Biological Physics · Cross-listed from q-bio.NC
Statistics of correlations in nonlinear recurrent neural networks
German Mato, Facundo Rigatuso and Gonzalo Torroba
The statistics of correlations are central quantities characterizing the collective dynamics of recurrent neural networks. We derive exact expressions for the statistics of correlations of nonlinear recurrent networks in the limit of a large number N of
neurons, including systematic 1/N corrections, in the regime of Gaussian quenched disorder. Our approach uses a path-integral representation of the network
stochastic dynamics, which reduces the description to a few collective variables and enables efficient computation. This generalizes previous results on linear networks to include a wide family of nonlinear activation functions, which enter as interaction terms in the path integral. These interactions can resolve the instability of the linear theory and yield a strictly positive participation dimension. We present explicit results for power-law activations, revealing scaling behavior controlled by the network coupling. In addition, we introduce a class of activation functions based on Pade approximants and provide analytic predictions for their correlation statistics. Numerical simulations confirm our theoretical results with excellent agreement. We also compare with previous works that have studied the complementary case with annealed disorder, and based on this we propose a new self-consistent equation for the more general case of colored noise.
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History and Philosophy of Physics
Lorentz, Poincare, Einstein, and the Genesis of the Theory of Special Relativity
Hector Giacomini
.This article reexamines the genesis of special relativity by situating the contributions of Lorentz, Poincare, and Einstein within the scientific, documentary, and editorial context of the years 1895–1913. It emphasizes the rapid circulation of Lorentz 1904 work, in particular through German-speaking channels such as the Beiblatter zu den Annalen der Physik, and reassesses the significance of Richard Gans 1905 review as a concise access point to Lorentz results. The article also discusses Poincaré role in formulating the principle of relativity, interpreting local time, establishing the group property of the Lorentz transformations, and developing an invariant formulation of electrodynamics. Against this background, Einstein 1905 paper appears not as an isolated creation, but as a powerful reformulation of problems already posed by Maxwellian electrodynamics and by the failure to detect motion through the ether. The article finally examines the subsequent construction of the Lorentz–Einstein–Minkowski canon and the relative exclusion of Poincare from that narrative. Its central claim is that special relativity should be understood as the crystallization of a broader electrodynamic transformation of physics, rather than as a sudden break detached from its immediate scientific context.
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Accelerator Physics
A Beamdump Facility at Jefferson Lab
Patrick Achenbach, Andrei Afanasev, Pawel Ambrozewicz et al. (+47 more)
This White Paper is exploring the potential of intense secondary
muon,
neutrino, and (hypothetical) light dark matter beams produced in interactions of high-intensity electron beams with beam dumps. Light dark matter searches with the approved Beam Dump eXperiment (BDX) are driving the realization of a new underground vault at Jefferson Lab that could be extended to a Beamdump Facility with minimal additional installations. The paper summarizes contributions and discussions from the International Workshop on Secondary Beams at Jefferson Lab (BDX & Beyond). Several possible
muon physics applications and
neutrino detector technologies for Jefferson Lab are highlighted. The potential of a secondary
neutron beam will be addressed in a future edition.
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All authors Patrick Achenbach, Andrei Afanasev, Pawel Ambrozewicz, Adi Ashkenazi, Dipanwita Banerjee, Marco Battaglieri, Jay Benesch, Mariangela Bondi, Paul Brindza, Alexandre Camsonne, Eric M. Christy, Ethan W. Cline, Chris Cuevas, Jens Dilling, Luca Doria, Stuart Fegan, Marco Filippini, Antonino Fulci, Simona Giovannella, Stefano Grazzi, Heather Jackson, Douglas Higinbotham, Cynthia Keppel, Vladimir Khachatryan, Michael Kohl, Hanjie Liu, Zhen Liu, Camillo Mariani, Ralph Marinaro, Kevin McFarland, Claudio Montanari, Vishvas Pandey, Eduard Pozdeyev, Jianwei Qiu, Patrizia Rossi, Riccardo Rossini, Todd Satogata, Glenn Schrader, Adrian Signer, Daniel Snowden-Ifft, Marco Spreafico, Diktys Stratakis, Manjukrishna Suresh, Holly Szumila, Julia Tena Vidal, Davide Terzania, Charlie Velasquez, Michael Wood, Takayuki Yamazaki, Yuhong Zhang
Physics and Society
Mapping Socio-Economic Divides with Urban Mobility Data
Yingche Liu and Mengyang Li
The massive digital footprints generated by bike-sharing systems in megacities like Shanghai offer a novel perspective on the urban socio-economic fabric. This study investigates whether these daily mobility patterns can quantitatively map the city's underlying social stratification. To overcome the persistent challenge of acquiring fine-grained socio-economic data, we constructed a multi-layered analytical
dataset. We annotated 2,000 raw bike trips with local economic attributes, derived from a novel data enrichment methodology that employs a Large
Language Model (LLM), and integrated contextual features of the built environment. A Random Forest model was then utilized as an interpretable framework to determine the key factors governing the relationship between mobility behavior and local economic status. The analysis reveals a compelling and unambiguous finding: a neighborhood's economic level, proxied by housing prices, is the single most dominant predictor of its bike-sharing patterns, substantially outweighing other geographic or temporal factors. This economic determinism manifests in three distinct ways: (1) a spatial clustering of resources, a phenomenon we term the club effect, which concentrates mobility infrastructure and usage in affluent areas; (2) a functional dichotomy between necessity-driven, utilitarian usage in lower-income zones and flexible, recreational usage in wealthier ones; and (3) a nuanced inverted U-shaped adoption curve that identifies the urban middle class as the system's primary user base.
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Physics and Society
Trends and Performance Visualization of Clutch Time in Japan's Professional B.League
Shota Shiiku and Jun Ichikawa
Reflecting the recent rise in Japanese basketball's competitiveness and pivotal outcomes in international tournaments, clutch-time performance has become increasingly critical. We examine clutch-time performance in Japan's B.League using play-by-play and box-score data from the 2023-24 season. Defining clutch time as the final five minutes with a score margin within five points, we compare efficiency and shot selection between clutch and non-clutch windows. We focus on effective field-goal percentage (eFG%) by spatial category, including In the Paint, Mid-Range, and 3-Point, and investigate league-wide and team-level trends. We further profile player archetypes in clutch minutes via K-means clustering on filtered box-score features. Results show that paint touches and clean three-point looks remain comparatively efficient under pressure, whereas mid-range outcomes are more context-dependent. Championship games exhibit tighter defense and scouting, moderating three-point accuracy for many teams. Our findings highlight the need for tactical flexibility, balancing efficient shot selection with adaptive counters to defensive pressure. We discuss strategic implications for late-game play-calling, spacing, and lineup choices, and outline limitations and future directions.
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General Physics
On the Invariant and Geometric Structure of the Holomorphic Unified Field Theory
J. W. Moffat and E. J. Thompson
We present the invariant structure of a Holomorphic Unified Field Theory in which
gravity and gauge interactions arise from a single
geometric framework. The theory is formulated using a product principal bundle, with one connection, and
curvature equipped with a Hermitian field on a complexification of spacetime. From a single $\mathrm{Diff}(M)\times G$-invariant action, variation yields the Einstein and Yang-Mills equations together with their paired Bianchi identities. A compatibility condition is implemented either definitionally or through an auxiliary penalty functional. It enforces that the antisymmetric part of our Hermitian field is the gauge field's exact
curvature on the real slice.
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Instrumentation and Detectors
Non-destructive diagnostics of fiber orientation in large planar fiber-reinforced concrete specimens
Václav Papež, Karel Künzel, Petr Konrád et al. (+2 more)
The mechanical performance of fiber-reinforced concrete is critically dependent on the orientation and concentration of its reinforcing fibers. This paper presents a non-destructive method for diagnosing fiber parameters in large planar specimens. The proposed technique utilizes an electromagnetic measurement system using electrical coils with commercial LCR meters, but also a novel custom-made meter suitable for factory environments, offering a practical solution for quality control in prefabrication of high-performance structural elements. This study details the theoretical background, experimental setup and methodology, and provides an evaluation of the diagnostic system's effectiveness and accuracy. The results demonstrate a strong correlation between the electromagnetic measurements and the actual fiber parameters, confirming the method's reliability.
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All authors Václav Papež, Karel Künzel, Petr Konrád, Kristýna Carrera, Petr Konvalinka
Computational Physics · Cross-listed from quant-ph
Asymptotic Vanishing of the Success Probability in Shor's Algorithm
João P. da Cruz
Shor's factoring
algorithm guarantees a success probability of at least one half for any fixed modulus N = pq with distinct
primes p and q. We show that this guarantee does not extend to the asymptotic regime. As N -> infinity, the multiplicative groups Omega_N = (Z/NZ)^x form a non-tight family of probability spaces, and the probability weight associated with successful bases, proportional to p(success | a', N) p(a' | N), decays as 1/phi(N). The ensemble of uniform measures {mu_N} therefore admits no weak limit, implying an asymptotic loss of ergodicity. Monte Carlo simulations up to N <= 10^6 confirm this decay and the absence of a stationary success probability. These results demonstrate that the "expected
polynomial time" in order finding is only locally defined: no global expectation exists once the arithmetic domain expands. The asymptotic vanishing of success probability explains the empirical absence of large-N implementations of Shor's
algorithm and sets a fundamental limit on the scalability of
quantum factoring.
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Instrumentation and Detectors
Detectors and Shieldings: Past and Future at LUNA
Chemseddine Ananna, Lucia Barbieri, Axel Boeltzig et al. (+11 more)
Nuclear reactions are responsible for the chemical
evolution of
stars,
galaxies and the Universe. Unfortunately, at temperatures of interest for
nuclear astrophysics, the cross-sections of the thermonuclear reactions are in the pico-femto-barn range and thus measuring them in the laboratory is extremely challenging. In this framework, major steps forward were made with the advent of underground
nuclear astrophysics, pioneered by the Laboratory for Underground
Nuclear Astrophysics (LUNA). The
cosmic background reduction by several orders of magnitude obtained at LUNA, however, needs to be combined with high-performance detectors and dedicated shieldings to obtain the required sensitivity. In the present paper, we report on the recent and future detector-shielding designs at LUNA.
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All authors Chemseddine Ananna, Lucia Barbieri, Axel Boeltzig, Matteo Campostrini, Fausto Casaburo, Alessandro Compagnucci, Laszlo Csedreki, Riccardo Maria Gesue, Jordan Marsh, Daniela Mercogliano, Denise Piatti, Duncan Robb, Ragandeep Singh Sidhu, Jakub Skowronski
Instrumentation and Detectors
SHADES – $^{22}$Ne($\alpha$,n)$^{25}$Mg reaction rate in the Gamow window
David Rapagnani, Chemseddine Ananna, Antonino Di Leva et al. (+4 more)
Neutron capture reactions are the main contributors to the synthesis of the heavy elements through the s-process. Together with $^{13}$C($\alpha$,n)16O, which has recently been measured by the LUNA collaboration in an energy region inside the Gamow peak, 22Ne({\alpha},n)25Mg is the other main
neutron source in
stars. Its cross section is mostly unknown in the relevant
stellar energy (450 keV < Ecm < 750 keV), where only upper limits from direct experiments and highly uncertain estimates from indirect sources exist. The ERC project SHADES (UniNa/INFN) aims to provide for the first time direct cross section data in this region and to reduce the uncertainties of higher energy resonance parameters. High sensitivity measurements will be performed with the new LUNA-MV accelerator at the INFN-LNGS laboratory in Italy: the energy sensitivity of the SHADES hybrid
neutron detector, together with the low background environment of the LNGS and the high beam current of the new accelerator promises to improve the sensitivity by over 2 orders of magnitude over the state of the art, allowing to finally probe the unexplored low-energy cross section. Here we present an overview of the project and first results on the setup characterization.
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All authors David Rapagnani, Chemseddine Ananna, Antonino Di Leva, Gianluca Imbriani, Matthias Junker, Marco Pignatari, Andreas Best
Instrumentation and Detectors
Analytic timing calculations and timing limits with prompt photons, high-aspect-ratio crystals, and complex TOF-kernels in TOF-PET
Nicolaus Kratochwil, Emilie Roncali and Gerard Arino-Estrada
Modeling the timing performance of light-based radiation detectors accurately is essential for optimizing time-of-flight positron emission
tomography (TOF-PET). We present an analytic framework that combines existing models to predict the timing behavior of high-aspect ratio
crystals, including contributions from
prompt photons such as Cherenkov radiation. This framework is built on a closed-form solution for optical light transport, convolved with the photodetector response and
photon production characteristics. Using conditional and joint probability distributions, we compute the first-
photon arrival time distribution for hybrid detectors with scintillation and Cherenkov light. The detection time distribution is then self-convolved to derive the time delay spectra and three timing metrics are used to characterize complex TOF kernels. Additionally, we perform Cramér-Rao Lower Bound calculations with and without depth-of-interaction bias to evaluate the theoretical timing limits. Our analytic predictions align well with Monte Carlo simulations for BGO detectors under varying
crystal thicknesses and single
photon time resolution considering a digital photodetector. We show that the TOF shape is significantly affected by
prompt photon statistics,
crystal thickness, scintillation yield, and photodetector properties resulting in distinct metric-dependent timing performance. The proposed model enables rapid timing predictions for polished
crystals, with the calculation time of a detector configuration in under a second, allowing for comprehensive parametric studies. This makes it a powerful tool for guiding detector development in fast-timing applications.
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Chemical Physics · Cross-listed from cond-mat.soft
Surface Excess Energy Governs the Non-Monotonic Behavior of Active Diffusivity with Activity
A. Arango-Restrepo and J.M. Rubi
Self-propulsion of particles is typically explained by phoretic mechanisms driven by externally imposed chemical, electric, or thermal gradients. In contrast, chemical reactions can enhance particle
diffusion even in the absence of such external gradients. We refer to this increase as active diffusivity, often attributed to self-diffusiophoresis or self-electrophoresis, although these mechanisms alone do not fully account for experimental observations. Here, we investigate active diffusivity in catalytic Janus particles immersed in reactive media without imposed gradients. We show that interfacial reactions generate excess surface energy and sustained interfacial stresses that supplement thermal energy, enabling
diffusion beyond the classical thermal limit. We consistently quantify this contribution using both dissipative and non-dissipative approaches, assuming that the aqueous bath remains near
equilibrium. Our framework reproduces experimentally observed trends in diffusivity versus activity, including the non-monotonic behaviors reported in some systems, and agrees with data for nanometric Janus particles catalyzing charged substrates as well as vesicles with membrane-embedded enzymes driven by ATP hydrolysis. These results demonstrate that chemical reactions can induce and sustain surface-tension gradients and surface excess energy, providing design principles for tuning mobility in synthetic active matter.
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Chemical Physics · Cross-listed from cond-mat.soft
The roles of elasticity and dimension in liquid-gel phase separation
Shichen Wang and Peter D. Olmsted
We compare six elastic models for
polymer networks in the context of phase separation within a gel, including a new model that combines the finite extensible Arruda-Boyce model and the slip tube model for entangled chains. We study incompressible uniaxial stretch and compression, and three volume-changing constrained-dimension deformations, in which the material can only deform in the designated dimensions(s) while the constrained direction(s) remain(s) the same. Each model responds differently to large deformations, and our proposed model successfully describes both strain softening and strain hardening, which are both present in well-entangled elastomers. When considering phase separation, we show that the commonly-used neo-Hookean model fails to admit a common tangent construction for phase coexistence for 3D deformations. This can be resolved by using a model with finite extension, such as the Arruda-Boyce model. In constrained-dimension deformations, where the gel's volume is allowed to change, for elastic models in which phase coexistence is possible, the critical temperatures increases and the critical concentration decreases with increasing deformation dimensions. This strong dependence of the phase diagram on spatial dimension and geometry distinguishes phase separation elastic media from conventional phase separation.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Imaging Nanoscale Carrier, Thermal, and Structural Dynamics with Time-Resolved and Ultrafast Electron Energy-Loss Spectroscopy
Wonseok Lee, Levi D. Palmer, Thomas E. Gage et al. (+1 more)
Time-resolved and ultrafast electron energy-loss spectroscopy (EELS) is an emerging technique for measuring photoexcited carriers,
lattice dynamics, and near-fields across femtosecond to microsecond timescales. When performed in either a specialized scanning transmission electron microscope or ultrafast electron microscope (UEM), time-resolved and ultrafast EELS can directly image charge carriers,
lattice vibrations, and heat dissipation following photoexcitation or applied bias. Yet recent advances in theoretical calculations and electron optics are often required to realize the full potential of ultrafast EEL spectrum imaging. In this review, we present a comprehensive overview of the recent progress in the theory and instrumentation of time-resolved and ultrafast EELS. We begin with an introduction to the technique, followed by a physical description of the loss function. We outline approaches for calculating and interpreting ground-state and transient EEL spectra spanning low-loss plasmons to core-level excitations analogous to X-ray absorption. We then survey the current state of time-resolved and ultrafast EELS techniques beyond
photon-induced near-field electron microscopy, highlighting abilities to image carrier and thermal dynamics. Finally, we examine future directions enabled by emerging technologies, including electron beam monochromation, in situ and operando
cells,
laser-free UEM, and high-speed direct electron detectors. These advances position time-resolved and ultrafast EELS as a critical tool for uncovering nanoscale dynamic processes in
quantum materials and
solar energy conversion devices.
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All authors Wonseok Lee, Levi D. Palmer, Thomas E. Gage, Scott K. Cushing
Chemical Physics · Cross-listed from quant-ph
Photoswitchable radicals as reporter spins for quantum sensing with spin defects in diamond
Lakshmy Priya Ajayakumar, David J. Durden, Aksshay Nandakumar Regeni et al. (+5 more)
The rapid decay of target signal strength with distance from the sensor presents a key challenge in nanoscale
magnetic sensing with nitrogen-vacancy (NV) centers in diamond, limiting both sensitivity and spatial resolution. Here we introduce a strategy to overcome this limitation by using radical anions formed from rhodamine-derived dyes as reporter
spins localized to the diamond surface. These radicals, generated through photoreduction, are optically identifiable and stable on timescales exceeding an hour. We experimentally demonstrate their coherent manipulation and detection using single, shallow NV centers for readout. We observe heterogeneity in the local
magnetic environments of the photoactivated
spins from site to site, likely due to variations in inter-radical couplings across our measurements. Looking forward, our approach enables correlative nanoscale
magnetic and optical imaging, and opens new pathways toward single-molecule
magnetic resonance studies.
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All authors Lakshmy Priya Ajayakumar, David J. Durden, Aksshay Nandakumar Regeni, Mingcai Xie, Swastik Hegde, Gustavo Aldas, Kyle Haggard, Mikael P. Backlund
Chemical Physics
GMTHRASHpy: Forward Convolutions of Crossed Molecular Beams Experiments in Python
Kazuumi Fujioka and Rui Sun
We introduce GMTHRASHpy, a Python-based application to do forward convolution fits of crossed molecular beams experiments. The code is designed to be easy-to-use and widely-available, so as to be of value to anyone wanting to reproduce data or fits from these experiments. GMTHRASHpy has been benchmarked to replicate the original GMTHRASH executable for a wide variety of published reactions. The inputs and
algorithm guiding it are explained. The code is open-source and can be downloaded at: github.com/kaka-zuumi/GMTHRASH. It can be installed with pip as gmthrash.
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Computational Physics
New GPU developments in the Madgraph CUDACPP plugin: kernel splitting, helicity streams, cuBLAS color sums
Andrea Valassi
The first production release of the CUDACPP plugin for the Madgraph5_aMC@NLO generator, which speeds up
matrix element (ME) calculations for leading-order (LO) processes using a data parallel approach on vector CPUs and GPUs, was delivered in October 2024. This was described in previous publications by the team behind that effort. In this paper, I describe my work on some additional developments and optimizations of CUDACPP, mainly but not exclusively for GPUs. The new approach, which represents a major restructuring of the CUDACPP computational engine, primarily consists in splitting the ME calculation, previously performed using a single large GPU kernel, into many smaller kernels. A first batch of changes, involving the move to separate "helicity streams" and the optional offloading of QCD color sums to BLAS, was recently merged into a new CUDACPP release, in collaboration with my colleagues. Since then, I have completed a second batch of changes, involving the possibility to split the calculation into groups of Feynman diagrams in separate source code files. This new feature makes it possible to compute QCD
matrix elements for physics processes with a larger number of final state
gluons: in particular, I present the first performance results from CUDACPP for the $2\!\rightarrow\!6$ process $gg\!\rightarrow\!t\bar{t}gggg$ on CPUs and GPUs and the $2\!\rightarrow\!7$ process $gg\!\rightarrow\!t\bar{t}ggggg$ on CPUs, which involve over 15k and 230k Feynman diagrams, respectively. I also take this opportunity to describe in detail some previously undocumented features of the CUDACPP software, both in the GPU and vector CPU implementations.
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Fluid Dynamics
Thermodynamic selection of stationary Rayleigh-Bénard flow states with slip and no-slip boundaries
Robert Hołyst, Paweł Jan Żuk, Konrad Giżyński et al. (+3 more)
Multiple stationary flow states may exist under the same external/boundary conditions, while the hydrodynamic equations alone do not provide a global criterion for determining which of these states is preferentially selected. Here, we formulate and test such a criterion for stationary Rayleigh-Bénard (RB) convection within a global non-
equilibrium thermodynamic description (Hołyst et al., EPL 149, 30001 (2025)). We find that each stationary flow state in RB convection is characterized by the state function $\mathcal{F}=-E_k-\Psi$, where $E_k$ is the macroscopic kinetic energy of the flow and $\Psi$ is a thermodynamic state function that emerges from the nonlinear inertial term in the Navier-Stokes equation and is associated with the compression and redistribution of the gas accompanying the formation of the convective state. Changes in $\mathcal{F}$ correspond to path-independent work between stationary states. We show that, among dynamically accessible stationary states, the state with the lower value of $\mathcal{F}$ is more stable and is preferentially selected. Both the macroscopic kinetic energy acquired by the flow and the accompanying thermodynamic reorganization of the gas therefore contribute in the same direction to lowering $\mathcal{F}$ and stabilizing the stationary state. We test the criterion using numerical solutions of the hydrodynamic equations for Rayleigh-Bénard convection with both slip and no-slip boundary conditions. For both types of boundary, the observed selection of competing stationary states is consistent with the thermodynamic prediction. The resulting state function provides a global criterion for the selection and stability of stationary hydrodynamic states. It establishes a direct connection between the nonlinear dynamics of the Navier-Stokes equation, thermodynamic work, and macroscopic flow stability.
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All authors Robert Hołyst, Paweł Jan Żuk, Konrad Giżyński, Jakub Wróbel, Anna Maciołek, Peter Vaughan Elsmere McClintock
Computational Physics · Cross-listed from cs.LG
Physics-Informed Neural Networks with Fourier Features and Attention-Driven Decoding
Rohan Arni and Carlos Blanco
Physics-Informed Neural Networks (PINNs) are a useful framework for approximating partial differential equation solutions using deep learning methods. In this paper, we propose a principled redesign of the PINNsformer, a
Transformer-based PINN architecture. We present the Spectral PINNSformer (S-Pformer), a refinement of encoder-decoder PINNSformers that addresses two key issues; 1. the redundancy (i.e. increased parameter count) of the encoder, and 2. the mitigation of spectral bias. We find that the encoder is unnecessary for capturing spatiotemporal correlations when relying solely on self-
attention, thereby reducing parameter count. Further, we integrate
Fourier feature
embeddings to explicitly mitigate spectral bias, enabling adaptive encoding of multiscale behaviors in the frequency domain. Our model outperforms encoder-decoder PINNSformer architectures across all
benchmarks, achieving or outperforming MLP performance while reducing parameter count significantly.
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Optics · Cross-listed from quant-ph
Levitated optomechanics with cylindrically polarized vortex beams
Felipe Almeida and Peter Barker
Optically levitated and cooled nanoparticles are a new
quantum system whose application to the creation of non-classical states of motion and
quantum limited sensing is fundamentally limited by
recoil and bulk heating. We study the creation of stable 3D optical traps using optical cylindrically polarized
vortex beams with radial and azimuthal polarization and show that a significant reduction in
recoil heating by up to an order of magnitude can be achieved when compared with conventional single Gaussian beam tweezers. Additionally these beams allow trapping of larger particles outside the Rayleigh regime using both bright and dark tweezer trapping with reduced
recoil heating. By changing the wavelength of the trapping
laser, or the size of the particles, non-linear and repulsive potentials of interest for the creation of non-classical states of motion can also be created.
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Physics and Society · Cross-listed from math.PR
Critical thresholds in stochastic rumors on trees
Jhon F. Puerres, Valdivino V. Junior and Pablo M. Rodriguez
The vertices of a tree represent individuals in one of three states: ignorant, spreader, or stifler. A spreader transmits the rumor to any of its nearest ignorant neighbors at rate one. At the same rate, a spreader becomes a stifler after contacting nearest-neighbor spreaders or stiflers. The rumor survives if, at all times, there exists at least one spreader. We consider two extensions and prove phase transition results for rumor survival. First, we consider the infinite Cayley tree of coordination number $d+1$, with $d\geq 2$, and assume that as soon as an ignorant hears the rumor, the individual becomes spreader with probability $p$, or stifler with probability $1-p$. Using coupling with branching processes we prove that for any $d$ there is a phase transition in $p$ and localize the critical parameter. By refining this approach, we extend the study to an inhomogeneous tree with hubs of degree $d+1$ and other vertices of degree at most $k=o(d)$. The purpose of this extension is to illustrate the impact of the distance between hubs on the dissemination of rumors in a network. To this end, we assume that each hub is, on average, connected to $\alpha (d+1)$ hubs, with $\alpha\in (0,1]$, via paths of length $h$. We obtain a phase transition result in $\alpha$ in terms of $d,k,$ and $h$, and we show that in the case of $k=\Theta(\log d)$ phase transition occurs iff $h \lesssim \Theta( \log d / (\log \log d))$.
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Optics
Novel phase unwrapping approach based on lateral resolution
Alim Yolalmaz and Jeroen Kalkman
The phase unwrapping plays a key role in obtaining a ground-truth phase of the wrapped phase. High-accurate unwrapped phases are demanded in various research fields such as optical holography, optical diffraction
tomography, and
magnetic resonance imaging. Unfortunately, the ground-truth phase is not accessible due to 2pi ambiguity which arises from phase jumps in the wrapped phase. In this paper, we propose a novel approach to improve the accuracy of unwrapping process. We increase the sampling frequency by employing a magnifying objective to reconstruct the unwrapped phase with high accuracy for the application of optical holography. Our result shows that optical magnification enables us to improve the accuracy of the true phase by 42%. We deeply believe that our approach will demonstrate significant achievement in obtaining ground-truth phases in various research fields such as optical holography,
magnetic resonance imaging, and optical diffraction
tomography.
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Optics
Programmable emergence through hierarchical self-organisation
Aladin Şura and F. Ömer Ilday
Predictively steering self-organising systems with hierarchical structure toward intended outcomes across widely separated dynamical scales remains a fundamental challenge. Despite decades of progress, hierarchy remains a descriptive property rather than a mechanism for control. Here, we show how a high-dimensional
stochastic system can be steered toward preselected target states by exploiting its internal hierarchy of timescales. Fast variables lock to slower collective variables; iterating this locking across scales progressively reduces the effective dynamics to a small set of externally controllable parameters. This enables directing the system while maintaining dynamical insulation from noise across scales, thereby turning hierarchy from an observation into a mechanism for programmable emergence. We experimentally demonstrate this approach in a fully tractable platform: a mode-locked
laser, in which we assemble and stabilise more than 100 pulses into harmonic patterns over timescales spanning 10 orders of magnitude. Phenomena such as nucleation,
quantum-noise-induced annihilation, long-range interactions and annealing-like ordering are predicted and exploited to transition the system to preselected states. Our results establish a route to programming emergent behaviour in driven-dissipative systems, with implications ranging from optics to materials.
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Optics
Learning the detector in optical tomography
Zijian Wang, Andreas Hauptmann, Lu Lu et al. (+1 more)
We propose a method to reconstruct the optical absorption of a highly-scattering medium probed by diffuse light. The method consists of learning the optical detection system and then using this result to reconstruct the absorption. Our results are illustrated by numerical simulations.
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All authors Zijian Wang, Andreas Hauptmann, Lu Lu, John C. Schotland
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Machine Learning Interatomic Potentials Enable Molecular Dynamics Simulations of Doped MoS2
Abrar Faiyad and Ashlie Martini
Dopants can tune the performance of MoS2 in various applications, but use of molecular dynamics simulations for doped MoS2 materials discovery is limited by the lack of multi-dopant interatomic potentials. Universal machine learning interatomic potentials (MLIPs) could be a solution, but the accuracy of these potentials must first be evaluated. Here, we evaluate the accuracy of a recently developed MLIP, META's Universal Model for Atoms (UMA), for 25 different MoS2 dopants spanning metals, non-metals, and transition metals in Mo substitution, S substitution, and intercalated positions by benchmarking the MLIP-predicted formation energy and the dopant-induced structural change against density functional theory calculations. The computational framework for MLIP validation and simulations are described in detail and the source code is made open source. The MLIP is then demonstrated by performing heating-cooling simulations of MoS2 supercells with all 25 dopants. These simulations capture complex phenomena including dopant clustering, MoS2 layer fracturing, interlayer
diffusion, and chemical compound formation at orders-of-magnitude reduced computational cost compared to density functional theory. This work provides a computational workflow for application-oriented design of doped-MoS2, enabling high-throughput screening of dopant candidates and optimization of compositions for targeted tribological, electronic, and optoelectronic performance. Github Repo Link: https://github.com/AbrarFaiyad/Machine-Learning-Interatomic-Potential-UMA-Enables-MD-Simulations-of-MoS2-Doped
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Medical Physics
A Novel Helical Thin-Film Flow Diverter: Design, Fabrication, and Computational Assessment of Hemodynamic Performance
Samuel Voss, Philipp Berg, Janneck Stahl et al. (+5 more)
Flow diversion has become a key treatment modality for selected intracranial aneurysms, relying on the principle that a dense mesh of stent wires disrupts blood flow into the aneurysm sac, promoting thrombosis and vessel reconstruction. Despite its clinical success, a subset of patients experiences incomplete occlusion or complications. This study investigates innovative helical thin-film implants (HTFIs), aiming to evaluate their flow-diverting efficacy. Highly resolved computational fluid dynamics simulations were performed on two representative patient-specific aneurysm models. Two HTFI design variants were tested at various configurations (two rolling angles and three deployment positions). A total of 28 unsteady hemodynamic simulations were performed, comparing six hemodynamically relevant parameters against the pre-interventional state and a conventional braided flow diverter. The HTFIs induced significant changes in intra-aneurysmal flow. Both designs performed similarly overall, with the shorter configurations (smaller rolling angle) demonstrating superior efficacy. These achieved average hemodynamic reductions of 52.2% and 58.4%, outperforming the
benchmark braided flow diverter device (47.4%). Sensitivity to positioning was modest, with the best configuration showing an average variation of only 5.3%, suggesting good robustness despite the helical design's heterogeneous porosity. These findings indicate that HTFIs offer promising flow-diverting capabilities. With further refinement in design and hemodynamic optimization, these implants hold potential as a next-generation alternative for the endovascular treatment of intracranial aneurysms, especially in applications requiring compatibility with smaller delivery systems.
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All authors Samuel Voss, Philipp Berg, Janneck Stahl, Daniel Behme, Gabor Janiga, Rodrigo Lima de Miranda, Eckhard Quandt, Prasanth Velvaluri
Fluid Dynamics
Frozen states in shear-induced coagulation: When history matters
Mingliang Xie
We discover a frozen state in decaying turbulent coagulation where the moment ratio M_C stabilizes at 4.5, defying the theoretical prediction of 2 for homogeneous systems. This persistent state emerges from historical
memory effects that freeze spatial correlations, challenging the reduction of spatially extended systems to zero-dimensional models. Our findings fundamentally reshape the understanding of long-term coagulation dynamics with immediate implications for aerosol science and industrial processing.
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Fluid Dynamics
Flow Development in the Entrance Region of Slender Converging Pipes
Vinicius Maron Sauer
This work presents an analytical investigation of the hydrodynamic entrance region in laminar flows through slender converging pipes. Extending previous analyses for straight pipes, the model radially divides the flow into a viscous wall region and a central core where both inertia and viscous effects are important. The study analyzes the impact of the inlet Reynolds number and convergence angle on the velocity profile and pressure drop. Results show that a converging geometry, which imposes a favorable pressure gradient, significantly shortens the hydrodynamic entrance length compared to a straight pipe. Analytical solutions show good agreement with numerical simulations.
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Plasma Physics
Difference in Neoclassical Edge Flows Between Strongly Negative and Positive Triangularities in the XGC Gyrokinetic Simulation
S. Ku, C. S. Chang, R. Hager et al. (+2 more)
The neoclassical baseline study of a strongly negative triangularity (NT)
plasma and the corresponding positive triangularity
plasma is performed using the edge-specialized, total-f gyrokinetic code XGC. A DIII-D-like
plasma is used, based on the negative triangularity discharge of DIII-D \#193793. An artificial positive triangularity (PT)
equilibrium has been constructed to compare the edge rotation physics at the same triangularity strength, but with opposite sign, while keeping the same elongation and other
geometric parameters. Carbon(+6) ions are added to the deuterium
plasma at an experimentally relevant level. By using the experimental profile of carbon toroidal rotation profile as an input, XGC finds that the deuteron rotation is significantly different from the carbon rotation at the inboard and outboard midplanes, mostly caused by the difference in the Pfirsch-Schluter rotation. More importantly, significant difference in the X-point orbit loss physics, thus the rotation source, is found between the positive and negative triangularity
equilibrium models. However, it is also found that the agreement between the present neoclassical simulation and the experimental NT data is validated only within the middle of pedestal slope, indicating the importance of edge
turbulence. This study could establish baseline for the multiphysics, multiscale studies that include
turbulence of negative triangularity
plasmas.
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All authors S. Ku, C. S. Chang, R. Hager, L. W. Schmitz, A. O. Nelson
Computational Physics
SHarmonic: A fast and accurate implementation of spherical harmonics for electronic-structure calculations
Xavier Andrade, Jacopo Simoni, Yuan Ping et al. (+2 more)
The authors present SHarmonic, a new implementation of the spherical harmonics targeted for electronic-structure calculations. Their approach is to use explicit formulas for the harmonics written in terms of normalized Cartesian coordinates. This approach results in a code that is as precise as other implementations while being at least one order of magnitude more computationally efficient. The library can run on graphics processing units (GPUs) as well, achieving an additional order of magnitude in execution speed. This new implementation is simple to use and is provided under an open source license, it can be readily used by other codes to avoid the error-prone and cumbersome implementation of the spherical harmonics.
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All authors Xavier Andrade, Jacopo Simoni, Yuan Ping, Tadashi Ogitsu, Alfredo A. Correa