Applied Physics
A novel approach to modelling the properties of HEMTs operating in the saturation region
Kaiyuan Zhao, Guangfen Yao, Xiaoyu Cheng et al. (+3 more)
Currently, the ASM-HEMT model, QPZD model and EPFL model are all based on the three-terminal potential as the core, and relate the electrical characteristics such as I-V and C-V to Vd, Vs and Vg, so as to accurately build the HEMT model with high accuracy and fast convergence. However, there has not yet been a model based on three-terminal potentials that can quickly model the velocity saturation effect as well as the carrier concentration distribution and the electric field distribution inside the HEMT, which makes the existing models have to rely on a number of empirical parameters in the modelling process, which lacks the actual physical significance. In previous publications, models for the electric field, carrier concentration distribution based on the effective length of the gate were presented. In this paper, the model proposed in previous publications is improved to enable: (1) the calculation of the current Ids without relying on the Newton iterative method with fast simulation convergence behavior; (2) The Vdsat when the HEMT reaches saturation at different Vgo is redefined instead of using Vdsat = Vgo; (3) The expression of the v-E relationship is redefined relying on the different transport of carriers, which solves the problem of the large model error of the electric field distribution in the region below the gate, and makes the model's accuracy of the I-V characteristic further improved. The model was validated by characterising the I-V and E-V of the HEMT through TCAD simulation with RMSE below 5%.
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All authors Kaiyuan Zhao, Guangfen Yao, Xiaoyu Cheng, Luqiao Yin, Kailin Ren, Jianhua Zhang
Instrumentation and Detectors · Cross-listed from nucl-ex
First non-zero measurement of a nuclear electric dipole moment
Gary Prézeau
This paper reports the first non-zero measurement of a
nuclear electric dipole moment using a novel method based on the rate of change of a supercurrent first proposed in 2016~\cite{https://doi.org/10.48550/arxiv.1604.02152} and fleshed out in this current paper. The theory, experimental concept and implementation are described in detail. The non-zero
nuclear electric dipole moment measured with over 1000 hours of data was that of $^{181}$Ta producing a best value $|d_\text{e}^\text{Ta}|=(3.39\pm0.31_\text{stat})\cdot10^{-32}e\cdot\text{cm}$ and $|d_\text{e}^\text{Ta}|=(3.39\pm3.18)\cdot10^{-32}e\cdot\text{cm}>0$ at 99.985%CL. There is an uncertainty on the value of overall multiplicative parameters such as the self-inductance of the superconducting
circuit ($\pm4\%$), the mutual inductance between the SQUID pickup coil and the sample wire ($\pm15\%$), and the magnitude of the solenoid current ($\pm5\%$). An upper-limit was estimated for the control element, $^{207}$Pb, $|d_\text{e}^\text{Pb}|\lesssim1.2\cdot10^{-31}e\cdot\text{cm}$ at 95%CL.
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Fluid Dynamics
Water wave scattering by a surface-mounted rectangular anisotropic elastic plate
Ben Wilks, Michael H. Meylan, Zachary J. Wegert et al. (+2 more)
This paper considers the problem of water wave scattering by a rectangular anisotropic elastic plate mounted on the ocean surface, with either free, clamped or simply-supported edges. The problem is obtained as an expansion over the dry modes of the elastic plate, which are computed using a Rayleigh–Ritz method. In turn, the component diffraction and radiation problems are solved by formulating a boundary integral equation and solving numerically using a constant panel method. The results are presented to highlight the resonant responses of the plate under different forcing scenarios. In particular, we illustrate how the excitation of certain modes can be forbidden due to
symmetry.
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All authors Ben Wilks, Michael H. Meylan, Zachary J. Wegert, Vivien J. Challis, Ngamta Thamwattana
Computational Physics · Cross-listed from cond-mat.mes-hall
Near-field radiative heat transfer in the dual nanoscale regime between polaritonic membranes
Livia Correa McCormack, Lei Tang and Mathieu Francoeur
The enhancement and attenuation of near-field radiative heat transfer between polaritonic SiC, SiN and SiO2 subwavelength membranes is analyzed. Fluctuational electrodynamics simulations combined with a modal analysis show that all membranes support corner and edge modes, which can induce a large 5.1-fold enhancement for SiC and a 2.1-fold attenuation for SiO2 of the heat transfer coefficient with respect to that between infinite surfaces. The enhancement or attenuation is directly related to material losses which reduce the density of available electromagnetic states between the membranes.
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Physics and Society
CARDIO-Affect: A Hamiltonian-Variability Framework for Spatio-Temporal Emotional Pattern Recognition with Manifold-Based Individual and Group Profiling
Xiao Sun
We present CARDIO-Affect, a complex-systems theoretical framework for long-term emotional dynamics in bounded social groups, with explicit uncertainty quantification at every layer. Long-period naturalistic
emotion in stable small groups exhibits hallmarks of complex systems – multi-stable attractors, weak chaos, long-range
memory, and sparse heterogeneous coupling – invisible to conventional short-clip facial-
emotion analysis. CARDIO-Affect treats individual
emotion as a multi-stable nonlinear
stochastic dynamical system and group
emotion as a sparsely-coupled network with emergent macrostates, formalised through six propositions and four pillars: (i) statistical mechanics with neural-parameterised
Hamiltonian SDE over asymmetric potentials; (ii) information geometry on a 45-dimensional Fisher-Rao
manifold; (iii) topological data analysis for invariant trajectory signatures; (iv) HRV-inspired Emotional Variability Analytics (EVA) decomposing each person-day into multi-scale time/frequency/nonlinear measures. We validate on the first 30.1-month longitudinal in-the-wild facial-
emotion corpus (companion: arXiv:2510.15221) by discovering three falsifiable paradoxes: Sparse-Contagion (R_0=0.36, density 2.7%, 8 BH-FDR edges), Asymmetric-Persistence (negative dwell 5.85x positive, 1.77D potential gap), and Crisis-Inversion (Shanghai 2022 lockdown naive d=-0.40 collapses to permutation-p=0.94 under BSTS + synthetic-control). On synthetic
benchmarks, CARDIO-EBM v2 matches asymptotically optimal Granger on linear VAR data (Class A AUROC 0.984+/-0.012 vs Granger 0.997+/-0.001, 5 seeds) but fails on tanh-coupled nonlinear data (Class B AUROC 0.490 vs Granger 0.796), a documented limitation of the linear mask-self
estimator. We release framework code and the full reproduction pipeline.
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Physics and Society
The Probability of Vacuum Metastability and Artificial Vacuum Decay: Expert Survey Results
Jordan Stone, Youssef Saleh, Darryl Wright et al. (+1 more)
Vacuum decay posits that the universe's apparent
vacuum is metastable and could transition to a lower-energy state. According to current physics models, if such a transition occurred in any location, a region of "true
vacuum" would propagate outward at near light speed, destroying the accessible universe as we know it by deeply altering the effective physical laws. Understanding whether advanced technology could potentially trigger such a transition has implications for existential risk assessment and the long-term trajectory of technological civilizations. We present results from what we believe to be the first structured survey of physics experts (n = 20) regarding both the theoretical possibility of
vacuum decay and its potential technological inducibility. The average responded probability that our
vacuum is metastable was 45.6%, with an average estimated 18.8% probability that arbitrarily advanced technology could induce
vacuum decay if our
vacuum is metastable. However, the survey revealed substantial disagreement among respondents on both whether the
vacuum is metastable, and, if it is, whether
vacuum decay could be artificially induced with arbitrarily advanced technology. According to participants, resolving these questions primarily depends on developing theories that go beyond the Standard Model of particle physics. Among respondents who considered
vacuum decay theoretically possible, it was generally expected that artificial induction would pose significant technological challenges even for a civilization with
galactic resources.
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All authors Jordan Stone, Youssef Saleh, Darryl Wright, Jess Riedel
Optics
Visible Imaging of Incoherent 1200-nm Light via Triplet–Triplet Annihilation Upconversion
Pournima Narayanan, Rabeeya Hamid, Linda Pucurimay et al. (+13 more)
Upconversion of low-energy
photons to higher-energy
photons provides an opportunity to surpass traditional limitations in fields such as 3D printing, photovoltaics, and photocatalysis. Triplet–triplet annihilation upconversion (TTA-UC) is particularly appealing for such applications as it can efficiently upconvert low-intensity, incoherent light. However, previously demonstrated thin-film TTA systems are simultaneously constrained by modest efficiencies and limited reach into the near infrared (NIR). Here, we design a single-layer thin-film bulk heterojunction that integrates PbS
quantum dots (QDs) as tunable NIR absorbers within an organic
semiconductor matrix of TES-ADT, achieving large anti-Stokes shifts up to 500 nm and high internal
quantum efficiencies across the NIR-I and NIR-II windows (800-1200 nm). Through the incorporation of 5-tetracene carboxylic acid ligands on the PbS QD surface, the yield of sensitized triplets was boosted, as confirmed by transient absorption and time-resolved photoluminescence measurements. The resulting films demonstrated a 15-fold improvement in UC efficiency. Furthermore, we demonstrate visible imaging of incoherent 1200 nm light via thin-film TTA-UC at incident intensities at the imaging mask as low as 20 mWcm$^2$, marking a significant advance toward practical implementation of solid-state NIR-to-visible upconversion.
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All authors Pournima Narayanan, Rabeeya Hamid, Linda Pucurimay, Ona Segura Lecina, Ben P. Carwithen, Jacob Schopp, Justin S. Edwards, Oluwaseun Noah Adeyeye, Demeng Feng, Diptarka Hait, Todd J. Martinez, Timothy W. Schmidt, Michael P. Nielsen, Murad J. Y. Tayebjee, Mikhail A. Kats, Daniel N. Congreve
Applied Physics · Cross-listed from quant-ph
Superconducting Gap Engineering in Tantalum-Alloy-Based Resonators
Chen Yang, Faranak Bahrami, Guangming Cheng et al. (+7 more)
Utilizing tantalum (Ta) in superconducting
circuits has led to significant improvements, such as high
qubit lifetimes and quality factors in both
qubits and resonators, underscoring the importance of material optimization in
quantum device performance. In this work, we explore superconducting gap engineering in Ta-based devices as a strategy to expand the range of viable host materials. By alloying 20 atomic percent hafnium (Hf) into Ta thin films, we achieve a superconducting transition temperature ($T_c$) of 6.09~K, as measured by DC transport, reflecting an increased superconducting gap. We systematically vary deposition conditions to control film orientation and transport properties of the Ta-Hf
alloy films. The enhancement in $T_c$ is further confirmed by microwave measurements at millikelvin temperatures. Despite the 40% increase in $T_c$ relative to pure Ta, the loss contributions from two-level systems (TLS) and quasiparticles (QPs) remain unchanged in the low-temperature regime. These findings highlight the potential of material engineering to improve superconducting
circuit performance and motivate further exploration of engineered
alloys for
quantum technologies.
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All authors Chen Yang, Faranak Bahrami, Guangming Cheng, Mayer Feldman, Nana Shumiya, Stephen A. Lyon, Nan Yao, Andrew A. Houck, Nathalie P. de Leon, Robert J. Cava
Chemical Physics
Helical orbitals in electrical uni-directional molecular motors
Štěpán Marek, Wulf Wulfhekel, Ferdinand Evers et al. (+1 more)
The generation of unidirectional motion has been a long-standing challenge in engineering of molecular motors. Here, a mechanism driving the rotation is presented based on electron current through helical orbitals on a $\pi$-bonded carbon chain. Such electron current through helical orbitals has been shown to be circulating around the carbon chain. It is natural to expect that the associated electronic angular momentum drives a rotation when the current is turned on. As intuitive as this relation might seem, it is also incomplete because a formal definition of helicality in terms of a physical observable has not yet been given. Such a definition is proposed here. Based on this definition, we show how helicality determines the motor's sense of rotation. We exemplify the relation between helicality and angular momentum in Hückel models of linear carbon chains (cumulenes and oligoynes). We attribute the previously reported opposite helicality sense of frontier orbitals (HOMO and LUMO) to the approximate sub-
lattice symmetry. For oligoynes, this
symmetry is hidden in the sense that it does not reduce to a mere labeling of atoms. Sub-
lattice symmetry, combined with time-reversal invariance, allows us to derive Onsager-type reciprocal relations of various linear response coefficients, dictating e.g. an odd energy dependence of angular momentum response to voltage bias. We propose an observable consequence of the approximate sub-
lattice symmetry: If the carbon chain is employed as an axle of a molecular rotor, the sense of rotation is independent on the direction of the current.
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All authors Štěpán Marek, Wulf Wulfhekel, Ferdinand Evers, Richard Korytár
Medical Physics · Cross-listed from cs.LG
An Advanced Two-Stage Model with High Sensitivity and Generalizability for Prediction of Hip Fracture Risk Using Multiple Datasets
Shuo Sun, Meiling Zhou, Chen Zhao et al. (+8 more)
Hip fractures are a major cause of disability, mortality, and healthcare burden in older adults, underscoring the need for early risk assessment. However, commonly used tools such as the DXA T-score and FRAX often lack sensitivity and miss individuals at high risk, particularly those without prior fractures or with osteopenia. To address this limitation, we propose a sequential two-stage model that integrates clinical and imaging information to improve prediction accuracy. Using data from the Osteoporotic Fractures in Men Study (MrOS), the Study of Osteoporotic Fractures (SOF), and the UK Biobank, Stage 1 (Screening) employs clinical, demographic, and functional variables to estimate baseline risk, while Stage 2 (Imaging) incorporates DXA-derived features for refinement. The model was rigorously validated through internal and external testing, showing consistent performance and adaptability across cohorts. Compared to T-score and FRAX, the two-stage framework achieved higher sensitivity and reduced missed cases, offering a cost-effective and personalized approach for early hip fracture risk assessment. Keywords: Hip Fracture, Two-Stage Model, Risk Prediction, Sensitivity, DXA, FRAX
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All authors Shuo Sun, Meiling Zhou, Chen Zhao, Joyce H. Keyak, Nancy E. Lane, Jeffrey D. Deng, Kuan-Jui Su, Hui Shen, Hong-Wen Deng, Kui Zhang, Weihua Zhou
Plasma Physics · Cross-listed from astro-ph.HE
Magnetohydrodynamic-guiding-center-particle-in-cell Method for Multiscale Plasma Kinetic Simulations
Zitao Hu, Xue-Ning Bai and Xiaochen Sun
We present the formulation,
algorithm and numerical tests of the magnetohydrodynamic-particle-in-
cell (MHD-PIC) method with particles treated under the guiding center approximation, which we term the MHD-gPIC method, and it is implemented in the Athena++ MHD code. The new MHD-gPIC model consists of thermal (cold) fluid and high-energy particles whose dynamics are integrated through guiding center equations including drift motion, with carefully evaluated source terms as particle backreaction. The code is validated with a series of tests, and it is expected to be primarily applicable to study particle acceleration and transport in systems where gyro-resonance is considered insignificant. We also present preliminary studies of particle acceleration during non-relativistic
magnetic reconnection.
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Fluid Dynamics
On the effect of airfoil geometry on extreme vortex-gust encounters
Barbara Lopez-Doriga, Anya R. M. Jones and Kunihiko Taira
Historically, investigations on gust encounters have been limited to thin airfoils. In this work, we examine
vortex-gust encounters by a family of airfoils at a chord-based Reynolds number Re_c=100, which includes variations in the gust ratio, initial gust position, gust radius, angle of attack, airfoil thickness, and airfoil camber. We examine differences in the flow fields, lift-element distributions, and aerodynamic responses across several airfoil-gust interactions. We observe a large deviation of the flow fields and aerodynamic responses with respect to the baseline flows for increasing gust ratios and gust sizes. The initial position of the
vortex gust influences the magnitude of the velocity gradients observed near the leading edge, effectively heightening or mitigating the amplitude of the lift response. Moreover, the lift fluctuation increases with the angle of attack until it flattens around $10^\circ$, reminiscent of an unsteady stall-like regime. Furthermore, we report a decrease in the amplitude of the gust-induced lift fluctuations for thicker airfoils, which we attribute to a decrease in the vorticity production levels from the leading edge. The exploration of a sensitive subset of the parameter space uncovers relevant trends, shedding light on regions that have received limited
attention in past studies, with special focus on the influence of airfoil geometry.
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Optics
Qili Hu, Raymond Lopez-Rios, Zhengdong Gao et al. (+5 more)
Femtosecond
laser, owing to their ultrafast time scales and broad frequency bandwidths, have substantially changed fundamental science over the past decades, from chemistry and bio-imaging to
quantum physics. Critically, many emerging industrial-scale photonic technologies – such as optical interconnects, AI accelerators,
quantum computing, and
LiDAR – also stand to benefit from their massive frequency parallelism. However, achieving a femtosecond-scale
laser on-chip, constrained by size and system power input, has remained a long-standing challenge. Here, we demonstrate the first on-chip femtosecond
laser, enabled by a new mechanism – photorefraction-assisted
soliton (PAS) mode-locking. Operating from a simple, low-voltage electrical supply, the
laser provides deterministic, turn-key generation of sub-90-fs
solitons. Furthermore, it provides electronic reconfigurability of its pulse properties and features an exceptional optical coherence with a 53 Hz intrinsic comb linewidth. This demonstration removes a key barrier to the full integration of chip-scale photonic systems for next-generation sensing, communication, metrology, and computing.
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All authors Qili Hu, Raymond Lopez-Rios, Zhengdong Gao, Jingwei Ling, Shixin Xue, Jeremy Staffa, Yang He, Qiang Lin
Optics
Wafer-Scale All-Dielectric quasi-BIC Metasurfaces: Bridging High-throughput Deep-UV Lithography with Nanophotonic Applications
Aidana Beisenova, Wihan Adi, Wenxin Wu et al. (+5 more)
High quality-factor (Q) dielectric metasurfaces operating in the visible to near-infrared range usually require sub-200 nm features, limiting their fabrication to expensive, low-throughput electron beam lithography. Here, we demonstrate wafer-scale metasurfaces fabricated using deep ultraviolet lithography (DUVL), a workhorse technology in the
semiconductor industry. Using a radius and depth perturbation technique in a hole array patterned into a silicon nitride slab, we achieve quasi-bound states in the continuum (qBIC) resonances with measured Q-factors of 150. Critically, we introduce DUV exposure dose as a Q-factor engineering parameter and demonstrate how hole depth control circumvents DUVL resolution limits. Despite
stochastic nanoscale variations, the fabricated metasurfaces exhibit spatial uniformity, a consequence of the nonlocal nature of the qBIC resonances. Proof of concept refractive index sensing demonstrates 129 nm/RIU sensitivity while maintaining simple CMOS camera-based resonance shift interrogation. This work bridges scalable
semiconductor manufacturing with high-performance nanophotonics, establishing a practical pathway for commercializing metasurface-based sensors, on-chip spectrometers, and integrated photonic systems.
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All authors Aidana Beisenova, Wihan Adi, Wenxin Wu, Shovasis K Biswas, Samir Rosas, Biljana Stamenic, Demis D. John, Filiz Yesilkoy
Data Analysis and Statistics · Cross-listed from hep-ex
Systematic Uncertainties in Unfolding Considering the Likelihood Formalism
Lydia Brenner, Carsten Burgard and Vincent Alexander Croft
This paper describes the treatment of systematic uncertainties in a Likelihood formalism. RooUnfold, which includes most of the unfolding methods that are commonly used in particle physics, is used to compare a newly implemented method inside this toolkit to existing methods. The interface with the RooFit statistical software package is used for the treatment of systematic uncertainties. The RooUnfold package with RooFit interface, commonly called RooFitUnfold, provides a common interface to unfolding
algorithms as well as common uniform methods to evaluate their performance in terms of bias, variance and coverage. This paper exploits this common interface to compare the performance of unfolding with a Tikhonov regularisation term directly in the likelihood with an unfolding method that optimises a Tikhonov regularisation applied separately of the likelihood formalism. Comparisons are made with and without the treatment of (systematic) uncertainties and are applied to an example problem.
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Computational Physics · Cross-listed from cond-mat.stat-mech
Cluster percolation and dynamical scaling in the Baxter–Wu model
Alexandros Vasilopoulos, Michail Akritidis, Nikolaos G. Fytas et al. (+1 more)
We investigate the percolation behavior of Fortuin-Kasteleyn–type clusters in the
spin-$1/2$ Baxter–Wu model with three-
spin interactions on a triangular
lattice. The considered clusters are constructed by randomly freezing one of the three sublattices, resulting in effective pairwise interactions among the remaining
spins. Using Monte Carlo simulations combined with a finite-size scaling analysis, we determine the percolation temperature of these
stochastic clusters and show that it coincides with the exact thermal critical point of the model. The critical exponents derived from cluster observables are consistent with those of the underlying thermal phase transition. Finally, we analyze the dynamical scaling of the multi-cluster and single-cluster
algorithms resulting from the cluster construction, highlighting their efficiency and scaling behavior with system size.
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All authors Alexandros Vasilopoulos, Michail Akritidis, Nikolaos G. Fytas, Martin Weigel
Atomic Physics
Optical-field-induced dips and splits in nonlinear spectra of selective reflection from high-density atomic vapor
V.A. Sautenkov, S.A. Saakyan, A.A. Bobrov et al. (+1 more)
We discuss nonlinear spectra of selective reflection from high-density rubidium atomic vapor, where the self-broadening of the resonant transition $5S_{1/2}-5P_{3/2}$ dominates over the Doppler width. In the experiments, the hole-burning technique with probe and pump
lasers is used. The reflection of weak probe beam is investigated at four atomic densities in the range $(1.2\text{--}3.6)\times10^{17}$~cm$^{-3}$ and various pump beam intensities. To enhance the spectral resolution, the frequency derivative $\text{d}R/\text{d}\nu$ of the reflection coefficient $R$ is analyzed. Increasing the atomic number density changes the character of self-broadening from inhomogeneous to homogeneous. At the highest density, the strong pump field splits the observed spectra into two homogeneously broadened symmetric resonances. The appearance of the optical-field-induced resonances can be explained within the framework of "dressed atomic states" approach. At lower densities the spectral profiles are inhomogeneously broadened. Spectral profiles of the frequency derivative are separated by optically saturated dips. The width of such dips is a combination of the homogeneous component of self-broadening and intensity-dependent field broadening. Careful study of the transition from inhomogeneous to homogeneous broadening may initiate further development of the theory of interatomic interactions in high density atomic gas media.
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All authors V.A. Sautenkov, S.A. Saakyan, A.A. Bobrov, B.B. Zelener
Computational Physics · Cross-listed from math.NA
Fast spectral separation method for kinetic equation with anisotropic non-stationary collision operator retaining micro-model fidelity
Yue Zhao and Huan Lei
We present a generalized, data-driven collisional operator for one-component
plasmas, learned from molecular dynamics simulations, to extend the collisional kinetic model beyond the weakly coupled regime. The proposed operator features an anisotropic, non-stationary collision kernel that accounts for particle correlations typically neglected in classical Landau formulations. To enable efficient numerical evaluation, we develop a fast spectral separation method that represents the kernel as a low-rank tensor product of univariate basis functions. This formulation admits an $O(N \log N)$
algorithm via fast
Fourier transforms and preserves key physical properties, including discrete conservation laws and the H-
theorem, through a structure-preserving central difference discretization. Numerical experiments demonstrate that the proposed model accurately captures
plasma dynamics in the moderately coupled regime beyond the standard Landau model while maintaining high computational efficiency and structure-preserving properties.
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Instrumentation and Detectors
A low-cost, open-source maskless photolithography stepper for microfabrication
B. Joel Gonzalez, Elio Bourcart, J. Kent Wirant et al. (+10 more)
Photolithography is a key part of modern
semiconductor process flows, and photolithography steppers have been used for decades to achieve precise patterning for device fabrication. However, these tools are often large and expensive, which restricts their use to industry and well-funded university laboratories. In this paper, we propose a \$3000 maskless photolithography stepper that is affordable, open-source, and easy to assemble. The stepper, which uses a Digital Light Processing (DLP) projector as its optical engine, is able to achieve an optical resolution of under 2 microns. The stepper also features a motorized nanopositioning system, which is able to align features with sub-micron precision. RF-DETR, an object detection computer
vision model, is used to detect fiducials on chip for automatic fine-grain
alignment and stitching of patterns. These capabilities allow for use of the stepper for microfabrication to produce micron-scale devices such as NMOS transistors.
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All authors B. Joel Gonzalez, Elio Bourcart, J. Kent Wirant, Rachel Jiang, Peiyu Lin, Michael Casey Honaker, Toby Yang, Jessica Alacce, Jocelyn Xu, Michael Juan, Justin Wang, William Gao, Matthew T. Moneck
Fluid Dynamics
On Turbulent Behavior of the Generalized Surface Quasigeostrophic Equations
Chengzhang Fu, Michael S. Jolly, Anuj Kumar et al. (+1 more)
Turbulent behavior of the two-parameter family of generalized surface quasigeostrophic equations is examined both rigorously and numerically. We adapt a cascade mechanism argument to derive an energy spectrum that scales as $\kappa^{2\beta/3-3}$ where $\beta$ controls the regularity of the velocity ($\beta=1$ in the special case of the SQG). Direct numerical simulations indicate that this fits better than $\kappa^{\beta/3-3}$ which was derived in earlier work. Guided by earlier work on the 2D Navier-Stokes equations, we prove a certain condition implies a direct cascade of enstrophy, as well as an upper bound on the enstrophy dissipation rate, and sharp bounds on a dissipation wavenumber. The dependence of these rigorous results on the two parameters is demonstrated numerically.
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All authors Chengzhang Fu, Michael S. Jolly, Anuj Kumar, Vincent R. Martinez
Plasma Physics
Geometric scaling of laser-driven proton focusing from hemispherical foils
Jesse Griff-McMahon, Xavier Vaisseau, William Fox et al. (+7 more)
We systematically characterize the focusing behavior of
laser-driven
proton beams from hemispherical targets of various diameters using mesh radiography. The
proton focal location is inferred to be near the geometrical center for the smallest tested hemisphere ($\Psi=D_{hemi}/D_{Laser}=6.1$). However, larger hemispheres ($\Psi=14.6$) degrade the focusing behavior and behave more like flat foils with focal location significantly inside the hemisphere. We also infer a tight virtual focus of $9\pm3~\mu$m through a mesh transition analysis.
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All authors Jesse Griff-McMahon, Xavier Vaisseau, William Fox, Kirill Lezhnin, Krish Bhutwala, Ryan Nedbailo, Valeria Opsina-Bohórquez, Timo Karpowski, Pravesh K. Patel, Sophia Malko
Fluid Dynamics
Computational study of vertical-axis MHK turbines using a coupled flow-sediment-turbine modeling approach
Mehrshad Gholami Anjiraki, Mustafa Meriç Aksen, Samin Shapourmiandouab et al. (+2 more)
We present a coupled large-eddy simulation (LES) and bed morphodynamics study to investigate the influence of sediment dynamics on the performance of a utility-scale marine hydrokinetic vertical-axis turbine (VAT) parametrized by an actuator surface model. By resolving the two-way interactions between turbine-induced flow structures and bed
evolution, the study offers insights into the environmental implications of VAT deployment in riverine and marine settings. A range of tip speed ratios is examined to evaluate wake recovery, power production, and bed response. The actuator surface method (ASM) is implemented to capture the effects of rotating vertical blades on the flow, while the immersed boundary method accounts for fluid interactions with the channel walls and sediment layer. The results show that higher TSRs intensify
turbulence, accelerate wake recovery over rigid beds, and enhance erosion and deposition patterns beneath and downstream of the turbine under live-bed conditions. Bed deformation under live-bed conditions induces asymmetrical wake structures through jet flows, further accelerating wake recovery and decreasing turbine performance by about 2%, compared to rigid-bed conditions. Considering the computational cost of the ASM framework, which is nearly $4\%$ of the turbine-resolving approach, it provides an efficient yet robust tool for assessing flow-sediment-turbine interactions.
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All authors Mehrshad Gholami Anjiraki, Mustafa Meriç Aksen, Samin Shapourmiandouab, Jonathan Craig, Ali Khosronejad
Physics and Society
The Physics of News, Rumors, and Opinions
Guido Caldarelli, Oriol Artime, Giulia Fischetti et al. (+5 more)
The boundaries between physical and social networks have narrowed with the advent of the Internet and its pervasive platforms. This has given rise to a complex adaptive information ecosystem where individuals and machines compete for
attention, leading to emergent collective phenomena. The flow of information in this ecosystem is often non-trivial and involves complex user strategies from the forging or strategic amplification of manipulative content to large-scale coordinated behavior that trigger misinformation cascades, echo-chamber reinforcement, and opinion polarization. We argue that statistical physics provides a suitable and necessary framework for analyzing the unfolding of these complex dynamics on socio-technological systems. This review systematically covers the foundational and applied aspects of this framework. The review is structured to first establish the theoretical foundation for analyzing these complex systems, examining both structural models of complex networks and physical models of social dynamics (e.g., epidemic and
spin models). We then ground these concepts by describing the modern media ecosystem where these dynamics currently unfold, including a comparative analysis of platforms and the challenge of information disorders. The central sections proceed to apply this framework to two central phenomena: first, by analyzing the collective dynamics of information spreading, with a dedicated focus on the models, the main empirical insights, and the unique traits characterizing misinformation; and second, by reviewing current models of opinion dynamics, spanning discrete, continuous, and coevolutionary approaches. In summary, we review both empirical findings based on massive data analytics and theoretical advances, highlighting the valuable insights obtained from physics-based efforts to investigate these phenomena of high societal impact.
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All authors Guido Caldarelli, Oriol Artime, Giulia Fischetti, Stefano Guarino, Andrzej Nowak, Fabio Saracco, Petter Holme, Manlio de Domenico
Optics
Non-Hermitian topological filters
Vinzenz Zimmermann, Amin Hashemi, Kurt Busch et al. (+2 more)
We introduce a non-Hermitian photonic filter that harnesses dissipation to selectively isolate a desired topological state. In science and engineering, dissipation is often used to filter incoherent waves, producing a pure coherent output. Here, we apply this principle to topological states, creating a linear filter that effectively isolates a specific topological state regardless of the initial input's coherence properties. This approach creates a dissipation-free topological subspace, where the desired states are preserved and their topological protection is enhanced. Our work provides a versatile and simple method for topological state selection, opening the door to new applications in integrated topological photonics.
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All authors Vinzenz Zimmermann, Amin Hashemi, Kurt Busch, Andrea Blanco-Redondo, Armando Perez-Leija
Optics
A Second-Order Optical Butterworth Fabry-Pérot Filter
Zeyang Li, Abhishek V. Karve, Xin Wei et al. (+1 more)
Filters with flat-top pass-bands are a key enabling technology for signal processing. From communication to sensing, the ability to choose a pass band, rather than a single pass frequency, while still efficiently suppressing backgrounds at other frequencies, is a critical capability for ensuring both detection sensitivity and power efficiency. Efficient transmission of a single frequency can be achieved by a single-pole resonator – which in optics is a Fabry-Pérot cavity offering linewidths from kHz to GHz and beyond. Coupling multiple resonators allows for the construction of flat-top multi-pole filters. These, although straightforward from RF to THz where resonators are macroscopic and tunable, are more difficult to control in the optical band and typically realized with dielectric stacks, whose passband widths exceed 100 GHz. Here, we bridge the gap to narrower bandwidth flat-top filters by proposing and implementing a second-order Butterworth-type optical filter in a single two-mirror Fabry-Pérot cavity, by coupling the two polarization modes. We demonstrate a pass-band width of 2.68(1)~GHz, a maximum stopband suppression of 43~dB, and a passband insertion loss of 2.2(1)~dB, with out-of-band power suppression falling as the fourth power of detuning. This approach is viable down to much narrower filters, and has the potential to improve high-frequency phase noise performance of
lasers, enhance the sensitivity of
LIDARs, and provide higher quality narrowband filtering, for example, for Raman spectroscopy.
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All authors Zeyang Li, Abhishek V. Karve, Xin Wei, Jonathan Simon
Data Analysis and Statistics · Cross-listed from stat.ML
Reliable data clustering with Bayesian community detection
Magnus Neuman, Jelena Smiljanić and Martin Rosvall
From neuroscience and genomics to systems biology and ecology, researchers rely on clustering similarity data to uncover modular structure. Most methods work in two steps: first reduce noise, then cluster. The first step runs without regard to the second: it forces arbitrary choices, discards useful information, and can impose structure where none exists. Here we bring the two steps together. Using established
Bayesian community detection methods, we let one minimum description length criterion choose both how much to sparsify the data and how to cluster it. This one-step approach keeps all the samples for inference, removes the arbitrary threshold choice, and returns a single cluster when there is no real structure. On synthetic data, our approach recovers clusters under more noise and with fewer samples than standard methods. On gene co-expression data from the human
brain, it finds more coherent and more stable clusters than WGCNA, the standard tool in the field. Uniting sparsification and clustering in a single model-selection step provides a principled, noise-resistant way to uncover modular structure in similarity data across fields.
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Accelerator Physics
FAIR Commissioning - Towards First Science
S. Reimann, H. Albers, R. W. Assmann et al. (+16 more)
The international Facility for Antiproton and Ion Research (FAIR) is under construction at the GSI Helmholtz Centre in Darmstadt. The first project stage includes the superconducting 100 Tm heavy-ion synchrotron SIS100, the Super Fragment Separator, and associated beam transport lines. Part of GSI's existing accelerator chain, comprising UNILAC and SIS18, will serve as injector. Installation work in the FAIR accelerator tunnels and supply buildings has been ongoing since early 2024. As progress continues, special
attention is now on the start of commissioning, beginning in 2025 with the cryogenic plant. Commissioning of the transport line will follow at the end of 2025, and beam commissioning is scheduled for the second half of 2027. This paper outlines the current status of the project, commissioning strategy and timeline.
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All authors S. Reimann, H. Albers, R. W. Assmann, P. Gasik, O. Geithner, F. Hagenbuck, A. Herlert, P. Hofmann, V. Kamerdzhiev, M. Kauschke, H. Kollmus, S. Pietri, N. Pyka, T. Radon, C. Schroeder, S. Schwarz, H. Simon, P. Spiller, K. Vogt
Atomic Physics · Cross-listed from hep-ph
Nucleon Electric Dipole Moments in Paramagnetic Molecules through Effective Field Theory
Wouter Dekens, Jordy de Vries, Lemonia Gialidi et al. (+3 more)
Electric dipole moment (EDM) measurements using paramagnetic molecules have significantly advanced over the last decade. Traditionally, these experiments have been analyzed in terms of the electron EDM. However, paramagnetic molecules are also sensitive to hadronic sources of charge-parity (CP) violation, highlighting the need for a new framework to interpret the experimental results. In this Letter, we introduce an effective field theory framework to relate molecular EDMs to the EDMs of
neutrons and
protons. We identify the dominant contributions through power counting and pinpoint the necessary
nuclear matrix elements. As a practical application, we employ the
nuclear shell model to calculate these
nuclear matrix elements for the polar molecule BaF. Finally, we estimate the limits on the nucleon EDMs set by current molecular EDM experiments.
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All authors Wouter Dekens, Jordy de Vries, Lemonia Gialidi, Javier Menéndez, Heleen Mulder, Beatriz Romeo
Optics
Resonance Engineering via Harnessing Anti-Parallel Dipole Image Coupling
Dip Sarker and Abdoulaye Ndao
Precise control of plasmonic resonances across a broad spectral range is central to the development of tunable optical devices. Yet, achieving both
redshifts and blueshifts within a single nanostructure has remained elusive. Here we introduce a metal-dielectric-metal (MDM) nanodisk array that enables bidirectional tuning of resonance wavelengths throughout the near-infrared (NIR) region. The observed spectral
evolution follows the plasmon ruler relationship, with unprecedented tuning properties. In particular, we report a record blueshift response of 457.82 nm for a small nanodisk thickness variation of only 5-10 nm, the highest blueshift response demonstrated in plasmonic architectures to date. This platform offers finely tunable resonances spanning an exceptionally wide NIR range, providing new insights into electromagnetic (EM) coupling mechanisms and establishing a foundation for next-generation tunable devices in sensing, optical communications, and dynamic displays.
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Biological Physics
Sound Masking Strategies for Interference with Mosquito Hearing
Justin Faber, Alexandros C Alampounti, Marcos Georgiades et al. (+2 more)
The use of auditory masking has long been of interest in psychoacoustics and for engineering purposes, in order to cover sounds that are disruptive to humans or to species whose habitats overlap with ours. In most cases, we seek to minimize the disturbances to the communication of wildlife. However, in the case of pathogen-carrying insects, we may want to maximize these disturbances as a way to control populations. In the current work, we explore candidate masking strategies for a generic model of active auditory systems and a model of the mosquito auditory system. For both models, we find that masks with all acoustic power focused into just one or a few frequencies perform best. We propose that masks based on rapid frequency modulation are most effective for maximal disruption of information transfer and minimizing intelligibility. We hope that these results will serve to guide the avoidance or selection of possible acoustic signals for, respectively, maximizing or minimizing communication.
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All authors Justin Faber, Alexandros C Alampounti, Marcos Georgiades, Joerg T Albert, Dolores Bozovic