Chemical Physics
Foundation Models for Discovery and Exploration in Chemical Space
Alexius Wadell, Anoushka Bhutani, Victor Azumah et al. (+26 more)
Accurate prediction of atomistic, thermodynamic, and kinetic properties from molecular structures underpins materials innovation. Existing computational and experimental approaches lack the scalability required to navigate chemical space efficiently. Scientific foundation models trained on large unlabelled
datasets offer a path towards navigating chemical space across application domains. Here, we develop MIST, a family of molecular foundation models with up to an order of magnitude more parameters and data than prior works. Trained using a novel tokenizer, Smirk, which comprehensively captures
nuclear, electronic, and
geometric information, MIST learns a diverse range of molecules. MIST models have been fine-tuned to predict more than 400 structure-property relationships and have been shown to match or exceed state-of-the-art performance across diverse
benchmarks, from physiology to electrochemistry. We demonstrate the ability of these models to solve real-world problems across chemical space from multiobjective electrolyte solvent screening to stereochemical
reasoning for organometallics and mixture property prediction. The clearest demonstration of a foundation model is its ability to solve problems that were neither explicit targets of training nor central to the intentions of its developers. We identify olfactory perception mapping as such a problem, and show that MIST accurately predicted scent profiles and learned a hierarchical representation of olfactory space consistent with
hyperbolic geometry. We formulated hyperparameter aware
Bayesian neural scaling laws which eliminate the need for hyperparameter sweeps at every scale, making training large compute-optimal models feasible on a limited compute budget. The methods and findings presented here represent a significant step towards accelerating materials discovery, design, and optimization using foundation models.
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All authors Alexius Wadell, Anoushka Bhutani, Victor Azumah, Austin R. Ellis-Mohr, Andrew J. Stier, Kareem Hegazy, Alexander Brace, Hancheng Zhao, Celia Kelly, Anuj K. Nayak, Yuhan Chen, Dimitrios Simatos, Hongyi Lin, Murali Emani, Venkatram Vishwanath, Kevin Gering, Melisa Alkan, Tom Gibbs, Jack Wells, Wesley W. Qian, Richard C. Gerkin, Benjamin Amorelli, Alexander B. Wiltschko, Lav R. Varshney, Bharath Ramsundar, Karthik Duraisamy, Michael W. Mahoney, Arvind Ramanathan, Venkatasubramanian Viswanathan
Physics and Society
Production and Just Distribution in Diverse Society
Maria Roginskaya
In this paper, we want to investigate dynamics of productivity in a society which is diverse when it comes to both the productivity and the perception of justice in distribution.
Computational Physics · Cross-listed from quant-ph
A Quantum Algorithm for the Finite Element Method
Ahmad M. Alkadri, Tyler D. Kharazi, K. Birgitta Whaley et al. (+1 more)
The finite element method (FEM) is a cornerstone numerical technique for solving partial differential equations (PDEs). Here, we present $\textbf{Qu-FEM}$, a fault-tolerant era
quantum algorithm for the finite element method. In contrast to other
quantum PDE solvers, Qu-FEM preserves the
geometric flexibility of FEM by introducing two new primitives, the unit of interaction and the local-to-global indicator
matrix, which enable the assembly of global finite element arrays with a constant-size linear combination of
unitaries. We study the modified Poisson equation as an
elliptic problem of interest, and provide explicit
circuits for Qu-FEM in Cartesian domains. For problems with constant coefficients, our
algorithm admits block-encodings of global arrays that require only $\tilde{\mathcal{O}}\left(d^2 p^2 n\right)$ Clifford+$T$ gates for $d$-dimensional, order-$p$ tensor product elements on grids with $2^n$ degrees of freedom in each dimension, where $n$ is the number of
qubits representing the $N=2^n$ discrete grid points. For problems with spatially varying coefficients, we perform numerical integration directly on the
quantum computer to assemble global arrays and force vectors. Dirichlet boundary conditions are enforced via the method of Lagrange multipliers, eliminating the need to modify the block-encodings that emerge from the assembly procedure. This work presents a framework for extending the
geometric flexibility of
quantum PDE solvers while preserving the possibility of a
quantum advantage.
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All authors Ahmad M. Alkadri, Tyler D. Kharazi, K. Birgitta Whaley, Kranthi K. Mandadapu
Medical Physics
Measuring multi-site pulse transit time with an AI-enabled mmWave radar
Jiangyifei Zhu, Kuang Yuan, Akarsh Prabhakara et al. (+5 more)
Pulse Transit Time (PTT) is a measure of arterial stiffness and a physiological marker associated with cardiovascular function, with an inverse relationship to diastolic blood pressure (DBP). We present the first AI-enabled mmWave system for contactless multi-site PTT measurement using a single radar. By leveraging radar beamforming and deep learning
algorithms our system simultaneously measures PTT and estimates diastolic blood pressure at multiple sites. The system was evaluated across three physiological pathways - heart-to-radial artery, heart-to-carotid artery, and mastoid area-to-radial artery – achieving correlation coefficients of 0.73-0.89 compared to contact-based reference sensors for measuring PTT. Furthermore, the system demonstrated correlation coefficients of 0.90-0.92 for estimating DBP, and achieved a mean error of -1.00-0.62 mmHg and standard deviation of 4.97-5.70 mmHg, meeting the FDA's AAMI guidelines for non-invasive blood pressure monitors. These results suggest that our proposed system has the potential to provide a non-invasive measure of cardiovascular health across multiple regions of the body.
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All authors Jiangyifei Zhu, Kuang Yuan, Akarsh Prabhakara, Yunzhi Li, Gongwei Wang, Kelly Michaelsen, Justin Chan, Swarun Kumar
Atmospheric and Oceanic Physics
Digestible Pieces: comparing three options for partitioning the Northeast Pacific Coast for S2S sea surface height prediction
Laura Thapa, Marybeth Arcodia and Elizabeth A. Barnes
We discuss the utility of applying clustering as a preprocessing step for identifying subseasonal to seasonal forecasts of opportunity of coastal sea level using convolutional neural networks (CNNs). Clustering leverages potential covariance among points along the same coastline or in the same ocean basin. To evaluate the utility of clustering for reliably identifying forecasts of opportunity, we compare CNNs trained to predict sea level probability distributions in three ways: over the whole Northeast Pacific Coast simultaneously, over predetermined clusters within this coastline, and at individual gridpoints near tide gauges. All CNN prediction tasks (Whole Coast, Cluster, Point), outperform climatology by a similar margin at Week 3 when the entire test set is used to evaluate CNN skill. However, when comparing the skill of each tasks' 20% most confident predictions, we find the skill of the Cluster and Point tasks to be on par with each other and substantially more skillful than the Whole Coast task. Of the Cluster and Point task, the Cluster task represents all gridpoints in the Northeast Pacific Coast with minimal tunable parameters. Throughout this exercise we learned that clustering gridpoints as a pre-processing step is the preferred approach between the three for making S2S predictions of coastal sea level.
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Classical Physics · Cross-listed from cond-mat.soft
Elastohydrodynamic instabilities of a soft robotic arm in a viscous fluid
Mohamed Warda and Ronojoy Adhikari
The design and control of soft
robots operating in fluid environments requires a careful understanding of the interplay between large elastic body deformations and hydrodynamic forces. Here we show that this interplay leads to novel elastohydrodynamic instabilities in a clamped soft robotic arm driven terminally by a constant pressure in a viscous fluid. We model the arm as a Cosserat rod that can stretch, shear and bend. We obtain invariant, geometrically exact, non-linear equations of motion by using Cartan's method of moving frames. Stability to small perturbations of a straight rod is governed by a non-Hermitian linear operator. Eigenanalysis shows that stability is lost through a
Hopf bifurcation with the increase of pressure above a first threshold. A surprising return to stability is obtained with further increase of pressure beyond a second threshold. Numerical solutions of the non-linear equations, using a geometrically exact spectral method, confirms stable limit-cycle oscillations between these two pressure thresholds. An asymptotic analysis in the beam limit rationalizes these results analytically. This counterintuitive sequence of bifurcations underscores the subtle nature of the elastohydrodynamic coupling in Cosserat rods and emphasizes their importance for the control of the viscous dynamics of soft
robots.
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History and Philosophy of Physics · Cross-listed from quant-ph
Incomplete yet existent objects: a Nuclear Meinongian approach to quantum metaphysical indeterminacy
Raoni Arroyo and Renato Semaniuc Valvassori
This article proposes a reading of
quantum metaphysical indeterminacy from the perspective of Parsons'
Nuclear Meinongianism. In doing so, we identify a fundamental incompatibility between a key feature of Parsons' theory and standard
quantum mechanics. Our approach interprets
quantum indeterminacy as property incompleteness. However, this move, when combined with Parsons' framework, leads to what we term the “Incompleteness-Entails-Nonexistence Principle” (IENP), which implausibly entails the nonexistence of
quantum objects. For Meinongianism to be a suitable tool for the metaphysics of
quantum mechanics, this principle must be addressed. We argue for dropping the IENP and discuss the resulting metaphysical and metametaphysical consequences.
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Fluid Dynamics
In vivo evidence of blood flow slippage: failure of the no-slip boundary condition assumption
Alena Jarolímová, Jaroslav Hron, Karel Tůma et al. (+3 more)
The assumption that blood adheres to vessel walls, the “no-slip” boundary condition, is an essential premise of cardiovascular fluid dynamics. Yet, whether it holds true in vivo has not been established. Using 4D flow
magnetic resonance imaging of the human thoracic aorta and modeling blood as a Navier–Stokes fluid, we quantify the velocity of blood at the wall. We find tangential wall velocities of about 30–80% of the mean luminal velocity, providing clear evidence of blood slippage. To our knowledge, this is the first demonstration that the no-slip condition does not apply to blood flow in vivo. This finding challenges a fundamental assumption in cardiovascular modeling and directly affects key blood flow characteristics such as pressure drop, vorticity, wall shear stress, and energy dissipation, all of which play important roles across a wide range of cardiovascular conditions.
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All authors Alena Jarolímová, Jaroslav Hron, Karel Tůma, Josef Málek, Radomír Chabiniok, Keshava Rajagopal
Optics · Cross-listed from quant-ph
Virus Spreading in Quantum Networks
Junpeng Hou, Mark M. Seidel and Chuanwei Zhang
Recent advances in
quantum communication have enabled long-distance secure information transfer through
quantum channels, giving rise to
quantum networks with unique physical and statistical properties. However, as in classical networks, the propagation of viruses in these systems could have severe consequences. Here, we investigate the critical problem of virus spreading in
quantum networks. We develop quantitative tools, particularly a modified nonlinear dynamical system model, for performing epidemiological analyses on
quantum networks. Our results show that
quantum networks tend to be more resilient to viral infections, exhibiting higher epidemic thresholds than classical networks with identical graph
topologies. This apparent robustness, however, arises primarily from the sparser connectivity inherent to the
quantum networks. When the comparison is made at a fixed average connectivity, classical and
quantum networks display comparable epidemic thresholds. These findings provide key insights into the security and reliability of future large-scale
quantum communication systems. Our work bridges the fields of
quantum information science, network theory, and epidemiology, paving the way for future studies of
quantum epidemiological dynamics.
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Fluid Dynamics
How Do Water Filled Traffic Barriers Shake a Suspension Bridge?
Guanni Qu, T. Yue, X. Zhang et al. (+1 more)
The present study stems from the realization that the general problem relating to the analysis of wind-induced vibrations in suspension bridges still requires significant
attention. Sidewalk railings, overhaul tracks, and deflectors are known to largely affect such dynamics. Here, the influence of a row of water-filled traffic barriers on the response of a sample suspension bridge is investigated numerically. It is shown that the existence of water barriers causes flow separation and non-negligible
vortices with respect to the condition with no water barriers. The
vortex shedding frequency at the far end is around 41.30 Hz, relatively close to the real vibration frequency. It is also shown how different incoming angles of attack can change the flow field around the bridge cross-section and the
vortex detachment frequency.
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All authors Guanni Qu, T. Yue, X. Zhang, S. Wei
Geophysics
Developing an Open-access Telegram Bot for Automated, estimation and IA-based interpreted of OpenQuake Ground-Motion intensity measures
Boumediene Derras
The prediction of Intensity Measures (IMs) using Ground-Motion Models (GMM) is a fundamental component of seismic hazard assessment. However, the best estimation of IMs traditionally requires specialised searchers, programming expertise, and the manual sourcing of regression coefficients. This complexity creates a significant barrier to rapid, scenario-based analysis for engineers, researchers, and students. To address this challenge, we have developed the OpenGSIM bot, an automated and conversational workflow that provides on-demand access to the entire OpenQuake-engine GMM library via the Telegram messaging application. The system leverages the n8n workflow automation platform to orchestrate a user interaction, guiding the selection from over 21 IMs along with their associated total standard deviation (aleatory variability) and more than 500 distinct GMMs classes. The bot interactively elicits the necessary physical parameters, accounting for source, path, site, geological, tectonic, and regional effects as required by the chosen model. A Python wrapper executes the calculation and generates a comprehensive report. A Large
Language Model is used to provide an automated interpretation of different types of response spectrum. By abstracting the complexities of software installation and programming, OpenGSIM democratises access to advanced seismic hazard tools, enabling robust IM estimation on any device and without the installation of any software or code package.
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Optics
Mechanically Reconfigurable Terahertz Bandpass Filter Based on Double-Layered Subwavelength Metallic Rods
Sanaz Zarei
Tunable bandpass terahertz filters are demanded in various key applications such as hyperspectral imagers, miniaturized spectrometers, and high-speed wireless communication systems. Here, a mechanically reconfigurable double-layered subwavelength metallic structure is presented for frequency-agile terahertz transmission bandpass filtering. The theoretically demonstrated polarization-insensitive filter shows remarkable performance metrics. By varying the vertical interlayer spacing of the metallic layers from 20 um to 4 um, the operation frequency tunes from 0.81 THz to 1.32 THz, and the full width at half maximum bandwidth changes from 209 GHz to 135 GHz, with maximum transmission efficiency greater than 98% and quality factor ranging between 3.88 and 9.77. A larger variation range of the vertical interlayer spacing leads to an enhanced frequency tuning range of the filter. Furthermore, simultaneous vertical and lateral interlayer displacements can provide polarization-dependent behavior for the filter. The underlying physical mechanism governing the filter's frequency response and tuning capability is analyzed by examining the electromagnetic field distributions within the double-layered subwavelength metallic structure and its Fabry-Perot-like behavior. The presented scheme holds significant promise for many terahertz applications due to its large tuning range, easy tuning mechanism, simple structure, and compatibility with fabrication materials and processes.
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Computational Physics
Committors without Descriptors
Peilin Kang, Jintu Zhang, Enrico Trizio et al. (+2 more)
The study of rare events is one of the major challenges in atomistic simulations, and several enhanced sampling methods towards its solution have been proposed. Recently, it has been suggested that the use of the committor, which provides a precise formal description of rare events, could be of use in this context. We have recently followed up on this suggestion and proposed a committor-based method that promotes frequent transitions between the metastable states of the system and allows extensive sampling of the process transition state ensemble. One of the strengths of our approach is being self-consistent and semi-automatic, exploiting a variational criterion to iteratively optimize a neural-network-based parametrization of the committor, which uses a set of physical descriptors as input. Here, we further automate this procedure by combining our previous method with the expressive power of graph neural networks, which can directly process atomic coordinates rather than descriptors. Besides applications on
benchmark systems, we highlight the advantages of a graph-based approach in describing the role of solvent molecules in systems, such as ion pair dissociation or ligand binding.
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All authors Peilin Kang, Jintu Zhang, Enrico Trizio, TingJun Hou, Michele Parrinello
Optics
Terahertz Switch Using an Array of Subwavelength Metallic Holes-coupled-disks
Sanaz Zarei
Broadband switching of terahertz waves at room temperature is demonstrated using a reconfigurable subwavelength metallic hole coupled disk array. The interaction between a metallic membrane featuring periodically arranged circular holes and a substrate bearing a correspondingly periodic array of metallic disks - precisely aligned at their centers - significantly enhances the light coupling within each individual metallic structure, leading to an improved optical transmission and the appearance of a new transmission peak. By mechanical displacement of the metallic membrane with respect to the substrate with metallic disks, the light transmission through the structure can be reconfigured. The device exhibits a polarization-insensitive high-contrast switching performance of 89.4 dB at 942 GHz. The full-width at half-maximum bandwidth of the switch is 288 GHz. By proper design of the device's
geometric dimensions, the operation frequency and bandwidth of the switch can be scaled.
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Physics and Society
Asymmetric Outcomes in Two-Actor Conflict Dynamics: Stability, Bifurcations, and Emergent Behaviors
Eduardo Jacobo-Villegas, Josué Manik Nava-Sedeño and Bibiana Obregón-Quintana
In this paper we present an analytical and numerical study of a generalized model of two-actor cooperative-competitive conflict of the Continuous Opinions and Discrete Actions (CODA) type. Theoretically, we note that the in troduction of a new parameter allows generalizing feedback as strong and weak. Furthermore, we show that for positive-positive and negative-negative feedback there exists a supercritical pitchfork bifurcation, and that the model does not admit limit cycles in any case, and we study the effect of different parameter values and initial conditions by using a difference equation approximation of the model. Additionally, our model offers important insight on social phenomena such as false levels of support among cooperators, often observed in agreement negotiations; instances of “non-strict consensus” when two people support the same political position, albeit with different intensities; and competitive situations, such as in competitions with disproportionate profit and losses. Thus, this generalized model offers an enhanced descriptive power compared to previously proposed models.
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Optics
Comment on "Brilliant source of 19.2 attosecond soft X-ray pulses below the atomic unit of time"
Meng Han
A recent preprint by Ardana-Lamas et al. (Ref. [1], arXiv:2510.04086) re-analyzes the data set of the attosecond streaking experiment on krypton atoms originally reported in Phys Rev X 7, 041030 (2017) [2], and claims the characterization of a 19.2 attosecond light pulse with an overall
photon flux of 4.8*10^10
photons per second. In this comment, we highlight a series of physical and technical issues concerning both the original experiment [2] and the new characterization [1]. Specifically, without accounting for the contribution of Auger electrons or employing filters to remove low-energy harmonics and compensate for the intrinsic pulse chirp, the authors attribute the measured photoelectrons predominantly to the 3d inner-shell orbital of krypton and claim to have retrieved a nearly chirp-free pulse based on the single atomic orbital. In comparison with our recent attosecond streaking experiments on krypton atoms, these physical and technical issues raise significant doubts about the validity of the characterization results.
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Chemical Physics
Discovering How Ice Crystals Grow Using Neural ODE's and Symbolic Regression
Kara D. Lamb, Jerry Y. Harrington, Alfred M. Moyle et al. (+5 more)
Depositional ice growth is an important process for cirrus cloud
evolution, but the physics of ice growth in atmospheric conditions is still poorly understood. One major challenge in constraining depositional ice growth models against observations is that the early growth rates of ice
crystals cannot be directly observed, and proposed models require assumptions about the functional dependence of physical processes that are still highly uncertain. Neural ordinary differential equations (NODE's) are a recently developed machine learning method that can be used to learn the derivative of an unknown function. Here we use NODE's to learn the functional dependence of unknown physics in the depositional ice growth model by optimizing against experimental measurements of ice
crystal mass. We find a functional form for the depositional ice growth model that best fits 290 mass time series of ice
crystals grown in a levitation
diffusion chamber. We use symbolic regression to derive an equation for the function learned by the NODE model, which includes additional terms proportional to ice
crystal mass in the capacitance growth model. We evaluate this functional form against experimental data sets from the AIDA Aerosol and Cloud Chamber, finding that our new proposed model for depositional ice growth accurately reproduces experimental results in the early stages of ice
crystal growth.
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All authors Kara D. Lamb, Jerry Y. Harrington, Alfred M. Moyle, Gwenore F. Pokrifka, Benjamin W. Clouser, Volker Ebert, Ottmar Möhler, Harald Saathoff
Fluid Dynamics
Optimal Control from a Fluid Dynamics Perspective
J. Pratt, M. Schneider and A. Perloff
An optimal control problem described by the Hamilton-Jacobi-Bellman equation can be developed into a problem that can be solved by general computational fluid dynamics packages. We describe how this formulation would allow a classical problem in optimal control, Zermelo's problem, to be treated as a multi-fluid problem. This approach has the advantage of allowing optimal
navigation problems to be conducted over large areas, as well as to include moderately larger numbers of ships. We draw comparisons between this approach and the field of fluid control for fluid animations in movies.
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Optics
Circular Huygens Dipoles: Unidirectional Spin-Angular Momentum from Achiral Nanoparticles
Esmaeel Zanganeh and Antonio Lombardo
Simultaneous control over the directionality and
spin of light at the nanoscale is a central goal in nanophotonics with applications ranging from
quantum information to advanced biosensing. We introduce the concept of the Circular Huygens Dipole and numerically demonstrate its realization in a single Si nanocuboid. We show that the polarization of an incident linear wave controls the interference between co-located circular electric and
magnetic dipoles excited in phase quadrature. This enables deterministic switching of the forward-scattered radiation between purely right- and left-circularly polarized states. The system also functions as a directional
spin-to-linear polarization converter. Our findings establish a robust, passive method for reconfigurable
spin-directional control in a simple, monolithic silicon nanostructure, opening avenues for chip-scale
spin-optics,
chiral quantum interfaces, and novel sensing platforms.
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Applied Physics
Quench rate dependence of center formation in Er implanted Si
Mark A. Hughes, Huan Liu and Yaping Dan
Er implanted Si (Er:Si) is a promising candidate for scalable planar
quantum memory (QM) applications. Er has a preference to coordinate with O
impurities, and multiple types of Er center are typically formed after a post implant anneal. Float zone Si was implanted with 1018 cm-3 Er and separate samples were annealed using a rapid quench annealing technique at 950 degC for 10 min with quench rates of 5, 23, 46, 93, 185 and 400 degC/s. The
evolution of photoluminescence (PL) peaks and their associated Er centers was tracked as a function of quench rate. Across all samples, five distinct Er centers were identified. Two centers, one with mixed Si and O coordination and one with Si-only coordination, exhibited fully resolved
crystal-field splitting of the 4I15/2 ground state together with 2 to 3 hot lines from the 4I13/2 excited state; fitting of
crystal-field parameters for both was consistent with C2v
symmetry. The mixed Si and O coordinated center was suppressed at quench rates above 185 degC/s, while the Si-only coordinated center was progressively enhanced with increasing quench rate up to the maximum of 400 degC/s. These results demonstrate that rapid quench annealing has the potential to selectively stabilize a single, Si-coordinated Er center in Er:Si, which is required for QM applications.
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Biological Physics · Cross-listed from cond-mat.soft
Thickness of epithelia on wavy substrates: measurements and continuous models
Nicolas Harmand, Julien Dervaux, Christophe Poulard et al. (+1 more)
We measured the thickness of MDCK epithelia grown on substrates with a sinusoidal profile. We show that while at long wavelength the profile of the epithelium follows that of the substrate, at short wavelengths
cells are thicker in valleys than on ridges. This is reminiscent of the so-called {\guillemotleft} healing length {\guillemotright} in the case of a thin
liquid film wetting a rough solid substrate. We explore the ability of continuum mechanics models to account for these observations. Modeling the epithelium as a thin
liquid film, with surface tension, does not fully account for the measurements. Neither does modeling the epithelium as a thin incompressible elastic film. On the contrary, the addition of an apical active stress gives satisfactory agreement with measurements, with one fitting parameter, the ratio between the active stress and the elastic modulus.
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All authors Nicolas Harmand, Julien Dervaux, Christophe Poulard, Sylvie Hénon
Accelerator Physics
TCLK Must Stay! CAMAC Must Go! How Does Fermilab Move Forward
M. R. Austin, L. Carmichael, D. McArthur et al. (+2 more)
The current Timing System at Fermilab has been around for 40 years and currently relies on 7 CAMAC crates and over 100 CAMAC cards to produce the Tevatron Clock (TCLK). Thanks to the ingenuity of those before us, this has allowed Fermilab the flexibility to change the timing and Events for its accelerator as beamlines and projects have changed over the years. With the advent of the
Proton Improvement Plan-II (PIP-II), the Timing System at Fermilab is being reimagined into a single chassis with even greater flexibility and functionality for decades to come while tackling the ever-challenging task of maintaining backwards compatibility.
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All authors M. R. Austin, L. Carmichael, D. McArthur, E. Milton, A. Quilty
Classical Physics
Lattice-induced sound trapping in biperiodic metasurfaces of acoustic resonators
Nikita Ustimenko, Andrey B. Evlyukhin, Vicky Kyrimi et al. (+2 more)
A referential example of a physical system that supports bound states in the continuum (BICs) with an infinite quality factor ($Q$ factor) is a metasurface of discrete scatterers (resonators), whose response can be significantly modified by exploiting
lattice interactions. In this work, we explore the multipole-interference mechanism for realizing accidental acoustic BICs (trapped modes) at $\Gamma$-point (in-plane Bloch wave vector $\mathbf{k}_{\parallel} = \mathbf{0}$) of biperiodic metasurfaces of acoustic resonators with one resonator per unit
cell. To do so, we expand the pressure field from the metasurface into a series of scalar zonal ($m = 0$) spherical multipoles, carried by a normally incident plane wave, and formulate analytical conditions on the resonator multipole moments under which an eigenmode becomes a BIC. The conditions enable us to determine the
lattice constant and frequency values that facilitate the formation of an axisymmetric BIC with a specific parity, resulting from destructive interference between zonal multipoles of the same parity, despite each moment radiating individually. By employing the T-
matrix method for acoustic metasurfaces, we numerically investigate the BIC resonance in various structures, including finite arrays, and also the transformation of such resonances into high-$Q$ quasi-BIC regimes, which can be excited by a plane wave at normal incidence.
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All authors Nikita Ustimenko, Andrey B. Evlyukhin, Vicky Kyrimi, Alexander V. Kildishev, Carsten Rockstuhl
Physics and Society · Cross-listed from cs.DS
The Marked Edge Walk: A Novel MCMC Algorithm for Sampling of Graph Partitions
Atticus McWhorter and Daryl DeFord
Novel Markov Chain Monte Carlo (MCMC) methods have enabled the generation of large ensembles of redistricting plans modeled as a graph partitioning problem. However, existing
algorithms such as Reversible Recombination (RevReCom) and Metropolized Forest Recombination (MFR) have strong preferences for distributions related to the spanning tree measure. In this paper we introduce the Marked Edge Walk (MEW), a novel Markov chain proposal for sampling from the space of graph partitions. The walk operates on the space of spanning trees with marked edges, allowing for calculable transition probabilities for use in the Metropolis-Hastings
algorithm. Empirical results on real-world dual graphs show convergence under a broad class of target distributions less constrained by spanning tree counts, including policy-based distributions, such as competitiveness on New Hampshire that are independent of spanning trees, and compactness and partisan
symmetry distributions on New Hampshire and Texas that, while related to spanning trees, can now be properly targeted with a smaller degree of spanning tree bias, which represents an advancement in flexible ensemble generation.
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Optics · Cross-listed from cond-mat.other
The advancement of Brillouin Light Scattering with the assistance of nanoplasmonic structures. Enhancement and amplification
E. Bortchagovsky, A.V. Chumak and V. Lozovski
Brillouin light scattering (BLS) is a key technique in studying magnonic systems, but its sensitivity is often limited. While nanoplasmonic systems can enhance BLS through near-field effects, we propose a novel approach for additional amplification. In this conceptual paper, we show how to actively supply energy to a surface collective electromagnetic resonance (SCR) supported by a sparse layer of metal nanoparticles on a
magnetic film. Proposed methods are designed to significantly amplify the efficiency of surface-enhanced Brillouin light scattering without increasing the intensity of the primary excitation. In the proposed scheme, the pump extends the propagation length of the SCR, leading directly to BLS amplification. We analyze the conditions for such amplification, with numerical estimates indicating a potential gain of more than an order of magnitude in the surface-wave amplitude. This gain far surpasses the modest increase achievable through passive enhancement alone. These findings outline a practical pathway to achieving BLS amplification in integrated magnonic platforms. The feasibility of the proposed approaches is discussed in light of recent experimental and theoretical advances in plasmonics, magneto-plasmonics, and magnonics.
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Accelerator Physics
Testing the DAE LLRF system with a PIP-II SSR2 Cavity
R. Nasery, P. Varghese, S. Raman et al. (+3 more)
The PIP-II linac is an international collaboration project with in kind contributions of key subsystems from multiple countries including India (DAE). In the research and development phase of the project, the LLRF and resonance control systems were jointly developed by BARC and Fermilab and were delivered to Fermilab for testing and validation. Initial testing of the LLRF system was carried out using Fermilabs analog cavity emulator. Following successful emulator testing, the LLRF system was deployed at STC on a PIP-II 325 MHz SSR2 cavity. The cavity was operated in both SEL and GDR modes at a gradient of 5 MV/m. The results of the testing are presented here.
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All authors R. Nasery, P. Varghese, S. Raman, M. Guran, L. Reyes, A. Agashe
Chemical Physics
Local Proton Disorder Induced Intermolecular H-H Coupling in Ionization of Dense Ammonia
Yu Tao, Li Lei, Jingyi Liu et al. (+1 more)
Under cold compression, hydrogen bonding was considered to dominate intermolecular interaction during the ionization of ammonia. Here, we provide experimental and theoretical evidence of intermolecular HH coupling in dense ammonia. Ab initio molecular dynamics simulations (AIMD) reveal an increasing degree of
proton disorder in ammonia with increasing pressure, which promotes intermolecular H-H coupling. At pressure below the ionization phase transition pressure (135 GPa), intermolecular HH coupling gives rise to a unique dissociation pathway in ammonia. Sporadic molecular hydrogen was observed without
laser heating, accompanied by the absence of molecular nitrogen. At pressure above 135 GPa, intermolecular HH coupling serves as an intermediate state in the ionization of ammonia. Two fingerprint Raman modes previously assigned to the ionic phase disappear upon further compression or heating. Together with
proton transfer based on hydrogen bond, a dual path mechanism exists in the ionization of ammonia. Our results demonstrate a case of hydrides phase transition pathway that occurs independently of hydrogen bonding under high pressure.
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All authors Yu Tao, Li Lei, Jingyi Liu, Binbin Wu
Biological Physics · Cross-listed from cond-mat.soft
Curvature instability of an active gel growing on a wavy membrane
Kristiana Mihali, Dennis Wörthmüller and Pierre Sens
Cell shape changes are largely controlled by the actin cytoskeleton, a dynamic filament network beneath the
plasma membrane. Several
cell types can form extended free-standing protrusions not supported by an extracellular substrate or
matrix, and regulated by
proteins that modulate cytoskeletal dynamics in a way sensitive to the
curvature of the
cell membrane. We develop a theoretical model for the mechanics of a free-standing viscous actin network growing on a corrugated membrane. The model couples the dynamics of the viscous active gel with membrane deformation and the recruitment of
curvature-sensitive actin nucleators. We show that an actin layer polymerising uniformly on the membrane always exerts a stabilising effect that reduces membrane deformation. However,
curvature-sensitive actin nucleator
proteins can render the membrane linearly unstable, depending on the interplay between membrane and actin dynamics, giving rise to spontaneous membrane deformation which could initiate extended free-standing cellular protrusion.
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Instrumentation and Detectors
Real-Time Readout System Design for the BULLKID-DM Experiment: Enhancing Dark Matter Search Capabilities
T. Muscheid, R. Gartmann, L. E. Ardila-Perez et al. (+41 more)
The BULLKID-DM experiment aims to detect WIMP-like potential Dark Matter particles with masses below 1 GeV/c^2. Sensing these particles is challenging, as it requires
nuclear recoil detectors characterized by high exposure and an energy threshold in the order of 100 eV, thus exceeding the capabilities of conventional
semiconductor detectors. BULLKID-DM intends to tackle this challenge by using cryogenic Kinetic Inductance Detectors (MKIDs) with exceptional energy thresholds to sense a target with a total mass of 800 g across 16 wafers, divided into over 2000 individually instrumented silicon dice. The MKIDs on each wafer are coupled to a single transmission line and read using a frequency division multiplexing approach by the room-temperature data acquisition. In this contribution, we describe and assess the design of the room-temperature readout electronics system, including the selected hardware components and the FPGA firmware which contains the real-time signal processing stages for tone generation, frequency demultiplexing, and event triggering. We evaluate the system on the ZCU216 board, a commercial evaluation card built around a
Radio-Frequency System-on-Chip (RFSoC) with integrated high-speed DACs and ADCs, and connected it to a custom-designed analog front-end for signal conditioning.
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All authors T. Muscheid, R. Gartmann, L. E. Ardila-Perez, A. Acevedo-Rentería, L. Bandiera, M. Calvo, M. Cappelli, R. Caravita, F. Carillo, U. Chowdhury, D. Crovo, A. Cruciani, A. D'Addabbo, M. De Lucia, G. Del Castello, M. del Gallo Roccagiovine, D. Delicato, F. Ferraro, M. Folcarelli, S. Fu, M. Grassi, V. Guidi, D. Helis, T. Lari, L. Malagutti, A. Mazzolari, A. Monfardini, D. Nicolò, F. Paolucci, D. Pasciuto, L. Pesce, V. Pettinacci, C. Puglia, D. Quaranta, C. M. A. Roda, S. Roddaro, M. Romagnoni, G. Signorelli, F. Simon, M. Tamisari, A. Tartari, E. Vázquez-Jáuregui, M. Vignati, K. Zhao
Applied Physics · Cross-listed from cond-mat.soft
General Purpose Inverse Design of Heterogeneous Finite-Sized Assemblies
Livia A. J. Guttieres, Ryan K. Krueger, Remi Drolet et al. (+1 more)
Designing heterogeneous, self-assembling systems is a central challenge in soft matter and biology. We present a framework that uses gradient-based optimization to invert an analytical yield calculation, tuning systems toward target
equilibrium yields. We design systems ranging from simple dimers to temperature-controlled shells to polymerizing systems, achieving precise control of self- and non-self-limiting assemblies. By operating directly on closed-form calculations, our framework bypasses trajectory-based instabilities and enables efficient optimization in otherwise challenging regimes.
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All authors Livia A. J. Guttieres, Ryan K. Krueger, Remi Drolet, Michael P. Brenner