Optics
Scalable and Programmable Topological Transitions in Plasmonic Moire Superlattices
Bo Tian, Xi Zhang, Ruitao Wu et al. (+3 more)
Topological transitions are fundamental phenomena in electronics, photonics, and
quantum technologies. However, the scalability and tunability of Topological transitions in these systems have still been constrained by their material properties or structural
rigidities. Here, we demonstrate that plasmonic Moire superlattices offer a platform for large-range and programmable topological transitions via wavefront engineering. By tailoring the phases of elementary evanescent waves in hexagonal systems, we create Moire-structured optical skyrmion
lattices whose topological invariants evolve programmably and scalably. Theoretical calculations indicate that the topological invariants span from -58 to +58 and are extendable by tuning the Moire angle. Remarkably, their values are constrained by
symmetry to exclude integer multiples of 3/2, revealing an intrinsic link between
symmetry and topological quantization. Our work establishes a versatile real-space
topology control platform for exploring topological transitions mechanisms and studying topologically critical phenomena, and further promoting breakthroughs in structured light, photonic computing, and condensed matter physics.
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All authors Bo Tian, Xi Zhang, Ruitao Wu, Yuquan Zhang, Luping Du, Xiaocong Yuan
Atomic Physics
Second-order correlations in directed emissions in sodium atoms
Ara Tonoyan, Sushree Subhadarshinee Sahoo, Anahit Gogyan et al. (+4 more)
We report on measurements of second-order intensity correlations $g^{(2)}(\tau)$ of infrared emission under bichromatic excitation at 589.2\,nm and 569.0\,nm of sodium atoms contained in a buffer-gas-free and uncoated 10-cm-long vapor
cell. Directional emissions at $2.34\,\mu$m in the forward direction and $2.21\,\mu$m in both forward and backward directions under different experimental parameters are considered for this study. The measured values of $g^{(2)}(0)$ in all cases are found to exceed unity, while remaining significantly below the thermal light limit of 2. Cross-correlation measurements reveal that forward- and backward-propagating $2.21\,\mu$m radiations are correlated. Oscillatory features in $g^{(2)}(\tau)$ are observed over a broad range of excitation powers, and the dependence of the oscillation frequency on
laser power can be attributed to AC Stark shifts, with contributions from hyperfine atomic structure in selected atomic velocity groups even in the presence of Doppler broadening. Our study establishes that the observed mid-infrared emission arises from a phase-matched, continuous-wave cooperative process that combines features of lasing and collective amplified spontaneous emission. The results highlight the buildup of long-range dipole coherence and velocity-selective coupling of atomic groups, which together govern the observed
photon correlations and forward-backward emission
symmetry. The demonstrated backward emission is of particular interest for applications in
laser guidestar generation and mesospheric remote sensing, where understanding the statistical properties of the emitted light is essential for optimizing sodium-based light sources.
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All authors Ara Tonoyan, Sushree Subhadarshinee Sahoo, Anahit Gogyan, Oleg Tretiak, Razmik Aramyan, Alexander Akulshin, Dmitry Budker
Fluid Dynamics
Fluid-kinetic multiscale solver for wall-bounded turbulence
Akshay Chandran, Praveen Kumar Kolluru, Berni J. Alder et al. (+2 more)
We present a two-level (fluid-kinetic) coupling procedure for the simulation of wall-bounded flows at Reynolds numbers up to thousands. The method combines a kinetic Direct Simulation Monte Carlo (DSMC) treatment of the near-wall layer, with a high-order
Lattice-Boltzmann (HOLB) scheme as a fluid solver in the bulk flow. Given the kinetic nature of HOLB, this coupling is expected to provide a physically accurate treatment of the near-wall instabilities which trigger the transition to
turbulence above a critical threshold around $Re_c \sim 750$. The coupled DSMC-HOLB solver is validated by simulating plane Poiseuille and Couette flows far from
equilibrium, i.e at finite Knudsen number regimes. Based on this validation, we provide the first preliminary evidence that the combination of HOLB and DSMC permits to observe the regeneration cycles of coherent structures which arise above a critical value of the Reynolds number. This task would be hardly attainable by either of the two solvers separately; while DSMC can capture strong near-wall non-
equilibrium effects, it lacks the compute power to deal with both near-wall and bulk flow at the same time. We look to HOLB to make it computationally feasible to perform such a simulation. The present two-level coupling procedure may pave the way to a new generation of fluid-kinetic simulations of wall-bounded turbulent flows, thus helping to gain deeper insights into the role of wall micro-corrugations in triggering the dynamic instabilities that drive the transition to turbulent regimes.
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All authors Akshay Chandran, Praveen Kumar Kolluru, Berni J. Alder, Sauro Succi, Santosh Ansumali
Physics and Society · Cross-listed from astro-ph.IM
High-impact Scientific Software in Astronomy and its creators
Johannes Buchner
In the last decades, scientific software has graduated from a hidden side-product to a first-class member of the astrophysics literature. We aim to quantify the activity and impact of software development for astronomy, using a systematic survey. Starting from the Astrophysics Source Code Library and the Journal of Open Source Software, we analyse 3432 public git-based scientific software packages. Paper abstract text analysis suggests seven dominant themes: cosmology, data reduction pipelines,
exoplanets, hydrodynamic simulations, radiative transfer spectra simulation, statistical inference and
galaxies. We present key individual software contributors, their affiliated institutes and countries of high-impact software in astronomy & astrophysics. We consider the number of citations to papers using the software and the number of person-days from their git repositories, as proxies for impact and complexity, respectively. We find that half of the mapped development is through US-affiliated institutes, and a large number of high-impact projects are led by a single person. Our results indicate that there are currently over 200 people active on any given day to improve software in astronomy.
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Optics
Multimodal Fusion Network for Micro-displacement Measurement via Michelson Interferometer
Zixing Jia, Jiawei Li, Ziping Chen et al. (+1 more)
We propose a
multimodal fusion network (MFN) for precise micro-displacement measurement using a modified Michelson interferometer. The model resolves the intrinsic half-wave displacement ambiguity that limits conventional single-wavelength interferometry by introducing a dual-head learning mechanism: one head performs sub-half-wave displacement regression, and the other classifies integer interference orders. Unlike dual-wavelength or iterative fitting methods, which require high signal quality and long computation time, MFN achieves robust, real-time prediction directly from interferometric images. Trained on 2x10^5 simulated interferograms and fine-tuned with only about 0.24% of real experimental data (about 500 images), the model attains a displacement precision of 4.84(15) nm and an order-classification accuracy of 98%. Even under severe noise, MFN maintains stable accuracy (about 16 nm RMSE), whereas conventional heuristic
algorithms exhibit errors exceeding 100 nm. These results demonstrate that MFN offers a fast, noise-tolerant, and cost-efficient solution for single-wavelength interferometric metrology, eliminating the need for multi-wavelength hardware or complex phase fitting.
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All authors Zixing Jia, Jiawei Li, Ziping Chen, Xin Li
Chemical Physics
Chemistry-Enhanced Diffusion-Based Framework for Small-to-Large Molecular Conformation Generation
Yifei Zhu, Jiahui Zhang, Jiawei Peng et al. (+3 more)
Obtaining 3D conformations of realistic polyatomic molecules at the
quantum chemistry level remains challenging, and although recent machine learning advances offer promise, predicting large-molecule structures still requires substantial computational effort. Here, we introduce StoL, a
diffusion model-based framework that enables rapid and knowledge-free generation of large molecular structures from small-molecule data. Remarkably, StoL assembles molecules in a LEGO-style fashion from scratch, without seeing the target molecules or any structures of comparable size during training. Given a SMILES input, it decomposes the molecule into chemically valid fragments, generates their 3D structures with a
diffusion model trained on small molecules, and assembles them into diverse conformations. This fragment-based strategy eliminates the need for large-molecule training data while maintaining high scalability and transferability. By
embedding chemical principles into key steps, StoL ensures faster convergence, chemically rational structures, and broad configurational coverage, as confirmed against DFT calculations.
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All authors Yifei Zhu, Jiahui Zhang, Jiawei Peng, Mengge Li, Chao Xu, Zhenggang Lan
Optics
Photonic spin Hall effect in $\mathcal{PT}$-symmetric non-Hermitian cavity magnomechanics
Shah Fahad, Muzamil Shah and Gao Xianlong
Non-Hermitian cavity magnomechanics (CMM), which incorporates the
magnon-
photon and
magnon-
phonon interactions simultaneously, enables rich physical phenomena, including exceptional-point-enhanced sensing, and offers pathways toward topological transitions and nonreciprocal
quantum transformation. These interactions exert a pivotal influence on the optical response of a weak probe field and pave the way for novel applications in
quantum technologies. In this work, we consider a yttrium-iron-garnet (YIG) sphere coupled to a microwave cavity. The
magnon mode of the YIG sphere is directly excited through microwave field coupling, whereas the cavity mode is probed via a weak-field interrogation scheme. The direct interaction of a traveling field with the
magnon mode induces gain in the system, thereby establishing non-Hermitian dynamics. The parity-time (PT)-symmetric behavior of a hybrid non-Hermitian CMM is designed and investigated.
Eigenvalue spectrum analysis demonstrates that a third-order exceptional point (EP_3) emerges under tunable effective
magnon-
photon coupling when the traveling field is oriented at an angle of \pi/2 relative to the cavity's x-axis. The photonic
spin Hall effect (PSHE) in a reflected probe field is subsequently examined in such a system. Under balanced gain and loss conditions and in the presence of effective
magnon-
phonon coupling, tunable effective
magnon-
photon coupling enables coherent control of the PSHE across the broken PT-symmetric phase, at the EP_3, and in the PT-symmetric phase. Investigation reveals that the PSHE can be significantly enhanced or suppressed via effective
magnon-
photon coupling. The influence of intracavity length on the PSHE is further explored, providing an additional parameter for fine-tuning the transverse shift. These findings establish a direct correspondence between the PSHE and the underlying non-Hermitian
eigenvalue spectrum.
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Computational Physics · Cross-listed from cs.LG
FGM optimization in complex domains using Gaussian process regression based profile generation algorithm
Chaitanya Kumar Konda, Piyush Agrawal, Shivansh Srivastava et al. (+1 more)
This manuscript addresses the challenge of designing functionally graded materials (FGMs) for arbitrary-shaped domains. Towards this goal, the present work proposes a generic volume fraction profile generation
algorithm based on Gaussian Process Regression (GPR). The proposed
algorithm can handle complex-shaped domains and generate smooth FGM profiles while adhering to the specified volume fraction values at boundaries/part of boundaries. The resulting design space from GPR comprises diverse profiles, enhancing the potential for discovering optimal configurations. Further, the
algorithm allows the user to control the smoothness of the underlying profiles and the size of the design space through a length scale parameter. Further, the proposed profile generation scheme is coupled with the genetic
algorithm to find the optimum FGM profiles for a given application. To make the genetic
algorithm consistent with the GPR profile generation scheme, the standard simulated binary crossover operator in the genetic
algorithm has been modified with a projection operator. We present numerous thermoelastic optimization examples to demonstrate the efficacy of the proposed profile generation
algorithm and optimization framework.
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All authors Chaitanya Kumar Konda, Piyush Agrawal, Shivansh Srivastava, Manish Agrawal
Plasma Physics
Comparison of the Impacts of Three Types of Plasma-Activated Water on the Seed Germination and Plant Growth of Lettuce (Lactuca sativa)
Ramin Mehrabifard, Adriana Misuthova and Zdenko Machala
Cold air
plasma typically generates reactive oxygen and nitrogen species (RONS), which are transported into water to produce
plasma-activated water (PAW). This study examines the effect of PAW produced by three different
plasma systems on lettuce: transient spark, fountain dielectric barrier discharge, and microwave
plasma. Physiochemical PAW properties and concentrations of RONS (ozone, hydrogen peroxide, nitrite, and nitrate) were measured. Seed germination parameters were recorded in 8-day paper tests. The effect of PAW irrigation was investigated after 6 weeks of plant growth in the soil by measuring the germination rate, plant and root length, dry and fresh plant weight, number of leaves, and photosynthetic pigments. PAW, dependent upon its RONS contents, enhances plant development and affects its physiological parameters.
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Fluid Dynamics
Controlled particle displacement by hydrodynamic obstacle interaction in non-inertial flows
Partha Kumar Das, Xuchen Liu and Sascha Hilgenfeldt
Systematic deflection of microparticles off of initial streamlines is a fundamental task in microfluidics, aiming at applications including sorting, accumulation, or capture of the transported particles. In a large class of setups, including Deterministic Lateral Displacement and porous media filtering, particles in non-inertial (Stokes) flows are deflected by an array of obstacles. We show that net deflection of force-free particles passing an obstacle in Stokes flow is possible solely by hydrodynamic interactions if the flow and obstacle geometry break fore-aft
symmetries. The net deflection is maximal for certain initial conditions and we analytically describe its scaling with particle size, obstacle shape, and flow geometry, confirmed by direct trajectory simulations. For realistic parameters, separation by particle size is comparable to what is found assuming contact (roughness) interactions. Our approach also makes systematic predictions on when short-range attractive forces lead to particle capture or sticking. In separating hydrodynamic effects on particle motion strictly from contact interactions, we provide novel, rigorous guidelines for elementary microfluidic particle manipulation and filtering.
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Optics
Three-Photon Saturable Absorption in Atomically Thin Phlogopite
Nabarun Mandal, Sagnik Chakraborty, Ranjeet Singh et al. (+10 more)
Two-dimensional (2D) materials, due to their remarkable physical and chemical properties, hold significant potential for future optical and electrical applications. In this study, the synthesis of 2D phlogopite (magnesium-rich mica) via
liquid-phase exfoliation (LPE) is reported using an efficient and scalable procedure. XRD structural analysis revealed a preferential orientation along the (033) plane, whereas AFM and SEM demonstrated a nanoscale thickness and homogeneous morphology. Optical characterisation by UV-Vis and Raman spectroscopy shows tuneable band gaps up to 4.52 eV for the exfoliated 2D phlogopite and distinct vibrational modes indicative of structural
evolution. At intense
laser conditions, three-
photon saturable absorption (3PSA) behaviour was evidenced by light-modulated electrical property studies, which emphasise the potential for optical limiting, switching, and mode-locking applications. The present investigation indicates 2D phlogopite as a versatile material for next-generation optoelectronic devices of high-intensity light modulation.
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All authors Nabarun Mandal, Sagnik Chakraborty, Ranjeet Singh, Jhionathan de Lima, Saswata Goswami, Binay Bhushan, Rahul Rao, Nicholas R. Glavin, Ajit K. Roy, Vidya Kochat, Cristiano Francisco Woellner, Prasanta Kumar Datta, Chandra Sekhar Tiwary
Atomic Physics
Response time of electrons to light in strong-field ionization of polar molecules
Jiayin Che, Sheng Ye, Shiqi Shen et al. (+2 more)
We study tunneling ionization of HeH+ in strong elliptical
laser fields numerically and analytically. The calculated photoelectron momentum distribution (PMD) show two different offset angles corresponding to ionization events occurring in the first and the second half cycles of one
laser cycle. When the larger angle is greater than the angle of a model symmetric molecule with a similar ionization potential to the polar molecule, the smaller angle is smaller than the symmetric molecule. Using a developed strong-field model that consider effects of both the permanent dipole (PD) and the asymmetric Coulomb potential, we are able to quantitatively reproduce these phenomena. We show that the PD effect can increase (decrease) the response time of electrons within polar molecules to light in photoemission, thereby increasing (decreasing) the offset angle related to the first (second) half cycle of a
laser cycle. The
laser-dressed asymmetric Coulomb potential near the atomic
nuclei also plays an important role in the sub-cycle-related response time and offset angle. This model may be useful for quantitatively studying attosecond ionization dynamics of polar molecules in strong
laser fields.
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All authors Jiayin Che, Sheng Ye, Shiqi Shen, Weiyan Li, Yanjun Chen
Optics
Observation of Joule-Thomson photon-gas expansion
Marco S. Kirsch, Georgios G. Pyrialakos, Richard Altenkirch et al. (+9 more)
In recent years, a self-consistent optical thermodynamic framework has emerged that offers a systematic methodology to understand, harness and exploit the complex collective dynamics of multimode nonlinear systems. These developments now allow consideration of a series of longstanding problems in optics, including the prospect of funnelling the entire power flowing in a multimode system into its ground state, for which no methodology currently exists. Here, we demonstrate an all-optical Joule-Thomson expansion process mediated by
photon-
photon interactions whereby the temperature of the optical gas drops abruptly to zero. Our experiments in various configurations of coupled multicore nonlinear waveguide arrangements illustrate how light undergoing expansion-induced cooling can be channelled from arbitrary input states into the fundamental mode with near-unity efficiency. We show that the stability of the post-expansion state is ensured through an irreversible process of energy conversion. The all-optical thermodynamic phenomena explored in this study may enable innovative techniques where various uncorrelated but identical sources are merged into a unified spatially coherent state, offering a route for direct beam combining.
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All authors Marco S. Kirsch, Georgios G. Pyrialakos, Richard Altenkirch, Mahmoud A. Selim, Julius Beck, Tom A. W. Wolterink, Huizhong Ren, Pawel S. Jung, Mercedeh Khajavikhan, Alexander Szameit, Matthias Heinrich, Demetrios N. Christodoulides
Optics
Overcoming Residual Timing Jitter in Pump-Probe Interferometry via Weak Value Amplification and Deep Learning
Jing-Hui Huang and Xiang-Yun Hu
We introduce a hybrid methodology that synergistically combines weak value amplification (WVA) and deep learning to suppress the limiting effects of residual timing jitter in pump-probe interferometry, achieved through simulations of pump-induced time delays at a few-attosecond resolution. The WVA protocol, employing real weak values, amplifies the minute delay induced by sample perturbation, thereby translating it into a measurable shift of interference fringes. However, this amplification introduces significant fringe distortion. To address this, we deploy deep learning architectures as high-precision parameter
estimators: a convolutional neural network regressor (CNN-Regressor) for direct delay estimation and a classifier (CNN-Classifier) for discrete delay categorization. These are systematically benchmarked against traditional
Fourier-transform-based analysis. Two key conclusions are drawn: (i) The WVA technique consistently enhances measurement precision across all
estimators by effectively increasing the signal-to-noise ratio (SNR). (ii) Both deep learning models surpass the traditional FFT approach; the CNN-Regressor achieves a higher SNR at small weak values, while the CNN-Classifier enables accurate estimation even under a challenging "$\pi$ phase shift" condition where conventional analysis fails. This synergistic combination of WVA and deep learning establishes a powerful framework for attosecond metrology, paving the way for enhanced precision in ultrafast spectroscopy.
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Optics
100 Mfps ghost imaging with wavelength division multiplexing
Shin Motooka, Noriki Komori, Tomoaki Niiyama et al. (+1 more)
Ghost imaging (GI) and single-pixel imaging (SPI) techniques enable image reconstruction without spatially resolved detectors, offering unique access to wide spectral ranges and challenging imaging environments. Yet, their adoption has been limited by the slow generation of mask patterns, which constrains achievable frame rates. Here, we demonstrate ultrafast GI that achieves a spatial-temporal information flux of 78.4 gigapixels per second across five wavelengths, which is at least two orders of magnitude larger than that reported for previous training-data-free GI approaches. This breakthrough is enabled by 25 GHz speckle pattern switching and allows parallelizing the pattern illumination using a wavelength-division multiplexing (WDM) technique. We show that the proposed approach is capable of reconstructing 28$\times$28-pixel images at the exposure time of 10 ns, achieving 100 megaframes per second (Mfps), and demonstrate the GI of a microsecond-scale dynamic event. This approach opens avenues for studying rapid processes in physics, chemistry, and biology, where conventional cameras are limited by detector bandwidth, readout speed, or cost.
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All authors Shin Motooka, Noriki Komori, Tomoaki Niiyama, Satoshi Sunada
Optics
Temperature bandgaps and engineered thermal state access in driven nanophotonic resonators
Punnag Padhy, Mohammad Asif Zaman and Jennifer Dionne
We show that strong thermo-optic feedback in nanophotonic resonators creates forbidden steady state temperatures that are unreachable under any static excitation. This temperature bandgap opens when thermo-optic feedback gain overcomes optical and thermal dissipation, splitting an otherwise continuous thermal landscape into disconnected accessible bands. We experimentally map this temperature band structure using quasi-bound states in the continuum resonances in silicon metasurfaces. Continuous wavelength scans exploit spectrally accumulated thermal energy to access the forbidden interval, reaching up to ~88{\deg}C higher temperature than static excitation, both at the same wavelength and maximum power. A characteristic three-stage temperature rise near the band edge confirms the -1/2 critical exponent of saddle-node bifurcations and enables quantitative extraction of band-edge wavelengths. Combining external thermal bias with optical excitation drives programmable interband transitions, enabling nearly 8.5-fold amplification of temperature rise and wavelength-selective switching between thermal states separated by just 1 nm in excitation wavelength. The bandgap is fully designable through metasurface geometry and hybrid material integration, which tune optical absorption, confinement and resonance linewidth. These results establish the temperature bandgap as a designable degree of freedom in driven nanophotonic systems, opening routes toward all-optical thermal logic and programmable photothermal control of chemical and biological processes.
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Optics
Optical multistability in a compact microcavity enabled by near-exceptional coupling
Zhen Liu, Xuefan Yin, Andrey Bogdanov et al. (+5 more)
Multistability – the emergence of multiple stable states under identical conditions – is a hallmark of nonlinear complexity and an enabling mechanism for multilevel optical
memory and photonic computing. Its realization in a compact footprint, however, is limited by intrinsically weak optical nonlinearities and the enlarged free spectral range that raises the multistability threshold. Here, we overcome this constraint by engineering a pair of spectrally close, ultra-high-Q resonances in a photonic
crystal microcavity. Leveraging structural perturbations that deliberately introduce non-Hermitian coupling through a shared radiation channel, we drive the resonances toward an exceptional point with nearly degenerate wavelengths and balanced quality factors approaching $10^6$. This configuration substantially enhances thermo-optical nonlinearity and produces pronounced tristability and hysteresis loops within a footprint of 20 {\mu}m at input powers below 240 {\mu}W. We further demonstrate proof-of-concept optical random-access
memory through controlled switching among multistable states. These results establish a general strategy for nonlinear microcavities to achieve energy-efficient multistability for reconfigurable all-optical
memories, logic, and neuromorphic processors.
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All authors Zhen Liu, Xuefan Yin, Andrey Bogdanov, Yujia Nie, Yi Zuo, Hongbin Li, Feifan Wang, Chao Peng
History and Philosophy of Physics
Bessel-Hagen on the extension of Noether's theorems and their application to classical electromagnetism
Valeriya Chasova
This work analyses the 1921 article by Erich Bessel-Hagen entitled Über die Erhaltungssätze der Elektrodynamik ("On the conservation laws of electrodynamics"). The article is based on Noether's
theorems, which were formulated by Emmy Noether in 1918 and concern consequences of
symmetries of actions, including conservation laws. Bessel-Hagen firstly extends Noether's
theorems to
symmetries up to a divergence and next applies them to the n-body problem and to classical electromagnetism, especially to its conformal
symmetries. The work explains the context in which Bessel-Hagen's article was written, the way his explanations proceeded and the significance of his results. It is argued in particular that Bessel-Hagen's article as much as Noether's are best considered as elements of Felix Klein's Erlangen programme. A close reading of Bessel-Hagen's text is also provided, as is its comparison with relevant works, including recent works by philosophers of physics Katherine Brading, Harvey Brown and Peter Holland. Such an approach helps to see where Bessel-Hagen's treatment is confused and to clarify it, as well as to estimate the advancement in our understanding of the relevant topics made within the last one hundred years.
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Atomic Physics
Hyperfine-Resolved Spectroscopy of Dysprosium Monoxide (DyO) for Precision Measurements of the Nuclear Schiff Moment
Zack D. Lasner, Aidan T. Ohl, Nicole M. Albright et al. (+5 more)
We perform
laser spectroscopy of dysprosium monoxide (DyO) to determine the hyperfine structure of the ground X8 and excited [17.1]7 states in the $^{161}$Dy and $^{163}$Dy isotopologues. These dysprosium
nuclei have non-zero
nuclear spin and dynamical octupole deformation, which gives them high sensitivity to time-reversal-violating new physics via the
nuclear Schiff moment (NSM). The DyO molecule was recently identified as being amenable to optical cycling – the basis for many
laser cooling and
quantum control techniques – which makes it a practical candidate for NSM searches. The measurements reported here are prerequisites to implementing optical cycling, designing precision measurement protocols, and benchmarking calculations of molecular sensitivity to
symmetry-violating effects. The measured hyperfine parameters are interpreted using simple molecular orbital diagrams and show excellent agreement with relativistic
quantum chemical calculations.
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All authors Zack D. Lasner, Aidan T. Ohl, Nicole M. Albright, Kendall L. Rice, Charlene Peng, Lan Cheng, John M. Doyle, Benjamin L. Augenbraun
Optics
Channel Ordering for Fairness in Elastic Optical Networks via a LLM-Guided Bottleneck TSP Solver
Liangshun Wu, Wen Chen and Qingqing Wu
In flexible-grid elastic optical networks (EONs), the ordering of frequency channels plays a crucial role in managing inter-channel interference and ensuring signal quality. We address the Channel Ordering Problem (COP) by reformulating it as a Bottleneck Traveling Salesman Problem (BTSP), where interference among channels is represented as edge weights in a graph structure. To tackle this challenge efficiently, we develop a scalable approach that integrates statistical exploration with guidance from large
language models (LLMs). Extensive simulations using both the Gaussian Noise (GN) model and the split-step
Fourier method demonstrate that our method achieves near-optimal signal-to-noise ratio (SNR) performance and offers robust scalability across diverse network settings, making it well-suited for practical deployment in large-scale optical communication systems.
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Plasma Physics
An Adjoint Formulation of Energetic Particle Confinement
Christopher J. McDevitt and Jonathan S. Arnaud
An adjoint formulation of energetic particle confinement in axisymmetric tokamak geometry is derived and evaluated using a physics-informed neural network (PINN). The PINN estimates the mean escape time of energetic ions by solving an inhomogeneous adjoint of the drift kinetic equation with a Lorentz collision operator, yielding predictions of fast ion loss in tokamak geometry due to direct ion orbit loss and collisional transport. To our knowledge, this is the first time a PINN has been used to solve the drift kinetic equation in tokamak geometry, a challenging problem due to the large time scale separation between the rapid transit time of energetic ions and their slow collisional time scale. It is shown that a careful and intentional design of a PINN is able to learn the mean escape time across the majority of the
plasma volume, suggesting a path toward constructing a rapid surrogate for use within a broader optimization framework.
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Plasma Physics
Parallelized Real-time Physics Codes for Plasma Control on DIII-D
A. Rothstein, K. Erickson, R. Conlin et al. (+2 more)
A real-time safe multi-threading library was developed on the DIII-D
plasma control system to optimize the realtime TORBEAM and real-time STRIDE physics codes. These physics codes are crucial for future fusion power plant operation as they provide information about electron cyclotron wave propagation and heating as well as inform about ideal
plasma stability limits. The real-time TORBEAM code executed consistently in under 20 ms while the real-time STRIDE code computes in 100 ms. The multi-threading library developed in this work can be applied to other real-time physics-based codes that will be crucial for the next generation of fusion devices.
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All authors A. Rothstein, K. Erickson, R. Conlin, A. Bortolon, E. Kolemen
Fluid Dynamics
Triaxial Asymmetry Driven Rotational Dynamics and Lateral Equilibrium Position in Inertial Flow
Takayuki Suzuki, Anna B. Stephenson, Jinsik Yoon et al. (+7 more)
The growing use of triaxial particles in microfluidic, microrobotic, and biological systems makes it essential to understand how their rotational dynamics couples with lateral migration in microscale flows. Our experiments in inertial Poiseuille flow reveal that
geometric asymmetry in triaxial, multifaceted disks governs their orientation, migration, and rotational period, distinguishing them from classical axisymmetric objects. We identified a Reynolds- and geometry-dependent shift in preferred rotational orientation, arising from the Dzhanibekov effect, with transition modes determined by the particle's principal-axis configuration. We quantified a scalar offset from Jeffery's orbit prediction and introduced a fitting parameter that generalizes the Jeffery equation to include moment-of-inertia effects on rotational dynamics. Finally, we report the diameter of gyration as a predictor of the lateral
equilibrium position of inertially focused triaxial particles. Our results link particle asymmetry to migration and rotation in flow, expanding our understanding of particle dynamics.
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All authors Takayuki Suzuki, Anna B. Stephenson, Jinsik Yoon, Junghyun Bae, Sung-Eun Choi, Kilho Son, Diego Alba Burbano, Harrison Khoo, Wook Park, Soojung Claire Hur