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Physics Physics

physics Watch Physics

Wednesday 22 July

Applied Physics

Elastic Trapped States at Dislocation Defects in Scaled Coupling and Hofstadter Models

Yangkai Liu, Cheng Lin, Yuan Liu et al. (+4 more)

Elastic topological dislocations provide a pathway for trapping elastic wave energy at internal defects, rather than being confined solely to external boundaries or corners, which are typically associated with topological insulators (TIs). However, two practical constraints persist. First, highly confined dislocation states based on conventional Su-Schrieffer-Heeger (SSH) dimerization usually require a large coupling contrast and a correspondingly enlarged bandgap, which may be challenging to realize. Second, some Hamiltonians with richer topological physics often contain complex hopping terms, synthetic gauge fields or nonlocal couplings, which substantially increase the geometric complexity of experimental samples. Here, dislocation-induced trapped states are demonstrated in both a scaled coupling (SC) model and a Hofstadter model (HM) within an elastic platform. In the SC model, the trapped mode is treated as a higher localized state in the continuum rather than an in-gap mode in the SSH model. Consequently, the SC-induced dislocation can trap an enhanced mode without the requirement of an enlarged bandgap. For the HM, Householder tridiagonalization is used to map the original tight-binding Hamiltonian with complex hopping terms onto a tridiagonal matrix with only positive-real-valued nearest-neighbour (NN) hopping terms. Truncation at a weak-hopping position preserves the topological phenomena and allows a dislocation defect to be constructed from the shortened aperiodic chain. The results establish a practical route for designing highly localized modes without relying solely on bandgap enlargement or complex couplings, which advance the topological physics of elastic wave systems and promise enhanced possibilities for elastic functional devices.
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All authors Yangkai Liu, Cheng Lin, Yuan Liu, Jiao Shen, Yifan Zhu, Haiyan Fan, Hui Zhang

Optics

Band Engineering of Exciton Polaritons in Resonant Polaritonic Metasurfaces

Polina Pantiukhina, Daria Smirnova and Kirill Koshelev

Polaritonic metasurfaces provide a versatile platform for engineering hybrid light-matter states through the interplay of optical resonances and excitonic excitations. Yet, predictive models often remain phenomenological and rely on coupled-mode equations. Here, we develop an effective Hamiltonian framework for exciton polaritons in resonant polaritonic metasurfaces, derived from a semiclassical single-pole description of excitonic polarization and a Green's-function description of guided-mode resonances. The resulting non-Hermitian Hamiltonian rigorously incorporates resonant photonic harmonics, multiple excitonic degrees of freedom, and radiative losses. The model reveals selection rules governing photonic-excitonic coupling classified by orbital multipole index and polarization, and shows that the minimal number of excitonic degrees of freedom equals the number of relevant photonic modes. We apply the framework to a bulk van der Waals WS$_2$ metasurface patterned into a hexagonal lattice of triangular holes and uncover a new geometry-controlled topological transition driven by dipole-quadrupole band inversion, distinct from the conventional breathing-honeycomb-lattice transition. Full-wave simulations confirm the predicted topological phase diagram and the emergence of photonic and polaritonic edge states at a topological interface. Our results establish a theoretical multimode framework for geometry-controlled bandstructure engineering in polaritonic metasurfaces, with applications in topological, chiral, and quantum integrated photonics.
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Atomic Physics

Toroidal Transitions in Hydrogenic and Alkali Atoms

Kai Xiang Lee, Vincent Mancois, Kelvin Lim et al. (+1 more)

In addition to electric and magnetic multipoles, the expansion of current density also yields toroidal terms, a lesser-known family of multipoles. A recent proposal, I. Kuprov $\textit{et al.}$, Science Adv. 8 abq6751 (2022), explores the possibility of a direct observation of optical toroidal transitions in hydrogen and alkali atoms in the presence of a large magnetic field that decouples the spin and the angular momentum of the electron. However, the difficulty of observing these transitions against the nearby electric dipole (E1) transitions were underestimated because of extra admixture coming from diamagnetic coupling. Here, we revisit the toroidal coupling in atoms, taking diamagnetic contribution into account, and discuss the technical challenges of observing toroidal coupling in atomic physics. We show that toroidal transition should be searched in transitions with low principal quantum numbers. The remaining strong electric-dipole contribution could be removed using an appropriate differential measurement.
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All authors Kai Xiang Lee, Vincent Mancois, Kelvin Lim, David Wilkowski

Optics · Cross-listed from cond-mat.str-el

Spatially Dispersive Second-Harmonic Generation in Ferroaxial Systems

Takumi Shiro and Satoru Hayami

Spatially dispersive second-harmonic generation (SHG) provides a powerful probe of centrosymmetric multipolar states beyond the electric-dipole approximation. We develop a gauge-consistent microscopic theory of spatially dispersive SHG that treats electric-quadrupole (EQ) and magnetic-dipole (MD) processes on equal footing. Applying the formulation to a minimal triangular cluster model with ferroaxial order, which is closely related to an electric toroidal dipole, we show that the nonlinear optical response directly reflects the ferroaxial order parameter. The agreement between length- and velocity-gauge calculations confirms the gauge consistency of the formulation. We further demonstrate that the EQ and MD contributions exhibit different spectral weights despite sharing the same resonance energies. In particular, the MD channel can dominate over the EQ channel at selected resonances, indicating that it is not merely a perturbative correction. Our results establish that both EQ and MD processes are essential for a quantitative description of spatially dispersive SHG in ferroaxial materials and provide a microscopic basis for interpreting nonlinear optical signatures of centrosymmetric multipolar order.
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Optics

Super-Resonance: Interference-Driven Suppression of Radiative Decay Across Wave Physics

Igor V. Minin, Oleg V. Minin and Ilia L. Rasskazov

Super-resonance has been coined independently for collective modes of acoustic cavity arrays (Tolstoy), extreme high-$Q$ states of dielectric resonators in photonics, and magnon-polaron bound states in magnonics, and is now applied interchangeably to physically distinct phenomena. We organise this review around the one usage admitting a precise, field-agnostic definition: a mode whose radiative linewidth is driven toward zero by destructive interference among its radiation channels, $\gamma_{\rm rad}/\gamma_{\rm rad}^{\rm cl}\to0$, while the bare single-channel coupling remains large. The canonical realisation is the Friedrich-Wintgen scenario of two modes sharing a continuum. The same non-Hermitian eigenvalue structure recurs in Tolstoy's acoustic arrays, photonic bound states in the continuum and quasi-BIC supercavity modes, anapoles, dark modes of coherent perfect absorbers, parity-time-symmetric devices near exceptional points, magnonic dark modes, and topological edge modes. We survey these realisations field by field and distil transferable design rules and figures of merit. We then disambiguate super-resonance from two families sharing the "super-" prefix: coherent enhancement, in which coupling to the continuum is collectively increased rather than suppressed (Dicke super-radiance, superscattering, whispering-gallery modes); and integer-commensurability locking (mean-motion, wave-particle, and Floquet resonances). Amplification, as in black-hole super-radiance, is likewise distinguished.
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Chemical Physics

Hypothesis-and-Refinement Learning of Organic Structures from Multimodal Spectroscopic Data

Chengchun Liu, Zhiyuan Yan, Li Yuan et al. (+5 more)

Determining molecular structures from spectroscopic data remains fundamentally challenging because the inverse problem is intrinsically underdetermined: individual spectra are sparse, low-dimensional, and encode only partial structural evidence relative to the vast space of possible molecules. We address this challenge by formulating automated structure elucidation as a scalable hypothesis-refinement paradigm that tightly integrates spectral evidence with large-scale molecular priors. To supply structure-resolving NMR signals for multimodal learning, we construct QM9SPIN, a DFT-derived dataset comprising diverse 1D and 2D spectra, including J-coupling, DEPT experiments, and explicit spin–spin interactions. On this foundation, we introduce SpectroMol, a spectrum-to-structure model that proposes chemically valid molecular hypotheses conditioned on multimodal spectral inputs. Complementarily, we develop MS-Mol2Mol, a high-resolution mass-constrained molecular generator that integrates molecular formula, exact mass, and degree of unsaturation within a conditional generative prior trained on 400 million molecules, ensuring global compositional consistency and chemically realistic refinement. The integrated system achieves 93.8% top-1 accuracy on the simulated benchmark, adapts effectively from simulated to experimental spectra with limited experimental fine-tuning, and further improves experimental predictions through mass-guided refinement, establishing a scalable route toward automated, data-driven organic structure elucidation.
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All authors Chengchun Liu, Zhiyuan Yan, Li Yuan, Hao Li, Boxuan Zhao, Yonghong Tian, Bartosz A. Grzybowski, Fanyang Mo

Physics Education

The Collection of Didactic Physics Instruments of the Istituto Maria SS.ma del Rosario in Palermo

Aurelio Agliolo Gallitto

In the autumn of 2025, the Istituto Maria SS.ma del Rosario (IMSSR) in Palermo donated a collection of didactic physics instruments to the Department of Physics and Chemistry - Emilio Segre' of the University of Palermo, Italy. The instruments have been identified, catalogued, classified by disciplinary area, and are now displayed within the Historical Collection of Physics Instruments, housed in the historic building at 36 Via Archirafi, Palermo. The collection, consisting of approximately sixty instruments primarily intended for teaching classical physics at the upper-secondary school programmes, represents a significant example of the experimental culture of physics education in the first half of the twentieth century. This paper reconstructs the historical origins of the collection, illustrates its disciplinary areas and the main typologies of instruments, and analyses its scientific and educational value from a descriptive and historical museological perspective, with particular attention to the role of commercial catalogues as tools of didactic and technical mediation.
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Optics · Cross-listed from cond-mat.mtrl-sci

Numerical exploration on unveiling the photovoltaic potential of MgXS3(X = Ti, Zr, Hf) chalcogenide perovskites

Md. Mizanur Rahman, Md. Nahid Hasan, Tanvir Ahmed et al. (+1 more)

Lead-free chalcogenide perovskites offer a nontoxic and thermally robust path beyond Pb-based perovskite solar cells (PSCs), but their device-level behavior in realistic three-dimensional geometries remains insufficiently characterized. In this work, we investigate ZnSe/MgXS3(X = Ti, Zr, Hf)/Sb2S3 solar cell architecture where MgXS3 absorbers from the II-IV-VI chalcogenide perovskite family is employed as the absorber layer. The device is analyzed using 3D finite-element simulations in COMSOL Multiphysics that self-consistently couple optical generation, drift-diffusion carrier transport, and heat transfer under AM 1.5G 1-sun illumination, following a fully coupled opto-electro-thermal framework. For each absorber composition, the impacts of absorber thickness, doping, and defect density are systematically investigated, and the contribution of an Sb2S3 back-surface-field (BSF) layer to carrier collection and spectral response is quantified. Under optimized conditions, MgZrS3, MgTiS3, MgHfS3-based devices achieves a simulated power conversion efficiency (PCE) of 28.18%, 26.72%, and 28.16%, respectively. The corresponding open-circuit voltage (VOC) values are 0.94 V, 0.74 V, and, 1.07 V while the short-circuit current density (JSC) values are 34.46 mA/cm2, 42.69 mA/cm2, and 29.89 mA/cm2, with fill factor (FF) values of 86.99%, 84.58%, and 88.02%, respectively. Coupled electro-thermal simulations further reveal a small spatially non-uniform steady-state temperature rise across the ultrathin cell stack, mainly governed by non-radiative recombination and Joule dissipation within the active layers. Overall, these results confirm MgXS3(X = Ti, Zr, Hf) chalcogenide perovskites as promising lead-free absorber materials and offer practical design guidance for achieving high-efficiency, thermally stable three-dimensional device architectures.
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All authors Md. Mizanur Rahman, Md. Nahid Hasan, Tanvir Ahmed, Jaker Hossain

Fluid Dynamics

The spectral picture of self-similar collapse in the Constantin-Lax-Majda equation

Jie Xu

We give a spectral description of the self-similar collapse profile of the Constantin-Lax-Majda (CLM) equation, the $a=0$ anchor of the generalized family $w_t + a\,u\,w_x = u_x\,w$, $u_x = Hw$. Linearizing about the exact profile $\Omega(y) = -y/(y^2+1/4)$ and realizing $L_0$ as a closed operator on the origin-$H^2$ space, we prove three things at $a=0$. Its essential spectrum meets the closed half-plane $\{\mathrm{Re}\,\lambda \ge -1/2\}$ in the single vertical line $\{\mathrm{Re}\,\lambda = -1/2\}$: the line is placed by a log-widening Weyl sequence, and an explicit Hardy-Mellin resolvent bound constructively empties the rest of the half-plane apart from $0$ and $1$. Its full point spectrum over $\mathbb{C}$, on the odd realization, is exactly $\{0,1\}$, the scaling and time-shift symmetry modes, with no embedded eigenvalues; removing these by the standard modulation leaves a spectral gap of $1/2$ on $X$. The linear semigroup and its exact decay rate $e^{-\tau/2}$ are computed in closed form, but on a weighted space of the conjugated variable reached from $X$ by a bounded transfer map; we keep the two separate, since $L_0$ is non-normal and a spectral gap does not by itself give a decay rate in the $X$ norm. A realization dichotomy identifies the in-strip smear of generic discretizations as the faithful spectrum of the maximal $L^2$ realization, which origin-$H^2$ removes. For $a>0$ we prove a conditional two-line inclusion for each admissible smooth focusing profile, recompute the branch $c_l(a)$ of Lushnikov, Silantyev, and Siegel as a cross-check, and record the formal scaling-relevance exponent $s^*(a) = 1/c_l(a)$, below which fractional dissipation is asymptotically subdominant in self-similar variables for fixed sufficiently regular data. The contribution is the realization-dependent spectral picture of the collapse profile itself.
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Physics and Society

From risk to flourishing: Seeds for responding to a complex world

Ryan M. McGranaghan, Elisabeth H. Krueger, Alexandre Dunant et al. (+6 more)

Complex risk arises when interacting hazards, infrastructures, ecological systems, institutions, and human behaviors produce nonlinear impacts that cannot be inferred from any component in isolation. We call the study of these dynamics complex risk science. Flourishing is the actualization of all beings toward their good–individually and collectively–answering the question of `how do we live well with and for each other?'. In science as in society, the tendency to reduce, segregate, specialize, and settle has precluded embracing the concept of flourishing as a guiding principle. We describe how complex risk science reframes risk science research so that it can promote the flourishing of socio-ecological-technological systems, and explore how its practice may point society toward a more flourishing future. Our exploration mirrors the unsettled and searching nature of flourishing: examine ideologies traditionally believed to be rigidly in opposition and consider what emerges in the space(s) and conversation between them. We call this a dialectical approach: not a means of resolving contradiction, but a practice of sustaining it, so that systems, and our understanding of them, remain capable of reframing as conditions change. Within this dialectical paradigm, we revisit longstanding tensions in risk science: physical|social, determinism|uncertainty, and contextuality|generality. Examining the conversation among these tensions reveals five seeds that are dispositions for practicing complex risk science: interdependence, responsivity, participation, pluralism, and ongoingness. They can support any scientific endeavor to embrace complexity and promote flourishing. Practicing these seeds at scale will depend on institutional reform: creating collectives toward complex risk science, supporting them with skillfully governed commons, and centering care in our research and evaluation.
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All authors Ryan M. McGranaghan, Elisabeth H. Krueger, Alexandre Dunant, Guillaume Falmagne, Lynee L. Turek-Hankins, Sara M. Constantino, Raissa D'Souza, Elke U. Weber, Graydon W. Manzke

Chemical Physics

Nuclear Quantum Effects as a Denoising Problem

Weizhou Wang, Jonathan Weare and Aaron R. Dinner

Nuclear quantum effects are rigorously captured by imaginary-time path integrals, which map the quantum Boltzmann distribution onto a ring polymer of classical replicas. Yet the nuclear masses, the coupling to the environment, and the boundary conditions of the path remain hard-wired in the simulation or the trained model, even though this quantum context enters the path measure only through a quadratic action known in closed form. Here we show that a denoiser trained on classical Boltzmann statistics alone, composed at sampling time with an analytic Gaussian component carrying the entire quantum context, yields the quantum Boltzmann distribution of the nuclei. Such a composition exists and is exact whenever the training noise does not exceed the intrinsic quantum uncertainty of the target ensemble, and it is invariant across all quantum contexts admitted by this bound. We show exact transfer across temperature, isotopic mass, dissipation strength, and the boundary conditions of the path in theory and in numerical experiments, without retraining. The last yields the end-to-end displacement and momentum distributions of a tagged nucleus from open imaginary-time paths. The same invariance extends in principle to the permuted boundary conditions of bosonic exchange, with the identical denoiser. In this view, the noise of generative modeling and the quantum fluctuations of the nuclei are two faces of the same quadratic structure.
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Optics

An integrated super resolution THz 3D imaging system based on a linear nonlocal achromatic freeform Bessel beam lens and high power oscillator radiator array

Jin Chen, Liang Gao, Hao Guo et al. (+5 more)

High performance terahertz (THz) 3D imaging is critical for non-destructive evaluation. However, conventional architectures are fundamentally limited by severe chromatic aberrations, modest spatial resolution, restricted depths of focus (DOF), and the bulky nature of commercial transceivers. While metasurfaces offer a compact alternative, achieving broadband achromatic super-resolution with an extended DOF remains a formidable challenge. Here, we present a highly integrated 3D THz imaging platform that synergizes a 3D printed nonlocal freeform Bessel-beam lens with a high power, 65nm CMOS oscillator radiator array. Harnessing nonlocal interactions within the lens, we generate an achromatic super resolution Bessel beam (0.3 to 1 THz) with a subdiffraction full width at half maximum (FWHM) of 0.65{\lambda} and a robust 4.7-mm DOF. Crucially, the system overcomes conventional sidelobe limitations, enabling high-fidelity 2D imaging of intricate sub-millimeter targets (e.g., USAF 1951 charts and QR codes) alongside robust 3D volumetric imaging through highly scattering media, such as printed circuit boards. By converging standard CMOS technology with additive manufacturing, this work establishes a versatile, cost-effective paradigm for next-generation integrated THz photonics
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All authors Jin Chen, Liang Gao, Hao Guo, Zhi Chao Chen, Kang Jie Lin, Kam Man Shum, Ka Fai Chan, Chi Hou Chan

Optics · Cross-listed from nlin.SI

On the global well-posedness for the nonlocal Fokas-Lenells equation with the weighted Sobolev initial data on the line

Zhenya Yan, Guoqiang Zhang and Guancheng Zhu

We establish the global well-posedness of the Cauchy problem for the reverse space-time nonlocal Fokas-Lenells equation with the weighted Sobolev initial data $q_0(x)\in H^{3}(\mathbb{R}) \cap H^{2,1}(\mathbb{R})$ on the line. We develop the inverse scattering transform formulated via the associated Riemann-Hilbert problems to study this issue. A spectral uniformization transform is introduced to resolve the singular behavior inherent in the KN-type negative flow spectral problem. Owing to the reverse space-time reduction, reflection coefficients no longer satisfy the usual Hermitian conjugation symmetry, and the coercivity of the jump matrix is therefore not available a priori. The quantitative smallness condition on the initial data yields uniform bounds on the reflection coefficients and ensures the uniform positive definiteness of the Hermitian part of the associated jump matrix. The resulting coercivity allows us to establish the bounded invertibility of the associated singular integral operator through a Fredholm and vanishing-lemma argument. Under this condition, we prove an $L^{2}$-Sobolev bijective correspondence between the potential and scattering data, exclude spectral singularities on continuous spectra, and obtain the global existence and uniqueness of solutions. Moreover, the associated solution map is Lipschitz continuous on the admissible initial-data class.
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Biological Physics

Decoding molecular distributional codes through collective instabilities

Mason N. Rouches, Dongyang Li, Michael B. Elowitz et al. (+1 more)

Biological information is often encoded in molecular variants that differ in just a few chemical traits, such as the number of phosphorylated sites or ubiquitin chain length, rather than in arbitrarily distinct species. These molecular distributions carry information about cellular state, yet reading them with conventional molecular circuits requires prohibitively many distinct sensors. In contrast, we show that collective physical instabilities can naturally integrate the information encoded in such distributions. Using an information-theoretic matching condition between an encoded distribution and a physical readout, we derive a geometric condition that any good decoder must satisfy, and establish that phase separation, percolation, and membrane curvature instabilities all approach it for biologically natural distributions while simple mass-action binding does not. Using mean-field theory and lattice Monte Carlo simulations, we find that phase separation reads the shape of a distribution beyond its mean, robustly capturing its variance and, more weakly, its skewness, whereas mass-action binding detects only the mean. Near phase boundaries the readout captures nearly all the information present in the molecular population. Finite valency, through the threshold for network formation, adds discriminatory power invisible to mean-field theory. These results suggest that cells can exploit collective physical instabilities as natural, compact, yet near-optimal sensors for decoding molecular distributional codes.
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All authors Mason N. Rouches, Dongyang Li, Michael B. Elowitz, Arvind Murugan

Tuesday 21 July

Instrumentation and Detectors

Cavity optomechanical magnetometer actuated by substrate bending

D. D. Florizone, I. E. Rabuka, K. D. Hiltz et al. (+5 more)

We describe a magnetic field sensor based on a monolithic Fabry-Perot cavity. The cavities were fabricated in a thin-film buckling process at one surface of a fused silica chip, and the chip was subsequently bonded to a giant magnetostrictive material (GMM). External magnetic fields drive flexural modes of the assembly and the associated bending stresses are efficiently mapped to changes in the cavity height, with enhanced response at kHz-range mechanical resonance frequencies. A key attribute of this platform is that the size of the transducing material is decoupled from the size of the optical cavity. The buckled cavity operates in low mode order and with moderate Q ~ 103, providing a high optomechanical coupling coefficient while also enabling a straightforward tuned-to-slope readout technique. Peak sensitivity ~ 2 pT/Hz1/2 was achieved in an unshielded laboratory environment, limited by laser phase and electronics noise in the readout system. With future reductions in these noise sources, we predict that a broadband thermomechanical-noise-limited sensitivity in the ~ 0.1 pT/Hz1/2 range is feasible.
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All authors D. D. Florizone, I. E. Rabuka, K. D. Hiltz, I. Grobbellaar, E. F. DeCorby, A. Chen, K. G. Scheuer, R. G. DeCorby

Chemical Physics · Cross-listed from quant-ph

Quantum-Classical Fragmentation with the Effective Fragment Molecular Orbital Method

Federico Zahariev, Vassiliki-Alexandra Glezakou and Mark S. Gordon

We present the quantum effective fragment molecular orbital (Q-EFMO) method, a hybrid framework that evaluates selected molecular-fragment correlation energies with the variational quantum eigensolver and assembles them through the size-consistent EFMO energy expression. A Hartree-Fock EFMO calculation supplies monomer references, many-body polarization, and distant-pair EFP interactions; independent VQE/UCCSD calculations provide correlation increments for monomers and selected near-field dimers. Consequently, the maximum quantum register is determined by the largest active fragment or fragment pair rather than by total system size. For a three-layer LiH benchmark in STO-3G, a full 2.5 to 3.5 Angstrom separation scan shows that two orbital-reduction schemes approach the full CCSD reference monotonically. The more aggressive scheme remains below 1 kcal/mol for separations of 2.6 Angstrom and greater and reaches 0.10 kcal/mol at 3.5 Angstrom, using 6 qubits for monomers and 12 for the largest dimers, compared with 14 qubits for the frozen-core dimer baseline. An implementation-specific cost proxy decreases from 1000 to 40, a factor of 25. These noise-free results establish the equations, software path, and resource scaling; broader chemical validation, larger bases, and hardware tests remain necessary.
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Chemical Physics · Cross-listed from quant-ph

Quantum-Classical Effective Fragment Potential Embedding for Condensed-Phase Quantum Chemistry

Federico Zahariev, Vassiliki-Alexandra Glezakou and Mark S. Gordon

Quantum simulation of chemistry in realistic environments is constrained by the orbital cost of explicit solvent, ions, and other surroundings. We present the quantum-classical effective fragment potential (Q-EFP) method, in which a chemically active region is treated with a quantum algorithm and the environment is represented by the effective fragment potential (EFP) in GAMESS. Coulomb and polarization potentials enter the active-region one-electron Hamiltonian, while EFP-EFP and short-range environment contributions are assembled classically. Statevector UCCSD/STO-3G benchmarks for LiH in a mixed water/methanol environment, H2O in a five-water environment, and BeH2 in an ammonium/nitrate environment differ from matched classical CCSD/EFP calculations by 0.03, 0.38, and 0.01 kcal/mol, respectively. The active calculations require 4 to 8 qubits, compared with estimated full-system counts of approximately 84 to 246 qubits, corresponding to register reductions of about 10-fold to 35-fold. These proof-of-concept results validate the embedded Hamiltonian and Q-GAMESS workflow while separating environmental size from quantum-register size. Q-EFP is complementary to real-space Q-EFMO fragmentation and virtual-orbital Q-FVO reduction, enabling a layered route to larger solvated systems.
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Plasma Physics · Cross-listed from astro-ph.HE

Chaotic cosmic ray acceleration in nonlinear Alfven waves

Maxim Lyutikov

We demonstrate that motion of a particle in a single coherent linearly polarized (LP) Alfven wave with relative amplitude $\delta = B_w /B_0 \gtrsim 0.25 $ becomes chaotic. As a result, a sufficiently strong, near resonant Alfven waves ($r_L k_\parallel \sim 1$, $r_L $ is relativistic cyclotron radius, $k_\parallel$ is wavevector) can lead to transient trapping and phase mixing, imitating classical scattering. Evolution of pitch angle via Alfven chaos is non-diffusive - a particle on trapped trajectory can reverse its velocity in one scattering event. This both avoids the problem of the 90$^\circ$ barrier, and increases the acceleration rate for those special particle.
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Optics · Cross-listed from cs.CV

scMIR: a vision-language foundation model for single-cell light microscopy image representation

Yifan Shang, Jiahui Tan, Xiangxiang Zeng et al. (+1 more)

Single-cell light microscopy images have become an important data source for characterizing cell phenotypes, but their complexity and heterogeneity pose challenges to high-throughput automated analysis. Existing representation learning methods mostly rely on task-oriented modeling, which is limited by specific datasets and predefined tasks, making them difficult to generalize across different cell types and microscopy modalities, and experimental conditions. Although general-purpose methods have improved the generalization ability of image representation in recent years, their limited utilization of experimental background and biological context information still poses challenges in complex phenotypic analysis. Here, we propose scMIR, a vision-language foundation model for single-cell light microscopy image representation. By synergistically combining self-supervised image reconstruction with text-guided cross-modal alignment, scMIR can simultaneously encode morphological and biological semantic information in a unified representation space. scMIR is pre-trained on 207,957 image-text pairs, covering various cell types, microscopy modalities, and perturbation conditions. scMIR outperforms existing general models and task-oriented methods as systematically evaluated on various complex tasks using 16 benchmark datasets, including cell classification, clustering, phenotype inference, and batch effect correction tasks. Furthermore, scMIR shows a strong generalization ability across various tasks without requiring task-specific fine-tuning. With its unique advantages, we envision scMIR may promote the standardization and automation of high-throughput phenotyping workflows through supporting various downstream analysis tasks.
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All authors Yifan Shang, Jiahui Tan, Xiangxiang Zeng, Renjie Zhou

Fluid Dynamics

Influence of Electrohydrodynamic on Droplet Stability in Leaky Dielectric Media

Saurabh Sharma, Franck Lefebvre, Mostafa S Shadloo et al. (+1 more)

This work examines the deformation dynamics of dielectric liquid droplet when exposed to a uniform electric field. The experimental investigation involves two-phase configurations, here as silicone oil droplets suspended in castor oil. The droplet dynamics including deformation, elongation, oscillation, and rotation are investigated over a range of electric field strengths using shadow-imaging. In parallel, fluorescent tracer particles were employed to perform threedimensional Lagrangian Particle Tracking (3D-LPT) using the Shake-The-Box (STB) technique, allowing for a detailed characterization of the internal electrohydrodynamic flow within the droplet subjected to a uniform electric field. For silicone oil droplets in castor oil medium (S/R > 1), the droplets initially deform into oblate shape. At sufficiently high electric field strengths, the droplet undergoes an Electrohydrodynamic instability, aligning their axis at an angle to the direction of electric field due to the imbalance in induce electric torque. Upon further increasing the field strength, the droplets display oscillatory deformation before settling into a transiently stable configuration. The current study identifies and characterizes the distinct regimes of droplet behaviour, from initial deformation at low electric fields to oscillatory behaviour at high field strengths depending upon the relative dielectric and fluid properties of the liquid phases.
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All authors Saurabh Sharma, Franck Lefebvre, Mostafa S Shadloo, Bertrand Lecordier

General Physics

Gravitational Effects on Light Propagation in Linear Magnetoelectrics and Plasmas

Elda Guzmán-Herrera, Vitorio A. De Lorenci and Renato Klippert

A covariant formalism for electromagnetism is used to investigate the effects of light propagation within certain material systems under the influence of a background gravitational field. Specifically, dielectric media described by linear constitutive relations, as well as magnetized plasma media, such as the magnetosphere of neutron stars, are examined. Estimates for detecting gravitational effects through precise refractive index measurements within these scenarios are provided.
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Fluid Dynamics

svMultiPhysics: a finite element-based solver for cardiovascular simulations

David Codoni, Sujal Dave, David W. Parker et al. (+10 more)

Heart disease remains the leading cause of death in the United States, motivating extensive efforts to improve its diagnosis, treatment, and prevention. Over the past decade, computational modeling has emerged as a powerful tool to advance cardiovascular research by enabling detailed, patient-specific studies of cardiac physiology and pathology. svMultiPhysics is an open-source, parallel finite element solver written in C++ specifically designed for multiphysics cardiovascular problems. It provides a unified framework for simulating the partial differential equations that govern solid mechanics, fluid dynamics, diffusion, and cardiac electrophysiology. These equations can be solved independently or in a coupled fashion, allowing researchers to investigate interactions between physical processes in a modular yet integrated way. The solver's main strength lies in its ability to seamlessly couple multiple physics modules, enabling the study of complex, highly nonlinear systems. For example, svMultiPhysics can capture the interplay between cardiac electrophysiology, myocardial tissue mechanics, and blood flow dynamics, processes that are essential to understanding vascular and cardiac physiology and function in health and disease. Preliminary GPU-enabled simulations show up to approximately $30\times$ wall-clock speedup for selected linear solver configurations over CPU-based simulations. By offering a robust, extensible, and freely available platform, svMultiPhysics empowers researchers to explore multiphysics problems in cardiovascular science. As the primary 3D solver in the SimVascular open source project, it forms a key component of an end-to-end open source software ecosystem for image based patient specific modeling in the cardiovascular system. It is maintained and openly developed on GitHub, fostering transparency, reproducibility, and collaboration.
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All authors David Codoni, Sujal Dave, David W. Parker, Aaron L. Brown, Javiera Jilberto, Han Zhao, Divya Adil, Zachary A. Sexton, Martin R. Pfaller, Michele Bucelli, Shawn C. Shadden, Charles A. Taylor, Alison L. Marsden

Optics

Controllable localization and manipulation of optical hollow traps by means of optical-vortex diffraction

O.V. Angelsky, A.Y. Bekshaev, C.Y. Zenkova et al. (+2 more)

An optical vortex (OV) is coupled with the local intensity zero and is thus a field configuration suitable for "hollow" optical traps and optical tweezers. When an incident circular OV beam experiences diffraction at a rectilinear screen edge (SE), and the conditions of weak diffraction perturbation (the SE is far enough from the beam axis) are fulfilled, the main consequence is the OV-core displacement from its initial (axial) position. Based on the model of incident Laguerre-Gaussian (LG) beam, we investigate analytically and numerically the ways of controlling the OV-core position in the diffracted-field cross section by means of changing the SE position with respect to the incident-beam axis. The results show that regulating the SE position with ~1 mcm accuracy (which is available for existing mechanical tools), controllable OV-core motion with a sub-nanometer accuracy can be realized. Possible modifications of this motion depending on the incident beam topological charge, wavefront curvature, SE properties (semitransparent screen, phase-step screen) and the distance between the diffraction plane and the observation plane are analyzed. The conditions most favorable for the micro-object trapping and manipulation are specified and discussed.
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All authors O.V. Angelsky, A.Y. Bekshaev, C.Y. Zenkova, I.I. Mokhun, X. Zhang

Optics

Self-stabilization of microcombs

Krishna Twayana, Fuchuan Lei, Junyong Choi et al. (+2 more)

Optical frequency combs form phase-locked spectral lines arranged on an equidistant grid fully defined by two degrees of freedom, i.e., the repetition rate and frequency offset. Stabilizing these parameters to a common frequency reference results in a coherent frequency ruler, central for modern precision metrology. However, extending this level of stability to chip-scale microcombs remains an outstanding challenge. Here, we demonstrate a self-stabilizing mechanism based on self-injection locking of a selected comb line via an external feedback loop. This process establishes a second anchor point in addition to the pump, thereby constraining the comb's frequency noise dynamics. We show that, with an appropriate choice between pump frequency noise and feedback strength, collective fluctuations of the repetition rate are strongly suppressed. The result is a microcomb exhibiting ultralow phase noise and dramatically reduced timing jitter. In a 100 GHz silicon nitride soliton microcomb, we achieve an unprecedented combination of high-conversion efficiency, sub-Hertz intrinsic linewidth across the entire C band, and an integrated timing jitter of 1 fs. This approach enables chip-scale microcombs with remarkable noise performance and fs-level pulse stability, surpassing conventional noise limits and opening new avenues for precision metrology at the chip scale.
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All authors Krishna Twayana, Fuchuan Lei, Junyong Choi, Jungwon Kim, Victor Torres-Company

Accelerator Physics

Design Study of an Endless RF Phase Shifter Using Ferroelectric Capacitors

Ilan Ben-Zvi

An endless radio-frequency (RF) phase shifter is designed using ferroelectric capacitors. An endless phase winds continuously and without bound while every control voltage executes a bounded periodic cycle. A new scheme for an endless RF phase shifter is proposed and studied in the framework of an equivalent circuit. Besides the endless property, this phase shifter offers an exceptionally low insertion-loss, high-speed and high-power capability. The device may perform as an exact frequency translator whose offset is locked to the bias repetition frequency. Optimized realizations are given at 400 and 800 MHz with full conductor-loss accounting: 0.19 and 0.28 dB average insertion loss. A phase advance rate of a few microseconds per turn is limited only by the bias electronics, and power capability on the order of 100 kW may be achieved through stacked-wafer construction. An instantaneous bandwidth of approximately 2.5% is loss-limited rather than mechanism-limited. The design surpasses the best endless phase shifter in the literature, the rotary-field ferrite device, in speed, loss, and power, and improves on the serrodyne ferroelectric frequency translator in efficiency and drive electronics requirements.
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Geophysics

Juxtaposition of Shallow Reservoir-Triggered Seismicity and Deep Tectonic Locking in the Qiaojia-Dongchuan Seismic Gap

Yuxin Zhou, Huai Zhang, S. Mostafa Mousavi et al. (+5 more)

Identifying the critical state of mature seismic gaps is challenging, especially when anthropogenic stress perturbations, such as reservoir impoundment, superimpose on tectonic loading. Here, utilizing a high-resolution dense array catalog from the Qiaojia-Dongchuan seismic gap (hosting the second-largest hydropower station in the world), we reveal a distinct vertical decoupling mechanism. The shallow activities exhibit high b-values (1.0), indicative of fluid-driven reservoir-triggered seismicity. Conversely, deep seismicity (20 km) outlines a 'locked asperity' characterized by low b-values (less than 0.8) and high Coulomb stress accumulation rate. We further identify a complex dipping structure, suggesting compound fault kinematics. Additionally, the calculated stress accumulation suggests this seismic gap is in a critical state with elevated rupture potential. Our findings indicate that shallow induced seismicity can mask the silent accumulation of deep tectonic strain. This decoupling model provides a new framework for assessing seismic risks in reservoir-fault systems globally.
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All authors Yuxin Zhou, Huai Zhang, S. Mostafa Mousavi, Guangyao Yin, Pei He, Yicun Guo, Shuang Yi, Yaolin Shi

Biological Physics

Sensing, Traffic, and Construction in Termites

Yufei Xiao, Qinglin Wu, Kukhyun Lim et al. (+4 more)

Subterranean and mound-building termites excavate, transport, and build within the same granular substrate that later regulates how they sense, move, and deposit material. From antennal-scale contacts through body-scale traffic to meter-scale architecture, this review synthesizes three linked problems: how workers sense local geometry and physical cues during search and excavation; how traffic moves through narrow, evolving conduits; and how excavation and deposition remodel the substrate that guides later behavior. Across these length scales, noisy local interactions couple sensing, transport, and construction through a shared material medium, leading to emergent order at the colony scale. We emphasize what is established experimentally, where evidence remains sparse or limited to a few model systems, and how emerging imaging, tracking, and modeling tools are making these feedbacks quantitatively accessible. We use this synthesis to motivate a quantitative physics-of-life framework for termite colonies that continually rewrite the medium through which they sense, move, and build.
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All authors Yufei Xiao, Qinglin Wu, Kukhyun Lim, Nan-Yao Su, Paul Bardunias, Atanu Chatterjee, Saad Bhamla

Optics

Enantioselective optical trapping and characterization of all dielectric disorder-enabled chiral particles

Guilherme T. Moura, Tanja Schoger, Kainã G. Diniz et al. (+9 more)

We trap submicroscopic silica spheres coated with randomly distributed titanium dioxide nanoparticles in optical tweezers with Laguerre-Gaussian modes and observe orbital dynamics that differ from those of achiral silica spheres. We show that the disordered nanoparticle coating generates an effective chiral geometry, giving rise to enhanced enantioselective chiral optical forces and a measurable modification of the orbital period. A theoretical model based on the Mie-Debye formalism, including optical aberrations, not only quantitatively explains the experimental results but also allows to characterize the Pasteur parameter quantifying the chiroptical response of individual composite particles. These findings constitute direct experimental evidence of chiral optical forces exerted by structured light beams on individual chiral particles and identify disorder-enabled, all-dielectric particles as a versatile material platform to tailor chiral optical forces at the nanoscale.
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All authors Guilherme T. Moura, Tanja Schoger, Kainã G. Diniz, Marcel A. B. Morte, Diney S. Ether Jr, Leonardo de S. Menezes, Yicui Kang, Emiliano Cortés, Cyriaque Genet, Nathan B. Viana, Felipe A. Pinheiro, Paulo A. Maia Neto

Fluid Dynamics

Cavitation Acoustic Perturbation Equations: A Computational Framework for Source-Resolved Multiphase Hydroacoustics

Zhi Cheng and Rajeev K. Jaiman

This work develops a cavitation-consistent acoustic perturbation framework for predicting sound generation and propagation in cavitating flows. Unlike conventional acoustic perturbation equations for single-phase or weakly compressible flows, the proposed formulation embeds cavitation physics directly into the acoustic equations. The cavitation acoustic perturbation equations (CAPE) incorporate vapor mass transfer, mixture compressibility, and pressure-rate effects within a unified formulation, allowing cavitation-induced noise sources to be resolved in the computational domain. The numerical framework is verified using one-dimensional wave-propagation problems. The solutions become insensitive to further mesh and time-step refinement, the perfectly matched layer suppresses boundary reflections, and the predicted attenuation over a range of source frequencies follows Stokes' sound attenuation law. The framework is then applied to cavitating flow past a circular cylinder and a NACA hydrofoil. The non-cavitating benchmark shows dipole-like radiation associated with unsteady loading, whereas cavitating cases exhibit monopole-like or geometry-modulated radiation caused by volumetric phase change. Source-term analyses identify tonal frequencies associated with vortex shedding, cavity shedding, and collapse-induced excitation. The phase-change terms provide a direct volumetric contribution to the monopole-like source, while localized collapse events appear through amplification of the pressure-rate source. The proposed framework extends acoustic perturbation methods to cavitating multiphase flows and provides an efficient tool for hydroacoustic prediction, source localization, and mechanism analysis in marine and hydraulic applications.
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Fluid Dynamics

Sidewall effects on the onset of interfacial Holmboe waves in stratified exchange flows at high Schmidt number

Guilherme Siqueira de Aquino, Metten M. de Lange, Adrien Lefauve et al. (+1 more)

Predicting the onset of interfacial instabilities is central to understanding turbulent mixing in natural and engineered stratified shear flows. Here, we study the onset of travelling Holmboe waves in confined exchange flows along a slope. Earlier stratified inclined duct experiments have mapped this transition, and stability analyses based on measured or prescribed profiles have explained their emergence. However, a predictive criterion linking forcing, geometry, base flow, and wave onset was still lacking. We closed this gap with a long-duct, sharp-interface asymptotic theory for the three-dimensional laminar exchange flow, including the effects of sidewall friction. The resulting analytical solution naturally identifies a confinement-adjusted Froude number, $Fr^*$, which unifies the effects of forcing and confinement into a single measure of the effective laminar exchange flow. Using this solution to parameterise sidewall drag in a practical width-averaged model, we perform linear stability analyses and numerical simulations at high Schmidt number. Together, linear stability analysis, direct numerical simulations, and existing experiments across a range of duct widths show that wave onset is accurately predicted by an approximately constant critical value of $Fr^*$. Deviations arise only in very narrow ducts, where sidewalls influence instability not only by modifying the laminar exchange flow but also by directly damping perturbations and delaying wave onset. These findings provide a predictive criterion for wave onset, reconcile long-standing discrepancies among experimental configurations, and establish lateral confinement as a fundamental control on the transition from laminar exchange to wave-driven mixing in stratified shear flows.
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All authors Guilherme Siqueira de Aquino, Metten M. de Lange, Adrien Lefauve, Matias Duran-Matute