Optics
Neural Networks for Inverse Design of Cascaded-Mode Near-Field Landscapes
Wannes Luts De Martelaere, Joeri Lenaerts and Vincent Ginis
Structuring optical near-fields is important for applications in microscopy and nanoparticle manipulation. Traditionally, near-fields are structured using
antenna nanostructures that locally convert propagating far-fields into bound near-fields. Recently, a remote structuring approach was proposed using cascaded mode interference in a multimode waveguide. However, determining the complex coefficients of the optimal modal combination needed to obtain specific near-fields remains a challenge. We address this inverse design problem using artificial neural networks. We model the relationship between the design parameters and near-field landscapes using multilayer neural networks. After training, these networks are used for gradient-based optimization to reconstruct target near-field profiles. We implement this methodology to design longitudinal and lateral field variations. Our approach designs simple and complex longitudinal landscapes, demonstrating accurate prediction and flexibility. Lateral field reconstruction is more challenging but improved with training data selection and augmentation. This work establishes deep learning as an efficient and scalable framework for cascaded-mode near-field inverse design.
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Atmospheric and Oceanic Physics
Learning Climate Variability from Scarce Data with Diffusion Models: A Test Case for ENSO
Lluis Palma, Vincent Verjans, Amanda Duarte et al. (+2 more)
Diffusion models are increasingly applied to
climate emulation, but whether they capture the correct modes of variability remains unclear, a concern amplified by data scarcity at longer timescales. We investigate this using synthetic tropical Pacific SST fields from Linear Inverse Models (LIMs), whose known low-order structure bypasses the overlapping and confounding modes of real observations. With sufficient training data, our model recovers the correct structure of both Gaussian and non-Gaussian LIMs, including ENSO's Eastern/Central Pacific asymmetry. Yet an ablation study on the number of monthly training samples reveals that the 700 observations in ERSSTv5 fall an order of magnitude short of the 7,000 samples needed for convergence, and that not all
diffusion parameterisations recover the correct low-order structure. Pre-training on CMIP6 with a learned model
embedding, followed by fine-tuning on scarce observations, closes this gap, reproducing observed statistics more faithfully than both Gaussian and non-Gaussian LIMs.
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All authors Lluis Palma, Vincent Verjans, Amanda Duarte, Albert Soret, Markus Donat
Computational Physics
GPU-accelerated superiorization on constrained physical problems with SupPy
Tobias Becher, Yair Censor, Kay Barshad et al. (+1 more)
The superiorization method (SM) is situated between feasibility-seeking and constrained optimization. Instead of aiming at the minimum of a given objective function over a constraint set, it seeks a feasible point at which the objective function value is reduced - though not necessarily minimal - rather than hard targets, or in which a mathematically optimal solution is not strictly required. While the method has been investigated for several applications in physics, its broader use has been limited, in part due to the lack of openly available software for researchers wishing to explore it. In this work we apply superiorization to three problems from applied physics: seismic image reconstruction, low-dose CT reconstruction and intensity-modulated radiotherapy treatment planning. These experiments are conducted with SupPy, an open-source modularized Python toolbox developed for this work, which supports execution of feasibility-seeking
algorithms and their superiorized version on both the CPU and the GPU. In all three cases the superiorized
algorithms achieve favorable results compared to feasibility-seeking alone, with reduced noise in the imaging examples and lowered body dose in the radiotherapy plans. For the radiotherapy case we further observe that superiorization produces clinically viable plans on infeasible constraint sets.
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All authors Tobias Becher, Yair Censor, Kay Barshad, Niklas Wahl
Biological Physics
Efficient Proton Relay Orchestrated by Covalent Bond Switching of Active Amino Acids in Protein Channels
Xiangyu Su, Yuwei Cao, Shuyang Zhao et al. (+1 more)
Through systematic mutational simulations of the key site in a
proton channel, we find that 13 of the 20 canonical amino acid residues are active for
proton transfer through covalent bond switching, whereas the remaining 7 residues, whose side chains terminate in sp3 hybridized carbon-hydrogen covalent bonds, do not undergo such bond switching and are therefore inactive. All active residues have a negative electrostatic potential extremum at the
proton accepting atom and lower energy barriers for
proton relay orchestrated by bond switching, whereas the inactive residues have positive electrostatic potential extremum and significantly higher barriers for bond switching. We further find that the active residues tend to be distributed within the pore to mediate
proton transfer, while the inactive residues are enriched in the periphery to stabilize the structure. This bond switching activity can also be observed in respiratory complex I. These findings establish a new classification criterion for amino acids based on their covalent bond switching activity, providing insights into how life utilizes the 20 types of amino acids.
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All authors Xiangyu Su, Yuwei Cao, Shuyang Zhao, Wanlin Guo
Instrumentation and Detectors · Cross-listed from nucl-ex
Half-Life Measurements of $^{110}$Sn, $^{113}$Sn, $^{117\mathrm{m}}$Sn, and $^{123\mathrm{m}}$Sn Produced via Photon Activation of Natural Tin
O Nusair, D Devries and M Toto-Gonzalez
We report independent determinations of the ground-state half-lives of $^{110}$Sn, $^{113}$Sn, and the isomeric states $^{117\mathrm{m}}$Sn (J$^{\pi} = 11/2^{-}$) and $^{123\mathrm{m}}$Sn (J$^{\pi} = 3/2^{+}$), produced via
photon activation of natural tin using a TT-300HE Rhodotron accelerator. The activated samples were monitored over several months using a high-purity germanium (HPGe) detector. Time-dependent $\gamma$-ray spectra were analyzed using Gaussian peak fitting for the \SI{280.49}{keV}, \SI{391.697}{keV}, \SI{158.56}{keV}, and \SI{160.34}{keV} transitions, yielding half-lives of \SI{4.165(25)}{h} for $^{110}$Sn, \SI{116.08(94)}{d} for $^{113}$Sn, \SI{13.95(1)}{d} for $^{117\mathrm{m}}$Sn, and \SI{39.95(12)}{min} for $^{123\mathrm{m}}$Sn. Agreement with
Nuclear Data Sheets (NDS) recommended values is generally observed for $^{110}$Sn, $^{113}$Sn, and $^{123\mathrm{m}}$Sn, with deviations consistent within combined uncertainties when quantified using standardized differences (z-scores). In contrast, $^{117\mathrm{m}}$Sn exhibits a statistically significant deviation from the evaluated value of \SI{13.76(4)}{d}, with a z-score indicating a discrepancy well beyond expected statistical fluctuations. This result suggests a systematic difference warranting further investigation, with potential implications for applications relying on precise decay data, including calibration, dosimetry, and astrophysical modeling.
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Optics
Observation of Non-Hermitian Skin Dynamics in the Liouvillian Regime
Shu Yang, Yeyang Sun, Lingrui Hong et al. (+1 more)
Open
quantum systems generally do not perfectly preserve phase coherence: coupling to uncontrolled environments requires a density-
matrix description based on the Liouvillian framework beyond pure-state wave
evolution. Realizing and probing such dynamics in a programmable platform is therefore essential for connecting coherent physics to realistic dissipative settings. Here we implement a tunable open-system
quantum walk in a photonic mesh
lattice, where controlled phase noise produces adjustable dephasing and non-reciprocal gain-loss imbalance provides an independently tunable non-Hermitian drive. This allows us to continuously interpolate between coherent
quantum walks and incoherent classical walks, and to observe how directional transport evolves in the Liouvillian regime. Using non-Hermitian skin dynamics as a probe, we measure the center-of-mass drift over both the coherence and non-Hermiticity parameters, revealing a crossover from coherence-enhanced to decoherence-enhanced transport in quantitative agreement with
quantum-channel simulations. We further program spatial and temporal interfaces to demonstrate interface accumulation and a long-time drift governed by the instantaneous channel. Our results establish a controllable photonic platform for simulating open
quantum dynamics and show that decoherence can actively reshape non-Hermitian transport.
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All authors Shu Yang, Yeyang Sun, Lingrui Hong, Yi Yang
Optics · Cross-listed from eess.SP
Low Complexity Kolmogorov-Arnold Network-based DPD for Analog RoF Fronthaul
Carlos Daniel Fontes da Silva, Tianyu Jiang, Lu Zhang et al. (+5 more)
This paper proposes and demonstrates experimentally for the first time a Kolmogorov-Arnold Network (KAN)-based digital predistortion (DPD) model, named envelope time-delay KAN (ETDKAN), for mitigating nonlinear distortions in analog
radio-over-fiber (A-RoF) systems. The ETDKAN model incorporates physical constraints of
radio-frequency (RF) nonlinear devices and, through KAN symbolization, achieves a significant reduction in computational complexity while improving interpretability. The proposed model is numerically implemented and optimized alongside multilayer perceptron (MLP) and
memory-
polynomial-based DPDs. Results show that the resulting symbolic ETDKAN (symbETDKAN) attains ACLR and EVM performance comparable to neural network-based models, while maintaining a computational complexity close to that of
memory polynomials. Experimental validation using an A-RoF system confirms the practical feasibility of the proposed approach, which resulted in a 4-5 dB reduction in ACLR in the analyzed scenario.
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All authors Carlos Daniel Fontes da Silva, Tianyu Jiang, Lu Zhang, Vjaceslavs Bobrovs, Xianbin Yu, Xiaodan Pang, Oskars Ozolins, Edson Porto da Silva
Optics
In-plane vector-field imaging of propagating surface phonon polaritons
Richarda Niemann, Dorothée S. Mader, Gonzalo Alvarez-Pérez et al. (+9 more)
Polariton interferometry through optical near-field microscopy has become a powerful tool in nanophotonics, enabling direct spatial access to the propagation characteristics of strongly confined, evanescent polariton modes. Scattering-type near-field optical microscopy has matured as the
prime tool for such studies, yet mostly the out-of-plane components of the optical near fields are probed, owing to the elongated geometry of the nanotip. Here, we demonstrate a complementary far-field nonlinear microscopy approach which allows to selectively probe in-plane polariton field components. Accessing the full vector field is interesting when studying complex mode patterns such as
hyperbolic polaritons or skyrmions, where the in-plane field components are typically only inferred from the out-of-plane component but not measured directly. To this end, we use nonlinear infrared-visible wide-field sum-frequency generation microscopy, where the short visible wavelength of the nonlinear signal provides the high spatial resolution to access evanescent modes in the infrared. The
symmetry selection rules of the nonlinear process further enable polarization-selective imaging of both in-plane polariton field components through spatial interferometry. The concept is demonstrated experimentally using surface
phonon polaritons at the AlN-air interface launched by a gold
antenna. A simple, semi-analytical model reproduces the peculiar propagation patterns. Hyperspectral imaging with a tunable narrowband
laser further gives access to the polariton dispersion. The wide-field methodology holds high promise for in-depth and high-throughput studies of infrared nanophotonic structures.
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All authors Richarda Niemann, Dorothée S. Mader, Gonzalo Alvarez-Pérez, Ana I. F. Tresguerres-Mata, Aitana Tarazaga Martín-Luengo, Stefan Partel, Joshua D. Caldwell, Niclas S. Mueller, Martin Wolf, Javier Martín-Sánchez, Pablo Alonso-González, Alexander Paarmann
Optics
Temporal wave trapping from dynamical pump pulses
T. Torres, R. Terrier, J. Fatome et al. (+3 more)
Temporal reflection in nonlinear optical fibers provides a powerful framework for manipulatinglight. In this work, we theoretically and experimentally demonstrate a novel mechanism for wavetrapping induced by the dynamical
evolution of a single high-order
soliton pulse. Experimentalmeasurements performed in a 5-km-long nonlinear dispersion shifted fiber confirm the coexistence ofreflected, transmitted, and trapped components, in excellent agreement with theoretical predictions.These results establish a simple and versatile route toward dynamic temporal waveguiding using asingle optical pulse, opening new opportunities for all-optical control and manipulation of ultrafastsignals.
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All authors T. Torres, R. Terrier, J. Fatome, B. Kibler, G. Millot, G.P. Agrawal
Atomic Physics
Quantum statistics on atom-ion Feshbach resonances
Joachim Siemund, Fabian Thielemann, Jonathan Grieshaber et al. (+5 more)
We investigate three-body recombination in a hybrid atom-ion system consisting of a single trapped Ba$^+$ ion immersed in a two-component
Fermi gas of Li atoms near an atom-ion Feshbach resonance. By tuning the
spin composition at constant density and temperature, we isolate the role of
quantum statistics in atom-atom-ion collisions. The measured ion loss rate exhibits a pronounced nonlinear dependence on
spin polarization, revealing a reduced contribution of recombination pathways involving identical
fermions already at the level of experimental observables. The observations are consistent with a two-step recombination picture and an adiabatic hyperspherical approach, where antisymmetrization restricts the available entrance channels and gives rise to interference between indistinguishable recombination pathways. Our work establishes atom-ion systems as a platform for controlling three-body collisions via
quantum statistics and demonstrates that exchange-
symmetry effects remain robust even under thermal averaging that obscures the underlying threshold-law behavior.
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All authors Joachim Siemund, Fabian Thielemann, Jonathan Grieshaber, Wei Wu, Patrick Mullan, Panagiotis Giannakeas, Krzysztof Jachymski, Tobias Schaetz
Fluid Dynamics
Excitation of non-modal perturbations in hypersonic boundary layers by free stream forcing. Part II: asymptotic theory and key mechanisms
Ming Dong, Mingze Sun, Qinyang Song et al. (+1 more)
Recently, Zhao & Dong (J. Fluid Mech. 2025, vol. 1013: A44) developed a high-efficiency, high-accuracy numerical framework, the shock-fitting harmonic linearised Navier-Stokes (SF-HLNS) approach, which enables a systematic study of the receptivity of non-modal perturbations in hypersonic blunt-body boundary layers over a wide parameter range. In this Part II, we employ a high-Reynolds-number asymptotic analysis to elucidate the physical mechanism of the receptivity process. A distinct slow-down convection mechanism is identified in the nose region, amplifying the perturbation streamwise vorticity from the post-shock position to the boundary layer around the stagnation point by a factor of O(\sqrt{R}), where R is the Reynolds number based on nose radius. Downstream, the lift-up mechanism further leads to a transient growth of the perturbation streamwise velocity up to an amplitude of O(R). Based on these mechanisms, a reduced model is developed to predict the downstream
evolution of the non-modal perturbations initiated by receptivity, whose predictions agree well with SF-HLNS calculations. This model can also be used to investigate the effects of wall temperature and nose radius on non-modal receptivity efficiency, as will be detailed in Part III of this work series.
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All authors Ming Dong, Mingze Sun, Qinyang Song, Lei Zhao
Optics
Refractive indices of Y$_2$SiO$_5$ in the near-infrared
Shijun Zhang, Jérôme Debray, Benoît Boulanger et al. (+2 more)
Y$_2$SiO$_5$ is a reference birefringent material for optical
quantum technologies. The refractive index is primarily known in the visible spectrum, whereas this
crystal is also used in the near-infrared. We begin by analysing historical measurements, as well as the modelling proposed at the time. The absence of refractive index tabulated values in the near- and mid-infrared ranges motivated us to carry out independent measurements. Using interferometric techniques in the telecom wavelength range, we demonstrate the ability to determine the principal refractive indices and propose a model spanning a broad spectral range based on Sellmeier equations for which we explicitly give the coefficients and discuss the achievable accuracy. Conversely, as an illustration, white-light interference enables us to precisely determine the thickness of a Y$_2$SiO$_5$ thin film on the order of ten micrometers.
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All authors Shijun Zhang, Jérôme Debray, Benoît Boulanger, Pierre Lemonde, Thierry Chanelière
Fluid Dynamics
Hydrodynamic theory of premixed flames under Darcy's law: Interfacial conditions and effects of nonunity Lewis number and heat loss
Prabakaran Rajamanickam and Joel Daou
Premixed flames propagating in porous media or Hele-Shaw channels are governed by Darcy's law, which accounts for the strong frictional forces imposed by the solid
matrix or confining walls. Prior theoretical studies of such flames have typically employed phenomenological Markstein-type corrections and have assumed unity Lewis numbers and adiabatic conditions. In this work, we develop a rigorous hydrodynamic theory for premixed flames under Darcy's law that incorporates nonunity Lewis numbers and heat losses. Using large activation-energy asymptotics for a one-step Arrhenius chemistry model and a systematic multiple-scale analysis, we derive the interfacial jump conditions across the flame from first principles. The conventional continuity requirements of mass flux and pressure at an interface under Darcy's law acquire corrections to the finite thickness of the flame. The adiabatic burning rate is shown to involve three distinct Markstein numbers, corresponding to
curvature, tangential flow strain, and
gravity-induced strain. The
gravity term is unique to Darcy's law and has no counterpart in classical Navier–Stokes formulations. Moreover, the
curvature Markstein number and the tangential strain Markstein number are found to be unequal, in contrast to the classical Navier–Stokes case where they coincide in the one-step chemistry model. Explicit formulas for the Markstein numbers are provided, and the resulting new dispersion relation, linking the perturbation wave number $k$ to the growth rate $s$, takes the form $s=(a|k|-bk^2-d|k|^3)/(1+c|k|)$. This relation, applicable under Darcy's law, is to be compared to the classical Clavin–Garcia dispersion relation derived from the Navier–Stokes equations. The theory provides a rigorous foundation for flame dynamics in strongly confined environments, with direct applications to porous media combustion and Hele-Shaw
cell experiments.
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Physics Education · Cross-listed from quant-ph
On the simple derivation of the Casimir effect
Hai-Chau Nguyen and Matthias Kleinmann
The Casimir effect in its simplest form describes the attraction of two parallel conducting plates at close distance due to the
vacuum fluctuation of the electromagnetic field. Its derivation can be found in many introductory works on
quantum optics. Here we return to the original paper by Casimir and find subtle nuances in his derivation that are worth discussing to give a complete picture of a mathematically sound derivation of the effect.
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Chemical Physics
Perturbatively Corrected Linear Response Selected Configuration Interaction
Peter Reinholdt, Erik Kjellgren and Jacob Kongsted
Selected configuration interaction (SCI) methods have emerged as powerful, lower-cost alternatives to full configuration interaction (FCI) for ground- and excited-state energies. Still, calculating molecular response properties with SCI remains a significant challenge. In this work, we introduce perturbative corrections to the linear response selected configuration interaction (LR-SCI) framework, using an order-by-order Epstein-Nesbet perturbation expansion through second order. We demonstrate that in this theoretical framework, the finite-order perturbative treatment preserves the pole structure of the parent variational LR-SCI theory, which means that although the method can be useful for static properties, it is not suitable for frequency-dependent molecular response properties. Numerical
benchmarks targeting the static polarizabilities of water, ethene, boron hydride, and hydrogen chloride demonstrate systematic convergence toward the FCI limit for both ground and excited electronic states. While first-order corrections yield marginal improvements, the inclusion of second-order corrections substantially enhances accuracy over underlying variational treatments and diminishes oscillatory convergence behavior present in the parent variational LR-SCI method. Combined with extrapolation techniques, LR-SCI-PT achieves excellent agreement with high-level coupled-cluster references, establishing a powerful route toward near-FCI quality molecular properties for systems otherwise inaccessible to exact FCI treatments.
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Chemical Physics
A Givens-exchange ansatz for molecular variational eigensolvers
Azadeh Alavi, Fatemeh Kouchmeshki, Muhammad Usman et al. (+4 more)
Molecular ground-state energies help determine conformer rankings, reaction energetics, and electronic effects in computational drug discovery, but accurate calculations become difficult when strong correlation or large active spaces are important. Variational
quantum eigensolvers estimate these energies by optimizing a parameterized
quantum state, making ansatz design central to both accuracy and cost. We study a fixed-
topology Givens-exchange ansatz that avoids architecture search. The
circuit starts from the computational-basis state with the lowest diagonal
Hamiltonian expectation and applies local RY rotations with two ordered all-pair Givens exchange blocks. Parameters are optimized using
Hamiltonian expectation values, while exact diagonalization is used only after optimization to compute errors and fidelities. Across six fixed seeds, coefficient-verified LiH-6 and H2O-8
Hamiltonians, together with a BeH2-6 public-specification candidate, are chemically accurate in every run. The corresponding six-seed mean errors are 0.000000124 Hartree, equivalent to 0.000124 milli-Hartree; 0.000128558 Hartree, equivalent to 0.128558 milli-Hartree; and 0.000002152 Hartree, equivalent to 0.002152 milli-Hartree, respectively. On LiH-6 and H2O-8, these mean errors are lower than the published point errors of the compared
quantum-architecture-search methods, while the ansatz uses a larger pre-compilation macro budget. The method is therefore an accurate, reproducible, and search-free reference template for molecular variational eigensolvers.
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All authors Azadeh Alavi, Fatemeh Kouchmeshki, Muhammad Usman, Yongli Ren, Ke Deng, Hossein Akhoundi, Abdolrahman Alavi
Optics · Cross-listed from quant-ph
An ultralow-loss integrated photonic platform for discrete-variable quantum information processing
Ruiyang Chen, Zeying Zhong, Sanli Huang et al. (+9 more)
Photonic integrated
circuits offer a scalable and robust route toward
quantum information technologies by consolidating
photon sources and linear optical networks onto compact, wafer-manufacturable chips. Although silicon photonics has enabled diverse discrete-variable
quantum breakthroughs – spanning multiphoton
entanglement,
quantum networking, and photonic
qubit fusion for
quantum computing – scaling these platforms beyond proof-of-principle demonstrations remains severely constrained by a critical system-level bottleneck. Optical loss compounds rapidly across
photon generation, routing, and state analysis, causing multiphoton generation probabilities to plummet exponentially as
circuit depth and complexity grow. Here we overcome this rate-loss barrier by demonstrating a monolithic, ultralow-loss silicon nitride (Si$_3$N$_4$) integrated photonic platform engineered for high-performance discrete-variable
quantum information processing. Our architecture seamlessly integrates narrowband
photon-pair sources with low-loss
qubit-fusion
circuits and reconfigurable state-analysis interferometers. The on-chip sources prepare Einstein-Podolsky-Rosen (EPR) states with a fidelity of 0.9875(3) and exhibit near-unity
photon indistinguishability, yielding a heralded Hong-Ou-Mandel interference visibility of 0.990(6). By executing on-chip fusion of two EPR states, we synthesize and characterize four-
photon Greenberger-Horne-Zeilinger states with a record fidelity of 0.943(8) and a fourfold count rate of 27 Hz – more than two orders of magnitude higher than previous silicon-photonic implementations. Combined with standard CMOS-compatible fabrication on 150-mm-diameter wafers, these results establish ultralow-loss Si$_3$N$_4$ integrated photonics as a definitive, manufacturable platform for deployable, large-scale
quantum information processors.
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All authors Ruiyang Chen, Zeying Zhong, Sanli Huang, Sicheng Zeng, Zhenyuan Shang, Yue Hu, Zhen Chen, Yuan Chen, Shuyi Li, Xue Bai, Yi-Han Luo, Junqiu Liu
Optics
High order harmonic Optical Reconstruction by delayed time-depeNdent Ellipticity perturbaTion: HORNET
Lucas Perez, Corentin Picot, Stefan Skupin et al. (+2 more)
We present and demonstrate an all-optical in situ method for temporal characterisation of high-order harmonics generated in gas with a linearly polarised intense infrared (IR)
laser. By using a delayed cross-polarised replica of the IR pulse with a lower amplitude, we introduce a weak and time-dependent ellipticity in the IR driving field. Since the XUV emission is very sensitive to the ellipticity of the driving field, it is perturbed precisely at the times when ellipticity is significant. The detected emission is then reduced only if the unperturbed XUV emission is substantial at these times. Perturbed XUV spectra are recorded for several delays and exhibit changes both in amplitude and in their spectral content. An iterative ptychographic
algorithm is used to retrieve the electric field of individual harmonics in a very robust way. Experimental measurements are in good agreement with simulations. The reconstructed temporal profiles show a steady
evolution of the XUV pulse duration and chirp with the harmonic order. The highest harmonics exhibit a positive chirp and are emitted in the rising front of the IR driving pulse, while the lowest ones exhibit a negative chirp and are emitted throughout the entire pulse.
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All authors Lucas Perez, Corentin Picot, Stefan Skupin, Fabrice Catoire, Eric Constant
Fluid Dynamics
Influence of Park's Two-Temperature Model Control Temperature on the Flow Properties in Hypersonic Reentry Conditions
Gibson De Marchi Poltronieri, Farney C. Moreira and João Luiz F. Azevedo
Numerical simulations of reactive hypersonic flows under thermochemical non-
equilibrium conditions are presented for the FIRE II and Mars Pathfinder capsules. An 11-species chemical model is employed to simulate Earth's atmosphere, while an 8-species chemical model simulates Mars' atmosphere. The current formulation uses Park's two-temperature model to account for the non-
equilibrium phenomena. The present work analyzes the impact of different sets of weight factors used in Park's model to calculate the control temperature. The code used to simulate the hypersonic flow addressed in this work solves the Navier-Stokes equations for reacting gas flows. The findings are depicted in terms of the Mach number, temperature modes, and mass fraction distributions along the stagnation streamline in a region closer to the shock wave. The study also includes results regarding the stagnation point convective heat flux. The results presented are encouraging and show that the weight factors significantly impact the FIRE II test cases while having little impact on the Mars Pathfinder flows. In all cases, it is possible to observe some effect of the weight factor selection on property distributions. In summary, the weight factors influence the flow behavior with varying intensities depending on the flow conditions.
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Instrumentation and Detectors
HERETIX: A Hermetic, Enriched, Rare-Event Time Projection Chamber in Xenon
L. Althueser, N. Hargittai, J. Pienaar et al. (+4 more)
Xenon-based time projection chambers have established themselves as one of the most powerful technologies for rare-event searches. HERETIX is a proposed multi-tonne
liquid xenon observatory featuring two nested time projection chambers that enable the simultaneous optimisation of searches for weakly interacting massive particles and neutrinoless double beta decay ($0\nu\beta\beta$) of $^{136}$Xe. A hermetically sealed sapphire vessel containing xenon enriched to 90% $^{136}$Xe forms the inner detector, providing an ultra-low-background environment for $0\nu\beta\beta$ searches. Monte Carlo studies indicate that material-induced backgrounds can be effectively eliminated, yielding a projected $0\nu\beta\beta$ half-life sensitivity of $3.2 \times 10^{28} \, \mathrm{years}$ at 90% confidence level after a 10-year exposure, while the surrounding xenon volume, depleted in $^{136}$Xe, preserves the excellent dark matter sensitivity of large
liquid xenon detectors. HERETIX therefore offers a unified experimental approach capable of delivering leading sensitivity to two of the most compelling questions in fundamental physics.
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All authors L. Althueser, N. Hargittai, J. Pienaar, R. Braun, H. Landsman, C. Weinheimer, R. Budnik
Physics and Society
Human adaptive variability stabilises collective traffic dynamics
Shirui Zhou, Ching Jin, Junfang Tian et al. (+5 more)
Automated systems are often designed on the assumption that replacing human behavioural variability with precise, uniform algorithmic control improves collective performance. In automotive traffic, this principle underlies commercial adaptive cruise control (ACC). Using two large-scale human-driving experiments comprising 2.95 million car-following observations, a 25-vehicle platoon experiment and a controlled 11-driver protocol, cross-validated with 0.77 million observations from the NGSIM
dataset and data from 22 production ACC systems, together with empirically calibrated ACC simulations, we show the opposite: rigid algorithmic uniformity creates systemic fragility. Commercial rule-based controllers amplify small local perturbations into severe stop-and-go waves, increasing fuel consumption and carbon emissions by approximately 2.7- to 5.0-fold across scenarios. Human-driven platoons, by contrast, progressively dissipate disturbances and maintain smoother flow. We identify the behavioural mechanism behind this advantage: human car-following does not follow a fixed proportional spacing rule. Drivers continuously reshape their time-headway distributions across speed regimes, exhibiting a non-monotonic shift from efficiency-oriented to risk-sensitive regulation. This speed-dependent variability generates nonlinear damping that suppresses the synchronisation and propagation of local errors. Our findings challenge the view that human variability is merely suboptimal noise to be eliminated. More broadly, they suggest that robust large-scale interactive AI systems should embed adaptive, human-inspired behavioural flexibility rather than rely on rigid uniformity.
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All authors Shirui Zhou, Ching Jin, Junfang Tian, Shiteng Zheng, Rui Jiang, Shiquan Zhong, Shoufeng Ma, Vittorio Loreto
Optics
Low-Threshold Degenerate Optical Parametric Oscillations in Bichromatically-Pumped Normal-Dispersion Photonic-Crystal Microresonator
Valery E. Lobanov, Nadezhda S. Tatarinova, Artem E. Shitikov et al. (+3 more)
The process of excitation of degenerate optical parametric oscillations via bichromatic pump is studied numerically in normal-dispersion photonic-
crystal microresonator. It is demonstrated that the photonic-
crystal structure with two split modes placed symmetrically at the particular interval from the pumped modes provides significant reduction in pump power threshold for the considered process. The parameter range for this phenomenon is determined. Introduction of mode splitting at the signal mode located in the center between pumped modes leads to an increase in the generation threshold.
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All authors Valery E. Lobanov, Nadezhda S. Tatarinova, Artem E. Shitikov, Olga V. Borovkova, Igor A. Bilenko, Dmitry A. Chermoshentsev
Space Physics
Excursion-set structure factor of the auroral electric field
Magnus F Ivarsen, Kaili Song, Jean-Pierre St-Maurice et al. (+1 more)
A spacecraft crossing the aurora cannot tell whether structures in the field-aligned currents are short-lived or merely small. However, by tracking clusters of coherent radar echoes from aurorae and
Fourier-transforming motion-shifted echo pairs across radar snapshots, we can calculate the dynamic structure factor of the point-clouds, thereby quantifying the auroral electric field's spatial power and its persistence from 5 to 40 km, in regions where the radar look-direction is perpendicular to the geomagnetic field. This follows from the fact that coherent E-region radar echoes appear only where the ionospheric electric field exceeds the Farley-Buneman instability threshold, and so a point-target imaging radar naturally samples the field's excursion set; the field's spatiotemporal correlations are discernible from that point process. We find that the echo pattern moves with its cluster: large-scale structures persist for tens of seconds, but scales under 10 km renew within seconds, and conjunctions with Swarm satellite pairs replicate the same scale dependence in field-aligned currents. Coherent radar can thus quantify multi-scale variability in the auroral electric field on Alfvénic timescales.
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All authors Magnus F Ivarsen, Kaili Song, Jean-Pierre St-Maurice, Glenn C Hussey
Optics
Taming the single-cylinder scattering through time-modulation – The role of the modulation phase
J. Yan, I. Katsantonis, M. Mostafa et al. (+2 more)
Dielectric particles with time-modulated electromagnetic properties exhibit intriguing scattering phenomena, entailing unique response and possibilities in meta-structures made of such particles. In this work, we investigate the scattering properties of an infinitely-long cylinder with periodically time-modulated permittivity. We demonstrate parametric scattering amplification, depending on the strength of the modulation, as well as controllable angular scattering pattern, ranging from enhanced forward to enhanced backward, or even scattering cancellation. This angular tunability is achieved through appropriate control of the modulation phase, highlighting its critical role in multi-modal time-modulated scattering systems.
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All authors J. Yan, I. Katsantonis, M. Mostafa, V. Asadchy, M. Kafesaki
Instrumentation and Detectors · Cross-listed from hep-ex
Precision luminosity measurement in proton-proton collisions at a center-of-mass energy of 13 TeV with the CMS detector at the Large Hadron Collider
CMS Collaboration
Discovering new fundamental physics requires spotting subtle deviations between theoretical predictions and experimental data. This delicate comparison hinges on the precise knowledge of the integrated luminosity, the measure of how many particle interactions were actually delivered by the
collider. Here, we report a landmark measurement of the integrated luminosity by the Compact
Muon Solenoid (CMS) experiment for
proton-
proton collisions at a center-of-mass energy of 13 TeV at the CERN Large
Hadron Collider (LHC). By calibrating multiple independent monitors through specialized beam-separation techniques and rigorously validating their long-term stability against well-understood Z
boson production rates, we comprehensively map and minimize systematic uncertainties. Combining the findings yields a total integrated luminosity precision of 0.73% for the entire data set. This marks the most precise luminosity measurement ever achieved at a bunched-beam
hadron collider. Crossing the sub-percent precision threshold per data taking year fundamentally sharpens our ability to test the standard model and establishes a vital baseline for the upcoming High-Luminosity LHC era.
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Computational Physics
pyDOF: a Python library for the design of discrete forward and inverse filters
Z. Nikolaou, P. Domingo, L. Vervisch et al. (+1 more)
In this work, we present pyDOF, a Python-based software library which provides a domain-specific framework for the design of symmetric, physical-space, forward as well as inverse discrete filters. pyDOF is based on a constrained optimisation framework developed in our previous work [1, 2]. This framework allows the user to impose a wide range of constraints on the discrete filter transfer-function such as monotonicity, positivity, value-fixing, gradient-smoothing etc. amongst many others. pyDOF additionally includes an adaptive filter stencil selection option, and a van Cittert-based inverse-filter design with a user-controlled reconstruction order. The filter coefficients are computed automatically, and saved to a plain text file which can be readily parsed by any programming
language. pyDOF can be used to design a wide range of low-pass, high-pass, multi band-pass/band-stop etc. discrete filters. In addition, due to its generality and abstraction, pyDOF can be used to design specific filters for user-defined target filter transfer functions. Although developed primarily for application to computational fluid dynamics simulations, pyDOF can be used to design discrete filters for a wide range of signal processing applications.
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All authors Z. Nikolaou, P. Domingo, L. Vervisch, D. Drikakis
Data Analysis and Statistics · Cross-listed from nlin.CD
Emergence of Gamma-Type Upward-Phase Statistics in the Collatz Map: An Effective Poisson Process Mechanism
Weicheng Fu, Xiaobin Liu and Yisen Wang
The Collatz map is a simple deterministic transformation whose orbit structure remains highly nontrivial. A recent direction-phase decomposition partitions each orbit into upward and downward steps, and numerical observations indicate that the number of upward phases, $N_{\uparrow}$, follows an approximate Gamma distribution. In this work, we provide a mechanistic explanation for this statistical regularity by modeling the occurrence of upward phases in the odd-compressed, or Syracuse, version of the Collatz map as a homogeneous Poisson process. From the mean-field logarithmic balance and the
geometric distribution of $2$-adic valuations, we derive closed-form expressions for the Gamma parameters: the scale parameter $\theta = 2/(2-\log_2 3)^2 \approx 11.61$ is constant, whereas the shape parameter $K$ grows logarithmically with the maximal initial value $X_0=2L+1$. We also analyze the closure conditions for periodic orbits, showing that nontrivial cycles are severely constrained, which supports the plausibility of the statistical framework. Numerical validation for $L$ ranging from $10^5$ to $10^{15}$ confirms the theory with relative errors below $3\%$, and a bias-corrected mean estimate reduces the error to $10^{-3}$–$10^{-2}\%$. These results establish a quantitative link between the arithmetic properties of the Collatz map and Gamma-type statistics, and suggest possible extensions to generalized Collatz-type problems.
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Optics · Cross-listed from cond-mat.mtrl-sci
Giant and Broadband Circular Dichroism from Particle-Hole Symmetry Breaking in Weyl Semimetals
Xiangyu Jiang, Zeping Shi, Yuhan Du et al. (+14 more)
Circular dichroism originates from
symmetry breaking of material structure, leading to differential absorption of left- and right-circularly polarized light. However, circular dichroism in most materials is inherently weak and spectrally narrow, especially in the mid-to-far infrared. Here, we uncover
giant infrared circular dichroism in the
magnetic-field-forced Weyl semimetal Mn(Bi,Sb)2Te4, driven by extreme particle-hole
symmetry breaking. Helicity-resolved magneto-infrared spectroscopy reveals circular dichroism exceeding 3000 mdeg (~130 mdeg/nm) with above-degree response extending over the 6-13 {\mu}m spectral range. The optical resonances are enhanced by a strong band nesting effect intrinsic to the Landau levels of type-II Weyl dispersion. A
symmetry-based kp model reproduces these magneto-infrared responses and demonstrates that magnetization-induced asymmetric
spin-orbit coupling generates particle-hole
symmetry breaking, suppressing
spin-up, parity-even wavefunction components in the valence Landau band and thereby producing pronounced optical helicity selectivity. Our findings establish particle-hole
symmetry breaking as an effective route toward helicity-resolved optical control in
quantum materials.
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All authors Xiangyu Jiang, Zeping Shi, Yuhan Du, Haonan Chen, Jiayu Wang, Wenbin Wu, Guangyi Wang, Congming Hao, Mingfan Yao, Mingsen Zhou, Xin Chen, Chenyao Xu, Zhongbo Yan, Cheng Zhang, Hai-Zhou Lu, Junhao Chu, Xiang Yuan
Atmospheric and Oceanic Physics
Spectral condensation in a finite nonequilibrium atmospheric transition
Dan Zhao, Yongwen Zhang, Teng Liu et al. (+3 more)
Order parameters are difficult to define in high-dimensional nonequilibrium systems that lack a
Hamiltonian, a thermodynamic limit or an observed control coordinate. Here we show that such transitions can be diagnosed from the spectrum of occupations over data-derived eigen-microstates. We combine Eigen Microstate Theory with a Marchenko–Pastur random-
matrix baseline to isolate an emergent sector, whose
entropy quantifies competition among statistically significant collective states. As a finite atmospheric realization, we analyse 51 sudden stratospheric warmings in ERA5. The event-aligned ensemble undergoes spectral condensation, decondensation and recondensation: a polar-
vortex state dominated by a few eigen-microstates gives way to a high-
entropy regime of competing emergent states before selecting a reorganized weak-
vortex state. A
stochastic wave–mean-flow model, in which upward wave-activity flux provides a reduced control coordinate, reproduces the same
entropy maximum, collapse and top-down timing. These results identify emergent-sector
entropy as an order-parameter-like, state-based spectral diagnostic for non-
Hamiltonian transitions and place polar-
vortex breakdown within a broader class of finite nonequilibrium phase reorganizations.
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All authors Dan Zhao, Yongwen Zhang, Teng Liu, Wenqi Liu, Jingfang Fan, Xiaosong Chen
Space Physics
Magnetic Cloud Boundary Identification Using a Local-Normalized Magnetic Field Parameter
Ziwei Huang, Zhenjun Zhou, Wei Su et al. (+2 more)
Due to the lack of quantitative and reproducible criteria for identifying
magnetic cloud (MC) boundaries, we propose a parameter that characterizes short-timescale variability in
magnetic field strength. The parameter, referred to as the Local-Normalized
Magnetic field parameter (LNM), is defined as $\mathrm{LNM}(t)=\log_{10}\left(B(t)/\langle B \rangle_{\mathrm{5m\text{-}med}}(t)\right)$, where $B(t)$ is the total
magnetic field strength and $\langle B \rangle_{\mathrm{5m\text{-}med}}(t)$ is its 5-minute running median ending at time $t$. This parameter measures the deviation of the
magnetic field magnitude from its local background and reveals a clear contrast between the coherent
magnetic structure inside MCs and the more variable ambient
solar wind. Based on this parameter, we develop a semi-automated method for MC boundary identification, supported by Time Series Scalogram visualization. We further analyze 76 MC events using power spectral density (PSD) and slab fraction diagnostics. The results show that the dissipation-range spectral index inside MCs ($\sim f^{-2.21}$) is systematically smaller than that outside ($\sim f^{-2.59}$ and $f^{-2.89}$), and the slab fraction is reduced, indicating suppressed small-scale variability and enhanced anisotropy. These results support the applicability of the proposed parameter for MC boundary identification.
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All authors Ziwei Huang, Zhenjun Zhou, Wei Su, Yudong Ye, Yuming Wang