Applied Physics
DDSNet: Dual-domain Symmetry-aware Network for PCSEL Property Prediction
Cen Chen, Haitao Huang, Jiazhi Mao et al. (+3 more)
Efficient exploration of the photonic
crystal (PhC)
lattice design space is essential for developing photonic
crystal surface-emitting
lasers. While coupled-wave theory (CWT) provides an effective physical framework, its computational cost remains prohibitive for large-scale exploration, driving the demand for neural surrogates. However, existing AI models underexploit two key factors of PhC unit-
cell dielectric patterns indicated by CWT: spectral components and asymmetric structures, which largely govern devices' physical properties. This mismatch weakens surrogate accuracy and screening reliability, especially in structure-sensitive regions. To address this, we propose the Dual-Domain
Symmetry-Aware Network (DDSNet). It integrates translation-equivariant spectral filtering with a
symmetry-induced structural prior. The spectral filtering injects a spectral inductive bias into
vision model while preserving translation equivariance on
lattices. Meanwhile, the structural prior decomposes
lattice features into irreducible representation-associated,
symmetry-resolved components and processes them in separate branches. Experiments demonstrate that DDSNet significantly outperforms existing AI baselines in property prediction and high-throughput screening, exhibiting superior reliability in structure-sensitive regions. Crucially, component masking analyses reveal that the network successfully learns property-specific dependencies aligned with physical priors. These results indicate that DDSNet effectively captures physically meaningful structure-property relationships, establishing a highly reliable neural surrogate for PhC design space exploration.
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All authors Cen Chen, Haitao Huang, Jiazhi Mao, Feifan Xu, Zhe Zhuang, Yuxiang Ren
General Physics
Effective de Sitter-Schwarzschild Metrics
Moorad Alexanian
An earlier work that replaced the de Sitter-Schwarzschild metric for a cosmological constant Lambda <=0 by an effective anti-de Sitter black hole analytic at Lambda = 0 is here extended to the horizon structure through its three possible roots. We replace the de Sitter-Schwarzschild metric for all possible values of Lambda and the Schwarzschild radius R for the three possible available roots by either a Schwarzschild black hole whose radius depends on both R and Lambda or a de Sitter space whose cosmological constant depends on both R and Lambda.
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Instrumentation and Detectors
Tunable Light Scattering in Cast Organic Scintillators via BaSO$_4$ Nanoparticle Doping: A Short Summary
H. G. Zaunick, R. Bergert, K. T. Brinkmann et al. (+9 more)
We summarize the fabrication and optical characterization of small-format (2 x 2 x 2 cm$^3$) cast organic scintillators based on Eljen EJ-290 resin, doped with barium sulfate (BaSO$_4$) powder at mass fractions from 0 % to 5 %. The goal is to tune the scattering length of the scintillator largely independently of its absorption and light output, so that scintillation light is localized on a controllable spatial scale matched to the fiber pitch of wavelength-shifting (WLS) fiber read-out. The scattering length is found to decrease from 6.05(8) cm at 1 % to 0.83(1) cm at 5 %, while the absolute light yield falls by only about 15 %. These results are a first proof of concept that the
photon-transport scale in cast scintillators can be engineered on purpose, enabling position-sensitive scintillator tiles for fiber-readout sampling calorimeters and large-area
muon trackers. Full details are given in the accompanying paper.
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All authors H. G. Zaunick, R. Bergert, K. T. Brinkmann, V. Dormenev, K. Eichhorn, J. M. Friedrich, S. Glennemeier-Marke, D. Kazlou, H. Lacker, M. J. Losekamm, C. Scharf, I. M. Wöstheinrich
Quantum Physics
Bright-state source cancellation in dissipative shortcut Raman atom optics
Asad Ali, Saif Al-Kuwari, M. I. Hussain et al. (+3 more)
Spontaneous Raman scattering limits shortcut-assisted atom optics, but its microscopic origin is obscured once the lossy excited state is adiabatically eliminated. We organize the problem around a single quantity: in the instantaneous dark-bright basis the lower-
manifold optical source is carried entirely by the bright-state amplitude, $S=\Omega b$, so that primary spontaneous scattering reduces to the compact functional. This recovers the known dissipative-STIRAP loss in transparent form and makes the action of a shortcut explicit: ideal counterdiabatic STIRSAP cancels the bright-state source, not the optical decay coefficient. We show this cancellation is exact in the full three-level model at the counterdiabatic point, for arbitrary one-
photon detuning, Rabi frequency, and pulse duration. The residual source splits into orthogonal quadratures – shortcut mismatch (real) and two-
photon Doppler detuning (imaginary) – which invites a velocity-selective protocol that nulls the Doppler quadrature for a chosen momentum class with a second, phase-shifted lower-state field. Our central result is that this source nulling is never superior to simply chirping the two-
photon detuning: the two coincide only when the selected class $\delta_c$ is small compared with the bright-state gap, and the nulling degrades and then fails as $\delta_c\to|\mu|$ – precisely the regime of launched or warm clouds and high-order large-momentum-transfer (LMT) optics that motivates velocity selection. The controlling quantity is the magnitude of the residual
Hamiltonian perturbation a scheme leaves behind, not the residual source it cancels. As a complement to existing multi-pulse decay budgets, we cast a single-pulse mode-error budget for LMT interferometry entirely in terms of the bright-state source, and delineate when shortcut-assisted Raman control reduces the total scattering cost.
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All authors Asad Ali, Saif Al-Kuwari, M. I. Hussain, H. Kuniyil, M. T. Rahim, Saeed Haddadi
Quantum Physics
Self-Modulating Quantum Fast-Weight Programmers for Efficient Adaptive Sequential Learning
Samuel Yen-Chi Chen, Yifeng Peng, Kuo-Chung Peng et al. (+8 more)
Recent advances in
quantum machine learning have motivated efficient models for sequential data processing. In this paper, we propose Self-Modulating
Quantum Fast Weight Programmers, or Self-Modulating QFWP, which extends
Quantum Fast Weight Programmers by introducing adaptive modulation over both newly generated fast-weight updates and historical fast-weight
memory. Numerical results show that the proposed mechanism improves convergence stability and prediction performance across varying model settings, including different numbers of
qubits and input sequence lengths. We further provide theoretical arguments explaining how self-modulation balances new information injection with
memory retention, thereby enhancing temporal information propagation. These results suggest that Self-Modulating QFWP is a compact and effective framework for
quantum machine learning on time-series data.
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All authors Samuel Yen-Chi Chen, Yifeng Peng, Kuo-Chung Peng, Jiun-Cheng Jiang, Chun-Hua Lin, Junghoon Justin Park, Huan-Hsin Tseng, Hsin-Yi Lin, Kuan-Cheng Chen, Chen-Yu Liu, Shinjae Yoo
Quantum Physics
Recursive QLSTM with Dynamic Variational Quantum Circuit Adaptation
Samuel Yen-Chi Chen, Yifeng Peng, Jiun-Cheng Jiang et al. (+8 more)
Recent advances in
quantum computing and machine learning have motivated the development of
quantum models for sequential data processing. In this paper, we propose a Recursive
Quantum Long Short-Term
Memory model, or Recursive QLSTM, which extends QLSTM through metacore-based recursive constructions. We numerically test the model under different input sequence lengths, metacore designs, and recursive rules, and identify the best-performing architecture among these variants. For this selected model, we further provide theoretical arguments explaining why its recursive structure improves temporal information propagation and enhances learning performance. Our results suggest that Recursive QLSTM offers a flexible and effective framework for
quantum recurrent learning over input time series of various lengths.
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All authors Samuel Yen-Chi Chen, Yifeng Peng, Jiun-Cheng Jiang, Chun-Hua Lin, Kuo-Chung Peng, Junghoon Justin Park, Huan-Hsin Tseng, Hsin-Yi Lin, Kuan-Cheng Chen, Chen-Yu Liu, Shinjae Yoo
Mesoscale and Nanoscale Physics
Non-Abelian Anyon Braiding with Quantum-Antidot Interferometry
Junyu Tang and Gang v. Chen
Conventional Fabry–Perot interferometry accesses only full braids of anyons and therefore cannot directly probe the elementary \(\pi\)-rotation exchange. Motivated by the recent
quantum-antidot proposal for the Abelian anyons, we propose an interferometry for probing the elementary exchanges of non-abelian anyons using two gate-controlled
quantum antidots. By tuning two antidots independently, the device realizes distinct cooperative tunnelling processes, which correspond to different braids of non-abelian anyons. For the unresolved local fusion channels, the difference between the interference signals of the single and double cooperative processes allows us to measure the elementary exchange of the non-abelian anyons, providing a direct probe of their non-abelian statistics and topological
spins. For the resolved local fusion channels, the double-cooperative process is further distinguished by a reduced interference amplitude. Our work provides a promising and practical route for manipulating and detecting non-abelian braiding with the fundamental fractional statistics.
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High Energy Physics (Theory)
Null limit of large-charge correlators in planar $\mathcal{N}=4$ Super-Yang-Mills theory
Benjamin Basso, Thiago Fleury, Erkan Kaluç et al. (+1 more)
We present a
conjecture for the double-logarithmic behavior of the logarithm of large-charge correlators in the null limit in planar $\mathcal{N} = 4$ Super-Yang-Mills theory. Generalizing earlier results for four- and five-point functions, our proposal predicts this behavior for $n$-point functions to all loops in terms of the tilted cusp anomalous dimension. In the dual amplitude description, it reproduces the expected small-mass behavior of massive amplitudes in the equal-mass limit.
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All authors Benjamin Basso, Thiago Fleury, Erkan Kaluç, Didina Serban
Earth and Planetary Astrophysics
JWST Characterization of Earth Quasi-Satellite (469219) Kamo`oalewa
Benjamin N. L Sharkey, Vishnu Reddy, John W. Noonan et al. (+5 more)
Near-Earth asteroid (469219) Kamo`oalewa is a uniquely stable quasi-satellite of the Earth and a target of the Tianwen-2 spacecraft mission. Here we report observations taken with JWST's NIRSpec instrument in integral field unit (IFU) mode in February 2026. The JWST reflectance spectrum is notably less red (more neutral) from $1.0-2.5$ $\mu m$ than previous ground-based spectrophotometric observations. New observations made with LBT in April 2026, observed and processed similarly to the 2021 observations, find $zJ$ colors in agreement with JWST. Kamo`oalewa's infrared colors appear more similar to typical silicate-rich asteroids and unlike the reddened, space-weathered lunar-like silicates suggested by previous observations. In agreement with the ground-based spectrum, we detect a faint silicate absorption feature at $0.93\pm 0.01$ $\mu m$. We do not detect a 2.0 $\mu m$ silicate absorption. Models of Kamo`oalewa's faint thermal emission (beginning near 4.5 $\mu m$) find a mean diameter of $D=18\pm2\mathrm{m}$ and best-fit visible albedo $p_V = 0.59^{+0.25}_{-0.17}$, with models as low as $p_V = 0.36$ providing adequate model fits. This combination of color, albedo, and absorption bands is similar to oldhamite-bearing enstatite-rich compositions. Kamo`oalewa's brightness variations over the course of the JWST program provides independent confirmation of its rotation period of 27.9 minutes, with an axis ratio $\sim1.4$ ($D\sim15-21$ m).
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All authors Benjamin N. L Sharkey, Vishnu Reddy, John W. Noonan, Theodore Kareta, James M. Bauer, Bryan J. Holler, Yaeji Kim, Albert R Conrad
Fluid Dynamics
Effects of mean flow skew on turbulent shear layers. Part I. Numerical investigation
Vedant Kumar, Dipendra Gupta, Gregory Paul Bewley et al. (+1 more)
Skewed turbulent shear layers, formed by the interaction between two non-aligned turbulent boundary layers, are investigated using high-fidelity large eddy simulations in a temporally evolving framework. It is argued that a skewed shear layer of this form should be viewed, in the long-time limit, in a rotated reference frame as the superposition of a standard planar shear layer and an orthogonal jet-like component that decays in time. The skewed shear layer is found to have reduced vertical integral length scale, and the coherent pressure rollers characteristic of shear layers undergo transient realignment towards the direction orthogonal to mean shear, consistent with the long-time limiting planar shear layer. Numerical experiments using fictitious test cases indicate that these effects are primarily driven through misalignment in the mean flow, and that the two orthogonal flow components in the mean shear frame are only weakly coupled.
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All authors Vedant Kumar, Dipendra Gupta, Gregory Paul Bewley, Johan Larsson
High Energy Physics (Theory)
General Lagrangian formulations for mixed-antisymmetric tensor fields on flat backgrounds
Alexander A. Reshetnyak
Lagrangian formulations for (ir)reducible integer higher-
spin massless and massive Poincare group representations subject to Young tableau with $k$ columns $Y[\hat{s}_1,\hat{s}_2,...,\hat{s}_k]$ in $d$-dimensional Minkowski space-time are firstly presented. The particles are described in a metric-like formulation by tensor fields with $k$ groups of antisymmetric Lorentz indices $\Phi_{\mu^1[{\hat{s}_1}],\mu^2[{\hat{s}_2}],..., \mu^k[{\hat{s}_k}]}$ by means of the BRST procedure with complete, $Q$, and incomplete, $Q_c$, BRST operators. Starting from a description of bosonic mixed-antisymmetric higher-
spin fields in terms of an auxiliary Fock space associated with a special Poincare module, we realize a conversion of the initial operator constraint system into a system of first-class operator constraints. To this aim, we find, in first time, by means of Verma module the auxiliary representations of the constraint subalgebra, to be isomorphic due to Howe duality to $so(k,k)$
algebra, and containing the subsystem of second-class operators in terms of new oscillator variables forming the Fock module. An unconstrained (with $Q$) and constrained (with $Q_c$ and BRST invariant algebraic constraints) gauge Lagrangian formulations with equivalent dynamics, but different configuration spaces are found. Concept of consistent cubic interactions are suggested within $Q_c$-approach together with evaluation the structure of cubic vertices for $p\geq 3$ copies of interacting massless mixed-antisymmetric fields.
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High Energy Physics (Phenomenology)
Non-Standard Interactions and Light Z' Bosons from CEvNS Data at CONUS+
Ch. M. Benavides, C. S. Muñoz, B. C. Canas et al. (+1 more)
We analyze the first Conus+ reactor-antineutrino spectrum to constrain nonstandard
neutrino interactions (NSI) with
quarks and light vector $Z'$ mediators in $E_6$ and leptophilic $U(1)_{L_a-L_b}$ models. The prediction includes coherent elastic antineutrino–
nucleus scattering (CEvNS) and elastic antineutrino–electron scattering (EvES), with Standard Model (SM)–mediator interference in each channel and an analytically profiled normalization uncertainty. We formulate $L_e-L_\mu$ and $L_e-L_\tau$ in a common charge convention, combining direct electron scattering with the
nuclear interaction induced by
photon– $Z'$ mixing. The data remain compatible with the SM. Electronic scattering has little effect on the
quark-NSI and fixed-coupling $E_6$ angular regions, but substantially strengthens the low-mass coupling limits of the $E_6$
benchmarks. The leptophilic models share a common low-mass plateau dominated by electronic scattering, while their limits separate at larger mediator masses through their different
nuclear loop contributions.
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All authors Ch. M. Benavides, C. S. Muñoz, B. C. Canas, Eduardo Rojas
Quantum Physics
Picosecond Schrödinger cat states for ultrafast optical quantum processing
Mamoru Endo, Kan Takase, Takefumi Nomura et al. (+12 more)
Non-Gaussian states are essential resources for universal, fault-tolerant optical
quantum computing, but their generation rate remains limited by low heralding probabilities and operation in nanosecond temporal modes. Here, we demonstrate multi-
photon generalized
photon subtraction in picosecond optical wave packets, establishing the state-generation capability required for high-rate operation by addressing the temporal-mode bottleneck that has constrained the achievable rate. Two interfering ultrashort squeezed
vacua are heralded by
photon-number-resolving detection with a high-speed transition-edge sensor and characterized by pulsed homodyne detection matched to 10-ps temporal modes at a 5-MHz pump repetition rate. We reconstruct Wigner functions without loss correction that exhibit up to four distinct negative regions for four-
photon heralding, together with an effective cat-state amplitude of $\alpha_{\mathrm{eff}} = 1.69$. This amplitude approaches the range of practical relevance for fault-tolerant cat-code architectures and for adaptive breeding toward logical-
qubit generation, while the picosecond temporal mode establishes a platform compatible with high-rate, scalable time-multiplexed photonic architectures.
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All authors Mamoru Endo, Kan Takase, Takefumi Nomura, Tatsuki Sonoyama, Kazuma Takahashi, Sachiko Takasu, Daiji Fukuda, Takahiro Kashiwazaki, Asuka Inoue, Takeshi Umeki, Peter van Loock, Petr Marek, Radim Filip, Warit Asavanant, Akira Furusawa
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Cyclic Denoising Reveals Ultrastable Memories in Diffusion Models
Rishabh Sharma and Stefano Martiniani
We introduce cyclic denoising – repeated forward and reverse
diffusion at controlled noise amplitudes – as an extraction attack for image
diffusion models. Inspired by random organization in disordered solids, cyclic denoising exposes regions of the learned distribution that are largely inaccessible to standard sampling. The dynamics drive samples toward attractors with a broad stability spectrum. The deepest attractors are ultrastable: they regenerate after near-total corruption and persist through thousands of noising-denoising cycles. Many of these attractors correspond to memorized training images, including stock photographs, brand watermarks, and web-crawl artifacts. The attack requires only sampler-level control, with no gradients, weight inspection,
prompts, captions, or prior knowledge of the training data. Unlike generate-and-filter attacks, which rely on large-scale prompted generation and post-hoc similarity or membership-inference filtering, our main protocol is fully unconditioned. We demonstrate the phenomenon in Stable
Diffusion v1.4 and in a pixel-space DDPM, showing consistent behavior across latent- and pixel-space
diffusion models. Across noise amplitudes, we observe a yielding-like transition: low-amplitude cycling produces trivial absorbing fixed points or limit cycles, while larger amplitudes induce rearrangements, basin hopping, and long-lived trapping in structured memorized attractor basins. We also observe hierarchical partial absorption,
prompt-stabilized basins, and cross-initial-condition universality of the recovered attractor set. Our results therefore show that cyclic denoising is both a physics-inspired probe of generative landscapes and a practical tool for memorization
auditing, with implications for
privacy, copyright compliance, and model fingerprinting.
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Quantum Physics
Suppressing Self-Discharging of Quantum Batteries by Cavity Interactions
Anass Jad, Abderrahim El Allati and Mohammad B. Arjmandi
We analyse a two-cavity architecture, in which a lossy cavity hosting $N$
qubits is coherently coupled to an auxiliary cavity, as a resource for the storage phase of an open
quantum battery at non-zero temperature. Within a local Lindblad treatment in the resonant configuration, we find that the inter-cavity coupling enhances the suppression of self-discharging across every initial preparation, battery size, and temperature we examine, with the protection degrading smoothly as the mean thermal occupation increases. For a single
qubit, the energy-basis coherence of a pure superposition leads to better long-time retention than fully excited state, highlighting the beneficial role of
quantum coherence in protecting stored energy against thermal degradation. For two-
qubit batteries, Bell-state preparations exhibit enhanced long-time ergotropy retention compared with the fully excited state, while the inclusion of
qubit-
qubit interactions produces only a weak dependence on the interaction type and strength within the parameter regime considered. Extending the analysis to multi-
qubit GHZ-charged batteries with all-to-all Heisenberg interactions, we find that the normalized retained ergotropy increases monotonically with the number of
qubits. This behavior is consistent with the collective enhancement of the
qubit-cavity coupling in the symmetric Dicke
manifold, indicating that larger
quantum batteries can benefit from improved protection against self-discharge. These findings establish cavity-assisted protection as a promising strategy for mitigating self-discharging and realizing of long-lived
quantum batteries in experimentally accessible platforms.
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Superconductivity
Sayak Biswas, Rajdeep Sensarma and Mohit Randeria
The pairing
symmetry of magic-angle moiré
graphene is a fundamental question that remains unresolved. Combining experimental and theoretical inputs, we constrain the superconducting order parameters that can emerge from the incommensurate Kekulé spiral (IKS) normal state on the hole-doped side of $\nu = -2$. Imposing the additional experimental constraint of nodal superconductivity, we are left with the task of distinguishing between singlet or triplet pairing, and of determining the d-vector in the latter case. We propose definitive tests to identify the pairing
symmetry based on two classes of experiments using the response of the superconducting state to Zeeman field orientation. The first set of predictions is for spectroscopic and thermodynamic measurements sensitive to low-energy excitations near the nodes. The second set is for phase-sensitive measurements of topologically protected Andreev bound states near boundaries, whose spectroscopy is shown to provide a smoking gun signature of the pairing
symmetry.
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High Energy Physics (Experiment) · Cross-listed from cs.LG
Learning to Trigger: Reinforcement Learning at the Large Hadron Collider
Zixin Ding, Shaghayegh Emami, Giovanna Salvi et al. (+7 more)
High-throughput scientific facilities such as the Large
Hadron Collider depend on real-time event filtering (triggering) under tight constraints on bandwidth, latency, and storage. In practice, trigger menus are largely static and hand-tuned and can become suboptimal as detector conditions, pileup, and background composition drift over time. We cast online threshold tuning as a sequential decision-making problem: a reinforcement learning
agent ingests streaming summaries of recent rates and signal-sensitive features and updates trigger thresholds to maximize signal efficiency while tracking a target background rate within a tolerance band. We adapt Group-Filtered Policy Optimization (GFPO) to streaming control and introduce two variants (GFPO-F, GFPO-FR) that enforce background rate feasibility during training. On a
benchmark that emulates realistic
collider operation, we study two representative triggers: a total transverse energy ($H_{T}$) trigger sensitive to pileup variation, and an anomaly-detection (AD) trigger based on reconstruction loss for rare or non-standard signatures. On Monte Carlo streams, our
agent increases the fraction of in-tolerance time intervals by 48% ($H_T$) and 28% (AD), with a cumulative gain of up to 2% in signal efficiency on those in-tolerance intervals. Transferring from simulation to real collision data (CMS Run 283408), the same
agent, without fine-tuning, achieves a 56% ($H_T$) and 28% (AD) in-tolerance improvement over baselines, with further signal-efficiency gain on both triggers. To our knowledge, this is the first demonstration of RL-based trigger control on real Large
Hadron Collider collision data. Code is available at https://github.com/Zixind/GFPO_LHC (see repo for details).
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All authors Zixin Ding, Shaghayegh Emami, Giovanna Salvi, Cecilia Tosciri, Abhijith Gandrakota, Jennifer Ngadiuba, Nhan Tran, Christian Herwig, David W. Miller, Yuxin Chen
Mesoscale and Nanoscale Physics
Observation of even-denominator fractional quantum Hall states at $\nu = 3/4$ and 5/4 in the lowest Landau level
Siddharth Kumar Singh, Chengyu Wang, Adbhut Gupta et al. (+3 more)
Two-dimensional electron systems (2DESs) confined to wide GaAs
quantum wells provide a unique platform to study exotic fractional
quantum Hall states (FQHSs) because the 2DES has a
bilayer charge distribution with significant interlayer tunneling. Precise control over the 2DES density allows the tuning of the interlayer tunneling over a wide range. Here, we present our discovery of new even-denominator FQHSs in the lowest Landau level (orbital index N = 0) at filling factors $\nu = 3/4$ and 5/4 in an ultrahigh-quality 2DES confined to a 72.5-nm-wide GaAs
quantum well. The ground states at $\nu = 3/4$ and 5/4 both evolve from composite
fermion Fermi seas to FQHSs as the density is raised so that interlayer tunneling is sufficiently reduced and the 2DES becomes two-component, signaled by the behavior of the FQHSs flanking $\nu = 3/4$ and 5/4. The two-component nature of the $\nu=3/4$ and 5/4 FQHSs is also evident from their extreme sensitivity to the
bilayer charge distribution
symmetry: both states disappear quickly when the charge distribution is made asymmetric by only $\simeq 2\%$. We find a natural explanation for the 3/4 and 5/4 FQHSs in terms of two states linked by particle-hole
symmetry, and using the Scarola-Jain
bilayer composite
fermion framework which is a generalization of the well-known, two-component, Halperin state ($\Psi_{331}$ state). Our observations elucidate the crucial role of competing energy and length scales in wide
quantum wells in stabilizing new ground states.
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All authors Siddharth Kumar Singh, Chengyu Wang, Adbhut Gupta, Kirk W. Baldwin, Loren N. Pfeiffer, Mansour Shayegan
Optics
Attenuation scaling and error analysis of 2f and 4f architectures for free-space optical matrix-vector multiplication
Dawson Lyles and Spencer LaVere Smith
Free-space optical computing has been suggested as a scalable, high speed, and energy efficient platform for performing
matrix-vector multiplication (MVM). We present two free-space optical approaches for MVM, called the 2f and 4f architectures, and model them using wave optics simulations. After constraining the optical modulator in our models to have a maximum gain limit, we use our simulations to compare 2f and 4f MVM performance in terms of computational error and optical signal attenuation per MVM. We examine how 2f and 4f signal attenuation per MVM scales with increasing MVM problem size for different statistical distributions of
matrix elements and compare to the expected attenuation from a universal multiport interferometer (UMI), commonly used in integrated photonics for MVM. We find that the 2f and 4f architectures scale more favorably to large problem sizes, experiencing many orders of magnitude less attenuation than UMIs for
matrix dimension above a thousand elements. We furthermore examine how varying modulator space-bandwidth product and output slit aperture affect 2f and 4f attenuation and computational error across different distributions of
matrix elements. We conclude that the preference of 2f or 4f MVM depends on the statistics of the
matrix used, but that 4f may provide more flexibility than 2f.
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Biological Physics · Cross-listed from math.NA
Diagonal Frog: High-order positivity-preserving FD schemes for anisotropic Fokker-Planck equations
Andrey Itkin
The Fokker-Planck equation is fundamental to statistical mechanics, yet in settings with multiple state variables, anisotropic (cross-)
diffusion, and jumps, conventional discretizations frequently produce non-physical negative probability densities. Building on the operator approach of "A. Itkin, Pricing derivatives under Levy models. Modern finite difference and pseudo-differential operators approach, Springer, 2017, ISBN 978-1-4939-6792-6", we introduce a family of "Diagonal Frog" discretizations whose spatial operators are eventually M-
matrices (EM-
matrices). Although these operators lack a local M-
matrix structure, positivity of the directional sub-operators emerges in the spirit of Zeno's paradox: the
matrix exponential, assembled as the limit of infinitely many ever-smaller substeps, is provably nonnegative after a short transient even though no single substep is. For the mixed-derivative block, whose generator is not eventually nonnegative, positivity instead rests on a factorized resolvent solver and holds conditionally, on an explicit step-size window; discrete mass is conserved exactly by the splitting for every step size. The resulting schemes are second-order accurate in time and space and require O(m 2 N + m 3) operations per time step, where m is the dimension of the Krylov subspace used to apply the exponential. As stress tests, we solve a two-dimensional anisotropic Fokker-Planck equation in the strong cross-
diffusion regime against an exact Gaussian reference, a Kramers escape problem in a double-well potential, and an advection-dominated problem, and observe that the schemes remain stable, nonnegative, and mass-conservative for a wide range of Pécklet numbers (so, don't need any flux limiter). Finally, we extend the construction to multidimensional processes and to the backward Kolmogorov equation with jumps.
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Plasma Physics
The science of compressional heating on the LM26 magnetized target fusion experiment
S. J. Howard, D. P. Brennan, K. Epp et al. (+61 more)
The Lawson Machine 26 (LM26) at General Fusion has demonstrated compressional heating of a spherical tokamak deuterium
plasma as it was compressed by an imploding solid lithium liner. Results from the first 11 compression shots on LM26 are presented, the highest-performing of which show more than a 3x increase in $T_e$, a 10x increase in $n_e$, and a 10x increase in $B_{pol}$ within the
plasma driven by 3x radial compression. The experimental device and instrumentation are reviewed in detail, followed by observations about the liner trajectory and
evolution of
plasma properties, including increases in emission of
neutrons, X-rays, and visible radiation. Observations from fast-camera images during compression provide context for interpreting the spatial structure of
plasma-wall interaction. Overviews of relevant models and analysis are presented. Diagnostic data are used to reconstruct the experimental
equilibrium state in computational framework as a function of time. The results build confidence in the stability and transport analyses that support the primary conclusions. Trends across the full set of 11 compression shots are presented, and detailed examinations of the high-performance shots are given individually. The central conclusions of the integrated physics model specifically indicate that compressional heating was achieved in this set of experiments, as evidenced by the balance of heating power from compression, Ohmic heating from
plasma current, and losses to the boundary needed to match the experimental data. A majority of the temperature rise is attributable to compressional heating. An increase in
neutron flux is also observed during compression. The results provide a basis for planned improvements to the LM26 facility that will enable the compression of magnetized
plasma to increasingly higher densities and temperatures.
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All authors S. J. Howard, D. P. Brennan, K. Epp, P. Forysinski, D. Plant, M. Reynolds, A. Froese, N. Sirmas, D. Krotez, V. Suponitsky, R. Zindler, E. Love, C. Macdonald, N. Kumar, Z. Seifollahi Moghadam, K. Conquergood, A. Wong, W. Zawalski, B. Rablah, W. Kozicki, P. Carle, A. Rohollahi, C. Preston, A. M. D. Lee, J. Hobbis, L. Santos, X. Feng, M. Schellenberg-Beaver, R. Tingley, R. Underwood, J. Sanchez Rojo, J. Gorenstein, D. Froese, E. Cessford, J. Pratt, J. Crofts, J. Sardari, G. Faust, D. Ross, J. Wilkie, S. Bernard, S. Edwards, R. Oosterom, M. Yurkiv, J. Y. J. Cheng, C. Connor, S. Bolanos, C. Gutjahr, E. Chan, M. Greenwood, E. Ng, A. Massey, K. Chen, R. Svihra, A. Gromer, S. Lee, X. Zhu, L. Marshall, C. Eyrich, A. Mahoney, M. Davidson, H. Feng, A. Rudy, M. Laberge
High Energy Physics (Phenomenology)
Mapping jet substructure in heavy-ion collisions with track functions
João Barata, Yeonju Go and Daniel Pablos
We investigate the dynamics of high-energy QCD cascades in heavy-ion collisions, focusing on modifications to jets' substructure induced by the presence of a
quark-
gluon plasma (QGP). To this end, we study the properties and scale
evolution of track functions, non-perturbative objects encoding the flow of energy from an initiating parton to all charged
hadrons. In contrast to the more standard fragmentation functions, these objects have a non-linear renormalization group (RG)
evolution, being sensitive to the entire jet fragmentation process. Using the JEWEL and HYBRID Monte-Carlo models of jet quenching, we find that in both frameworks the higher moments and cumulants of the track functions' distributions exhibit sizable deviations from their
vacuum baselines, demonstrating that medium-induced energy loss imprints itself in the in-medium jet fragmentation pattern. We find that the quantitative magnitude of these modifications differs significantly between the two models. This identifies track functions as a class of observables capable of discriminating between competing microscopic pictures of jet-medium interactions. We further examined the (in-medium) RG flows for the leading moments, which remain in qualitative agreement with the in-
vacuum evolution. This provides an avenue to directly test the RG flows inside a QGP, linking heavy-ion jet measurements to basic QFT understanding of partonic branching. Finally, we comment on the feasibility and challenges associated with extracting track functions from experimental data.
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High Energy Astrophysical Phenomena
FAST Pulsar Database IV. Spike subpulses and quasi-periodic subpulses of 25 pulsars observed by FAST
Tao Wang, N. N. Cai, J. L. Han et al. (+6 more)
Fine structures of individual pulses can be detected when observations are conducted with a high time resolution and a great sensitivity. We examined
pulsar data observed by the Five-hundred-metre Aperture Spherical
radio Telescope (FAST) with a time resolution of 49~{\textmu}s, and detected a large number of spike subpulses of 21
pulsars and quasi-periodic subpulses from 13
pulsars. These spike subpulses cannot be or are marginally resolved by the FAST observation time resolution, and are generally strongly linearly polarized, which may be primary emission elements of subpulses. For the quasi-periodic subpulses from 13
pulsars, we measured their characteristic periods, generally a few tenths of a millisecond, and examined their possible correlation with
pulsar rotation period.
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All authors Tao Wang, N. N. Cai, J. L. Han, W. C. Jing, Z. L. Yang, Y. Yan, D. J. Zhou, P. F. Wang, C. Wang
Quantum Physics
Polynomial-time exact diagonalization via sparse guided eigenwalks
Zachary E. Chin, Mario Motta, Javier Robledo Moreno et al. (+3 more)
Computing
quantum ground states is generically difficult, but additional structure can sometimes allow diagonalization to be recast as a more feasible problem. For example, when the desired ground state is sparse in a given basis, diagonalization can be facilitated via graph search. We make this reformulation precise by introducing the eigenwalk problem, which seeks the support of a sparse eigenvector of a Hermitian
matrix by exploring the graph induced by its nonzero entries. However, it is not obvious whether the relevant support vertices must always be efficiently reachable by a search on the graph. To resolve this question, we prove that for every sparse eigenvector, there exists a (possibly different) sparse eigenvector with the same
eigenvalue whose support is tightly localized in the graph, with diameter scaling only linearly in the sparsity and independently of the total number of vertices. As a consequence, if a $2^n$-dimensional, ${\rm poly}(n)$-sparse
Hamiltonian has an $\mathcal{O}(1)$-sparse extremal eigenvector and one support element is known, then an exact eigenvector with the same
eigenvalue can be computed classically in ${\rm poly}(n)$ time. The same conclusion follows when the $\mathcal{O}(1)$-sparse eigenvector is non-extremal, provided that it is sparser than every eigenvector with a different
eigenvalue. These results hold with no assumptions on the degeneracy, locality, spectral width, or spectral gap of the
Hamiltonian, and the underlying support-localization principle also extends to problems beyond exact diagonalization, such as sparse principal component analysis.
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All authors Zachary E. Chin, Mario Motta, Javier Robledo Moreno, Antonio Mezzacapo, Isaac L. Chuang, William Kirby