order odd eigenmodes when the two potential wells are sufficiently separated radially. The ITG instability is also found to resonate with the
magnetic drift frequency, and its maximum growth occurs when the two rational surfaces are slightly separated. These results provide new physical insight into ITG mode behavior under reversed
magnetic shear and offer a compact, accurate theoretical framework that bridges simplified analytic models and global simulations.
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All authors B. Jia, Q. Zhong, Y. Li, Y. Xiao
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Perspective on Moreau-Yosida Regularization in Density-Functional Theory
Markus Penz, Michael F. Herbst, Trygve Helgaker et al. (+1 more)
Within density-functional theory, Moreau-Yosida regularization enables both a reformulation of the theory and a mathematically well-defined definition of the Kohn-Sham approach. It is further employed in density-potential inversion schemes and, through the choice of
topology for the density and potential space, can be directly linked to classical field theories. This perspective collects various appearances of the regularization technique within density-functional theory alongside possibilities for their future development.
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All authors Markus Penz, Michael F. Herbst, Trygve Helgaker, Andre Laestadius
Space Physics
Accelerometer Measurements for Orbit and Gravity Recovery: Challenges and Benefits for the BepiColombo Mission
Alireza HosseiniArani, Stefano Bertone, Daniel Arnold et al. (+3 more)
The European Space Agency's BepiColombo mission continues its pioneering voyage to Mercury, the innermost
planet of the
Solar System. Among the advanced instruments onboard the Mercury Planetary Orbiter (MPO) is the Italian Spring Accelerometer (ISA), whose scientific objectives are closely linked to the Mercury Orbiter
Radio-Science Experiment (MORE). Together, these instruments aim to provide high-precision data on the spacecraft's orbit, as well as Mercury's
gravity field and internal structure. This simulation study investigates how the modeling and parametrization of accelerometer measurements influence orbit and
gravity field recovery and explores strategies to overcome the challenges associated with the co-estimation of all parameters. We assess the integrated
retrieval accuracy of the spacecraft orbit,
gravity field, and accelerometer parameters under different noise levels and varying observation geometries during the mission. The MPO orbit is propagated, and Doppler and accelerometer measurements are simulated based on available noise models. Our results indicate that postponing the estimation of accelerometer biases until a preliminary
gravity field is established helps prevent
gravity field mismodelings from being absorbed into the accelerometer parameters. The daily estimation of bias was found to be essential. Using one year of Doppler tracking data and applying Kaula regularization, we demonstrate the potential to recover Mercury's
gravity field up to degree and order 40. Low-degree coefficients improve under more optimistic noise conditions. Errors in cross-track bias estimation rise sharply when the beta-Earth angle falls below 45{\deg}, corresponding to the degraded Doppler observability. Orbit determination achieved centimetre-level radial accuracy and metre-level along- and cross-track accuracy, with increased cross-track errors during low-observability periods.
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All authors Alireza HosseiniArani, Stefano Bertone, Daniel Arnold, William Desprats, Adrian Jäggi, Nicolas Thomas
Biological Physics · Cross-listed from cond-mat.soft
Coupling of Lipid Phase Behavior and Protein Oligomerization in a Lattice Model of Raft Membranes
Subhadip Basu and Oded Farago
Membrane
proteins often form dimers and higher-order oligomers whose stability and spatial organization depend sensitively on their lipid environment. To investigate the physical principles underlying this coupling, we employ a
lattice Monte Carlo model of ternary lipid mixtures that exhibit
liquid-disordered ($L_d$) and
liquid-ordered ($L_o$) phase coexistence. In this framework,
proteins are represented as small membrane inclusions with tunable nearest neighbor interactions with both lipids and other
proteins, allowing us to examine how
protein-lipid affinity competes with
protein-
protein interactions and lipid-lipid demixing. We find that the balance of these interactions controls whether
proteins remain dispersed, assemble into small oligomers, or form large stable clusters within $L_o$ domains, and that increasing the
protein concentration further promotes coarsening of the ordered phase. To incorporate ligand-regulated activation, we extend the model to a kinetic Monte Carlo scheme in which
proteins stochastically switch between inactive and active states with distinct affinities. The inverse switching rate, relative to the time required for a
protein to diffuse across the characteristic size of the $L_o$ domains, governs the aggregation behavior. Rapid switching yields only transient small oligomers, slow switching reproduces the static limit with persistent large clusters, and intermediate rates produce broad cluster-size distributions. These results highlight the interplay between lipid phase organization,
protein-lipid affinity, and activation dynamics in regulating membrane
protein oligomerization, a coupling that is central to signal transduction and membrane organization in living
cells.
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Applied Physics
Inversion of the impedance response towards physical parameter extraction using interpretable machine learning
Mahmoud Nabil, Isel Grau-García, Ricardo Grau-Crespo et al. (+2 more)
Interpreting the impedance response of perovskite
solar cells (PSCs) is challenging due to the complex coupling of ionic and electronic motion. While drift-
diffusion (DD) modelling is a reliable method, its mathematical complexity makes directly extracting physical parameters from experimental data infeasible. This work uses DD modelling to generate a large synthetic
dataset of impedance spectra for a standard TiO2/MAPI/spiro configuration. This
dataset trains machine learning (ML) models to predict recombination and ionic parameters from impedance measurements. A Gradient Boosting Regressor, using features from a generalized equivalent
circuit, showed the best performance. Interpretative analysis indicates that open-
circuit impedance experiments best probe recombination losses, while short-
circuit conditions are more adequate for extracting ionic features like concentrations and mobilities. The trained ML models were tested on experimental spectra, confirming the inferred physical parameters could reproduce the data. For the studied configuration, predicted ion concentrations were (1.3-3.3)e17 cm-3, ion mobilities were (5-7)e-11 cm2V-1s-1, and surface recombination velocities were 7-9 and 23-40 m/s. This approach provides insights into the physical information extractable from impedance measurements and paves the way for ML models to unambiguously derive efficiency-determining parameters for
solar cells.
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All authors Mahmoud Nabil, Isel Grau-García, Ricardo Grau-Crespo, Said Hamad, Juan A. Anta
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Challenges in predicting positron annihilation lifetimes in lead halide perovskites: correlation functionals and polymorphism
Kajal Madaan, Guido Roma, Jasurbek Gulomov et al. (+3 more)
Halide perovskites have emerged in the last decade as a new important class of
semiconductors for a variety of optoelectronic applications. A lot of previous studies were thus devoted to the characterisation of their point defects. Positron annihilation spectroscopy is a well recognized tool for probing vacancies in materials. Recent applications of this technique to APbX$_3$ halide perovskites are sparse, and the rare theoretical predictions of positron lifetimes in these materials, published in association with experiments, do not fully agree with each other. These works suggest that vacancies on the A site are not detected. In our theoretical study we focus on the role of the electron-positron correlation functional. We thoroughly revisit and compare several approximations when applied to methylammonium lead iodide (MAPbI$_3$) with or without vacancies, as well as inorganic perovskites CsPbI$_3$ and CsPbBr$_3$, in various phases. We show also the relationship between the size of the voids, through Voronoi volumes, and the calculated lifetimes. For the cubic phases we investigate in detail the role of polymorphism, including the distribution of vacancy formation energies and positron annihilation lifetimes. In our lifetimes calculations, apart from older and more recent semi-local approximations for the electron-positron correlation potential, we also consider the weighted density approximation (WDA), which is truly non-local and should better describe positron annihilation in regions with strong electronic density variations. We show that for this class of materials, and especially for cations vacancies, the influence of the chosen approximation is crucial, much stronger than in metals,
alloys and conventional
semiconductors. This influence may induce to reconsider the interpretation of experimentally determined lifetimes.
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All authors Kajal Madaan, Guido Roma, Jasurbek Gulomov, Pascal Pochet, Catherine Corbel, Ilja Makkonen
Computational Physics
The noiseless limit and improved-prior limit of the maximum entropy method and their implications for the analytic continuation problem
Thomas Chuna, Nicholas Barnfield, Paul Hamann et al. (+3 more)
Quantum Monte Carlo (QMC) methods are uniquely capable of providing exact simulations of
quantum many-body systems. Unfortunately, the applications of a QMC simulation are limited because extracting dynamic properties requires solving the analytic continuation (AC) problem. Across the many fields that use QMC methods, there is no universally accepted analytic continuation
algorithm for extracting dynamic properties, but many publications compare to the maximum
entropy method. We investigate when
entropy maximization is an acceptable approach. We show that
stochastic sampling
algorithms reduce to
entropy maximization when the
Bayesian prior is near to the true solution. We investigate when is Bryan's controversial optimization
algorithm [Bryan, Eur. Biophys. J. 18, 165-174 (1990)] for
entropy maximization (sometimes known as the maximum
entropy method) appropriate to use. We show that Bryan's
algorithm is appropriate when the noise is near zero or when the
Bayesian prior is near to the true solution. We also investigate the mean squared error, finding a better scaling when the
Bayesian prior is near the true solution than when the noise is near zero. We point to examples of improved data-driven
Bayesian priors that have already leveraged this advantage. We support these results by solving the double Gaussian problem using both Bryan's
algorithm and the newly formulated dual approach to
entropy maximization [Chuna et al., J. Phys. A: Math. Theor. 58, 335203 (2025)].
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All authors Thomas Chuna, Nicholas Barnfield, Paul Hamann, Sebastian Schwalbe, Michael P. Friedlander, Tobias Dornheim
Optics
Integrated soliton microcombs beyond the turnkey limit
Ze Wang, Tianyu Xu, Yuanlei Wang et al. (+10 more)
Soliton microcombs generated in optical microresonators are accelerating the transition of optical frequency combs from laboratory instruments to industrial platforms. Self injection locking (SIL) enables direct driving of
soliton microcombs by integrated
lasers, providing turnkey initiation and improved coherence, but it also pins the pump close to resonance, limiting both spectral span and tuning flexibility. Here we theoretically and experimentally demonstrate that introducing a thermally tunable auxiliary microresonator extends the bandwidth of SIL
soliton microcombs. By engineering hybridization of the pumped resonance, we achieve deterministic access to single
soliton states and then push operation into a far detuned regime inaccessible to direct initiation. The resulting combs reach a near 200 nm span at a 25 GHz repetition rate, while preserving the SIL-enabled noise suppression throughout. Moreover, the added degree of freedom afforded by the coupled resonator architecture enables orthogonal control of the comb's repetition rate and center frequency. These advances expand the spectral reach and controllability of integrated
soliton microcombs for information processing and precision metrology.
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All authors Ze Wang, Tianyu Xu, Yuanlei Wang, Kaixuan Zhu, Xinrui Luo, Haoyang Luo, Junqi Wang, Bo Ni, Yiwen Yang, Qihuang Gong, Yun-Feng Xiao, Bei-Bei Li, Qi-Fan Yang
Biological Physics
Theory of Semi-discontinuous DNA Replication
Janani G and Deepak Bhat
The replisome, a
protein complex that drives DNA replication, comprises multiple DNA polymerases. During replication, one polymerase synthesizes the leading strand continuously, while another synthesizes the lagging strand discontinuously, producing short transient segments known as Okazaki fragments and gaps between them. After the synthesis of each Okazaki fragment, the lagging-strand polymerase dissociates either spontaneously or upon collision with the preceding fragment; however, the relative contributions of these mechanisms remain unclear. Here, we develop a biophysical model of semi-discontinuous replication by incorporating the
stochastic dynamics of the lagging-strand polymerase. By computing the Okazaki fragment and gap-size distributions, we show the significance of polymerase dissociation in shaping these statistics. Applying the model to the T4 bacteriophage and B. subtilis replisomes, we find that collisions with preceding Okazaki fragments predominantly trigger polymerase dissociation.
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Atomic Physics
Optimizing Antihydrogen Production via Slow Plasma Merging
E D Hunter, M Bumbar, C Amsler et al. (+29 more)
We measure the time-dependent temperature and density distribution of antiprotons and positrons while slowly combining them to make antihydrogen atoms in a nested Penning-Malmberg trap. The total antihydrogen yield and the number of atoms escaping the trap as a beam are greatest when the positron temperature is lowest and when antiprotons enter the positron
plasma at the smallest radius. We control these parameters by changing the rate at which we lower the electrostatic barrier between the antiproton and positron
plasmas and by heating the positrons. With the optimal settings, we produce $2.3\times 10^6$ antihydrogen atoms per $15$-minute run, surpassing the previous state of the art – $3.1\times 10^4$ atoms in $4$ minutes – by a factor of $20$.
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All authors E D Hunter, M Bumbar, C Amsler, M Bayo, H Breuker, M Cerwenka, G Costantini, R Ferragut, M Giammarchi, A Gligorova, G Gosta, M Hori, C Killian, V Kraxberger, N Kuroda, A Lanz, M Leali, G Maero, C Malbrunot, V Mascagna, Y Matsuda, S Migliorati, D J Murtagh, M Romé, R E Sheldon, M C Simon, M Tajima, V Toso, S Ulmer, L Venturelli, A Weiser, E Widmann
Biological Physics
Beyond the tip: Lattice dynamics, seams, and the mechanism of microtubule fracture
Amir Zablotsky, Subham Biswas, Laura Schaedel et al. (+1 more)
The structural integrity of microtubules is paramount for cellular function. We present a theoretical analysis of their
lattice fracture, focusing on the influence of multi-seam structures arising from monomer defects and aiming to provide a more accurate estimation of GDP
lattice parameters. Our findings reveal that seams function as pre-existing pathways that accelerate damage propagation. Consequently, monomer vacancies destabilize the
lattice due to the inherent structural loss of tubulin-tubulin contacts and the additive acceleration of fracture through multiple seams. Importantly, the comparison of our simulations with experiments on
lattice fracture suggests that the intrinsic ratio of longitudinal to lateral binding energies is bounded at approximately 1.5, challenging previous predictions of
lattice anisotropy from tip-growth models and highlighting the urgent need to incorporate into current growth models parameters obtained from
lattice dynamics.
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All authors Amir Zablotsky, Subham Biswas, Laura Schaedel, Karin John
Physics and Society
Data-Driven Mixed-Methods Framework for Cybernetic Urban Mobility Governance
Oluwaleke Yusuf, Morten Breivik and Adil Rasheed
This study develops a cybernetically inspired mixed-methods framework that bridges the gap between policy formation and implementation through feedback-driven analysis of mobility transitions. Using a major campus consolidation in Trondheim, Norway as a case study, we examine how this framework supports sustainable mobility through integrated analysis of mobility patterns, constraints, and transition impacts. The consolidation eliminates over 1,300 parking spaces while increasing daily population by 9,300 people. We employ a mixed-methods approach combining qualitative survey data (n=573) with quantitative big data analysis of public transit and crowd movement patterns. This integrates three analytical components and provides grounded insights into commuting flows, modes, durations, distances, and congestion points, while addressing the spatiotemporal mobility realities of affected populations. The analysis reveals complex mobility constraints, with 59.3% of respondents having children and private cars dominating in winter (49.4%). Though there is broad support for sustainable mobility goals, 86.0% identify increasing travel duration as primary difficulty. Quantitative analysis highlights peak usage patterns and congestion risks, with seasonal variations. This study demonstrates integrating qualitative and quantitative analysis to anticipate negative impacts and enable efficient sustainable mobility policies. The results inform practical recommendations for data-driven mobility interventions that align sustainability goals with lived realities.
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Optics
Ultrasensitive surface plasmon resonance-based biosensor for efficient detection of SARS-CoV-2 Virus in the near-infrared region
R. Runthala, N. Grover and P. Arora
This work presents a high-performance, multilayered surface plasmon resonance (SPR)-based sensor designed to enhance performance parameters in the near-infrared (NIR) region through angular interrogation. The multi-layered sensor consists of a bimetallic layer (Aluminum (Al) & Gold (Au)), a dielectric layer (MgF2), and an optimized number of 2D nanomaterial (MoS2) layers. The proposed SPR sensor is numerically designed and analyzed through simulation using the transfer
matrix and finite element methods to achieve high sensitivity, figure of merit (FOM), and detection accuracy. The simulated results revealed that the proposed plasmonic sensor (Glass prism/Al/Au/MgF2/MoS2/sensing sample) exhibits a maximum sensitivity of 372{\deg}/RIU, FOM of 1690.90 RIU-1, and detection accuracy of 4.54 degree-1. The outcomes from this work indicate that the developed SPR sensor exhibits excellent detection capabilities for refractive index changes, including those caused by the novel coronavirus, making it a promising prospect for biosensing applications.
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Optics
Computational TIRF enables optical sectioning beyond the evanescent field for widefield fluorescence microscopy
Qiushi Li, Celi Lou, Yanfang Cheng et al. (+9 more)
The resolving ability of widefield fluorescence microscopy is fundamentally limited by out-of-focus background owing to its low axial resolution, particularly for densely labeled biological samples. Although total internal reflection fluorescence (TIRF) microscopy provides strong near-surface sectioning, they are intrinsically restricted to shallow imaging depths. Here we present computational TIRF (cTIRF), a deep learning-based imaging modality that generates TIRF-like sectioned images directly from conventional widefield epifluorescence measurements without any optical modification. By integrating a physics-informed forward model into network training, cTIRF achieves effective background suppression and axial resolution enhancement while maintaining consistency with the measured widefield data. We demonstrate that cTIRF recovers near-surface structures with performance comparable to experimental TIRF, and further enables both single-frame and volumetric sectioned reconstruction in densely labeled samples where conventional TIRF fails. This work establishes cTIRF as a practical and deployable alternative to hardware-based optical sectioning in fluorescence microscopy, enabled by rapid adaptation to new imaging systems with minimal calibration data.
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All authors Qiushi Li, Celi Lou, Yanfang Cheng, Bilang Gong, Xinlin Chen, Hao Chen, Baowan Li, Jieli Wang, Yulin Wang, Sipeng Yang, Yunqing Tang, Luru Dai
Biological Physics · Cross-listed from cond-mat.stat-mech
On the thermodynamic analogy of intracellular diffusivity fluctuations
Yuichi Itto
Two recent topics on a formal thermodynamic analogy of intracellular diffusivity fluctuations observed experimentally in normal/anomalous
diffusion are reported. Not only the analogs of the quantity of heat and work as well as the internal energy but also that of the Clausius inequality are identified. Then, the analog of the heat engine is constructed to characterize extraction of the diffusivity change as the analog of work during a cycle, the efficiency of which is formally equivalent to that of the Carnot engine, making the total change of the
entropy concerning the fluctuations vanish. The effect of the slow variation of the fluctuations on the efficiency is also briefly discussed.
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Optics
Synergistic Antenna-Modulator Integration for Monolithic Photonic RF Receiver
Changlin Liu, Yongtao Du, Xihua Zou et al. (+7 more)
Integrated
radio-frequency (RF) photonics plays a pivotal role in wireless communications, sensing, and radar due to its large intrinsic bandwidth, remote distribution capability, and compact footprint. However, despite significant advances in photonic integrated
circuits (PICs), the practical deployment of these systems remains constrained by the bulky nature of essential RF components (e.g., bulky
antennas, amplifiers, and cables), especially in covert, conformal, and space-constrained applications. To overcome these limitations, monolithic electronic-photonic integrated
circuits (EPICs), enabling miniaturized and synergistic integration of both RF and photonic components, are gaining notable
attention. As a groundbreaking advancement, we demonstrate a novel photonic RF receiver that monolithically integrates a bow-tie
antenna and a microring modulator on a thin-film lithium niobate platform. The chip innovatively leverages dual-resonance enhancement mechanism, RF resonance from the
antenna and optical resonance from the microring, to significantly boost the RF-to-optical conversion efficiency. A record-high figure of merit (FOM) of 3.88 W-1/2 is achieved within a compact footprint of 2*1.7 mm2. As the first demonstrations, the integrated receiver is deployed in an integrated sensing and communication (
ISAC) system, achieving centimeter-level radar ranging accuracy and 3.2 Gbps wireless communication capacity, as well as real-time
video transmission function in moving scenarios. This seminal work paves a new way for covert, conformal, and miniaturized frontends in wireless communication and sensing applications, including body area networks, unmanned aerial vehicles, high-speed
vacuum maglevs, and electronic warfare systems.
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All authors Changlin Liu, Yongtao Du, Xihua Zou, Fang Zou, Jiejun Zhang, Junkai Zhang, Xiaojun Xie, Wei Pan, Lianshan Yan, Jianping Yao
Fluid Dynamics
Magnetic modulation of flow reversals in liquid metal thermal convection
Yan-Wu Cao, Ming-Zhu Ai, Long Chen et al. (+2 more)
Flow reversals are rarely observed in low-Prandtl-number
liquid metal convection due to the fluid's exceptionally high thermal diffusivity. Here, we demonstrate that an external transverse
magnetic field can induce such reversals in a quasi-two-dimensional (Q2D) rectangular
cell with an aspect ratio ($\it\Gamma$) of $0.2$. Our experimental observations reveal that the system initially exhibits periodic dynamics at the onset of reversals before transitioning to
stochastic behavior as the ratio of Rayleigh number ($Ra$) to Hartmann number ($Ha$) increases. This transition is governed by the competition between buoyancy and Lorentz forces, with experimental data showing a linear scaling relationship between $Ra$ and $Ha$ at critical points. We develop a theoretical model that incorporates
magnetic field effects in low-Prandtl-number convection to predict the reversal frequencies. These findings provide new insights into how
magnetic fields can modulate flow regimes in low-Prandtl-number convection, establishing a controlled framework for investigating reversal dynamics in magnetohydrodynamic systems.
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All authors Yan-Wu Cao, Ming-Zhu Ai, Long Chen, Juan-Cheng Yang, Ming-Jiu Ni
Fluid Dynamics
Freezing and ice aging dynamics in saline water under natural convection
Feng Wang, Yihong Du, Xueyi Xie et al. (+2 more)
Understanding the coupled dynamics of
liquid-solid phase change and fluid flows is crucial in a wide range of geophysical and industrial applications. When freezing occurs in saline water, the newly formed ice is mushy, with a porous structure that traps the brine within the ice. In this work, which combines experiments and theoretical analyses, we investigate the long-term
evolution of saline ice, comprehensively accounting for the coupled dynamics of multiscale fluid flow, heat and mass transfer, and phase change. We show that in a closed convective system the rapid formation of a mushy ice layer is followed by desalination (i.e, the expulsion of salt from the ice) processes that might lead to a slow asymptotic decrease of the ice thickness. Desalination of mushy ice reduces its porosity, which alters the dynamic thermal
equilibrium and ice thickness by weakening buoyancy-driven convection within the mushy layer. In turn, changes in brine convection and ice thickness affect the further desalination of the ice. The long-term dynamics of the system can be accurately predicted by a one-dimensional model based on appropriate parameterizations of global heat and mass transfer properties. Furthermore, within the same theoretical model we explore the ice dynamics across a broader parameter space. Our findings advance the understanding of the coupled phase-change physics of saline solutions in the presence of convective fluid flows and provide a basis for explaining and predicting real-world phenomena such as the aging of sea ice.
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All authors Feng Wang, Yihong Du, Xueyi Xie, Enrico Calzavarini, Chao Sun
Applied Physics · Cross-listed from cond-mat.soft
Anomalous Enhancement of Yield Strength due to Static Friction
Ryudo Suzuki, Takashi Matsushima, Tetsuo Yamaguchi et al. (+2 more)
Friction is fundamental to mechanical stability across scales, from geological faults and architectural structures to granular materials and animal feet. We study the mechanical stability of a minimal friction-stabilized structure composed of three cylindrical particles arranged in a triangular stack on a floor under
gravity. We analyze the yield force, defined as the threshold compressive force applied quasi-statically from above at which the structure collapses due to sliding at the floor contact. Using singular perturbation analysis, we derive an expression which quantitatively predicts the yield force as a function of the static friction coefficient and a small dimensionless parameter $\epsilon$ characterizing elastic deformation.
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All authors Ryudo Suzuki, Takashi Matsushima, Tetsuo Yamaguchi, Marie Tani, Shin-ichi Sasa
Atomic Physics · Cross-listed from cond-mat.quant-gas
Broad Feshbach resonance with a large background scattering length in a fermionic atom-molecule mixture
Zhen Su, Tong-Hui Shou, Huan Yang et al. (+6 more)
We report the observation of a broad
magnetic Feshbach resonance with a large background scattering length in an ultracold fermionic mixture of $^{23}$Na$^{40}$K molecules and $^{40}$K atoms, with both species prepared in their lowest hyperfine states. The Feshbach resonance is characterized by measuring resonantly enhanced loss rates and elastic scattering cross sections via cross-species thermalization. The large background scattering length can drive the atom-molecule mixture into the hydrodynamic regime when the
magnetic field is far from the resonance. We observe that the center-of-mass motions of the atoms and molecules are phase-locked and oscillate with a common frequency due to hydrodynamic drag effects. This broad atom-molecule Feshbach resonance with its large background scattering length opens up a new avenue towards studying strongly interacting fermionic gases with mass imbalance.
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All authors Zhen Su, Tong-Hui Shou, Huan Yang, Jin Cao, Bo-Yuan Wang, Ting Xie, Jun Rui, Bo Zhao, Jian-Wei Pan
Accelerator Physics
Report on first plasma processing trial for a FRIB quarter-wave resonator cryomodule
Walter Hartung, Wei Chang, Yoo-Lim Cheon et al. (+6 more)
Plasma processing has been shown to help mitigate degradation of the performance of superconducting
radio-frequency cavities, providing an alternative to removal of cryomodules from the accelerator for refurbishment. Studies of
plasma processing for quarter-wave resonators (QWRs) and half-wave resonators (HWRs) are underway at the Facility for Rare Isotope Beams (FRIB), where a total of 324 such resonators are presently in operation.
Plasma processing tests were done on several QWRs using the fundamental power coupler (FPC) to drive the
plasma, with promising results. Driving the
plasma with a higher-order mode allows for less mismatch at the FPC and higher
plasma density. The first
plasma processing trial for FRIB QWRs in a cryomodule was conducted in January 2024. Cold tests of the cryomodule showed a significant reduction in field emission X-rays after
plasma processing.
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All authors Walter Hartung, Wei Chang, Yoo-Lim Cheon, Kyle Elliott, Sang-Hoon Kim, Taro Konomi, Patrick Tutt, Yuting Wu, Ting Xu
Geophysics
Recovering Sub-threshold S-wave Arrivals in Deep Learning Phase Pickers via Shape-Aware Loss
Chun-Ming Huang, Li-Heng Chang, I-Hsin Chang et al. (+2 more)
Deep learning has transformed seismic phase picking, but a systematic failure mode persists: for some S-wave arrivals that appear unambiguous to human analysts, the model produces only a distorted peak trapped below the detection threshold, even as the P-wave prediction on the same record appears flawless. By examining training dynamics and loss landscape geometry, we diagnose this amplitude suppression as an optimization trap arising from three interacting factors. Temporal uncertainty in S-wave arrivals, CNN bias toward amplitude boundaries, and the inability of pointwise loss to provide lateral corrective forces combine to create the trap. The diagnosis reveals that phase arrival labels are structured shapes rather than independent probability estimates, requiring training objectives that preserve coherence. We formalize this as the shape-then-align strategy and validate it through a conditional GAN proof of concept, recovering previously sub-threshold signals and achieving a 64% increase in effective S-phase detections. Beyond this implementation, the loss landscape visualization and numerical simulation techniques we introduce provide a general methodology for analyzing how label designs and loss functions interact with temporal uncertainty, transforming these choices from trial-and-error into principled analysis.
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All authors Chun-Ming Huang, Li-Heng Chang, I-Hsin Chang, An-Sheng Lee, Hao Kuo-Chen
Optics
Freespace twistronics for optical supertopologies
Vasu Dev and Yijie Shen
Twistronics, the study of moiré superlattices of twisted
bilayer 2D materials creating nontrivial physical effects, has recently revolutionized diverse subjects from materials to optoelectronics, nanophotonics, and beyond. Here, breaking the reliance on materials, we present twistronics in higher-dimensional free space, where the twisted
lattice is not a layer of 2D material but a 3D propagating light field with topological textures. Moiré structured light with a twist angle can generate a rich set of high-dimensional
topologies, including skyrmionium bags, skyrmion bag superlattices, skyrmion clusters, and optical quasicrystals, with controllable
symmetry. Many of these textures have not been reported before. Importantly, in contrast to prior moiré superlattices, our freespace optical moiré textures maintain their
topologies over a long propagation distances, showing nondiffractive behavior and robustness against perturbations and obstacles. Our work unlocks higher dimensions to manipulate moiré photonics with high-capacity
topologies to address modern challenges of robust information transfer and encryption.
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Fluid Dynamics
Evaporation Dynamics of Completely Pinned and Partially Pinned Sessile Droplets in Multi-Droplet Configurations
A. Hari Govindha, Sayak Banerjee, Saravanan Balusamy et al. (+1 more)
The evaporation of sessile droplets placed in close proximity is influenced by complex vapor-vapor interactions, producing a shielding effect that can significantly extend droplet lifetimes. This study presents a systematic experimental investigation of evaporation dynamics in multi-droplet configurations under ambient conditions, comparing completely pinned and partially pinned contact line modes. Completely pinned droplets are generated by introducing alumina nanoparticles, while partially pinned droplets consist of pure water. An isolated droplet is compared with arrays of two, three, and five droplets, each arranged at a fixed spacing ratio. High-speed shadowgraphy is used to measure droplet height, contact angle, volume, and lifetime. Results show that, although completely pinned droplets evaporate faster in absolute terms due to a constant contact radius, they experience a more pronounced relative lifetime increase from vapor shielding than partially pinned droplets. In five-droplet configurations, lifetimes increase by up to 89% and 124% compared to isolated droplets for partially pinned and completely pinned modes, respectively. A theoretical model incorporating evaporative cooling predicts central droplet lifetimes with good agreement. These findings underscore the coupled influence of contact line mobility and droplet proximity on evaporation rates.
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All authors A. Hari Govindha, Sayak Banerjee, Saravanan Balusamy, Kirti Chandra Sahu
Classical Physics
Multifunctional Lightweight Radiators for Small-Satellite Thermal Control
Karl Pederson, Sam Keller, Daniel Kindem et al. (+2 more)
Thermal management in small satellites is constrained by limited radiative area and strict mass budgets, necessitating the development of radiator structures that are simultaneously lightweight, thermally conductive, and mechanically robust. Here, we present a
topology-optimization and design-space analysis framework for multifunctional lightweight radiators that achieve high specific stiffness and high effective thermal conductivity through simultaneous structural and thermal optimization. Density-based optimization produces hierarchical architectures that naturally form continuous cavities suitable for high-conductivity channels such as embedded heat pipes. The resulting microarchitectures exhibit Pareto behavior indicating efficient trade-offs between mass, stiffness, and thermal conductivity, while maintaining dynamic stability across a broad range of design parameters. Coupled structural-thermal analysis shows that voids used as thermal channels yield nearly isothermal radiating surfaces, confirming efficient lateral and transverse heat flow through the radiator. This integrated framework contributes toward the development of thermo-mechanically optimized radiator panels for small-scale spacecraft, enabling compact and efficient thermal control solutions.
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All authors Karl Pederson, Sam Keller, Daniel Kindem, Hayden Hommes, Ognjen Ilic
Plasma Physics
The Non-thermal Energy Window for Laser-Driven Nuclear Reactions
Eunseok Hwang, Heamin Ko, Myung-Ki Cheoun et al. (+1 more)
Laser-driven
nuclear reactions proceed in non-
equilibrium plasma conditions, producing ion energy distributions that are not Maxwellian. Nevertheless, fusion yields in such experiments are often interpreted using effective thermal descriptions based on the conventional Gamow window. In this work, we develop an analytical framework for evaluating
nuclear reaction rates for non-thermal ions accelerated by the Target Normal Sheath Acceleration (TNSA) mechanism. Using a self-similar
plasma expansion model, we derive a closed form expression for an effective reaction energy window and the corresponding fusion reactivity. The resulting effective energies differ systematically from those predicted by thermal models, indicating limitations of interpretations based on the conventional Gamow window in
laser-driven environments. This framework provides a quantitative basis for analyzing fusion yields and for designing
laser-driven
nuclear experiments.
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All authors Eunseok Hwang, Heamin Ko, Myung-Ki Cheoun, Dukjae Jang
Applied Physics
Local metamaterials and transition layers
Kimya Yadollahpour, Hossein Khodavirdi and Ankit Srivastava
In this paper, we elucidate the concept of local acoustic metamaterials. These are composites which exhibit equi-frequency contours (EFC) which correspond to those expected of homogeneous local acoustic media. We show that EFCs for local acoustic media are conics in 2-dimension and quadrics in 3-dimension. In 2-D, the sure signature of negative properties is if the conic is a hyperbola and in 3-D, the sure signature is the presence of hyperboloids. We note that metamaterial coupling (Willis coupling) has the potential of translating these conics and quadrics in the wave-vector plane but that it does not fundamentally change the shape of these geometries. The local effective properties assigned to a composite in such cases are dispersive (frequency dependent) and they satisfy causality considerations. We finally also show that such properties truly characterize the composite in the sense that they can be used to solve scattering problems involving different samples of the composite. We show that this is made possible through the consideration of transition layers. While the sharp-interface model incurs scattering errors exceeding 20% at oblique angles, the Drude-layer model restores agreement to within 2% without requiring integral-equation or multi-mode expansions, thereby offering a simple yet highly efficient route to accurate scattering predictions in resonant local acoustic metamaterials.
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Atomic Physics
First Born Approximation of the Single Differential Cross Section (SDCS) for Electron Impact Ionization of H(3s)
Fahadul Islam and Sunil Dhar
This investigation is a rigorous theoretical study of the Single Differential Cross Section (SDCS) for the ionization of hydrogen in the 3s state by electron impact computed by means of the First-Born Approximation. The transition
matrix has been found by means of the integral process of Bethe-Lewis. The effect of the Coulomb attractive force and the continuum of outgoing radiation have been taken into account in conjunction with the hypergeometric function, which has been used to denote the states of collision. It has hence been possible to deduce the SDCS. for a considerable range of respective incoming electron energies (100 eV to 250 eV). The results show a very distinct marked peak in the rate of ionization taking place for these energies (about 200 eV) with a gradual fall-off after with an increase in energy. The diffuse structure of the wave function in the 3s state serves to a certain extent to make variations in the rate of ionization with that of the incoming electron increased. The final results have been arrived at by means of numerical integrations done so by means of a MATLAB computer, which has yielded very accurate numbers for the cross sections. The results show up very fatally, with experimental results existing at the present date and with theoretical deductions validating the procedure of the FBA. in giving the results of the ionization of excited hydrogen atoms within the field of ionizing processes of electron-atom impact systems. The work gives a most complete basis for the further study of those systems where the processes of ionization and the complexities of the scattering process take place in excited states.
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