Mathematical Physics · Cross-listed from cs.DC
Communication Strategy Selection for Multi-GPU 3D FDTD with Convolutional Perfectly Matched Boundary Layers
Victory C. Obieke
In this paper we describe a communication-strategy study for multi-GPU three-dimensional finite-difference time-domain computation with convolutional perfectly matched layer boundary conditions using CUDA. The metrics used to determine the most effective implementation include runtime, throughput in millions of output points per second, strong-scaling efficiency, CPML overhead, host-staged versus direct GPU-to-GPU exchange speedup, and enlarged-ghost speedup. On a single NVIDIA Quadro RTX 6000 GPU, the CPML implementation sustains 2,889–3,290 million output points per second with less than 1% boundary-layer overhead, providing the single-GPU baseline for the multi-GPU study. The results show that direct GPU-to-GPU peer exchange is the dominant optimization with a 2.46–2.76$\times$ speedup over host-staged exchange, while enlarged ghost regions give only modest benefits because the reduced communication frequency is partly offset by redundant computation and additional
memory traffic. On NVIDIA Quadro RTX 8000 GPUs, the implementation gives up to a 1.51$\times$ speedup on two GPUs for the tested strong-scaling cases, while four GPUs enable larger grids that approach or exceed single-GPU
memory capacity.
Read the full abstract ▾
Optics
Circular Raman responses from angular-momentum inequivalence in CoSi
Yuki Suganuma, Gakuto Kusuno, Kohei Miyazaki et al. (+8 more)
Circularly polarized Raman scattering in solids exhibits distinct phenomena such as Raman optical activity (ROA) and
chiral-
phonon-induced frequency splitting, whose relationship has remained unclear. Here we show that these seemingly different responses can be understood within a common framework based on the inequivalence of
phonon states carrying opposite
crystal angular momenta. Using helicity-resolved Raman spectroscopy of the
chiral crystal CoSi, we find that ROA and frequency splitting arise from different
symmetry channels, namely axial multipolar
symmetry and structural chirality, respectively. First-principles calculations reproduce both effects and clarify their
symmetry origins. These results establish angular-momentum inequivalence as a unifying principle of circular Raman responses and link helicity-resolved Raman spectroscopy to the angular-momentum structure of
chiral phonons in topological materials.
Read the full abstract ▾
All authors Yuki Suganuma, Gakuto Kusuno, Kohei Miyazaki, Hikaru Watanabe, Rikuto Oiwa, Ryotaro Arita, Satoshi Iwasaki, Yoshiki Yasuoka, Yusuke Kousaka, Yoshihiko Togawa, Takuya Satoh
Cosmology and Nongalactic Astrophysics
Inverse-Scattering Reconstruction of Inflation from Scalar and Tensor Primordial Spectra
Jorge Mastache and Allan Hurtado
We develop an inverse-scattering framework to reconstruct the effective inflationary potentials governing scalar and tensor perturbations. By recasting the Mukhanov–Sasaki equation as a Schrödinger-like problem on the half-line, we identify the Bunch–Davies initial condition with the asymptotic Jost solution and show that the freeze-out amplitude of the growing mode is encoded in the corresponding Jost function. This allows the scalar and tensor
primordial power spectra to be written in terms of $F^{(s)}_{\nu_s-\frac12}(k)$ and $F^{(t)}_{\nu_t-\frac12}(k)$, respectively, and leads to an inverse-scattering expression for the tensor-to-scalar ratio as a ratio of Jost amplitudes. We then test the reconstruction in the large-$k$ regime using the Born approximation, where the Marchenko equation becomes linear. As
benchmarks, we consider a smooth quadratic potential and a step potential that transiently violates slow roll and generates localized features in the
primordial spectra. The reconstructed effective potentials reproduce the dominant behavior of $z^{\prime\prime}/z$ and $a^{\prime\prime}/a$ for smooth slow-roll
evolution, while localized discrepancies arise in the scalar sector when sharp features induce stronger scattering. Our results show that inverse scattering provides a physically transparent method for connecting features in the
primordial spectra to the underlying inflationary dynamics, and that the Jost function acts as a sensitive diagnostic of departures from canonical slow-roll
evolution.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
MOSES – The MONET Star and Exoplanet Spectrograph
S. Schäfer, L. Schmidt, H. Anwand-Heerwart et al. (+2 more)
We introduce MOSES, the new High-Resolution Echelle Spectrograph designated for the 1.2m MONET
telescope at McDonald Observatory, Texas, USA. The science drivers are radial velocity experiments and activity monitoring in Sun-like
stars. Set for installation in the final quarter of 2026, MOSES features a white pupil design and aims for a spectral resolution greater than 80,000 over the 380-680 nm wavelength range. It incorporates a pixel sampling rate of 3.5 and uses two fibers to facilitate a simultaneous calibration mode. Encased within a
vacuum vessel and operating in a temperature-stabilized environment, MOSES is expected to achieve a radial velocity precision below 2 m/s, aided by a Fabry-Pérot etalon calibration system. This paper outlines the implementation of the fiber injection unit, the optical layout of the spectrograph, and the present status of the various subsystems under development.
Read the full abstract ▾
All authors S. Schäfer, L. Schmidt, H. Anwand-Heerwart, D. Jones, A. Reiners
Instrumentation and Methods for Astrophysics
The MICADO first light imager for the ELT: eliminating vibrations and excessive earthquake-loads on specific subsystems
H. Nicklas, S. Schäfer, H. Anwand-Heerwart et al. (+3 more)
Ensuring earthquake resilience is paramount for the upcoming Extremely Large
Telescope (ELT). Instruments positioned on the ELT's Nasmyth platform are anticipated to endure substantial seismic accelerations, peaking at 3.6g in specific scenarios. These instruments have to be designed not only to survive such events but also to only require minimal repairs for sustained optimal functionality. This paper presents our approach to mitigate the dynamic forces impacting the rotary platform. This platform hosts various critical components, including cryogenic control units and mosaic detector control systems, essential for the operation of MICADO in its mechanical de-rotating motion. Furthermore, this paper tackles the challenge of minimizing instrument-induced vibrations affecting the
telescope's structure. Given that the ELT's optical system, composed of 798 segments, operates very similar to an interferometer, maintaining an extremely stable wavefront is crucial - a key insight learned from the Very Large
Telescope Interferometer (VLTI). Our focus is on identifying potential sources of vibration within specific frequency ranges where the
telescope demonstrates increased sensitivity. We will explore strategies for mitigating these vibrations to maintain a wavefront error below 50nm.
Read the full abstract ▾
All authors H. Nicklas, S. Schäfer, H. Anwand-Heerwart, J.-O. Dette, J. Witschel, H. Huber
Solar and Stellar Astrophysics
Temperature Diagnostics of Chromospheric Fibrils using DKIST/ViSP Observations: K-Means Clustering Approach
Sanjay Gosain
The chromosphere is a critical layer of the
solar atmosphere situated between the photosphere and the corona. Studying its temperature structure is important to understand the complex dynamics and energy-transfer processes between these layers. We investigate the thermodynamic properties of chromospheric fibrils adjacent to a plage region using high-resolution DKIST/ViSP observations of the Ca II 854.2 nm spectral line. We analyze the spectral profiles with the non-LTE inversion code NICOLE combined with K-means clustering. The high spectral and spatial resolution of the DKIST observations allows us to trace thermodynamic properties temperature, density, line-of-sight velocity, and microturbulent velocity along and across the fibrils. We note that while the thermodynamic parameters are retrieved under the assumption of hydrostatic
equilibrium, the resulting density and temperature values should be interpreted with the caveat that dynamic and
magnetic terms are neglected. The temperature along the fibril length decreases smoothly by about 1000 K from the hotter footpoints toward the mid-axis. The temperature variation across the lateral boundary of fibrils is more abrupt and can vary by several hundreds of degree Kelvin across a megameter. Denser fibrils tend to be associated with cooler, downflowing
plasma, while less-dense fibrils do not show this trend. Furthermore, the hotter parts of the fibrils tend to exhibit higher microturbulent velocities than the cooler parts.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Tidal Disruption of Blanets by Supermassive Black Holes: From Test Particles to Planetary-Mass Bodies in Kerr Spacetime
Shreesham Pandey and Sunita Singh
Planetary-mass bodies formed in active
galactic nucleus (AGN) discs, termed "blanets", may undergo
tidal disruption by the central supermassive black hole (SMBH). We analyse this process in Kerr spacetime using Mino-time geodesics and the Marck
tidal tensor in a parallel-transported tetrad, treating the blanet as a test particle with finite size entering through the disruption criterion. For a blanet of $100 M_{\oplus}$ and $6 R_{\oplus}$ around a $10^7 M_{\odot}$ SMBH, the
tidal radius is 0.82 AU, or 8.3 gravitational radii, requiring a non-perturbative relativistic treatment. The Hills mass depends on bulk density as $M_{\rm Hills}\propto\rho_p^{-1/2}$ and is independent of blanet mass at fixed density. Rocky compositions yield a lower Hills mass than a Sun-like
star, while volatile-rich compositions yield a higher value, suggesting a potential composition diagnostic. The frozen-in fallback model gives a peak time of about 15 yr and a peak luminosity of $3.7\times10^{40}$ erg/s, about $3\times10^{-5}$ of the Eddington luminosity, predicting a faint, ultraviolet-peaked transient lasting roughly a century. Scalar resonant relaxation in the surrounding
nuclear star cluster may deliver blanets to disruptive orbits over $10^8$ to $10^9$ yr, implying an estimated per-AGN event rate of $10^{-7}$ to $10^{-6}$ per year. Gravitational waves from sub-Earth-mass debris fragments remain approximately nine orders of magnitude below
Laser Interferometer Space
Antenna sensitivity.
Read the full abstract ▾
Accelerator Physics
Learning Dynamic Aperture from One-turn Maps
Derong Xu
Dynamic aperture evaluation relies on long-term tracking, while existing machine-learning surrogates remain difficult to generalize across machines. We demonstrate that coarse-grained dynamic aperture can be learned directly from suitably encoded one-turn maps. By reformulating dynamic-aperture prediction as an image
segmentation problem, a deep surrogate model captures the long-term stability
topology and transfers to realistic multidimensional Electron-Ion
Collider Electron Storage Ring tracking. Failure analysis identifies a challenging resonant regime in which invariant
tori are strongly deformed yet remain unbroken. These results establish a proof-of-principle that practical surrogate models can be constructed from one-turn transport information.
Read the full abstract ▾
Fluid Dynamics
A Wall Function for Turbulent Boundary Layers under Rotation via Symbolic Regression
Yao Ma, Zhi Tao, Ruquan You et al. (+1 more)
This study employs symbolic regression to derive physically interpretable, white-box wall-function expressions for turbulent boundary layers under system rotation. Flows in a rotating frame are subject to Coriolis forces, which deflect the boundary layer profile from static case. The classical law of the wall, formulated under non-rotating conditions, is ill-suited to describing the effects of rotation. To obtain the wall function under rotation, we examine the deflection behavior of the turbulent boundary layers on the leading and trailing sides, and construct wall functions that are valid over a wide range of rotation numbers. The analytical expressions show that, as the rotation effect intensifies, the boundary layer on the leading side contracts whereas that on the trailing side expands, and the leading side exhibits a tendency towards relaminarization, consistent with high-fidelity numerical results. The resulting symbolic expressions are compact and interpretable. The wall functions obtained in this study complement conventional wall functions, and provide a new avenue for
turbulence model closure subject to system rotation.
Read the full abstract ▾
All authors Yao Ma, Zhi Tao, Ruquan You, Haiwang Li
Statistical Mechanics
Impact of capacity volatility and input substitutability on supply chain resilience
Jaeseok Hur, Juha Jang, Meesoon Ha et al. (+1 more)
Supply chains are intrinsically vulnerable to
stochastic shocks due to their sequential production dependencies. Building on the Feld-Barthelemy framework, we investigate how capacity
volatility and input substitutability determine critical demands in
stochastic supply chains. By modeling production capacity with a truncated normal distribution, we show that in long supply chains, reducing capacity
volatility is often more effective than increasing average capacity, emphasizing the need for firm-level synchronization. Furthermore, introducing a modified Leontief-type production function reveals that input substitutability effectively disperses
stochastic shocks. Supplier diversification inherently raises critical demands, even under fixed maximum capacities, by introducing the effect of network
topology that independently enhances the resilience of physical stock. Our findings demonstrate that mitigating capacity
volatility and structurally diversifying supply routes are just as crucial to supply chain resilience as traditional inventory expansion.
Read the full abstract ▾
All authors Jaeseok Hur, Juha Jang, Meesoon Ha, Hawoong Jeong
Nuclear Experiment
Measurement of energy-level splitting from Charge-Symmetry Breaking in $A$ = 4 mirror hypernuclei
The STAR Collaboration
Breaking of fundamental
symmetries is a ubiquitous phenomenon in physics, underlying the origin of mass and the emerging structure in the universe. The charge
symmetry of $\Lambda$ hyperon-nucleon interactions can be probed through the difference in the $\Lambda$ binding energy ($B_{\Lambda}$) between mirror hypernuclei. In this paper, the $B_{\Lambda}$ of mirror hypernuclei with atomic mass number $A$ = 4, $\rm ^4_{\Lambda}H$ and $\rm ^4_{\Lambda}He$, are measured in Au+Au collisions at the center-of-mass energy of $\sqrt{s_{\rm NN}}$ = 3 GeV with the
STAR experiment at RHIC. For the ground states, we obtain $B_{\Lambda}$($\rm ^4_{\Lambda}H$) = 2.24 $\pm$ 0.02 (stat.) $\pm$ 0.04 (syst.) MeV and $B_{\Lambda}$($\rm ^4_{\Lambda}He$) = 2.39 $\pm$ 0.05 (stat.) $\pm$ 0.05 (syst.) MeV, yielding a charge-
symmetry breaking (CSB) effect at the level of 0.15 $\pm$ 0.05 (stat.) $\pm$ 0.04 (syst.) MeV. In combination with previous measurements of $\gamma$-ray transitions from their $1^+$ excited states, the CSB in excited states is determined to be $-$0.17 $\pm$ 0.05 (stat.) $\pm$ 0.04 (syst.) MeV. These measurements provide a precise determination of CSB in the hypernuclear system, and establish that the $\Lambda$ binding energy differences in ground and excited states are comparable in magnitude but opposite in sign, offering new insight to the CSB effect in $\Lambda$-nucleon interactions.
Read the full abstract ▾
Earth and Planetary Astrophysics
The mass of TOI-1883 b: A low density super-Neptune in the ridge regime transiting an early-M dwarf
Izuru Fukuda, Norio Narita, Akihiko Fukui et al. (+36 more)
Recent large-scale transit surveys conducted by space
telescopes such as Kepler and TESS have revealed a vast number of
exoplanets, uncovering the diversity of their population. One of the remarkable findings is the presence of a deficiency region in the period-radius distribution of short-period (< 10 days) Neptune-sized
planets (4-8 Earth radii). This region is classified into the Neptune desert (< 3.2 days), the ridge (3.2-5.7 days), and the savanna (> 5.7 days) based on orbital period, each likely reflecting distinct evolutionary pathways. In this study, we used the InfraRed Doppler (IRD) instrument on the Subaru
Telescope to determine the mass of the super-Neptune TOI-1883 b, which resides in the ridge region (P ~ 4.51 days) orbiting an M
dwarf. We measured a planetary mass of Mp = 13.7 +6.8/-6.5 Earth masses and a mean density of 0.4 +0.3/-0.2 g cm^-3, with 3-sigma upper limits of 34.1 Earth masses, and 5-sigma upper limits of 47.7 Earth masses. These results suggest that TOI-1883 b is likely a low density super-Neptune. We also find that the boundary of the Neptune desert defined by
planets orbiting FGK-type
stars exhibits a similar distribution for
planets around M-type
stars. According to the population-based argument of Bourrier et al. (2025), this suggests that TOI-1883 b may have undergone disk-driven migration to reach its current orbit and experienced early atmospheric photoevaporation driven by strong
stellar XUV irradiation. The derived planetary mass is comparable to or exceeds the conventional critical core mass. We suggest that the high
metallicity of the host
star ([Fe/H] = 0.32 +/- 0.18) may have suppressed the onset of runaway gas
accretion. Furthermore, TOI-1883 b has a high Transmission Spectroscopy Metric (TSM > 140), making it an excellent target for future atmospheric characterization via transmission spectroscopy.
Read the full abstract ▾
All authors Izuru Fukuda, Norio Narita, Akihiko Fukui, Teruyuki Hirano, Masayuki Kuzuhara, Hiroyuki Kurokawa, Kai Ikuta, Jerome P. De Leon, Takuya Takarada, Hiroki Harakawa, Hiroyuki Tako Ishikawa, Yasunori Hori, Tadahiro Kimura, Takanori Kodama, Masahiro Ikoma, Akitoshi Ueda, Aoi Takahashi, Enric Palle, Felipe Murgas, Gaia Lacedelli, Hannu Parviainen, John H. Livingston, Jun Nishikawa, Keisuke Isogai, Kiyoe Kawauchi, Masashi Omiya, Mayuko Mori, Motohide Tamura, Nobuhiko Kusakabe, Noriharu Watanabe, Sébastien Vievard, Taiki Kagetani, Takashi Kurokawa, Takayuki Kotani, Takuma Serizawa, Tomoyuki Kudo, Vigneshwaran Krishnamurthy, Yugo Kawai, Yuya Hayashi
Nuclear Theory · Cross-listed from cs.LG
Product units in gated recurrent units improve nuclear-mass prediction
Ziyuan Li, Paulo S.A. Freitas, John W. Clark et al. (+1 more)
The prediction of masses of atomic
nuclei using machine learning can complement theoretical models and advance the exploration of poorly known domains of the
nuclear chart. We propose a machine learning technique based on gated recurrent units (GRU), which have demonstrated competitive performance in
nuclear-mass prediction by exploiting long-term dependencies. By integrating multiplicative interactions and product-unit transformations within recurrent units, we report significant improvements in
nuclear-mass prediction. Computations are performed in the complex domain to jointly capture amplitude and phase dynamics. For interpolation and temporal-extrapolation tasks based on the atomic mass evaluation (AME2016 and AME2020), the complex additive-multiplicative product-unit gated recurrent unit (AM-PU-GRU) model consistently achieves the lowest prediction errors, with an interpolation RMSE of 0.227 $\pm$ 0.004 MeV and an extrapolation RMSE of 0.179 $\pm$ 0.015 MeV. These results surpass other state-of-the-art machine learning models and also outperform the real-valued GRU baseline and product-unit ablation variants, while remaining robust to different theoretical priors, including WS4 and SEMF. Our findings establish complex-valued product-unit recurrent networks as a new
benchmark for sequence-based
nuclear-mass prediction.
Read the full abstract ▾
All authors Ziyuan Li, Paulo S.A. Freitas, John W. Clark, Babette Dellen
Mathematical Physics
Rational Heun operators on $q$-linear grids
Satoshi Tsujimoto, Luc Vinet and Alexei Zhedanov
Rational Heun operators on the $q-$linear grid are presented. They are second-order $q-$difference operators $W_q$ constructively defined from the requirement that they have a raising action on rational functions of type $[n/n]$, namely $W_q: [n/n] \rightarrow [n+1/n+1]$, with poles on $q-$linear grids. It will be observed that these operators are related to one family of the Ruijsenaars-van Diejen-Takemura
Hamiltonians. A distinguished subclass of $W_q$ called classical which shifts the pole structure while preserving the rational function type and a prescribed basis is also characterized.
Read the full abstract ▾
Optics
FLASH: Ultrafast beam quality characterization via spatial-to-temporal mapping
J. Qiu, Y. Xiong, X. Hua et al. (+2 more)
Accurate and real-time monitoring of spatial beam quality has emerged as the absolute prerequisite for intelligent optical field regulation and advanced
laser applications. However, modern high-power and multimode optical systems exhibit highly complex, nonlinear, and transient behaviors. In these systems, the spatial beam profile undergoes dramatic reorganizations within extremely short timeframes. Phenomena such as spatio-temporal mode-locking, transient beam self-cleaning, and
plasma-induced aberrations demand nanosecond-level dynamic characterization. Yet, capturing these ultrafast dynamics is fundamentally bottlenecked by the kilohertz frame rates of conventional two-dimensional image sensors. To break this dimensional and temporal barrier, we propose an ultrafast non-imaging beam quality monitoring technique, termed Fiber-based
Laser Assessment via Spatial-to-temporal High-speed-mapping (FLASH). By utilizing a multimode fiber to encode spatial beam variations into high-dimensional speckle fingerprints and a multicore fiber delay line array to serialize these features, we transform two-dimensional spatial information into high-speed one-dimensional temporal pulse sequences. Empowered by a deep learning model to decipher the serialized signals, the FLASH system achieves an unprecedented 100 MHz measurement rate with a minimal mean relative error of 0.32%. Realizing a five-order-of-magnitude speed improvement over standard camera-based methods, this spatial-to-temporal mapping paradigm provides a transformative spatial oscilloscope. It unlocks new possibilities for real-time intelligent adaptive control and the exploration of complex multimode nonlinear physics.
Read the full abstract ▾
All authors J. Qiu, Y. Xiong, X. Hua, H. Wu, M. Tang
Strongly Correlated Electrons
Complex Temperature-dependent Thermal Conductivity in a Sawtooth Chain Magnet Fe$_\mathrm{2}$SiSe$_\mathrm{4}$
Kunya Yang, Feihao Pan, Liran Wang et al. (+12 more)
Geometrically frustrated magnets provide an ideal platform for exploring the interplay between
lattice geometry and
spin degrees of freedom. Here, we investigate the interactions between
lattice and
spin via thermal-transport measurements on the triangular sawtooth-
lattice olivine magnet Fe$_\mathrm{2}$SiSe$_\mathrm{4}$, which exhibits successive
magnetic transitions at $T_1 = 110$ K (
antiferromagnetic) and $T_2 = 50$ K (ferrimagnetic). Although
phonons dominate the thermal conductivity, its temperature dependence displays a pronounced double-peak structure arising from
spin-
phonon coupling. In the intermediate temperature range between $T_1$ and $T_2$ , resonant scattering of
phonons by
magnetic excitations around 5 meV produces a broad maximum around 60 K. Below $T_2$, the resonant
spin-
phonon scattering is strongly suppressed, leading to a rapid increase in thermal conductivity upon cooling and a pronounced low-temperature peak near 11 K, characteristic of heat transport governed by conventional
phonon scattering mechanisms. Notably, this low-temperature peak is enhanced by a factor of $\sim 5$ compared to the broad maximum at higher temperatures. These results demonstrate the strong sensitivity of thermal transport to
spin-
lattice interactions and highlight
spin-
phonon scattering as an effective mechanism for tailoring thermal conductivity in geometrically frustrated magnets.
Read the full abstract ▾
All authors Kunya Yang, Feihao Pan, Liran Wang, Chenglin Shang, Ying Zhu, Xiancai Hu, Sanjiang He, Xinrun Mi, Long Zhang, Aifeng Wang, Yisheng Chai, Frederic Hardy, Christoph Meingast, Peng Cheng, Mingquan He
Chemical Physics
Distilling first-principles accuracy into compact machine learning potentials for condensed-phase chemistry
Sijia Chen, Niamh O'Neill, Benjamin X. Shi et al. (+1 more)
Accurate machine learning interatomic potentials (MLIPs) have made first-principles-quality potential energy surfaces increasingly accessible for condensed-phase chemistry, but their inference cost can still limit the sampling needed to compute experimentally relevant observables. In this work, we combine transfer learning and knowledge
distillation to construct compact "student" models that retain the accuracy of much larger "teacher" models obtained by applying transfer learning to foundation models. The resulting students reduce production simulation cost by roughly an order of magnitude, making high-accuracy sampling practical for challenging condensed-phase problems. We demonstrate this across three problems of increasing sampling complexity: finite-temperature NPT simulations of ice Ih, classical and path-integral simulations of
liquid water over 240-370 K, and path-integral umbrella-sampling simulations of water dissociation at the anatase TiO2(101)/water interface. In all cases, the distilled students reproduce the target observables of their teachers more reliably than models of the same size trained directly on the limited reference data. The
liquid-water student, distilled from a {\Delta}-learned CCSD(T)-quality teacher, reproduces thermodynamic, structural, transport, and
nuclear quantum properties over the full temperature range studied. At the TiO2/water interface,
distillation makes PIMD umbrella sampling practical and shows that
nuclear quantum effects lower the dissociation barrier by roughly 2 kcal/mol and shift the molecular-dissociated free energy difference into quantitative agreement with recent solid-state 17O NMR measurements. Our work demonstrates how knowledge
distillation can make accurate MLIPs practical for the sampling methods needed to connect condensed-phase reaction thermodynamics with experiment, notably for interfacial chemistry and catalysis.
Read the full abstract ▾
All authors Sijia Chen, Niamh O'Neill, Benjamin X. Shi, Venkat Kapil
Chaotic Dynamics
Loop Current Extension as an Effective Delayed Dynamical System
Francisco J. Beron-Vera, María J. Olascoaga and Philippe Miron
The Loop Current is the dominant circulation feature of the Gulf of Mexico and exhibits pronounced variability associated with northward extension, retraction, and eddy shedding. Despite decades of study, the extent to which this variability admits a reduced dynamical description remains unclear. We investigate this question using delayed-coordinate representations constructed from satellite-altimetry observations of Loop Current extension. Ridge regression, multilayer perceptron
forecasting, and Sparse Identification of Nonlinear Dynamics (SINDy) are applied to learn delayed
evolution maps from the extension time series. Forecast skill consistently exceeds persistence at lead times of 30–90 days while requiring only a small number of delayed coordinates. Ridge regression reveals saturation with delayed-state dimension, indicating that much of the predictive information is contained within a compact representation. Neural-network forecasts provide modest additional improvements, while delayed SINDy identifies sparse
evolution maps involving intraseasonal
memory scales, from approximately two weeks to a few months, that remain stable under recursive iteration. Physical diagnostics associated with Yucatan Channel inflow, Florida Straits
outflow, gateway geometry, and northern Caribbean vorticity contain predictive information but do not provide additional independent state information once the delayed Loop Current state is included. These results support the interpretation of Loop Current extension as an observable evolving on an effective low-dimensional delayed dynamical system. A substantial fraction of the predictable variability can be reconstructed from a small number of delayed observations and represented through compact delayed
evolution maps.
Read the full abstract ▾
Optics
High-Speed Multi-Dimensional Optical Field Measurement via MMF-MCF Spatial-Temporal Mapping Architecture
Yuxuan Xiong, Jingze Liu, Junjie Qiu et al. (+4 more)
Wavelength and state of polarization constitute fundamental dimensions of optical fields. While simultaneous quantification of these parameters is critical, existing methodologies often lack the speed required for real-time analysis. Here, we present a compact high-dimensional optical field analyzer employing a discrete spatiotemporal sampling architecture based on multimode and multicore fibers. An optical delay line array maps spatial speckle patterns into serial pulse sequences and facilitates efficient single-pixel detection. Leveraging a residual multilayer perceptron network, the system attains a wavelength mean absolute error of 0.25 pm and a polarization resolution of 0.2015 (in normalized Stokes space). Analysis of the spatial sampling density reveals that 5-6 sampling points are required to balance measurement rate and accuracy. Notably, the system exhibits isotropic fault tolerance against single-core failures. This confirms that optical field information is redundantly encoded across the entire fiber cross-section rather than localized in specific channels. This framework provides a solution for multiparameter decoupling under severe spatial downsampling and useful insights for the design of next generation high-speed and robust all-fiber analysis systems.
Read the full abstract ▾
All authors Yuxuan Xiong, Jingze Liu, Junjie Qiu, Zhuyixiao Liu, Zheng Gao, Hao Wu, Ming Tang
Optics
Ultralow shot noise limited giant passive resonant gyroscope for Earth rotation measurement
Yuhong Zhong, Yangsheng Cai, Zhanhao Liu et al. (+9 more)
Optical gyroscopes directly measure the Earth's rotation and are promising instruments for real-time geophysical observations and Earth orientation parameter (EOP) determination requiring both high precision and high temporal resolution. Large-scale ring
laser gyroscopes (RLGs) currently reach rotational resolutions around $10^{-11}\,\mathrm{(rad/s)/\sqrt{Hz}}$, but their
quantum noise limits make it challenging to meet the requirements of future high-temporal-resolution EOP measurements. Passive resonant gyroscopes (PRGs), on the other hand, offer a potentially lower
photon shot noise limit and more flexible power scaling, even if their demonstrated rotational resolutions are still about two orders of magnitude below those of leading RLGs. Here we demonstrate a $64\,\mathrm{m^{2}}$
giant passive resonant gyroscope HUST-2, and develop with an extremely low shot noise level. We experimentally obtain a shot noise limited of $5.7(1)\times10^{-13}\,\mathrm{(rad/s)/\sqrt{Hz}}$ at $1\,\mathrm{mW}$ incident optical power, following the characteristic $1/\sqrt{P}$ scaling. Through systematic suppression of dominant technical noise sources, HUST-2 further achieves a measured rotational resolution of $3\times10^{-11}\,\mathrm{(rad/s)/\sqrt{Hz}}$, bringing PRGs into the performance regime of leading large-scale RLGs for the first time. The gap between the present demonstrated rotational resolution and the shot noise limit indicates nearly two orders of magnitude further improvement potential. Reaching this limit would enable high-precision length-of-day (LOD) measurements with $10$-$100\,\mathrm{s}$ temporal resolution and lays the foundation for future large-scale gyroscope networks dedicated to real-time EOP determination.
Read the full abstract ▾
All authors Yuhong Zhong, Yangsheng Cai, Zhanhao Liu, Lei Zheng, Yunhe Wang, Xiaojun Huang, Zhiyuan Wang, Kui Liu, Liangcheng Tu, Jun Luo, Zehuang Lu, Jie Zhang
Quantum Physics
Cyclic ladder operators and hidden Weyl-Heisenberg structure in a Floquet system
Tianao Wu and Li Ge
Ladder operators, found in the
quantum harmonic oscillator and other quantized systems, provide an elegant approach to solving or understanding otherwise intricate physics problems. In this Letter, we discuss cyclic ladder operators in both Hermitian and non-Hermitian systems with a finite
Hilbert space, with the highest (lowest) level directly descending (ascending) to the lowest (highest) level via a single raising (lowering) operation. We show that an equally spaced energy ladder emerges when these systems have an underlying Weyl-Heisenberg commutation relation, with the cyclic ladder operators and the temporal
evolution operator behaving as the generators of the Weyl-Heisenberg group. We further illustrate such a system using a one-dimensional Floquet
lattice, where the cyclic ladder operators become diagonal and the temporal
evolution simplifies to a permutation
matrix after a Floquet period. Our findings reveal a hidden relation between non-trivial dynamics and algebraic principles in Floquet systems, which may exist for other
quantum numbers as well besides the energy levels.
Read the full abstract ▾
Computational Physics · Cross-listed from math.NA
Multiscale Nudging: From Macroscopic Observations to Microscopic Dynamics
Liyao Lyu, Xinyue Yu and Hayden Schaeffer
We introduce a measure-based nudging framework for assimilating macroscopic observations into microscopic mean-field particle dynamics. The central difficulty is a representation mismatch: the forecast is a labeled particle system, while the observations specify only a smoothed, permutation-invariant density. To address this mismatch, we define the forecast-observation discrepancy as a quadratic functional on probability measures after applying the same smoothing operator used by the observation process. The Wasserstein gradient of this functional induces a transport velocity on state space, which yields a particle-level correction without constructing particle-to-particle matching, linearizing the dynamics, or estimating ensemble covariances. For a fixed observation scale, we prove well-posedness of the assimilated McKean-Vlasov dynamics and propagation of chaos for the interacting particle approximation. Under exact smoothed observations and an observability condition at the kernel scale, we establish an $L^2$-stability estimate showing exponential decay up to a bias floor controlled by model misspecification. Numerical experiments on linear, bimodal, chaotic, kinetic, and collective-motion systems demonstrate that the method can recover macroscopic structure from incomplete density-level observations.
Read the full abstract ▾
Accelerator Physics
Particle swarm optimization fitting of long-range wake potentials for trapped-mode parameter characterization in the HALF storage ring
Haiyan Yao, Tianlong He, Xiaoyu Liu et al. (+2 more)
Accurate extraction of trapped-mode impedance parameters of complex storage ring components is essential for assessing their impact on coupled-bunch instabilities. This paper proposes a parameter extraction method based on particle swarm optimization. By constructing a multi-resonator fitting model, trapped-mode parameters are extracted from partially decayed long-range wake potentials.
Benchmark validation using a cylindrical pillbox cavity demonstrates that the proposed method yields results consistent with those obtained from the CST eigenmode solver and the existing differential
evolution method for both longitudinal and transverse cases, while significantly reducing the computational cost. The method is further applied to three critical components of the Hefei Advanced Light Facility storage ring, demonstrating its applicability to complex structures.
Read the full abstract ▾
All authors Haiyan Yao, Tianlong He, Xiaoyu Liu, Weiwei Li, Zhenghe Bai
Astrophysics of Galaxies
Radiation Pressure Instability in the "turn-on" Changing-Look AGN SDSS J1430+2303
Han He, Bei You, Marzena Śniegowska et al. (+3 more)
We aim to investigate the multi-wavelength variability, spectral, and timing properties of the changing-look active
galactic nucleus (CL AGN) SDSS J1430+2303, and to explore the physical origin of its peculiar variability pattern that has not been observed before in other CL AGN. We perform a multi-wavelength analysis using optical, ultraviolet, and X-ray observations. We investigate the long-term optical color variation, characterize the
evolution of the X-ray spectrum and timing properties, and construct broad-band spectral energy distributions to constrain the black hole mass,
spin, and Eddington ratio. The optical flux increased by an order of magnitude over four years, accompanied by a spectral transition from Seyfert 1.9 to 1.2. The long-term color variation follows the “bluer-when-brighter” trend, with a color-magnitude slope consistent with previous statistical results for CL and Type 1 AGNs. During the brightened high state, the optical, ultraviolet, and X-ray light curves exhibited rapid decaying periods with progressively decreasing amplitudes, a behavior not previously reported in other CL AGNs. X-ray spectral analysis reveals a remarkably weak soft excess that declines more steeply than the hard X-rays as the total luminosity decreases. X-ray timing analysis shows a nearly constant break frequency and a hard lag at $\sim10^{-4}$ Hz during the luminosity decline, suggesting a stable disk–corona geometry. Broad-band spectral energy distribution fitting constrains the black hole mass to $M_{\rm BH}=3.8-19.5\times10^7\,M_\odot$ and favors a high
spin ($a\gtrsim0.77$), while the correspondingly low Eddington ratio can account for the observed weak soft excess. We propose that the observed multi-wavelength decaying periods and their progressively decreasing amplitudes are associated with a shrinking unstable zone driven by radiation-pressure instability in the
accretion disk.
Read the full abstract ▾
All authors Han He, Bei You, Marzena Śniegowska, Bożena Czerny, Claudio Ricci, Xinwu Cao
Medical Physics
The First Human-Based In Vitro Flow Loop and Quantification for Fetal Aortic Hemodynamics
Kamlesh Kumar, Biao Si, Pritom Saha et al. (+2 more)
Coarctation of the aorta (CoA) is a common congenital defect that remains difficult to diagnose prenatally due to subtle and evolving anatomical features. In the fetus, the ductus arteriosus creates a dual-inflow configuration that generates complex three-dimensional flow patterns not captured by standard imaging. Improved characterization of fetal hemodynamics may enhance diagnostic accuracy beyond anatomy-based assessment. This study presents the first human-based in vitro flow loop of the fetal aorta, constructed from anatomies reconstructed using medical imaging data. Models representing normal and coarctation conditions were fabricated and integrated into a physiological flow loop. Velocity fields were measured using planar and stereoscopic particle image velocimetry (PIV) to resolve near-wall and three-dimensional flow structures, enabling quantitative assessment of velocity gradients and wall shear stress (WSS) under normal and coarctation configurations. The in vitro flow loop closely reproduced target fetal flow
segmentation, with segmental flow-rate errors generally below 6%. High-resolution planar and stereoscopic PIV revealed dual jets from the ascending aorta and the ductus arteriosus and predominantly planar flow in the normal aorta, but strong jet acceleration, separation, and reattachment in the coarcted geometry. Coarctation produced markedly elevated and spatially heterogeneous WSS, and 2-component PIV underestimated WSS by up to ~29% compared with 3-component measurements, especially in high-shear regions. These findings show that accurate three-component velocity measurements are critical for reliable WSS estimation and suggest that detailed hemodynamic metrics, such as WSS, may serve as potential biomarkers to enhance fetal CoA diagnosis beyond anatomy alone.
Read the full abstract ▾
All authors Kamlesh Kumar, Biao Si, Pritom Saha, Shuping Ge, Zhenglun Alan Wei
Optics
Passive all-optical synchronization for polarization-maintaining ultrafast fiber lasers
Kun Huang, Jing Zeng, Jiwei Gan et al. (+3 more)
We have proposed and implemented for the first time to our best knowledge a passive and all-optical pulse synchronization for polarization-maintaining ultrafast fiber
lasers. Specifically, the synchronization system was comprised of two independent Yb-doped and Er-doped mode-locked fiber
lasers in a master-slave configuration. Master pulses were injected into the slave
laser cavity consisting of a nonlinear amplifying loop mirror, which provided an effective fast intensity modulator due to the periodic introduction of nonreciprocal phase difference. As a result, robust and tight timing synchronization was achieved with a cavity mismatch tolerance of 800 $\mu$m and a relative timing jitter of 26 fs within 1-MHz bandwidth. In combination with all-polarization-maintaining structure of fiber
lasers, long-term stable operation was demonstrated over 12 hours without the need of temperature stabilization and vibration isolation. The implemented synchronous
laser system could find immediate applications such as pump-probe microscopy, two-color spectroscopy and nonlinear frequency mixing.
Read the full abstract ▾
All authors Kun Huang, Jing Zeng, Jiwei Gan, Qiang Hao, Ming Yan, Heping Zeng
Quantum Physics
Machine-Learning Optimization and Characterization of a High-Optical-Depth Two-Color Nanofiber Trap
W. Crump, M. Sadeghi and M.D. Hoogerland
Optical nanofibers provide a way of coupling
quantum information in cold atoms across large distances, however, this coupling requires atoms to reside close to the nanofiber surface. Atoms can be trapped close to the surface using a two-color dipole trap. Here we present our experimental realization of a two-color dipole trap. We optimize the number of trapped atoms using a machine learning
algorithm and measure the optical density via the transmission. We estimate the number of atoms in the trap to be approximately 1400 and the lifetime of the atoms in the trap to be 28 ms. Machine-learning optimization improved the on-resonance optical depth from 0.5 in the initial optimization stage to optical depths exceeding 15.
Read the full abstract ▾
Solar and Stellar Astrophysics
A Compact, Ultra-High Resolution VIPA Spectrograph for Solar Spectroscopic Observations: Astrocomb Characterization and First Light
Yutao Wang, Xiaoming Zhu, Xiaoli Yan et al. (+4 more)
We present a compact, high spectral resolution prototype spectrograph based on a Virtually Imaged Phased Array (VIPA), which is designed for
solar spectral observations. This fiber-fed instrument has a size of only 53 $\times$ 20 $\times$ 18 cm$^3$. Wavelength calibration using an astrocomb ($f_{\text{rep}}=25$ GHz) established an operational bandpass of 592.76–657.07 nm and revealed an asymmetric instrumental profile. A Fano-Lorentz product function provides a significantly better fit to this profile than a Gaussian. The measured spectral resolution ranges between 290,000 and 340,000 across the band. Initial on-sky validation at the New
Vacuum Solar Telescope (NVST, Yunnan Observatories) successfully demonstrated the prototype's capabilities: clear detection of
solar five-minute oscillations ($\pm 300 \, \text{m s}^{-1}$) in the \ion {Fe}{1} 6280.57 Å~ line, resolution of
magnetic broadening in sunspots using the \ion{Fe}{1} 6173.34 Å~ line, and the first ground-based definitive identification of the faint \ion{Si}{1} 6560.57 Å~ line within the H$\alpha$ band. These results validate the VIPA as a promising platform for high spectral resolution
solar spectroscopy. Its compact design and performance directly support future applications in multi-object
solar studies, high spectral resolution observations for time-domain astronomy, including
exoplanet detection, and potential space-borne instrumentation.
Read the full abstract ▾
All authors Yutao Wang, Xiaoming Zhu, Xiaoli Yan, P. F. Chen, Huiqi Ye, Dong Xiao, Jinping He
Superconductivity
Guodong Jiang, Aaron Dunbrack, Tero T. Heikkilä et al. (+1 more)
Superconductors of different types have distinct
magnetic properties; for example, they can form Abrikosov
vortices or alternating normal-superconducting domains. We predict that, in flat bands, a superconducting phase exhibiting walls of
magnetic flux is stable in an applied
magnetic field. This phase relies on the lack of a single particle energy penalty for forming condensates of any momentum in flat bands and, consequently, their superconducting free energy being a negative and periodic function of the vector potential at low temperatures. Using a minimal
lattice-periodic model of free energy, we study two types of
soliton modes of the wall phase: the kink and breather
solitons. They determine the lower critical field and the high-field behavior of the wall phase, respectively. The competition between the walls and
vortices in flat bands is also discussed. Our results suggest that flat bands help sustain superconductivity in the presence of large
magnetic fields.
Read the full abstract ▾
All authors Guodong Jiang, Aaron Dunbrack, Tero T. Heikkilä, Päivi Törmä
Plasma Physics
Flow-Regulated Suprathermal Particle Acceleration in Weakly Collisional Astrophysical Plasmas
Ji-Hoon Ha and Elena S. Volnova
We investigate the formation of suprathermal particle populations in weakly collisional
plasmas using a one-dimensional Fokker-Planck framework. A key element of this work is the introduction of a systematic velocity-space drift term that represents net energization relative to a background streaming flow. This term provides a minimal phenomenological description of competing relaxation and acceleration processes, enabling the incorporation of large-scale
plasma dynamics into kinetic particle
evolution. The model further includes spatial advection, velocity-space
diffusion associated with wave-particle interactions, and collisional relaxation. To explore the role of time-dependent large-scale
plasma dynamics, we consider three representative temporal profiles of the streaming velocity: accelerating, decelerating, and steady flows. We find that velocity-space
diffusion primarily governs the formation of suprathermal tails, while the streaming-induced drift regulates their efficiency and spectral properties. In particular, the overall fraction of suprathermal particles depends only weakly on the detailed temporal
evolution of the flow and is largely controlled by the time-averaged streaming velocity. These results suggest that large-scale streaming motions can be incorporated as an effective systematic energization mechanism in weakly collisional
plasmas, providing a minimal and flexible framework applicable to a broad range of space and astrophysical environments.
Read the full abstract ▾