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Physics Physics

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Friday 16 January

Geophysics

Mountain resonance shapes the distribution of earthquake-induced landslides

Ashok Dahal

Earthquake-induced landslides are among the most destructive cascading hazards, yet the physical mechanisms governing their spatial distribution and size remain incompletely understood. While amplification of seismic waves by local topography is well documented, the role of mountain-scale resonance has remained largely untested. Here we demonstrate that the resonant frequency of mountains exerts a statistically significant control on the occurrence, spatial pattern, and size of coseismic landslides. Using the 2015 Mw 7.8 Gorkha earthquake in Nepal, which triggered more than 25,000 landslides, we combine three-dimensional modal analysis of 3,130 mountain bodies with a high-resolution landslide inventory. Landslides preferentially occur on mountains whose resonant frequencies (0.5-1.2 Hz) overlap with the dominant frequency content of the earthquake. Mountains affected by landslides exhibit systematically lower resonant frequencies than stable mountains, and larger landslides are associated with lower-frequency mountains. These findings provide quantitative evidence that mountain-scale resonance amplifies seismic ground motion sufficiently to influence landslide triggering, highlighting an overlooked mechanism that should be incorporated into assessments of earthquake-induced landslide hazard.
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Optics

Light Propagation through Space-Time Non-Markovian Random Media

Chaoran Wang, Jinquan Qi, Shuang Liu et al. (+2 more)

Here, we introduce a stochastic partial differential equation (SPDE) formulation driven by temporally correlated noise to describe light propagation beyond the standard Markov approximation. By representing the squared refractive index fluctuations as a random field with explicit long-range temporal correlations, we demonstrate that the propagation dynamics map exactly onto the hyperbolic Anderson model. This rigorous mapping enables the derivation of new quantitative scaling relations that connect the environment's non-Markovian memory effects to the statistical properties of the emergent light field. We experimentally validate these analytical predictions in an outdoor atmospheric environment, confirming the memory-dependent statistical signatures of the propagated light. Our results establish a precise physical foundation for understanding memory-driven wave phenomena, providing crucial insights for free-space optical communication, remote sensing, and coherent imaging.
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All authors Chaoran Wang, Jinquan Qi, Shuang Liu, Chenjin Deng, Shensheng Han

Optics

Optical losses in pure crystalline silicon in the IR band measured using WGM microresonators

Artem Shitikov, Tatiana Tebeneva, Oleg Benderov et al. (+4 more)

The need for semiconductor technology for crystalline silicon of the highest purity and homogeneity has provided samples exhibiting low optical absorption in the infrared range. Such silicon has become the basis for photonic elements in the telecommunication band, including high-Q microresonators, which are particularly important. However, at longer wavelengths, the loss mechanisms have not yet been sufficiently studied. At the same time, this range is extremely important, especially for biological and medical applications and for fundamental research. We used optical microresonators with whispering gallery modes made from various types of silicon crystals as a tool to study the loss mechanisms. The study involved the pump wavelengths 1.5, 2.6, 6.1, and 8.6 $\mu$m and the maximum measured Q-factors were $1.5\cdot10^9$, $5\cdot10^8$, $1.6\cdot10^7$, and $5\cdot10^4$, respectively. We showed that the conductivity type does not noticeably influence the optical losses, while resistivity and the growing method are defining factors. Our study confirms the utility of WGM microresonators as loss measurement tools and provides significant potential for the development of silicon microresonator-based photonics in the mid-IR band.
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All authors Artem Shitikov, Tatiana Tebeneva, Oleg Benderov, Dmitry Mylnikov, Valery Lobanov, Dmitry Chermoshentsev, Igor Bilenko

Fluid Dynamics

Scale-resolving simulations and data-driven modal analysis of turbulent transonic buffet cells on infinite swept wings

David J. Lusher and Andrea Sansica

Transonic buffet is a class of shock-wave/boundary-layer interaction known to exhibit self-sustained two-dimensional (2D) chordwise shock wave oscillations (Strouhal number St=0.05-0.1), and three-dimensional (3D) spanwise-modulated flow separation/reattachment (St=0.2-0.4). Due to computational cost, scale-resolving simulations of span-periodic configurations to date have been limited to narrow airfoils, insufficient to accommodate the 3D buffet cell instability reported in low-fidelity simulations and experiments. In this work, implicit large-eddy simulations (ILES) and modal analysis are performed on infinite swept wings up to AR=3. The sensitivity of the 2D and 3D modes to crossflow is detailed. Two flow conditions are examined, corresponding to minimally and largely separated mean flow at the shock location. For the minimally separated case, the shock dynamics remain essentially spanwise-uniform (quasi-2D), with only weak and intermittent separation cells confined to the trailing-edge region and exhibiting negligible interaction with the shock. In contrast, increased mean separation leads to the emergence of pronounced 3D buffet cells with a characteristic spanwise wavelength: 1-1.5c. SPOD reveals that a quasi-stationary low-frequency 3D separation mode previously identified on unswept wings (St=0.02) becomes a spanwise travelling mode as sweep is imposed, shifting monotonically to intermediate frequencies (St=0.06-0.35). The 2D shock mode is largely insensitive to sweep, whereas the frequency and energy content of the 3D mode increase with sweep while its wavelength remains unchanged. The results demonstrate that transonic buffet on infinite wings arises from the superposition of distinct but coexisting 2D shock motion and separation-driven 3D instabilities, with mean flow separation at the shock identified as a necessary condition for dominant 3D buffet dynamics to emerge.
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Fluid Dynamics

A numerical study on the effect of rolling friction on clogging of pores in particle-laden flows

Sagar G. Nayak, Zhenjiang You, Yuchen Dai et al. (+2 more)

Particulate matter in a fluid injected into a porous reservoir impairs its permeability spatio-temporally due to pore clogging. As particle volume fraction increases near the pore throats, inter-particle contact mechanics determine their jamming and subsequent pore clogging behavior. During contact of particles submerged in a fluid, in addition to sliding friction, a rolling resistance develops due to a several micromechanical and hydrodynamic factors. A coefficient of rolling friction is often used as a lumped parameter to characterize particle rigidity, particle shape, lubrication and fluid mediated resistance, however its direct influence on the clogging behavior is not well studied in literature. We study the effect of rolling resistance on the clogging behavior of a dense suspension at pore scale using direct numerical simulations (DNS). A discrete element method (DEM) library is developed and coupled with an open-source immersed boundary method (IBM) based solver to perform pore and particle resolved simulations. Several 3D validations are presented for the DEM library and the DEM-IBM coupling and the effect of rolling resistance on clogging at a pore entry is studied.
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All authors Sagar G. Nayak, Zhenjiang You, Yuchen Dai, Geoff Wang, Prapanch Nair

Optics

The origin and influence of non-cavity modes in a micropillar Bragg microcavity

Matthew Jordan, Wolfgang Langbein and Anthony J. Bennett

Controlling the photonic environment of emitters is essential to the design of classical and quantum light sources. We study the case of a dipole-like emitter in a cylindrical pillar etched into a planar Bragg microcavity, which is a common design of quantum-dot single photon source. In addition to the well-known cavity modes created by the high-reflectivity of the Bragg mirrors at small in-plane wavevectors, we show the presence of broad spectral features that play a key role in controlling photon collection efficiency and Purcell enhancement. These non-cavity modes are insensitive to the periodic index modulation of the Bragg reflectors, but arise from the cylindrical pillar geometry, as we show by comparison with simulations of uniform pillars, which reproduce the non-cavity modes. This approach provides a tool for understanding and modelling these often-disregarded decay channels as a function of source height, cavity dimensions and surface layers.
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Medical Physics · Cross-listed from eess.IV

Generation of Chest CT pulmonary Nodule Images by Latent Diffusion Models using the LIDC-IDRI Dataset

Kaito Urata, Maiko Nagao, Atsushi Teramoto et al. (+3 more)

Recently, computer-aided diagnosis systems have been developed to support diagnosis, but their performance depends heavily on the quality and quantity of training data. However, in clinical practice, it is difficult to collect the large amount of CT images for specific cases, such as small cell carcinoma with low epidemiological incidence or benign tumors that are difficult to distinguish from malignant ones. This leads to the challenge of data imbalance. In this study, to address this issue, we proposed a method to automatically generate chest CT nodule images that capture target features using latent diffusion models (LDM) and verified its effectiveness. Using the LIDC-IDRI dataset, we created pairs of nodule images and finding-based text prompts based on physician evaluations. For the image generation models, we used Stable Diffusion version 1.5 (SDv1) and 2.0 (SDv2), which are types of LDM. Each model was fine-tuned using the created dataset. During the generation process, we adjusted the guidance scale (GS), which indicates the fidelity to the input text. Both quantitative and subjective evaluations showed that SDv2 (GS = 5) achieved the best performance in terms of image quality, diversity, and text consistency. In the subjective evaluation, no statistically significant differences were observed between the generated images and real images, confirming that the quality was equivalent to real clinical images. We proposed a method for generating chest CT nodule images based on input text using LDM. Evaluation results demonstrated that the proposed method could generate high-quality images that successfully capture specific medical features.
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All authors Kaito Urata, Maiko Nagao, Atsushi Teramoto, Kazuyoshi Imaizumi, Masashi Kondo, Hiroshi Fujita

Medical Physics · Cross-listed from eess.IV

Visual question answering-based image-finding generation for pulmonary nodules on chest CT from structured annotations

Maiko Nagao, Kaito Urata, Atsushi Teramoto et al. (+3 more)

Interpretation of imaging findings based on morphological characteristics is important for diagnosing pulmonary nodules on chest computed tomography (CT) images. In this study, we constructed a visual question answering (VQA) dataset from structured data in an open dataset and investigated an image-finding generation method for chest CT images, with the aim of enabling interactive diagnostic support that presents findings based on questions that reflect physicians' interests rather than fixed descriptions. In this study, chest CT images included in the Lung Image Database Consortium and Image Database Resource Initiative (LIDC-IDRI) datasets were used. Regions of interest surrounding the pulmonary nodules were extracted from these images, and image findings and questions were defined based on morphological characteristics recorded in the database. A dataset comprising pairs of cropped images, corresponding questions, and image findings was constructed, and the VQA model was fine-tuned on it. Language evaluation metrics such as BLEU were used to evaluate the generated image findings. The VQA dataset constructed using the proposed method contained image findings with natural expressions as radiological descriptions. In addition, the generated image findings showed a high CIDEr score of 3.896, and a high agreement with the reference findings was obtained through evaluation based on morphological characteristics. We constructed a VQA dataset for chest CT images using structured information on the morphological characteristics from the LIDC-IDRI dataset. Methods for generating image findings in response to these questions have also been investigated. Based on the generated results and evaluation metric scores, the proposed method was effective as an interactive diagnostic support system that can present image findings according to physicians' interests.
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All authors Maiko Nagao, Kaito Urata, Atsushi Teramoto, Kazuyoshi Imaizumi, Masashi Kondo, Hiroshi Fujita

Biological Physics

Unraveling the Allosteric Mechanism and Mechanical Stability of Partial and Complete Loss-of-Function Mutations in p53 DNA-Binding Domain

Han Zhou, Tao Zhou and Shiwei Yan

TP53 is the most frequently mutated tumor suppressor gene in human cancers, with mutations primarily in its DNA-binding domain (p53-DBD). Mutations in p53-DBD are categorized into hotspot mutations (resulting in complete loss-of-function) and non-hotspot mutations (inducing partial loss-of-function). However, the allosteric mechanisms underlying non-hotspot mutations remain elusive. Using p53 dimer as models, we constructed p53-WT, non-hotspot p53-E180R, and hotspot p53-R248W dimer-DNA complexes to compare the structural and functional impacts of these two mutation types. Our results reveal that both mutations weaken intramolecular interactions in p53-DBD and enhance structural flexibility. Specifically, E180R perturbs dimer interface interactions, impairing dimer stability and cooperative DNA binding; R248W disrupts interactions between the L3/L1 loops and DNA, leading to the loss of DNA-binding capacity. Steered molecular dynamics (SMD) simulations further confirm that both mutations accelerate p53 dimer dissociation, with E180R exerting the most prominent disruptive effect on the mechanical stability of the dimer interface.
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Applied Physics

ATSim3.5D: A Multiscale Thermal Simulator for 3.5D-IC Systems based on Nonlinear Multigrid Method

Qipan Wang, Tianxiang Zhu, Yibo Lin et al. (+2 more)

To resolve the rising temperatures in 3.5D-ICs, a thermal-aware design flow becomes increasingly crucial, necessitating an accurate and efficient thermal simulation tool. However, previous tools struggle to handle the unique heterogeneous multiscale structures in 3.5D-ICs and the nonlinear thermal effects caused by high temperatures. In this work, we present a multiscale thermal simulator for 3.5D-ICs. We propose a hybrid tree structure to generate multilevel grids and capture the multiscale features and employ the nonlinear multigrid method for quick solving. Compared to ANSYS Icepak, it exhibits high accuracy (mean absolute relative error <1%, max error $<\SI{2}{\degreeCelsius}$), and efficiency ($80\times$ acceleration), delivering a powerful means to evaluate and refine thermal designs.
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All authors Qipan Wang, Tianxiang Zhu, Yibo Lin, Runsheng Wang, Ru Huang

Applied Physics

ATSim3D: Towards Accurate Thermal Simulator for Heterogeneous 3D-IC Systems Considering Nonlinear Leakage and Conductivity

Qipan Wang, Tianxiang Zhu, Yibo Lin et al. (+2 more)

Thermal simulation plays a fundamental role in the thermal design of integrated circuits, especially 3D ICs. Current simulators require significant runtime for high-resolution simulation, and dismiss the complex nonlinear thermal effects, such as nonlinear thermal conductivity and leakage power. To address these issues, we propose ATSim3D, a thermal simulator for simulating the steady-state temperature profile of nonlinear and heterogeneous 3D IC systems. We utilize the global-local approach, combining a compact thermal model at the global level, and a finite volume method at the local level. We tackle the nonlinear effects with Kirchhoff transformation and iteration. ATSim3D enables local-level parallelization that helps achieve an average speedup of 40x compared to COMSOL, with a relative error <3% and a state-of-the-art resolution of 4096 x 4096, holding promise for enhancing thermal-aware design in 3D ICs.
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All authors Qipan Wang, Tianxiang Zhu, Yibo Lin, Runsheng Wang, Ru Huang

Plasma Physics

Study of circular cross-section plasmas in HL-2A tokamak: MHD equilibrium, stability and operational e̱ta} limit

SHEN Yong, DONG Jiaqi, SHI Zhongbing et al. (+6 more)

Circular cross-section plasma is the most basic form of tokamak plasma and the fundamental configuration for magnetic confinement fusion experiments. Based on the HL-2A limiter discharge experiments, the magnetohydrodynamic (MHD) equilibrium and MHD instability of circular cross-section tokamak plasmas are investigated in this work. The results show that when q_0=0.95, the internal kink mode of m/n=1/1 is always unstable. The increase in plasma e̱ta} (the ratio of thermal pressure to magnetic pressure) can lead to the appearance of external kink modes. The combination of axial safety factor q_0 and edge safety factor q_a determines the equilibrium configuration of the plasma and also affects the MHD stability of the equilibrium, but its growth rate is also related to the size of e̱ta}. Under the condition of q_a>2 and q_0 slightly greater than 1, the internal kink mode and surface kink mode can be easily stabilized. However the plasma becomes unstable again and the instability intensity increases as q_0 continues to increase when q_0 exceeds 1. As the poloidal beta (e̱ta}_p) increases, the MHD instability develops, the equilibrium configuration of MHD elongates laterally, and the Shafranov displacement increases, which in turn has the effect on suppressing instability. Calculations have shown that the maximum e̱ta} value imposed by the ideal MHD mode in a plasma with free boundary in tokamak experiments is proportional to the normalized current I_N (I_N=I_p (MA)/a(m)B_0 (T)), and the achievable maximum beta e̱ta}(max) is calibrated to be 2.01I_N,i.e. e̱ta}(max)~2.01I_N. The operational e̱ta} limit of HL-2A circular cross-section plasma is approximately e̱ta}_N^c~2.0. Too high a value of q_0 is not conducive to MHD stability and leads the e̱ta} limit value to decrease. When q_0=1.3, we obtain a maximum value of e̱ta}_N of approximately 1.8.
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All authors SHEN Yong, DONG Jiaqi, SHI Zhongbing, HE Hongda, ZHAO Kaijun, PENG Xiaodong, QU Hongpeng, LI Jia, SUN Aiping

Biological Physics · Cross-listed from cond-mat.soft

De novo emergence of metabolically active protocells

Nayan Chakraborty and Shashi Thutupalli

A continuous route from a disordered soup of simple chemical feedstocks to a functional protocell – a compartment that metabolizes, grows, and propagates – remains elusive. Here, we show that a homogeneous aqueous chemical mixture containing phosphorus, iron, molybdenum salts and formaldehyde spontaneously self-organizes into compartments that couple robust non-equilibrium chemical dynamics to their own growth. These structures mature to a sustained, dissipative steady state and support an organic synthetic engine, producing diverse molecular species including many core biomolecular classes. Internal spherules that are themselves growth-competent are produced within the protocells, establishing a rudimentary mode of self-perpetuation. The chemical dynamics we observe in controlled laboratory conditions also occur in reaction mixtures exposed to natural day-night cycles. Strikingly, the morphology and chemical composition of the protocells in our experiments closely resemble molybdenum-rich microspheres recently discovered in current oceanic environments. Our work establishes a robust, testable route to de novo protocell formation. The emergence of life-like spatiotemporal organization and chemical dynamics from minimal initial conditions is more facile than previously thought and could be a recurring natural phenomenon.
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Optics

Generation and Enhancement of Persistent Nanoscale Magnetization in All-Dielectric Metasurfaces by Optically Injected and Localized Free Carriers

Shivaksh Rawat, Samyobrata Mukherjee and Gennady Shvets

Time-varying dielectric metasurfaces that support sharp optical resonances with nontrivial electromagnetic field distributions constitute a unique platform for realizing temporal interfaces for metasurface-guided waves (MGWs). Rapidly changing metasurface resonance enables frequency conversion and temporal scattering of a concurrently propagating MGW. Using analytical methods and electromagnetic simulations, free carriers are generated locally to create frequency-shifted infrared MGWs. Such time interfaces can be utilized to generate large, highly localized quasistatic magnetic fields within the metasurfaces. The resulting nanoscale magnetization, supported by the residual circulating currents, persists for several optical cycles after the departure of the time-scattered MGWs. During the rectification process, the initial electromagnetic energy of the injected MGWs is partitioned between the temporally scattered MGWs, the residual motion of the free carriers, and a quasistatic magnetic field.
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Optics

Quantum-optical theory of the few femtosecond nonlinear optical response of Drude metals with a non-parabolic conduction band

Ieng-Wai Un, Subhajit Sarkar and Yonatan Sivan

We develop an energy-space density matrix framework to investigate the interaction of extremely short optical pulses (ESPs) with transparent conducting oxides (TCOs). This approach captures not only electron populations, material polarization, and the permittivity, but also the quantum coherences between states. Compared to traditional momentum-space models, the energy-space formulation offers substantial computational simplification while retaining accuracy. Building on but going beyond the scope of Ref.~\cite{single_cycle_nlty_Letter}, we focus on dynamical features previously unexplored. Our formulation reveals clear signatures of quantum coherence in the net absorption dynamics and highlights the emergence of strong excited-state absorption under intense excitation. It also clarifies that spontaneous emission can be neglected in this regime. Furthermore, we investigate the influence of pump pulse intensity on the local field's duration, spectral broadening and shift, and phase induced by carrier dynamics, highlighting the absorptive nature of the nonlinear response. Our results provide a unified framework for understanding nonlinear light-matter interaction in dispersive, low-density electron systems driven far from equilibrium by intense broadband excitation.
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Applied Physics · Cross-listed from astro-ph.IM

A Novel, Beam-based Formalism for Active Impedance of Phased Arrays

M. Deng and J. Wu

The active impedance is a fundamental parameter for characterizing the behavior of large, uniform phased array antennas. However, its conventional calculation via the mutual impedance matrix (or the scattering matrix) offers limited physical intuition and can be computationally intensive. This paper presents a novel derivation of the active impedance directly from the radiated beam pattern of such arrays. This approach maps the scan-angle variation of the active impedance directly to the intrinsic angular variation of the beam, providing a more intuitive physical interpretation. The theoretical derivation is straightforward and rigorous. The validity of the proposed equation is conclusively confirmed through full-wave simulations of a prototype array. This work establishes a new and more intuitive framework for understanding, analyzing and accurately measuring the scan-dependent variations in phased arrays, which is one of the main challenges in modern phased array designs. Consequently, this novel formalism is expected to expedite and simplify the overall design and optimization process for next-generation, large-scale uniform phased arrays.
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Chemical Physics · Cross-listed from eess.SY

A monolithic fabrication platform for intrinsically stretchable polymer transistors and complementary circuits

Yujia Yuan, Chuanzhen Zhao, Margherita Ronchini et al. (+20 more)

Soft, stretchable organic field-effect transistors (OFETs) can provide powerful on-skin signal conditioning, but current fabrication methods are often material-specific: each new polymer semiconductor (PSC) requires a tailored process. The challenge is even greater for complementary OFET circuits, where two PSCs must be patterned sequentially, which often leads to device degradation. Here, we introduce a universal, monolithic photolithography process that enables high-yield, high-resolution stretchable complementary OFETs and circuits. This approach is enabled by a process-design framework that includes (i) a direct, photopatternable, solvent-resistant, crosslinked dielectric/semiconductor interface, (ii) broadly applicable crosslinked PSC blends that preserve high mobility, and (iii) a patterning strategy that provides simultaneous etch masking and encapsulation. Using this platform, we achieve record integration density for stretchable OTFTs (55,000 cm^-2), channel lengths down to 2 um, and low-voltage operation at 5 V. We demonstrate photopatterning across multiple PSC types and realize complementary circuits, including 3 kHz stretchable ring oscillators, the first to exceed 1 kHz and representing more than a 60-fold increase in stage switching speed over the state of the art. Finally, we demonstrate the first stretchable complementary OTFT neuron circuit, where the output frequency is modulated by the input current to mimic neuronal signal processing. This scalable approach can be readily extended to diverse high-performance stretchable materials, accelerating the development and manufacturing of skin-like electronics.
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All authors Yujia Yuan, Chuanzhen Zhao, Margherita Ronchini, Yuya Nishio, Donglai Zhong, Can Wu, Hyukmin Kweon, Zehao Sun, Rachael K. Mow, Yuran Shi, Lukas Michalek, Haotian Wu, Qianhe Liu, Weichen Wang, Yating Yao, Zelong Yin, Junyi Zhao, Zihan He, Ke Chen, Ruiheng Wu, Jiuyun Shi, Jian Pei, Zhenan Bao

Thursday 15 January

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

Strain-transport superposition in shear-thinning dense non-Brownian suspensions

Rishabh V. More

Shear thinning in dense non-Brownian suspensions is often attributed to shear-induced microstructural evolution, including changes in alignment, anisotropy, and near-contact statistics, yet how these changes influence particle-scale dynamics remains unclear. Using particle-resolved simulations of dense suspensions that shear thin through diverse microscopic mechanisms, including short-range attraction, repulsion, and load-dependent friction, we show that the magnitude of nonaffine particle velocities is controlled solely by the imposed shear rate, independent of coordination number, structural anisotropy, and interaction details. In contrast, macroscopic stress and viscosity remain strongly sensitive to the underlying interactions. When mean-squared displacements transverse to the flow are rescaled by accumulated strain and the nonaffine velocity variance, all data collapse onto a single master curve, revealing strain-controlled transport with a robust ballistic-to-diffusive crossover. These results demonstrate a fundamental decoupling between particle-scale kinematics and macroscopic rheology and identify nonaffine velocity fluctuations as the emergent dynamical scale governing shear-driven transport.
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Atomic Physics

New energy conversion system based on charge-exchange and inner-shell electron transitions

Tianrui Li, Yi Jiang, Chen Zhao et al. (+4 more)

The rapidly growing demand for compact, high-energy power sources has outpaced the capabilities of conventional electrochemical systems that rely on outer-shell redox reactions. In this work, we present a new energy platform that utilizes inner-shell electron transitions that are previously inaccessible due to their high energy thresholds. By leveraging charge exchange processes between bare argon ions (Ar^18+) and neutral helium atoms, we provide clear evidence for the emission of soft X-ray and extreme-ultraviolet photons across a broad spectra range, resulting from inner-shell electron capture and cascade de-excitation. This strategy overcomes the limitations of radiative recombination by enhancing photon energy utilization through broader emission profiles more compatible with practical energy converters. Our design of a helium-filled chamber design enables precise control of output via pressure tuning, achieving a remarkable radiation power density of 6.29*10^8 W L^-1 and an unprecedented energy density of 2.64*10^6 Wh kg^-1. These results may provide a new and effective paradigm for energy conversion systems with ultra-high power and energy densities based on inner-shell electrons.
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All authors Tianrui Li, Yi Jiang, Chen Zhao, Bingsheng Tu, Peining Chen, Jiajun Qin, Huisheng Peng

Applied Physics

High-Frequency Switching in Superparamagnetic Magnetic Tunnel Junctions by Enhancing Damping

Qi Jia and Jian-Ping Wang

Superparamagnetic magnetic tunnel junctions (sMTJs) are promising components for true random number generation and probabilistic computing. Achieving high-frequency fluctuation while maintaining reliable control over output level is critical for applications. In this work, we systematically investigate the role of magnetic damping in regulating thermal switching rates using macrospin simulations. We show that enhanced damping accelerates the switching rate by increasing the escape rate over the energy barrier. We further compare two control mechanisms: spin-transfer torque (STT) and voltage-controlled exchange coupling (VCEC). Our results reveal that STT-based switching is strongly suppressed under high damping, whereas VCEC, by reshaping the energy landscape without relying on torque-driven dynamics, retains high control efficiency. These findings suggest that enhanced damping not only enables faster stochastic switching in sMTJs but also makes VCEC inherently better suited than STT for high-frequency applications.
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Chemical Physics

CO$_2$ collision-induced line parameters for the $\nu_3$ band of $^{12}$CH$_4$ measured using a hard-collision speed-dependent line shape and the relaxation matrix formalism

Thibault Bertin and Jean Vander Auwera

Ten high resolution Fourier transform spectra of the pentad region near 3.3 {\mu}m of methane diluted in carbon dioxide at total pressures up to 800 hPa have been recorded at 296.5(5) K. Including a high resolution spectrum of pure methane at low pressure, these spectra have been analyzed using multi-spectrum fitting techniques. The methane lines were modeled using hard-collision speed-dependent line profiles and line mixing was included in the strongest absorption regions, considering the first order Rosenkranz approximation and the relaxation matrix formalism. CO$_2$ broadening and shift coefficients have been measured, together with the speed dependence of broadening. Results obtained using the two line mixing models are intercompared and compared with previous work.
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Chemical Physics

Large Language Model Agent for User-friendly Chemical Process Simulations

Jingkang Liang, Niklas Groll and Gürkan Sin

Modern process simulators enable detailed process design, simulation, and optimization; however, constructing and interpreting simulations is time-consuming and requires expert knowledge. This limits early exploration by inexperienced users. To address this, a large language model (LLM) agent is integrated with AVEVA Process Simulation (APS) via Model Context Protocol (MCP), allowing natural language interaction with rigorous process simulations. An MCP server toolset enables the LLM to communicate programmatically with APS using Python, allowing it to execute complex simulation tasks from plain-language instructions. Two water-methanol separation case studies assess the framework across different task complexities and interaction modes. The first shows the agent autonomously analyzing flowsheets, finding improvement opportunities, and iteratively optimizing, extracting data, and presenting results clearly. The framework benefits both educational purposes, by translating technical concepts and demonstrating workflows, and experienced practitioners by automating data extraction, speeding routine tasks, and supporting brainstorming. The second case study assesses autonomous flowsheet synthesis through both a step-by-step dialogue and a single prompt, demonstrating its potential for novices and experts alike. The step-by-step mode gives reliable, guided construction suitable for educational contexts; the single-prompt mode constructs fast baseline flowsheets for later refinement. While current limitations such as oversimplification, calculation errors, and technical hiccups mean expert oversight is still needed, the framework's capabilities in analysis, optimization, and guided construction suggest LLM-based agents can become valuable collaborators.
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Accelerator Physics

U-Net-based surrogate modeling for attosecond X-ray free-electron lasers

Yufei Wei, Bingyang Yan, Chenzhi Xu et al. (+2 more)

Attosecond X-ray pulse generation in modern X-ray free-electron lasers relies on strongly compressed, precisely tailored electron bunches, making accurate diagnostics and control of the longitudinal phase space (LPS) essential. In the self-chirping scheme, collective effects in the linac generate a strong energy chirp that is converted into high peak current through pre-undulator compression, enabling isolated attosecond pulse generation. Reliable operation of this scheme depends on precise LPS control and fast diagnostics. In this work, we present a U-Net-based neural network surrogate that predicts two-dimensional LPS distributions directly from accelerator settings. The model exhibits excellent agreement with start-to-end simulation results. These results demonstrate the potential of neural network surrogates to facilitate real-time tuning and control in attosecond X-ray pulse generation.
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All authors Yufei Wei, Bingyang Yan, Chenzhi Xu, Jiawei Yan, Haixiao Deng

Optics

Dynamical correlations and chimera-like states of nanoemitters coupled to plasmon-polaritons in a lattice of conducting nanorings

Boris A. Malomed, Gennadiy Burlak, Gustavo Medina-Ángel et al. (+1 more)

We systematically investigate semiclassical dynamics of the optical field produced by quantum nanoemitters (NEs) embedded in a periodic lattice of conducting nanorings (NRs), in which plasmon polaritons (PPs) are excited. The coupling between PPs and NEs through the radiated optical field leads to establishment of a significant cross-correlation between NEs, so that their internal dynamics (photocurrent affected by the laser irradiation) depends on the NR's plasma frequency $\omega _{p}$. The transition to this regime,combined with the nonlinearity of the system, leads to a steep increase of the photocurrent in the NEs, as well as to non-smooth (chimera-like or chaotic) behavior in the critical (transition) region, where small variations of $\omega _{p}$ lead to significant changes in the level of the NE pairwise cross-correlations. The chimera-like state is realized as coexistence of locally synchronized and desynchronized NE dynamical states. A fit of the dependence of the critical current on $\omega _{p}$ is found, being in agreement with results of numerical simulations. The critical effect may help to design new optical devices, using dispersive nanolattices which are made available by modern nanoelectronics.
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All authors Boris A. Malomed, Gennadiy Burlak, Gustavo Medina-Ángel, Yuriy Karlovich

Plasma Physics

Learning collision operators from plasma phase space data using differentiable simulators

Diogo D. Carvalho, Pablo J. Bilbao, Warren B. Mori et al. (+2 more)

We propose a methodology to infer collision operators from phase space data of plasma dynamics. Our approach combines a differentiable kinetic simulator, whose core component in this work is a differentiable Fokker-Planck solver, with a gradient-based optimisation method to learn the collisional operators that best describe the phase space dynamics. We test our method using data from two-dimensional Particle-in-Cell simulations of spatially uniform thermal plasmas, and learn the collision operator that captures the self-consistent electromagnetic interaction between finite-size charged particles over a wide variety of simulation parameters. We demonstrate that the learned operators are more accurate than alternative estimates based on particle tracks, while making no prior assumptions about the relevant time scales of the processes and significantly reducing memory requirements. We find that the retrieved operators, obtained in the non-relativistic regime, are in excellent agreement with theoretical predictions derived for electrostatic scenarios. Our results show that differentiable simulators offer a powerful and computational efficient approach to infer novel operators for a wide rage of problems, such as electromagnetically dominated collisional dynamics and stochastic wave-particle interactions.
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All authors Diogo D. Carvalho, Pablo J. Bilbao, Warren B. Mori, Luis O. Silva, E. Paulo Alves

Physics and Society

The meaning of closeness to women and/or LGBTQ+ physicists: a social network analysis

Chase Hatcher, Adrienne Traxler, Lily Donis et al. (+4 more)

'Closeness' is well-defined as a quantitative measure of centrality in social network analysis (SNA), but it is not as well defined qualitatively as a description of social relationships. This paper presents a qualitative analysis of 'closeness' as it is defined both implicitly and explicitly in interviews with 100 women and/or LGBTQ+ PhD physicists. The interviews include a social network construction component, and we define a quantitative network parameter that serves as a proxy for closeness, which we examine in relation to attributes of network members. We find that physicists in this sample see trust, relaxed boundaries, reliance, and support as concepts that most directly define closeness in their relationships. Consistent interaction, positive affect, and commonalities are also often present in (and in some cases, defining of) these relationships. From the quantitative analysis, we find that these physicists tend to view family and partners, friends, and professional friends as comprising their closest relationships. These results are consistent with other studies which have sought to define closeness qualitatively, but the prevalence of trust in this dataset in particular suggests that these physicists see the ability to confide as uniquely important in their relationships. We make recommendations to institutions supporting and employing physicists on how to better support gender and sexual minority (GSM) physicists going forward, and we believe these results help us gain a better understanding of how GSM physicists find success in physics despite the barriers they face due to their identities.
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All authors Chase Hatcher, Adrienne Traxler, Lily Donis, Camila Amaral, Justin Gutzwa, Charles Henderson, Ramón Barthelemy

Optics

Rotation angle sensing via polarization-dependent mode superposition in a hollow-core fiber with two-fold symmetry

Enzo Dantas da Silva, Giovanna M. R. Castro, Murilo L. Batista et al. (+10 more)

Hollow-core photonic crystal fibers (HCPCF) have experienced tremendous advancements recently, leading to remarkable demonstrations of transmission loss reduction and deeper understanding of their guidance fundamentals. Indeed, this progress has entailed investigations into various HCPCF designs, allowing for attaining diverse properties of interest such as ultralow loss, polarization filtering, and specific modal operation. Among HCPCFs with tailored modal characteristics are fibers displaying microstructures with modified symmetry, which allow for changing the loss hierarchy between the guided modes, hence favoring the propagation of higher-order modes. In this context, we here demonstrate the realization of an angle sensor utilizing a tubular HCPCF with a two-fold symmetric cladding. This specific fiber design enables the generation of an output intensity profile resulting from the superposition of LP01 and LP11-like modes, whose excitation and resulting output intensity spatial distribution are dependent on the polarization angle of the incident light. Thus, by rotating the input beam's polarization and analyzing the evolution of the resulting output profile, we characterized a rotation angle sensor exhibiting a sensitivity of 25 counts/degree and an estimated resolution of 0.3{\deg}. We understand that this work broadens the framework of HCPCF applications, demonstrating that symmetry-modified hollow-core fibers can act as a promising platform for advanced sensing scenarios and polarimetric characterizations.
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All authors Enzo Dantas da Silva, Giovanna M. R. Castro, Murilo L. Batista, Flavio A. M. Marques, Alexandre A. C. Cotta, Jefferson E. Tsuchida, Julio C. Ugucioni, Leomar S. Marques, Matthieu Chafer, Benoît Debord, Frédéric Gérôme, Fetah Benabid, Jonas H. Osório

Instrumentation and Detectors

Stacked geometry concept for CosmicWatch based muon detectors in coincidence mode

Ishannita Banerjee, Swagato Banerjee, Douglas Jackson et al. (+1 more)

CosmicWatch-based muon detectors are inexpensive, handheld, battery-powered, portable instruments designed to measure the flux of secondary muons produced when primary cosmic rays continuously strike the Earth's atmosphere. As these muons pass through the detector, plastic scintillators generate light, which is collected by silicon photomultiplier (SiPM) sensors and converted to an electric signal. The signal is processed by an Arduino-based acquisition system and recorded as count rates corresponding to the cosmic muon flux. A stacked configuration consisting of two scintillator modules wrapped together and read by two SiPM sensors, which are operated in coincidence mode via linked Arduino microcontrollers, is presented. The novelty of this work is in demonstrating that detector geometry improves signal purity by defining a constrained solid angle and enabling coincidence filtering, thereby reducing uncorrelated background and local electronic noise. The system was deployed during the 2024 total solar eclipse, demonstrating stable field operation and reliable flux monitoring. The mechanical design, coincidence logic implementation, and performance characterization of the instrument are described. Overall, this work demonstrates a scalable, robust, and inexpensive architecture suitable for geographically distributed muon flux monitoring arrays.
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All authors Ishannita Banerjee, Swagato Banerjee, Douglas Jackson, John Naber

Geophysics

High-resolution measurement of sea ice mechanical characteristics using Distributed Acoustic Sensing

Sébastien Kuchly, Ludovic Moreau, Vasco Zanchi et al. (+6 more)

Sea ice mechanical properties are involved in dynamical processes acting from the scale of meters to several hundred kilometers. The current rapid changes in the state of polar sea ice require a better understanding and modeling of these processes and, therefore, accurate measurements of properties including sea ice thickness, density, Young's modulus and Poisson's ratio. These properties can be measured by tracking the propagation of elastic waves within the ice. Recent technological advances have enabled the use of fiber-optic cables as cost-effective, dense seismic arrays. Once connected to an interrogator unit and mechanically coupled to a medium, here the ice cover, these cables can monitor strain field propagation, using a technique called Distributed Acoustic Sensing (DAS). In this work, we describe the use of such an array of sensors in the coastal ice of the St. Lawrence Estuary, Canada, where a 600 m long optical fiber was deployed across three different morphological sea ice conditions. During hour-long recordings, we measured the propagation of both multi-modal seismic signals generated by active sources and hydro-elastic swell. We computed dispersion curves of active signals and used Continuous Wavelet Transform (CWT) to observe the evolution of swell characteristics in the different ice areas. The dispersion curves were successfully inverted to measure the spatial evolution of ice thickness, and Young's and flexural rigidity in each of these areas. We observed ice thicknesses from 25 cm to 68 cm and Young's modulus values between 4.5 GPa and 5.7 GPa, in good agreement with values derived from collocated geophone arrays and drill hole thickness measurements. DAS systems therefore appear to be effective in evaluating heterogeneous sea ice mechanical properties and thus sea ice formation history and dynamics.
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All authors Sébastien Kuchly, Ludovic Moreau, Vasco Zanchi, Nicolas Mokus, Véronique Dansereau, Madison M. Smith, Dany Dumont, Stéphane Perrard, Antonin Eddi

Plasma Physics

Vortex Solitons and Filamentation of Electromagnetic Beams in Relativistically Degenerate Plasmas

Nikolai Maltsev and Vazha I. Berezhiani

We study the propagation and stability of electromagnetic vortex beams in relativistically de generate plasmas. We show that such plasmas support localized vortex solitons carrying orbital angular momentum and analyze their linear and nonlinear stability. Vortex solitons undergo az imuthal symmetry-breaking instabilities whose growth rates depend on beam power, propagation constant, and topological charge, with the dominant mode determining the number of filaments formed during breakup. We further demonstrate that vortex solitons act as nonlinear attractors with a finite basin of attraction, while the vortex core remains topologically protected, maintaining a strictly zero field intensity at the beam center throughout the evolution. The results persist across a broad range of degeneracy parameters and are relevant to hard X-ray radiation propagating in dense astrophysical plasmas.
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