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Physics Physics

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Friday 26 December

Plasma Physics

Revealing the transient ionization dynamics and mode-coupling mechanisms of helicon discharge through a self-consistent multiphysics model

Jing-Jing Ma, Lei Chang, Ming-Yang Wu et al. (+6 more)

Helicon plasma sources play a central role in applications ranging from material treatment to space propulsion and fusion, yet the physical processes governing their ignition, transient ionization, and mode evolution remain incompletely understood. Here we develop a self-consistent, fully coupled multiphysics framework that integrates Maxwell equations, electron energy transport, drift-diffusion kinetics, and heavy-species chemistry to capture the complete spatiotemporal evolution of helicon discharges. The model reproduces experimental measurements across pressure, magnetic field, and frequency ranges, and reveals a previously unresolved transient ionization stage characterized by a rapid density rise within ~10-4 s, accompanied by a two-peak electron temperature structure that governs the formation of the dense plasma core. By tracking the RF power flow and field topology, we characterize the transient redistribution of RF energy during ignition. A short-lived phase of localized energy deposition accompanies the onset of ionization, followed by an evolution toward helicon-like field characteristics together with rapid density growth and profile restructuring. Systematic parametric scans further reveal the sensitivity of this mode-coupling process to gas pressure, magnetic field strength, and driving frequency. These results provide a unified picture of the ignition and mode-transition physics in helicon plasmas and establish a predictive tool for the design and optimization of RF plasma sources across space propulsion, manufacturing, and fusion technologies.
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All authors Jing-Jing Ma, Lei Chang, Ming-Yang Wu, Hua Zhou, Yi-Wei Zhang, Ilya Zadiriev, Elena Kralkina, Shogo Isayama, Shin-Jae You

Fluid Dynamics

Flow morphology and patterns in porous media convection: A persistent homology analysis

Marco De Paoli, Sergio Pirozzoli, Catherin Neena Lalu et al. (+1 more)

Convective mixing in porous media is crucial in both geophysical and industrial fields, spanning applications ranging from carbon dioxide sequestration to geothermal energy extraction. Key processes are affected by convective heat transport or diffusion of chemical species in porous formations. Intense convection flow and mixing create complex, dynamic patterns that are difficult to predict and measure. The present work focuses on the use of topological data analysis, in particular, the measures emerging from the growing field of persistent homology (PH), to quantify these patterns. These measures are objective and quantify structures across all temperature or concentration values simultaneously. These techniques, when applied to classical porous media setups, such as one-sided and Rayleigh-Bénard flow configurations, provide new insights into the system's structure, flow patterns, and macroscopic mixing properties. Using large datasets we make publicly available, comprising original simulations as well as those presented in previous works, we correlate the behaviour of the heat transport rate (quantified by the Nusselt number) with the evolution of the flow structures (quantified by the PH measures). Finally, we provide a detailed analysis of the flow evolution over a wide range of governing parameters, namely the Rayleigh-Darcy number and the domain size.
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All authors Marco De Paoli, Sergio Pirozzoli, Catherin Neena Lalu, Lou Kondic

Physics and Society

The Wiener Path Integral Interpretation of the 3:1 Combat Rule

Wei Liang and Ming Zhong

The Wiener path integral framework is proposed to model military combat dynamics by incorporating the neglected stochastic effects to the Lanchester's square law. This framework is applied to evaluate the empirical 3:1 combat rule, which posits that an attacker requires a threefold force superiority to achieve victory. Specifically, the attacker's winning probability is computed utilizing a semi-analytical Rayleigh-Ritz method. Numerical results demonstrate that the validity of the rule critically depends on specific parameter regimes, primarily contingent upon the relative combat effectiveness ratio between the opposing forces and the tolerance for attrition. This work establishes a physics-informed theoretical bridge between statistical mechanics and military operations research for analyzing uncertain combat systems.
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Fluid Dynamics

Tuning diffusioosmosis of electrolyte solutions by hydrostatic pressure

Elena F. Silkina, Evgeny S. Asmolov and Olga I. Vinogradova

When two reservoirs of a distinct salinity are connected by channels or pores, a fluid flow termed diffusio-osmotic is generated. This article investigates the flow emerging in an uniformly charged long slit whose thickness exceeds the local Debye screening length. Attention is focussed on the role of hydrostatic pressure drop $\Delta p$ in establishing diffusioosmosis at a finite concentration difference. For a thick slit we recover the known formula for a local diffusio-osmotic slip over a single wall, which is determined by the surface potential, salt concentration and its gradient. An equation for the global fluid flow rate $\mathcal{Q}$ is presented as a sum of the diffusio-osmotic and pressure-driven contributions. Although the diffusio-osmotic term itself remains unaffected by $\Delta p$, the nonlinear concentration and surface potential profiles along the slit, and consequently, the local slip velocity are dramatically modified. We present an equation relating the local concentration to $\mathcal{Q}$ and employ it to derive an expression describing the surface potential variation in the slit. Since $\mathcal{Q}$ can easily be tuned by $\Delta p$, the variety of possible concentration and surface potential profiles becomes very rich. Our theory provides a simple explanation of recent flow rate measurements and shows that experimental data provide rather direct information about concentration and surface potential profiles in the uniformly charged slit. The relevance of our results for sensing the salt dependence of surface potentials is discussed briefly.
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Instrumentation and Detectors · Cross-listed from astro-ph.IM

WST spectroscopic variability alerts: discovery space, data flow system requirements

Valenitn D. Ivanov

The enormous multiplexity of the WST opens up the possibility to trigger alerts for variable objects - an option that has been reserved so far only for imaging surveys. WST can go further by detecting spectroscopic line profile and line strength variations. I review previous alert-issuing surveys that are limited to imaging, and describe some of the new research possibilities that this feature of the data flow system (DFS) would open up. The latter range from variability of emission line stars, such as Bes, WRs and LBVs to variability of active galaxies and quasars, including the so-called changing look objects that shift between Type 1 and Type 2. Furthermore, I describe the requirements that the WST DFS must meet to make this feasible. The most critical aspect is the rapid data processing for timely follow-up. Next, the alert system is tightly connected with the data reduction and archive, because it will need an extensive and continuously updated spectral reference database. The new spectra will have to be compared against these reference spectra to identify variations. The reference spectra can either be "native" from the WST itself or they can originate from other spectroscopic surveys. Two options for the DFS are considered: one is to conduct an automated search of the WST's own archive, and potentially of other spectroscopic archives and a second option is to allow the users to submit reference spectra on their own. The spectroscopic alert system will open up a completely new discovery space that is not accessible to the existing or planned near-future surveys. Finally, I discuss the advantages of moving the variability detection to physical parameters by modeling the observed and reference spectra and comparing the derived fitting parameters. This strategy offers a robust method for alert ranking.
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Applied Physics

Interaction-Induced Spiral Motion and Breathing Dynamics of Neel Skyrmions in Ferromagnetic Thin Films

M. Al Busaidi, F. Al Ma'Mari and R. Sbiaa

Magnetic skyrmions exhibit particle-like stability and rich dynamical behaviour arising from their topological nature, making them promising building blocks for future spintronic devices. In this work, we investigate the interaction dynamics of two Neel-type skyrmions in an ultrathin ferromagnetic film through a combined analytical and numerical approach. Full micromagnetic simulations reveal that when the initial separation exceeds twice the skyrmion radius, the pair undergoes a repulsive interaction leading to an outward spiral trajectory whose radial and angular components depend sensitively on the Gilbert damping, consistent with particle-like models of skyrmion motion. The simulations further show a two-component oscillatory behaviour in the out-of-plane magnetization: a fast intrinsic breathing mode superimposed on a slower interaction-induced modulation. Using Thiele collective-coordinate model, an expression for the radial drift, angular decay, and logarithmic growth of the separation distance is derived. The analytical predictions show excellent agreement with numerical results, confirming the exponential form of the long-range interaction potential. A continuum micromagnetic analysis of the skyrmion tail explains the origin of the exponential decay and its role in governing the interaction strength. Together, these findings provide a unified framework for understanding spiral motion, breathing dynamics, and long-range repulsion in interacting skyrmion systems, offering insights relevant for multi-skyrmion information carriers and collective skyrmion-based devices.
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Chemical Physics · Cross-listed from quant-ph

Double-Layered Silica-Engineered Fluorescent Nanodiamonds for Catalytic Generation and Quantum Sensing of Active Radicals

Jia Su, Zenghao Kong, Fei Kong et al. (+9 more)

Fluorescent nanodiamonds (FNDs) hosting nitrogen-vacancy (NV) centers have attracted considerable attention for quantum sensing applications, particularly owing to notable advancements achieved in the field of weak magnetic signal detection in recent years. Here, we report a practical quantum-sensing platform for the controlled production and real-time monitoring of ultra-short-lived reactive free radicals using a double-layered silica modification strategy. An inner dense silica layer preserves the intrinsic properties of NV centers, while an outer porous silica layer facilitates efficient adsorption and stabilization of hydroxyl radicals and their precursor reactants. By doping this mesoporous shell with gadolinium (III) catalysts, we achieve sustained, light-free generation of hydroxyl radicals via catalytic water splitting, eliminating reliance on external precursors. The mechanism underlying this efficient radical generation is discussed in detail. The radical production is monitored in real time and in situ through spin-dependent T1 relaxometry of the NV centers, demonstrating stable and tunable radical fluxes, with concentration tunable across a continuous range from approximately 100 mM to molar levels by adjusting the catalyst condition. This study extends the technical application of nanodiamonds from relaxation sensing to the controlled synthesis of reactive free radicals, thereby providing robust experimental evidence to support the advancement of quantum sensing systems in intelligent manufacturing.
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All authors Jia Su, Zenghao Kong, Fei Kong, Xing Liu, Linyu Zeng, Zhecheng Wang, Zijian Zeng, Jie Liu, Jihu Su, Junhua Yuan, Guosheng Shi, Fazhan Shi

Atmospheric and Oceanic Physics · Cross-listed from cond-mat.soft

Impact of the sodium and calcium chlorides uptake on the interfacial behavior of ice: premelting, structure, and dynamics

Łukasz Baran and Luis G. MacDowell

Hypothesis: Seawater ice and frozen aqueous solutions in contact with air can exhibit a thin quasi-brine surface layer intruding between ice and vapor, but a detailed characterization of surface properties and its relation to three phase coexistence has been lacking. Using thermodynamic arguments we show how it is possible to characterize the surface layers by comparison to the three phase ice-brine-air bulk phase diagram, despite the difficulty to control or monitor all of the relevant thermodynamic fields of the two component system. Simulations: We performed computer simulations of surface briny layers of sodium and calcium chloride adsorbed on ice. Using suitable order parameters and a rigorous geometrical dividing surface, we are able to characterize the layer's thermodynamic state, measure its properties and relate them to the corresponding properties of the bulk solution. Results: Our results confirm that undersaturated briny surface layers can form down to the eutectic point, with a maximum concentration that is bound by the liquidus line of the ice-brine phase diagram. Such layers are distinct from finite size realizations of three phase coexistence, and can be regarded as genuine surface states, but their salt content can increase the premelting layer thickness by a factor of two or more. Owing to this significant thickness, these layers can be related to bulk electrolyte solutions of similar concentration, both as regards the structural organization of ions and the dynamical properties of the quasi-liquid film.
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Atmospheric and Oceanic Physics

beta plane corrections to nonlinear atmospheric flow patterns application to jupiters great red spot (GRS) drift dynamics

Oladiran Johnson Abimbola

The Great Red Spot (GRS) of Jupiter has been observed for over a century, with researchers studying its characteristics and dynamics, including its size, depth, movement, and interactions with its environment. Recently, the f-plane thin-shell asymptotic analysis was used to explain some of the GRS features, but the method failed to capture the observed westward drift of the GRS. In this study, the f-plane theory was extended by including the Rossby parameter in the \beta-plane approximation and using the dimensionless Rossby deformation parameter \gamma, to systematically apply perturbation theory. The westward drift velocity of 3.7 m/s was analytically predicted, which is 95% in agreement with the observed 3.9 m/s. The observed 90-day oscillation in drift rate was explained. Also explained is the north-south asymmetry in circulation patterns. The universality of the e̱ta}-plane theory was demonstrated by its application to the vortices on Saturn, Neptune and Earth, without free parameters. It was demonstrated in this study that for the understanding of long-lived atmospheric vortex dynamics, the planetary vorticity gradient is very critical.
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Optics

Arbitrary Reflectionless Optical Routing via Non-Hermitian Zero-Index Networks

Yongxing Wang, Zehui Du, Zhenshuo Xu et al. (+4 more)

Optical routers are fundamental to photonic systems, but their performance is often limited by unwanted reflections and constrained functionalities. Existing design strategies generally lack complete control over reflectionless pathways and typically require computationally intensive iterative optimization. A general analytical framework for the inverse design of arbitrary reflectionless routing has remained unavailable. Here, we present an analytical inverse-design approach based on non-Hermitian zero-index networks, which enables arbitrary reflectionless routing for nearly any desired scattering response. By establishing a direct algebraic mapping between target scattering responses and the network's physical parameters, we transform the design process from iterative optimization into deterministic calculation. This approach enables the precise engineering of arbitrary reflectionless optical routing. We demonstrate its broad utility by designing devices from unicast and multicast routers with full amplitude and phase control to coherent beam combiners and spatial mode demultiplexers in four-port and six-port networks. Our work provides a systematic and analytical route to designing advanced light-control devices.
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All authors Yongxing Wang, Zehui Du, Zhenshuo Xu, Pei Xiao, Jizi Lin, Yufeng Zhang, Jie Luo

Applied Physics

Enhancing Microwave Heating Uniformity in Cavities Using a 2-bit Coding Metasurface

Zhongyin Peng, Chengrong Wang, Changjun Liu et al. (+2 more)

A novel method for enhancing microwave heating uniformity using a 2-bit coding metasurface is proposed. This metasurface is specially designed to scatter incident waves into multiple directions at 2.45 GHz rather than just one, significantly improving the electric field distribution uniformity within a cavity, and eliminating the need to redesign the cavity itself or modify the power excitation. Simulated results demonstrate a reduction in the coefficient of variation (COV) of potato temperature from 0.694 to 0.461, indicating enhanced heating uniformity while maintaining efficiency. Additionally, the measured potato temperatures show excellent agreement with the simulated results, validating the effectiveness of the proposed method.
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All authors Zhongyin Peng, Chengrong Wang, Changjun Liu, Xiang Zhao, Liping Yan

Chemical Physics

A novel implementation of CCSD analytic gradients using Cholesky decomposition of the two-electron integrals and Abelian point-group symmetry

Luca Melega, Tommaso Nottoli, Jürgen Gauss et al. (+1 more)

We present a novel and efficient implementation of coupled-cluster with singles and doubles (CCSD) analytic gradients that combines the Cholesky decomposition (CD) of electron-repulsion integrals with the exploitation of Abelian point-group symmetry. This approach is particularly effective for medium-sized and large symmetric molecular systems. The CD of two-electron integrals is performed using a symmetry-adapted two-step algorithm, while the derivatives of the Cholesky vectors are computed with respect to symmetry-adapted nuclear displacements and contracted on-the-fly with the CCSD density matrices. Geometry optimizations of symmetric systems with several hundreds of basis functions have been carried out to assess the efficiency of our implementation and to quantify the computational gain provided by the exploitation of point-group symmetry.
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All authors Luca Melega, Tommaso Nottoli, Jürgen Gauss, Filippo Lipparini

Applied Physics · Cross-listed from cond-mat.str-el

Electrically induced ferromagnetism in an irradiated complex oxide

Nareg Ghazikhanian, Pavel Salev, Dayne Sasaki et al. (+2 more)

In metal-insulator transition materials, a small perturbation can shift the delicate balance between competing or coexisting electronic phases, leading to dramatic changes of the material's properties. Using La0.7Sr0.3MnO3, a prototypical metal-insulator transition manganite, we show that local low-dose focused ion beam irradiation increases resistivity by several orders of magnitude, converting the ferromagnetic-metal ground state into a paramagnetic-insulator. Surprisingly, we found that applying electric stimuli to the irradiated material induces a non-thermal insulator-to-metal transition, which results in low-power, repeatable volatile resistive switching. Magnetotransport measurements revealed that this voltage-induced metallic phase in the irradiated material is ferromagnetic, exhibiting clear anisotropic magnetoresistance. This work, thus, reports the discovery of a unique material in which the electrical triggering of the electronic phase transition results in the onset of magnetism, in stark contrast to the magnetic order suppression commonly observed in other metal-insulator transition switching materials. We demonstrate that local focused ion beam irradiation provides new and exciting opportunities to engineer electronic and magnetic functionalities that can find practical applications ranging from spintronics to neuromorphic hardware.
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All authors Nareg Ghazikhanian, Pavel Salev, Dayne Sasaki, Yayoi Takamura, Ivan K. Schuller

Biological Physics

Nascent biofilms on soft surfaces

Garima Rani, G. H. Philipp Nguyen, René Wittmann et al. (+2 more)

Soft surfaces, spanning vastly different environmental and biomedical settings, are frequently colonised by surface-associated bacteria. Yet, how soft surfaces govern bacterial dynamics and their self-organisation into colonies remains poorly understood. Using experiments and agent-based modelling, we report the self-organisation of bacterial cells into nascent biofilms on soft substrates. By tuning the elastic modulus over two orders of magnitude, we show that the colony morphology, spreading dynamics and collective behaviour depend on the substrate stiffness, wherein softer surfaces promote slowly expanding, geometrically anisotropic, multilayered colonies, while harder substrates drive rapid, isotropic expansion of bacterial monolayers before multilayer structures emerge. Supported a cell mechanical model and two-dimensional agent-based simulations, our results identify that anisotropic drag forces on soft substrates, emerging due to local deformations, underpin colony anisotropy and swift verticalisation. In contrast, reduced drag on hard surfaces allows rapid expansion of monolayers, thus delaying the transition to a multilayer structure. Surface compliance, a key but overlooked determinant of early-stage biofilm development, could be harnessed to engineer biofilm structures and dynamics for nature-inspired and biomedical applications.
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All authors Garima Rani, G. H. Philipp Nguyen, René Wittmann, Hartmut Löwen, Anupam Sengupta

History and Philosophy of Physics

Professor Hideki Yukawa's Anguish and a Lifelong Decision During a Three-Day Visit to Kochi to Unveil His First Bronze Statue: From a Cave Bat to the World

Shigeo Ohkubo

In 1954, following a five-year research period in the U.S., Professor Hideki Yukawa returned to Japan and visited Kochi on March 21 to attend the unveiling ceremony for the first statue of him ever built in Japan, a project initiated by the PTA of Yasu Elementary School in Yasu Town, Kochi Prefecture. By a coincidence of history, just three weeks prior on March 1, the U.S. had conducted a hydrogen bomb test at Bikini Atoll in the Pacific Ocean. Many Japanese fishing boats were operating there at the time and had not been informed in advance. As a result, numerous boats, including the Daigo Fukuryu Maru, were exposed to radiation. Upon his arrival at Kochi Station on the evening of March 21, Yukawa was relentlessly questioned by reporters about the Bikini hydrogen bomb. This was a source of deep anguish for Yukawa, a Japanese physicist who had won the Nobel Prize for his work on "atomic physics." He firmly refused to answer, stating that the topic was "outside the scope of my research." The next evening, at a public lecture in Kochi City on March 22, he again refused to speak about the Bikini hydrogen bomb or nuclear power, stating that he was an amateur in nuclear research and that there were many other experts. However, just four days later, on March 28, after returning to Kyoto, Yukawa drafted his famous essay, "The Turning Point for Humanity and Atomic Power," which was published in a newspaper on March 30. From that point on, he was drawn into the tumultuous issue of the Bikini hydrogen bomb and nuclear power. When did a tormented Yukawa make his decision? This article meticulously reveals, based on historical documents, what led the anguished Yukawa to make such a rapid decision within a single day and what caused the immense change in his mindset overnight.
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Biological Physics

Necking of epithelial tissues with cellular topological transition

Yuan He and Shi-Lei Xue

As the cover of embryos and adult organisms, epithelial tissues are subjected to substantial mechanical forces in tissue morphogenesis. However, the finite deformation behaviors of epithelial tissues remain largely unexplored. This study combines discrete vertex simulations with a multiscale constitutive model to investigate the necking behavior of epithelial tissues. In the multiscale model, the shape changes and topological transitions of single cells are mapped to the elastic and inelastic tissue deformations via a mean-field formulation. Our results show that the necking bifurcation of a stretched tissue arises from cellular topological transitions. The bifurcation condition and the steady state of necking propagation are predicted from the constitutive model and validated by vertex simulations. Furthermore, we find that topological defects in disordered tissues facilitate necking bifurcation but impede its propagation. These defects also induce the necked region to collapse into a thin thread, as observed in real tissues. Together, our work provides valuable insights into the deformation behaviors of epithelial tissues.
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Optics

Programmable Photonic Circuits with Embedded Feedback for Parallel Multi-Wavelength Operations

Kevin Zelaya, Jonathan Friedman and Mohammad-Ali Miri

Linear transformations are cornerstone operations utilized in modern computing, but are computationally expensive on current electronic platforms. Optical computing has been positioned as a new computing solution, promising high speed and energy efficiency by exploiting the available degrees of freedom of light. Although solutions exist in the optical domain, there is a continuous search for compact solutions that properly utilize the limited chip space and exploit various degrees of freedom of light. Here, we introduce and experimentally demonstrate a compact, programmable photonic integrated circuit (PIC) architecture that operates on both spatial and frequency degrees of freedom by leveraging embedded optical feedback loops. This architecture enables universal linear unitary transforms by combining resonators with passive linear mixing layers and tunable active phase layers. The strong dispersion achieved from the resonant loops enables multi-frequency operation and reduces the number of required active layers to achieve universality. This solution reduces the optical port requirements, minimizes power losses, and leverages resonances to enable massive parallel computing in the frequency domain. The fabricated samples are compatible with silicon-on-insulator platforms and operate at single- and dual-frequency modes. The experimental setup demonstrates the ability to perform in situ training in both cases, validating the parallel-computing capabilities of the PICs. This work highlights the potential of feedback-loop PICs for scalable, compact, and energy-efficient linear optical computing.
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Thursday 25 December

Space Physics

Spectral Properties and Energy Injection in Mercury's Magnetotail Current Sheet

Xinmin Li, Chuanfei Dong, Liang Wang et al. (+8 more)

Mercury's magnetotail hosts a thin and highly dynamic current sheet (CS), where magnetic reconnection and strong fluctuations frequently occur. Here, we statistically analyze magnetic field power spectra across 370 magnetotail CSs observed by MESSENGER. About 20% of the events are quasi-laminar, showing single power-law spectra, whereas 80% are turbulent, exhibiting a spectral break separating inertial and kinetic ranges. A dawn-dusk asymmetry is identified: inertial-range slopes are systematically shallower on the dawnside, whereas kinetic-range slopes are steeper, indicating more developed turbulence there, consistent with the higher occurrence of reconnection-related processes on the dawnside. Component analysis shows that the transverse components, orthogonal to the tail-aligned principal field (BX), display shallow slopes near -1 in the inertial range, suggesting energy injection at ion scales rather than a classical inertial range. These results demonstrate that Mercury's unique plasma environment fundamentally reshapes the initiation of turbulence and the redistribution of energy in the magnetotail.
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All authors Xinmin Li, Chuanfei Dong, Liang Wang, Sae Aizawa, Lina Z. Hadid, Chi Zhang, Hongyang Zhou, James A. Slavin, Jiawei Gao, Mirko Stumpo, Wei Zhang

Optics · Cross-listed from quant-ph

Quantization of Physical Interaction Strengths via Singular Moduli

Prasoon Saurabh

Since the 2019 redefinition of the SI units, precision metrology has sought to anchor all physical quantities to fundamental constants and integer invariants. While the optical frequency comb revolutionized timekeeping by discretizing the continuum of light into countable teeth, and the Quantum Hall Effect standardized resistance via topological invariants, a comparable standard for interaction strength remains elusive. Currently, measuring the coupling constant ($g$) between quantum systems is an estimation problem, inherently subject to drift, noise, and fabrication variance. Here, we introduce Interaction Metrology, a protocol that transforms the measurement of coupling strengths from an analog estimation into a topological counting problem. By engineering a specific class of algebraic catastrophe – the Unimodal $X_9$ singularity – in a driven-dissipative lattice, we prove that the system's interaction moduli are topologically forced to take discrete, quantized values, forming a "Geometric $k$-Comb." We derive the universality class of this quantization, showing that it arises from the discrepancy between the Milnor ($\mu$) and Tjurina ($\tau$) numbers of the effective potential, a strictly non-Hermitian effect forbidden in standard quantum mechanics. Finally, we provide an ab-initio blueprint for a silicon nitride implementation, demonstrating that this quantization is robust against disorder levels exceeding current foundry tolerances. This discovery establishes a universal standard for force sensing and quantum logic gates, enabling the calibration of interaction strengths with topological certainty.
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Instrumentation and Detectors

Quantitative acoustic monitoring of ensembles of weakly nonlinear microbubble oscillations in optically inaccessible environments

Hohyun Lee, Reza Pakdaman Zangabad, Chulyong Kim et al. (+4 more)

A growing class of ultrasound-mediated diagnostic and therapeutic technologies, including sonoporation and blood-brain barrier modulation, relies on microbubble contrast agents, where precise control of microbubble dynamics governs biological responses, efficiency, and safety. However, quantitative monitoring of microbubble oscillations in the stable, weakly nonlinear regime remains challenging, particularly in optically opaque and deep-tissue environments. Here, we introduce a linear acoustic wave propagation and superposition (LAWPS) framework that reconstructs microbubble radius-time dynamics directly from passively recorded acoustic emissions. By coupling Fourier-series representations of weakly nonlinear oscillations with linear monopole radiation theory, LAWPS extends classical monopole models to establish a reversible relationship between multi-frequency acoustic emissions and underlying radial bubble dynamics. Extending this framework to monodisperse microbubble ensembles, we derive optimal excitation and receive configurations and population-level correction factors that enable quantitative reconstruction of the ensemble-averaged microbubble dynamics. Using simultaneous optical and acoustic measurements, we demonstrate recovery of microbubble oscillations with ~5% relative error for oscillation amplitudes up to ~15% of equilibrium radius. Finally, we show that oscillations within the framework's operating regime (20% oscillation) generate sonoporation-relevant mechanical stress in vesicles as small as 10 micrometers (capillary number > 0.01), under physiologically relevant conditions. Together, this work establishes a quantitative framework for acoustic emission-based monitoring of weakly nonlinear microbubble oscillations in clinically relevant, optically inaccessible environments to enable improved control of emerging ultrasound diagnostic and therapeutic technologies.
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All authors Hohyun Lee, Reza Pakdaman Zangabad, Chulyong Kim, Victor Menezes, Juyoung Park, F. Levent Degertekin, Costas Arvanitis

Classical Physics

A novel large-strain kinematic framework for fiber-reinforced laminated composites and its application in the characterization of damage

Shivam and Sandipan Paul

In this paper, a novel kinematic framework for fiber-reinforced composite materials is presented. For this purpose, we use the multiple natural configurations in conjunction with the multi-continuum theory of Bedford and Stern~(1972). Keeping the underlying physics of the proposed kinematics consistent. The proposed kinematics results in a three-term decomposition of the deformation gradient i.e. $\mathbf{F}=\mathbf{F}^e\mathbf{F}^r_\alpha\mathbf{F}^d_\alpha$, where $\alpha$ represents either the matrix or the fiber. After discussing the kinematic framework in detail, we use this new kinematic framework to characterize the damage contents associated with four damage mechanisms. These damage mechanisms are matrix cracking, fiber breakage, interfacial slip or debonding, and delamination. While the first two are derived by measuring the incompatibility of the pertinent configuration occupied by individual constituents, the latter two involve a relative displacement between either the constituents or the laminæ. The geometric interpretation corresponding to these damage mechanisms is also presented using tools from differential geometry. The derived damage contents can be used in developing an appropriate constitutive model for laminated composites undergoing damage.
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Applied Physics · Cross-listed from cs.LG

Hierarchical Stacking Optimization Using Dirichlet's Process (SoDip): Towards Accelerated Design for Graft Polymerization

Amgad Ahmed Ali Ibrahim, Hein Htet and Ryoji Asahi

Radiation-induced grafting (RIG) enables precise functionalization of polymer films for ion-exchange membranes, CO2-separation membranes, and battery electrolytes by generating radicals on robust substrates to graft desired monomers. However, reproducibility remains limited due to unreported variability in base-film morphology (crystallinity, grain orientation, free volume), which governs monomer diffusion, radical distribution, and the Trommsdorff effect, leading to spatial graft gradients and performance inconsistencies. We present a hierarchical stacking optimization framework with a Dirichlet's Process (SoDip), a hierarchical data-driven framework integrating: (1) a decoder-only Transformer (DeepSeek-R1) to encode textual process descriptors (irradiation source, grafting type, substrate manufacturer); (2) TabNet and XGBoost for modelling multimodal feature interactions; (3) Gaussian Process Regression (GPR) with Dirichlet Process Mixture Models (DPMM) for uncertainty quantification and heteroscedasticity; and (4) Bayesian Optimization for efficient exploration of high-dimensional synthesis space. A diverse dataset was curated using ChemDataExtractor 2.0 and WebPlotDigitizer, incorporating numerical and textual variables across hundreds of RIG studies. In cross-validation, SoDip achieved ~33% improvement over GPR while providing calibrated confidence intervals that identify low-reproducibility regimes. Its stacked architecture integrates sparse textual and numerical inputs of varying quality, outperforming prior models and establishing a foundation for reproducible, morphology-aware design in graft polymerization research.
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Atomic Physics

Low-SWaP Magneto-optical Trap using both Planar Optical and Magnetic Components

Hao Gao, Yumeng Zhu, Zhilong Yu et al. (+8 more)

Compact, lightweight, and energy-efficient cold atom systems are crucial for advancing quantum technologies, yet their realization remains constrained by the bulky optical and magnetic components required in current atom trapping architectures. Here, we demonstrate a low-SWaP magneto-optical trap that seamlessly integrates planar optical and magnetic components into a unified platform. A monolithic dual-functional metasurface simultaneously polarized and shapes the cooling beam, replacing traditional lens-waveplate assemblies and converting a linearly polarized Gaussian beam into a circularly polarized flat-top beam. In parallel, a planar coil chip substitutes bulky anti-Helmholtz cols and generated the required quadrupole magnetic field with drastically reduced power consumption. Under D2 line cooling of 87Rb atoms, the fully planar system delivers nearly an order-of-magnitude improvement in trapping performance while operating at a fraction of the size, weight, and power of traditional systems. This compact, bulky-component-free approach offers a scalable, energy-efficient pathway toward chip-scale cold atom platforms.
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All authors Hao Gao, Yumeng Zhu, Zhilong Yu, Yuhui Hu, Zhelin Lin, Shiming Wei, Feng Zhao, Amit Agrawal, Zeyang Liu, Xiaochi Liu, Cheng Zhang

Chemical Physics · Cross-listed from cs.AI

Accelerating Scientific Discovery with Autonomous Goal-evolving Agents

Yuanqi Du, Botao Yu, Tianyu Liu et al. (+25 more)

There has been unprecedented interest in developing agents that expand the boundary of scientific discovery, primarily by optimizing quantitative objective functions specified by scientists. However, for grand challenges in science, these objectives may only be imperfect proxies. We argue that automating objective function design is a central, yet unmet need for scientific discovery agents. In this work, we introduce the Scientific Autonomous Goal-evolving Agent (SAGA) to address this challenge. SAGA employs a bi-level architecture in which an outer loop of LLM agents analyzes optimization outcomes, proposes new objectives, and converts them into computable scoring functions, while an inner loop performs solution optimization under the current objectives. This bi-level design enables systematic exploration of the space of objectives and their trade-offs, rather than treating them as fixed inputs. We demonstrate the framework through a wide range of design applications, including antibiotics, nanobodies, functional DNA sequences, inorganic materials, and chemical processes. Notably, our experimental validation identifies a structurally novel hit with promising potency and safety profiles for E. coli in the antibiotic design task, and three de novo PD-L1 binders in the nanobody design task. These results suggest that automating objective formulation can substantially improve the effectiveness of scientific discovery agents.
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All authors Yuanqi Du, Botao Yu, Tianyu Liu, Tony Shen, Junwu Chen, Jan G. Rittig, Kunyang Sun, Yikun Zhang, Aarti Krishnan, Yu Zhang, Daniel Rosen, Rosali Pirone, Zhangde Song, Bo Zhou, Cassandra Masschelein, Yingze Wang, Haorui Wang, Haojun Jia, Chao Zhang, Hongyu Zhao, Martin Ester, Nir Hacohen, Teresa Head-Gordon, Carla P. Gomes, Huan Sun, Chenru Duan, Philippe Schwaller, Wengong Jin

Fluid Dynamics

A Semi-Implicit Variational Multiscale Formulation for the Incompressible Navier-Stokes Equations via Exact Adjoint Linearization

Biswajit Khara, Suresh Murugaiyan, Suriya Dhakshinamoorthy et al. (+3 more)

A semi-implicit, residual-based variational multiscale (VMS) formulation is developed for the incompressible Navier-Stokes equations. The convection term is linearized using an extrapolated (Oseen-type) convecting velocity, producing a linear advection operator whose adjoint can be written exactly. Because of this exact adjoint, unresolved-scale contributions enter the weak form without spatial derivatives of the fine-scale velocity, thereby eliminating the case-by-case adjustments that often accompany nonlinear residual-based VMS implementations. The formulation is presented for a generalized linear convection operator encompassing the convective, skew-symmetric, and divergence forms. Since the discrete method is linear by construction and monolithic for velocity and pressure, each time step requires only one linear solve, reducing wall-clock time by a factor of $2$ to $5$ relative to fully implicit nonlinear formulations while maintaining comparable accuracy. Temporal convergence is verified, and validation is performed on the lid-driven cavity, flow past a cylinder, turbulent channel flow, and flow over a NACA0012 airfoil at a high Reynolds number, demonstrating the efficiency of the proposed approach on problems of practical scale.
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All authors Biswajit Khara, Suresh Murugaiyan, Suriya Dhakshinamoorthy, Makrand Khanwale, Ming-Chen Hsu, Baskar Ganapathysubramanian

Fluid Dynamics · Cross-listed from cond-mat.soft

Upper bounds on the colloid separation efficiency of diffusiophoresis

Fernando Temprano-Coleto, Jeongmin Kim, Marcel M. Louis et al. (+1 more)

The separation of colloidal particles from fluids is essential to ensure a safe global supply of drinking water, yet in the case of microscopic particles, it remains a highly energy-intensive process when using traditional filtration methods. Water cleaning through diffusiophoresis, spontaneous colloid migration in chemical gradients, effectively circumvents the need for physical filters, representing a promising alternative. This separation process is typically realized in internal flows, where a cross-channel electrolyte gradient drives particle accumulation at walls, with colloid separation slowly increasing in the streamwise direction. However, the maximum separation efficiency, achieved sufficiently downstream as diffusiophoretic migration (driving particle accumulation) is balanced by Brownian motion (inducing diffusive spreading), has not yet been characterized. In this work, we develop an asymptotic theory to predict colloid separation in this limit, deriving expressions for the water recovery, defined as the fraction of clean water that can be obtained from the suspension. We find that the mechanism by which the chemical permeates in the channel and the reaction kinetics governing its dissociation into ions play key roles in the process. Moreover, we identify four distinct regimes in which separation is controlled by different scaling laws involving Damköhler and Péclet numbers, which measure the ratios of reaction kinetics to ion diffusion and diffusiophoresis to Brownian motion, respectively. We also confirm the scaling of one of these regimes using microfluidic experiments where separation is driven by CO2 gradients. Our results shed light on pathways toward new, more efficient separations and are also applicable to quantify colloidal accumulation in the presence of chemical gradients in more general situations.
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All authors Fernando Temprano-Coleto, Jeongmin Kim, Marcel M. Louis, Howard A. Stone

Fluid Dynamics

Modeling complex motility patterns for autophoretic microswimmers

Anupriya Dutta Roy, Smita S. Sontakke, Arvind Kumar et al. (+2 more)

Symmetry breaking is essential for biological microswimmers to achieve locomotion in viscous environments. Such asymmetry in the swimming mechanism enables the generation of directional forces that overcome fluid resistance, leading to efficient motion and complex interactions. As synthetic analogues, autophoretic microswimmers including isotropic active colloids and active droplets exhibit spontaneous symmetry breaking of a chemical field, which generates interfacial flows and drives persistent self-propulsion. Modeling these systems is challenging because the chemical concentration and flow fields are strongly coupled through nonlinear advective transport of the chemical species. In this work, we propose a new numerical framework for modeling isotropic autophoretic microswimmers whose propulsion arises solely from self-generated chemical gradients, without any imposed geometric or chemical anisotropy. The framework employs a high-accuracy pseudospectral method to solve the fully coupled advection diffusion Stokes equations, without prescribing any slip velocity model.Slip velocities emerge self-consistently from instantaneous concentration gradients at the particle surface, driving propulsion and inducing flow disturbances through a stresslet representation of force and torque free swimmers. This approach naturally captures nonlinear advection, chemo-hydrodynamic feedback, and many-particle interactions within a unified framework. We demonstrate that the model reproduces complex emergent behaviors observed in experiments, including disordered swimming at higher fluid viscosities and chemotactically guided pairwise interactions. At each stage, numerical predictions are quantitatively compared with independent experiments on active droplets, validating the proposed framework as a robust tool for studying autophoretic microswimmers.
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All authors Anupriya Dutta Roy, Smita S. Sontakke, Arvind Kumar, Ranabir Dey, Anupam Gupta

Computational Physics · Cross-listed from cond-mat.stat-mech

On Critical Temperature and Finite Size Scaling of Continuous Spin $2d$ Ising Model

Swapna Mahapatra, Rudra Majhi, Jahangir Mohammed et al. (+3 more)

In this paper, we have studied the critical temperature $T_c$ of continuous spin $2d$ square-lattice Ising model using Monte-Carlo simulation. We have considered spins $s$ in a bounded interval, where $s \in [-1,+1]$ in square-lattice configuration with periodic boundary condition. We have observed that the critical temperature $T_c$ is approximately $0.925$, showing a clear second order phase transition. Considering finite size scaling, we have also obtained the critical exponents associated with susceptibility, specific heat, magnetization and we find that these values are in good agreement with the corresponding values obtained for the standard $2d$ Ising universality class.
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All authors Swapna Mahapatra, Rudra Majhi, Jahangir Mohammed, Subhashree Mohanty, Priyanka Priyadarshini Pruseth, Masoom Singh

Atomic and Molecular Clusters · Cross-listed from quant-ph

Properties of a Three-Level $\Lambda$-Type Atom Driven by Coherent and Stochastic Fields

Sajad Ahmadi, Mohsen Akbari, Shahpoor Saeidian et al. (+1 more)

We present a theoretical investigation of a three-level $\Lambda$-type atom driven by a strong coherent laser and a weak stochastic field exhibiting amplitude and phase fluctuations. The stochastic field is modeled as a complex Gaussian-Markovian random process with finite bandwidth to describe realistic laser noise. Using the Born-Markov and rotating-wave approximations, we derive a Lindblad-form master equation that incorporates spontaneous emission and noise-induced terms, and we solve for the steady-state regime. We examine level populations in both the bare and dressed bases and compute the incoherent resonance-fluorescence spectrum. Our analysis shows that the stochastic drive is not merely a source of decoherence but a versatile control parameter. By detuning the stochastic-field central frequency relative to the coherent drive (especially for narrow bandwidths), we observe pronounced changes in emission characteristics, including selective enhancement or suppression, and reshaping of the multi-peaked fluorescence spectrum when the detuning matches the generalized Rabi frequency. Numerical results reveal nontrivial steady-state modifications distinct from purely coherent driving, enabling precise control of populations and suggesting applications in quantum control, quantum technologies, spectroscopy, and noise-assisted manipulation of atomic systems.
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All authors Sajad Ahmadi, Mohsen Akbari, Shahpoor Saeidian, Ali Motazedifard

Instrumentation and Detectors

SiPM-based photodetectors for spectroscopic measurements in wide dynamic range

S.V.Evdokimov, A.M.Gorin, V.I.Izucheev et al. (+7 more)

The results of measurements of the characteristics of photodetectors based on large-area SiPM matrices with a wide dynamic range are presented. The potential application of SiPM-based photodetectors for electromagnetic calorimetry in the energy range from hundreds of keV to tens of GeV is explored. The potential application of SiPM in gamma-spectroscopy is also discussed.
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All authors S.V.Evdokimov, A.M.Gorin, V.I.Izucheev, Yu.V.Kharlov, B.V.Polishchuk, V.I.Rykalin, S.A.Sadovsky, A.A.Shangaraev, N.E.Voronkov, A.A.Zaitsev