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Physics Physics

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Friday 17 July

Atomic Physics

Three-dimensional three-photon Stark spectroscopy of a single Rb Rydberg atom in an ultrahigh-vacuum glass cell with eight electrodes

S. A. Spirin, E. A. Yakshina, A. K. Sologub et al. (+9 more)

Quantum computing and quantum simulation with ultracold neutral atoms require Rydberg excitation of individual atoms in atomic arrays. Rydberg states are extremely sensitive to external electric fields, therefore precise three-dimensional control of the electric field is essential. We performed a spectroscopic study of three-photon Rydberg excitation of a single Rb atom in an optical dipole trap in the presence of an external DC electric field. The field was generated by eight electrodes deposited on the inner surfaces of an ultrahigh-vacuum glass cell. The used three-photon scheme of laser excitation of Rydberg nP states allows the Stark shift and the splitting of the resonances to be observed simultaneously, which simplifies calibration of the electric field. In addition, in the commonly used two-photon Rydberg excitation schemes, the light shifts can complicate accurate determination of the DC Stark shift, particularly when the external electric field is scanned across different spatial directions, and different Stark components are excited. These shifts are absent in the three-photon excitation scheme used in our experiment. We demonstrated the ability to independently tune the electric field along all three spatial directions and to compensate for stray electric fields. The measured three-photon spectra exhibit Stark shifts and splittings of the three-photon resonance that are in good agreement with theoretical calculations. These results are also of interest for Rydberg electrometry.
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All authors S. A. Spirin, E. A. Yakshina, A. K. Sologub, G. Suliman, A. M. Minnigaliev, V. V. Gromyko, P.I. Betleni, D. B. Tretyakov, V. M. Entin, N. N. Bezuglov, I. I. Beterov, I. I. Ryabtsev

Applied Physics · Cross-listed from cond-mat.mtrl-sci

Two-step growth of (In,Ga)N pseudo-substrates on GaN templates by plasma-assisted molecular beam epitaxy

Huaide Zhang, Jingxuan Kang, Aidan F. Campbell et al. (+3 more)

(In,Ga)N layers are grown by plasma-assisted molecular beam epitaxy on GaN templates. We introduce a two-step protocol that involves switching the growth conditions from initially N-stable to metal-stable. Reflection high-energy electron diffraction as well as scanning electron and atomic force microscopy reveal that the first step results in a rough intermediate surface with open pits, whereas the final surface is smooth. The narrow linewidth of the photoluminescence band indicates an excellent compositional homogeneity of the upper layer. Its in-plane lattice constant is determined to be $\approx$3.26 Åfrom X-ray diffraction measurements. This combination of favorable properties makes these layers attractive as pseudo-substrates for the growth of red-emitting (In,Ga)N light-emitting diodes. In particular, the approach presented here does not require any complex external processing and is, thus, scalable and economical.
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All authors Huaide Zhang, Jingxuan Kang, Aidan F. Campbell, Jonas Lähnemann, Oliver Brandt, Lutz Geelhaar

Optics

Mid- and long-wavelength infrared computational ghost spectroscopy

Linzhen He, Han Wu, Wei Deng et al. (+7 more)

Spectral-domain ghost imaging enables high-resolution spectroscopy with a single-pixel detector. The technique does not rely on spectrally resolved detectors, which makes it inherently robust against turbulence and particularly adapted to weak-light conditions. These features are very attractive for spectral imaging in the mid-infrared region which hosts numerous molecular absorption features but lacks highly sensitive detectors. The implementation of spectral ghost imaging in the mid-infrared has however been limited by the absence of suitable light sources and detectors capable of generating and measuring spectral fluctuations in real time. Here, we demonstrate spectral-domain computational ghost imaging in the mid-infrared based on a nonlinear frequency downconversion scheme. Pre-programmed spectral patterns imposed on broadband light at 1.5 mm using a programmable spectral filter are transferred into the mid-infrared through difference-frequency generation in a nonlinear crystal. This enables computational ghost spectroscopy with a spectral resolution of 0.62 cm-1 using a single-pixel mid-infrared detector. The method is flexible, broadly applicable and, as proof of concept, we demonstrate ghost spectroscopy in mid-wavelength infrared and long-wavelength infrared bands using the nonlinear frequency conversion in chirped-poling lithium niobate and ZnGeP2 crystals, respectively. Our approach provides a new avenue for mid-infrared spectroscopy, remote sensing and spectral imaging.
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All authors Linzhen He, Han Wu, Wei Deng, Mingzhu She, Bo Hu, Zunwang Bo, Shensheng Han, Weili Zhang, Houkun Liang, Goëry Genty

Atomic Physics · Cross-listed from nucl-th

Growth of quartet correlations in neutron-rich tellurium isotopes within quartet Bardeen-Cooper-Schrieffer theory

Yixin Guo, Hiroyuki Sagawa and Masaaki Kimura

Quartet correlations in neutron-rich Te isotopes are investigated within the quartet Bardeen-Cooper-Schrieffer (BCS) framework. Taking $^{100}$Sn as an inert core, we consider two valence protons and valence neutrons occupying the $2d_{5/2} \oplus 1g_{7/2}$ model space, and solve the quartet BCS variational equations with a charge-independent isovector pairing interaction. The effective pairing strength is constrained from empirical neutron pairing gaps in the Te isotopic chain. We find that the valence quartet number increases as the valence neutron number is enlarged from $N_{\rm val}=2$ to $14$. The same increasing behavior is also found for the condensed quartet component. The proton occupation of the $1g_{7/2}$ orbit is strongly enhanced relative to the conventional like-particle BCS reference and is driven close to the degeneracy-weighted limit. These results suggest that additional valence neutrons enhance the quartet admixture in the correlated quartet BCS state, while redistributing the fixed proton weight from pair-like configurations to quartet configurations.
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Chemical Physics

$GW$ reduced density matrix from iterated linearized Dyson equation

Fabien Bruneval, Erik Verzijl, Arno Förster et al. (+1 more)

Iterating the Dyson equation with the static part of the self-energy leads to a concise and possibly improved expression of the one-body reduced density matrix from any self-energy approximation. Here we apply the procedure to Hedin's $GW$ approximation. The non-iterated $GW$ based density matrix was already known to yield accurate density matrices for molecular systems. We show that the Dyson-equation-based procedure is equivalent to the so-called variational Z-vector approach applied to the Random-Phase approximation energy functional, but only in the case of a Hartree-Fock mean-field starting point. When a generalized Kohn-Sham scheme is employed instead, the two approaches differ. By comparing the density matrix for a benchmark set of 34 small molecules to coupled-cluster reference values, we conclude that the iterated Dyson equation indeed produces improved density matrices for molecular systems. Interestingly, we observe that the excitation rank of the reference coupled-cluster matters much and that the inclusion of triple excitations (CCSDT) quantitatively changes the conclusions of the benchmark as compared to single and double excitations coupled-cluster (CCSD).
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All authors Fabien Bruneval, Erik Verzijl, Arno Förster, Mauricio Rodriguez-Mayorga

Plasma Physics

Linear Gyrokinetic Simulations of Micro-tearing Mode: Local versus Global

Yifei Liu, Haotian Chen, Yao Yao et al. (+3 more)

A systematic comparison of local and global linear gyrokinetic simulations of micro-tearing modes (MTMs) is performed using the GENE code. The analysis spans diverse plasma parameters, including the core regions with normal and weak magnetic shear, as well as the pedestal region with the strong plasma non-uniformity. The global simulations reveal a distinct MTM type characterized by a `parity mixing' mode structure, which can be significantly destabilized by trapped electrons. Moreover, in contrast to electrostatic drift wave instabilities, the current layer width ($ \Delta _c $) is identified as the crucial factor determining the importance of global effects. The MTM in the core region exhibits the slab-like feature with narrow $ \Delta _c $, leading to high consistency between local and global results. However, in the pedestal region, the steep pressure gradient broadens $\Delta_c$, driving quantitative deviations when $\Delta_c$ becomes comparable to the plasma pressure gradient scale length. For high-$n$ MTMs, $ \Delta _c $ can exceed the distance between adjacent mode rational surfaces. The resulted overlapping of current layers enhances the toroidal mode coupling effect, accounting for the substantial discrepancies observed between local and global simulations.
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All authors Yifei Liu, Haotian Chen, Yao Yao, Zhengji Li, Jiquan Li, Wei Chen

Atmospheric and Oceanic Physics

Green-Roof Energy Performance in New Zealand's Present and Future Climate Condition (2050)

Abdollah Baghaei Daemei

Green roofs are increasingly promoted as nature-based measures for reducing building energy demand, yet their performance in New Zealand's oceanic climates and under future weather remains insufficiently quantified. This condensed study compares an extensive green roof with a conventional bare roof on a standardized single-storey dwelling in Auckland, Christchurch, and Wellington. Dynamic annual simulations were conducted in DesignBuilder/EnergyPlus using present-day EnergyPlus Weather files and 2050 weather files generated with CCWorldWeatherGen. All non-roof building parameters were held constant so that differences in total fuel consumption (TFC) for heating and cooling could be attributed to the roof system. Under present weather, annual TFC decreased by approximately 3.1% in Auckland, 2.3% in Christchurch, and 1.5% in Wellington. Under 2050 weather, the corresponding reductions were 3.3%, 2.6%, and 1.1%. Summer benefits were larger in Auckland and Christchurch, reaching about 9.0% and 5.6%, respectively, in 2050, but remained marginal in Wellington. The findings show that green roofs can provide modest annual energy savings in oceanic climates, with stronger value as a summer heat-mitigation measure in warmer locations. Performance is strongly climate-dependent and should not be generalized without local simulation or field validation.
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Optics

Radially correlated partially coherent beams with a deterministic vortex structure

Xinru Lian, Yaning Zhou, Xin Liu et al. (+7 more)

Partially coherent beams have attracted considerable attention due to their intrinsic resilience against complex environmental perturbations. However, the intrinsic wavefront fluctuations make it fundamentally challenging to preserve well-defined orbital angular momentum during propagation. In this work, we propose and experimentally demonstrate a class of radially correlated, partially coherent beams that carry deterministic vortex structures, generated via optical conformal mapping from Cartesian to log-polar coordinates. The resulting beams exhibit a ring-shaped coherence distribution, characterized by low coherence in the radial direction and high coherence in the azimuthal direction. This unique feature of such a beam supports a well-defined deterministic vortex phase, thereby enabling the beam to preserve its ring-shaped coherence distribution during propagation through a focusing system. Our results provide new insights into the design of new partially coherent beams and may facilitate the development of applications in optical encoding, free-space information transmission, and ultrafast light-matter interactions.
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All authors Xinru Lian, Yaning Zhou, Xin Liu, Zhao Zhang, Qian Chen, Keyu Zhou, Weining Wang, Chunhao Liang, Yangjian Cai, Jingsong Liu

Optics

Near-field Dressing of Thermal Emission

Victor Guillemot, Raphael Mol, Riccardo Messina et al. (+4 more)

Radiative heat transfer at subwavelength distances is generally understood as enhanced energy exchange mediated by photon tunnelling between neighboring bodies. While near-field interactions can dramatically increase mutual heat transfer, whether they also modify the thermal radiation emitted by the bodies themselves remains an open question. Here we experimentally show that near-field electromagnetic coupling reshapes far-field thermal emission through a distance-dependent dressed emissivity. Using a dual-probe calorimetric platform, we independently monitor the radiative balance of two borosilicate microspheres over separations ranging from 120 micrometers to a few hundred nanometers, spanning the transition from the far field to the near field. Nanowatt-resolved differential radiometry reveals asymmetric heat fluxes and a non-monotonic response of the hotter sphere, demonstrating that thermal radiation is governed not only by emitter-bath interactions but also by coupling to the surrounding photonic environment. By analyzing the total power exchanged between the coupled system and the external thermal bath, we directly extract a dressed emissivity and show that near-field interactions renormalize the far-field thermal emission of the pair through a redistribution of the electromagnetic modes available to thermal fluctuations. These observations provide direct experimental evidence that thermal emitters are dressed by their electromagnetic environment, establishing a thermal analogue of the Purcell effect.
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All authors Victor Guillemot, Raphael Mol, Riccardo Messina, Valentina Krachmalnicoff, Philippe Ben-Abdallah, Wilfrid Poirier, Yannick De Wilde

Optics

Basis-Independent Geometric Phase Modulation in Circularly Birefringent Plasmonic Structures

Pasha Goz, Akash Das, Andre Yaroshevsky et al. (+1 more)

Geometric phase in metasurfaces is conventionally realized using spatially rotated linearly birefringent meta-atoms under circularly polarized illumination. Here we demonstrate that full $\sim2\pi$ geometric phase modulation can be achieved through circular birefringence and observed under linear polarization excitation. We introduce a plasmonic metasurface composed of spatially rotated chiral spiral unit cells designed to produce space-variant circular retardance. This generates a geometric phase ramp equivalent to a blazed grating, leading to $\pm1$ diffraction orders in momentum space. Using leakage radiation microscopy, we directly resolve these orders and show how their intensities depend upon the input linear polarization confirming the geometric origin of the phase. We theoretically analyze the phenomenon using a rotated Poincaré space and confirm our results by direct Stokes parameters measurement. These results establish basis-independent approach to geometric phase accumulation in circularly birefringent plasmonic metasurfaces.
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All authors Pasha Goz, Akash Das, Andre Yaroshevsky, Yuri Gorodetski

Atomic Physics · Cross-listed from quant-ph

Deterministic atom-shuttle interconnects via ultrafast atom-ion entangling gate

Mu Qiao

Neutral-atom arrays and trapped-ion crystals offer complementary strengths for fault-tolerant quantum computing but lack a fast way to deterministically interact. Here we propose a controlled-$Z$ gate generated by the charge-induced-dipole ($C_4$) force between a Rydberg-excited atom and a trapped ion, balanced by a spin-dependent optical Magnus force on the ion that closes phase-space trajectories within a few microseconds. Toggling the Rydberg state extends the scheme to multi-ion crystals at negligible overhead. The resulting ${\sim}5\,$kHz atom shuttle accelerates short-distance QCCD links and enables hybrid qLDPC memories in which atom logical qubits are written onto an ion block treated as a passive storage zone. We perform circuit-level Monte Carlo simulations and find that the hybrid architecture supports orders of magnitude more operations than atom-only or ion-only architectures at fixed code distance and logical error rate.
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Instrumentation and Detectors · Cross-listed from eess.SP

An Open-Source, Autonomous Platform for High-Resolution Energy Monitoring in Manufacturing

Vignesh Selvaraj, Aditya Nagaraj, Shengyuan Zhang et al. (+2 more)

High-resolution energy data is increasingly central to Industry 4.0, where electrical signals such as three-phase voltage and current carry rich information about machine condition, tool wear, and process dynamics. Capturing this information in practice remains difficult: commercial power analysis are largely proprietary, offer limited or no access to high-sampling rate data for transient analysis, restrict access to raw waveform data, and offer no customization, while general-purpose open hardware lacks the front-end accuracy, isolation, and robustness required for industrial measurement. This paper presents Autonomous Energy Monitoring System (AEMS), an open-source, low-cost, and modular platform supported by a host, edge-gateway, and optional cloud software stack that enables autonomous, long-duration acquisition independent of a continuously connected host and thereby closes this gap by combining research-grade fidelity with industrial deployability. The system acquires three-phase voltage and current through an isolated front-end and a 24-bit, simultaneously sampling analog-to-digital converter, managed by a dual-core architecture that separates deterministic acquisition and on-board logging from host communication and control. Industrial interfaces (Ethernet, RS-485/Modbus, and BLE) together with hardware-level synchronization enable scalable, time-aligned acquisition across multiple machines, supported by a complete host, edge-gateway, and optional cloud software stack. We validate the platform on a three-axis CNC machining center, where it resolves spindle, feed-drive, rapid-traverse, and material-removal energy states and detects feed-rate changes as small as 50 mm/min. By releasing the full hardware and firmware openly, this work aims to democratize access to high-fidelity energy monitoring for both researchers and small and medium-sized manufacturers.
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All authors Vignesh Selvaraj, Aditya Nagaraj, Shengyuan Zhang, Sina Sadeghian, Sangkee Min

Fluid Dynamics

Unified Deflection Estimation and Error Analysis for Background-Oriented Schlieren

Jiawei Li, Xiang Li, Chong Pan et al. (+1 more)

Background-Oriented Schlieren (BOS) has become a versatile quantitative diagnostic for density-varying flows, in which estimating the light-ray deflection from the measured displacement is the essential step linking the recorded images to the underlying refractive-index field. Two-dimensional BOS traditionally treats this through the intuitive deflection angle, whereas three-dimensional tomographic BOS relies on the rigorous deflection vector derived from the ray equation. These descriptions have evolved largely independently, and the assumptions bridging them, together with the systematic errors they introduce, have not been examined in a unified manner. Based on geometric optics, this study establishes a unified deflection estimation framework that reconciles the mainstream two- and three-dimensional methods into a single mathematical structure and exposes the hierarchy of approximations underlying each. By deconstructing four key assumptions, namely the thin phase object, the uniform boundary refractive index, the paraxial approximation, and the perpendicularity between the deflection vector and the optical axis, we derive rigorous unified deflection expressions in both two- and three-dimensional space and categorize the mainstream methods accordingly. Using phase objects constructed from one-dimensional chirp signals and two-dimensional turbulent fields from Direct Numerical Simulation, combined with high-fidelity nonlinear ray tracing as the ground truth, we quantitatively characterize and analytically interpret the deflection estimation error of each method under both uniform and non-uniform refractive-index boundary conditions. This work provides a theoretical toolkit for assessing and enhancing the accuracy of quantitative BOS diagnostics.
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All authors Jiawei Li, Xiang Li, Chong Pan, Yuan Xiong

Optics

Machine Learning-Driven Design of Mixed-Pitch Grating Couplers for Co-Packaged Optics Applications

Yu Dian Lim, Yun Da Chua, Wai Cheung Ma et al. (+2 more)

A mixed-pitch grating coupler which can couple a wide range of wavelengths is preferred in its application in co-packaged optics (CPO). However, the design and optimization of such grating coupler is complex. In this work, we developed software with integrated deep neural network (DNN) model to automatically design the mixed-pitch grating coupler from user-specified peak wavelengths and full-width half-maximum (FWHM) values. We first trained the DNN model with 10,000 rows of grating parameters-power spectrum datasets, where the power spectrum was simulated using finite-difference time domain (FDTD) technique. Upon training, we tested the model using ~1,000 different combinations of peak wavelengths and FWHM values. Among the combinations, 822 attempts have <15% error, while 351 attempts have <5% error when comparing the user-specified and FDTD-verified spectrum. Meanwhile, comparing the user-specified and FDTD-verified peak wavelengths, 844 attempts have peak wavelengths with absolute error (AE) < 2 nm. For FWHMs, 738 attempts have FWHM values with AE < 10 nm. We have also developed a graphical-user interface (GUI) to ease the usage of this software.
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All authors Yu Dian Lim, Yun Da Chua, Wai Cheung Ma, Yeow Kheng Lim, Chuan Seng Tan

Optics

Enhanced Third-Harmonic Generation in Diamond Photonic Crystal Slabs via Doubly Resonant Quasi-Bound States in the Continuum

Sangmin Ji, Satoshi Iwamoto and Hideki Gotoh

We propose and numerically demonstrate doubly resonant third-harmonic generation (THG) in a diamond photonic crystal (PhC) slab, in which the fundamental harmonic (FH) and the third harmonic (TH) modes are simultaneously resonant within the same membrane. A hexagonal-lattice slab with triangular air holes is designed so that a K-point band-edge FH mode and a $\Gamma$-point quasi-bound-state-in-the-continuum (quasi-BIC) TH mode satisfy the frequency-tripling condition $3\omega_1\approx\omega_3$. Modifying the hole shape from circular to equilateral triangular breaks the in-plane symmetry that otherwise forces the nonlinear coupling to vanish, thereby converting a TH mode with negligible overlap into one with finite while simultaneously reducing the required slab thickness. Guided by a closed-form expression for THG efficiency derived from coupled-mode theory, we design the unit cell and a PhC heterostructure cavity. Three-dimensional simulations of the designed cavity yield a normalized THG efficiency $\eta=2.7\times10^{-7}~\mathrm{W}^{-2}$ under moderate quality factors, which is projected to reach ~$0.034~\mathrm{W}^{-2}$ at the fabrication-limited quality factor (Q = 200,000). Because the operating wavelength is set by the lattice constant, this design, combined with the ultra-wide transparency window of diamond, can map a single geometry across various fabricable wavelengths, spanning from telecommunication bands to color-center-resonant visible and deep-UV outputs. These results establish a robust route toward efficient, monolithic on-chip frequency conversion in an all-diamond platform for quantum and nonlinear photonics.
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Physics and Society

Degree correlations in graphs with clique clustering

Peter Mann, V. Anne Smith, John B. O. Mitchell et al. (+1 more)

Correlations among the degrees of vertices in random graphs often occur when clustering is present. In this paper we define a joint-degree correlation function for vertices in the giant component of clustered configuration model networks which are composed of clique subgraphs. We use this model to investigate, in detail, the organization among nearest-neighbor subgraphs for random graphs as a function of subgraph topology as well as clustering. We find an expression for the average joint degree of a neighbor in the giant component at the critical point for these networks. Finally, we introduce a novel edge-disjoint clique decomposition algorithm and investigate the correlations between the subgraphs of empirical networks.
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All authors Peter Mann, V. Anne Smith, John B. O. Mitchell, Simon Dobson

Physics Education

A Tool-Invariant Framework for Teaching and Assessing Computational Methods in the Age of Agentic AI

Larry Engelhardt

Learning a computational method has always meant learning to operate a tool – pencil, slide rule, calculator, or programming language. Agentic artificial intelligence, which writes, executes, and revises simulation code from natural-language specifications, is the latest and largest step in a centuries-long migration of mechanical work from human to tool. I argue that what a learner must know has remained remarkably stable: the inputs and outputs of a method, the concept of what it does, the terminology to communicate about it, the judgment to evaluate its results, and the skill of operating the current tool. This paper organizes these requirements into a tool-invariant framework spanning single-digit addition to agent-orchestrated molecular dynamics, argues that verification – not code authorship – is now the load-bearing skill, and draws the consequence for assessment: when artifacts can be generated on demand, the artifact no longer certifies the student. I describe a practical response, designed for the small classes where the subject lives – AI-free in-class coding quizzes paired with oral defenses of comment-stripped, AI-assisted work – and argue that the real product of a computational physics course is the student's ability to explain and defend computational artifacts in the language of the discipline.
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Thursday 16 July

Optics

Per-Channel Launch-Power Optimization in Hollow-Core Fiber Systems

Md Ghulam Saber, Qingyi Guo and Zhiping Jiang

In single-mode fiber (SMF) the Kerr effect ties every channel's quality of transmission to its neighbors' launch powers through cross-phase modulation (XPM), four-wave mixing (FWM) and inter-channel stimulated Raman scattering (ISRS), forcing a jointly planned launch profile. Hollow-core fiber (HCF), with a Kerr coefficient three to four orders of magnitude below silica, turns the per-channel powers into nearly independent knobs limited only by the shared amplifier budget. We build a per-channel generalized signal-to-noise ratio (GSNR) budget for amplified HCF links, including amplified spontaneous emission (ASE) with a wavelength- and output-power-dependent erbium-doped fiber amplifier (EDFA) noise figure (NF), inter-modal interference (IMI), nonlinearity in amplifier pigtails, CO2 gas-line loss and a flat transceiver (TRx) noise ceiling, and derive a sensitivity law that predicts when power shaping pays: its gain is bounded by the ASE noise share, canceled by self-phase modulation (SPM) at the SMF single-channel optimum, and positive in HCF. Across 80x64-GBaud C-band links over 400-3200 km, per-channel optimization buys up to 1.0 dB of worst-channel GSNR over a flat launch as the EDFA NF spread grows to 4 dB, cuts cross-channel power sensitivity by more than two orders of magnitude relative to SMF, and reaches a given GSNR at about 3 dB lower aggregate amplifier output. At a fixed amplifier budget this becomes a 1.26 to 1.41 times worst-channel reach extension, against at most 15% on the nonlinearity-capped SMF link.
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Fluid Dynamics

Urban Wind Effects on UAV Operations in Building-Dense Low-Altitude Airspace

Yue Cao, Huanxia Wei, Chao Xia et al. (+3 more)

Urban low-altitude uncrewed aerial vehicle (UAV) operations are shaped by building-modified wind and constrained terrain-building clearance. Spatially heterogeneous wind can perturb short-horizon motion, but its clearance consequence depends on local airspace: similar perturbations may remain benign in open areas yet become clearance-sensitive near building walls, roof edges, or elevated terrain. This study develops a common-basis method for early clearance assessment before route buffers or corridor alignments are fixed. For each position-height state, nominal and wind-affected vehicle-sized trajectory envelopes are generated with a shared heading and sampling design, separating fixed-support wind loading, initial clearance exposure, and wind-induced clearance change. Applied to Shanghai and Beijing, the method uses lattice-Boltzmann method (LBM) wind fields co-registered with 20 m terrain-building scene grids, height layers of 60-340 m, and a representative light UAV. Results show distinct spatial and vertical patterns in baseline wind loading and clearance exposure. Wind-affected envelopes produce little domain-wide median shift in clearance exposure but generate spatially concentrated upper-tail responses in lower-altitude layers on the normalized clearance-exposure scale. Kilometer-Tile-level analysis links these responses mainly to baseline clearance sensitivity and horizontal wind-gradient magnitude, with fixed-support wind loading and mean wind speed playing secondary roles. Low-altitude planning should distinguish wind-loaded locations from clearance-sensitive locations. As an upstream diagnostic, the method identifies units where nominal trajectory envelopes approach terrain-building margins and local wind variation may further alter clearance exposure, with increases concentrated in the upper tail.
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All authors Yue Cao, Huanxia Wei, Chao Xia, Qing Jia, Yingying Xing, Zhigang Yang

Applied Physics · Cross-listed from quant-ph

Ancilla-assisted dark-state quantum gates in ultracold polar molecules

Yan Lu and Xiao-Feng Shi

High-fidelity entangling gates are useful for circuit-based quantum computing, yet their realization in a scalable platform is challenging. Optically trapped ultracold polar molecules offer a potentially scalable platform. Here, we introduce a two-qubit molecular entangling gate via a novel ancilla-assisted dark-state mechanism, where high fidelity is achievable. In particular, we find that by using appropriate qubit states for the ancilla and the data qubits, dark states can appear, and entanglement can emerge by driving the ancilla only. It is also feasible to extend the two-qubit gate to a multi-qubit gate via the same dark-state mechanism.
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General Physics

Probing dark energy dynamics through a new CPL-type $Om(z)$ parametrization in FLRW Universe

D. Revanth Kumar, Santosh Kumar Yadav and S. A. Kadam

In this work, we investigate a CPL-type $Om(z)$ parametrization given by $Om(z)=l+m\left(\frac{z}{1+z}\right)$ to study the evolution of dark energy and possible deviations from the standard $\Lambda$CDM cosmology. The model reduces to the flat $\Lambda$CDM scenario for $m=0$, while $m\neq0$ indicates dynamical evolution. The free parameters are constrained using Pantheon+SH0ES (PPS), Cosmic Chronometer (CC), and DESI BAO DR2 observations through Markov Chain Monte Carlo analysis. The obtained constraints yield $72.48\lesssim H_0\lesssim72.97~\mathrm{km\,s^{-1}\,Mpc^{-1}}$, while the evolution parameter remains negative for all dataset combinations, leading to decreasing $Om(z)$ evolution and favoring quintessence-like behaviour. The combined PPS+CC+DR2 analysis shifts the evolution closer to the $\Lambda$CDM limit. The statistical analysis based on $\chi^2$, AIC, and BIC indicates that the proposed model remains statistically competitive with $\Lambda$CDM. The deceleration parameter and total equation of state are further analyzed to examine the cosmic evolution. The transition from deceleration to acceleration occurs within $z_{tr}\approx0.66-1.01$, while the present values vary within $-0.459\lesssim q_0\lesssim-0.325$ and $-0.639\lesssim\omega_0\lesssim-0.550$ depending on the datasets. Overall, the proposed parametrization provides a flexible framework for studying late-time cosmic evolution.
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General Physics

A-Relativity: A General Theory of Gravity from Structure Sheaf

Ioannis Raptis

The aim of this paper is to introduce and disseminate to a wider readership of mathematicians, mathematical physicists and philosophers of mathematics and physics alike the basic theoretical, both conceptual and technical, tenets of Mallios's Abstract Differential Geometry, as well as to present and to summarise the main results from its applications in the last quarter of a century towards formulating an entirely homological algebraic, purely gauge-theoretic, finitistic, quantal and manifestly background geometrical smooth spacetime manifold independent vacuum Einstein gravity. New, previously unpublished, constructions and results are included in the paper.
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Physics and Society

Long-term Coexistence of Epidemics and Risk Awareness: Impacts of Adaptive Human Response and Fatigue

Mozzamil Mohammed and Abdallah Alsammani

Human behavior shapes epidemic dynamics, yet most models represent it by rescaling transmission, conflating behavior with biology and removing the memory carried by sustained protective behavior. We develop and analyze a susceptible-infected-recovered-aware model in which prevalence-driven awareness, eroded by fatigue, moves susceptible and infectious individuals between accessible and inaccessible states rather than modifying transmission probabilities. The basic reproduction number is $\mathcal{R}_0=\beta/(\gamma+\mu)$, independent of behavioral parameters, and a unique endemic equilibrium exists exactly when $\mathcal{R}_0>1$, excluding backward bifurcation. Infection and awareness are uniformly persistent whenever $\mathcal{R}_0>1$. We derive an exact decomposition of the reduction in endemic burden into susceptible withdrawal and infectious sequestration, establish the effect of each behavioral parameter, and show that the endemic state depends on awareness response and fatigue only through their ratio, with prevalence vanishing linearly as fatigue vanishes. In the instantaneous-relaxation limit, the model reduces to a transmission-modulating formulation whose endemic equilibrium is locally asymptotically stable. At finite relaxation rates, however, numerical stability and bifurcation analyses reveal a Hopf transition and self-sustained epidemic cycles without an imposed delay. Relative to the SIR benchmark, awareness lengthens transient inter-epidemic periods and slows damping rather than creating the underlying transient oscillations.
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Physics and Society

An exact N-strain epidemic model using bond percolation

Peter Mann, V. Anne Smith, John B.O. Mitchell et al. (+1 more)

In this paper we examine the emergent structures of random networks that have undergone bond percolation an arbitrary, but finite, number of times. We define two types of sequential branching processes: a competitive branching process - in which each iteration performs bond percolation on the residual graph (RG) resulting from previous generations; and, a collaborative branching process - where percolation is performed on the giant connected component (GCC) instead. We investigate the behaviour of these models, including the expected size of the GCC for a given generation, the critical percolation probability and other topological properties of the resulting graph structures using the analytically exact method of generating functions. We explore this model for Erdos-Renyi and scale free random graphs. This model can be interpreted as a seasonal N-strain model of disease spreading.
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All authors Peter Mann, V. Anne Smith, John B.O. Mitchell, Simon Dobson

Chemical Physics

A Mesoscopic Ginzburg–Landau Model for Vibrational Strong Coupling Enhanced Rayleigh Scattering in Molecular Liquids

Wenxiang Ying and Abraham Nitzan

Recent experiments by Sandeep et al. [Angew. Chem. Int. Ed. 65, e16917 (2026)] suggest that vibrational strong coupling (VSC) in molecular liquids can generate mesoscopic phenomena beyond single-molecule observables, including resonantly enhanced Rayleigh scattering, abrupt concentration thresholds, and thermal collapse. Motivated by these observations, we construct a mesoscopic Ginzburg–Landau model with two coupled fields: a cavity-controlled collective vibrational polarization $P$ and a secondary structural field $m$ whose long-wavelength susceptibility is renormalized by the collective vibrational polarization intensity $P^2$, assumed to govern long-wavelength density/dielectric fluctuations. With calibrated parameters, the model captures the observed Rayleigh enhancement, collective scaling relations, and threshold-like behavior, while explaining why polaritonic/IR signatures may persist when Rayleigh scattering disappears. The model further predicts enhanced long-wavelength density/dielectric correlations, enlarged mesoscopic correlation lengths, and slowed structural dynamics in the regime with strong Rayleigh enhancement, providing direct experimental tests through small-angle X-ray/neutron scattering and dynamic light-scattering probes.
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Medical Physics

Differentiable Cardiac Electrophysiology Simulations for Dynamical State and Parameter Estimation

Adarsh Pashikanti, Shrey Chowdhary, Alex Ho et al. (+3 more)

The heart's contractions are triggered by action potential waves, which propagate through the cardiac muscle and exhibit diverse spatio-temporal dynamics during different heart rhythms. The dynamics are modeled with partial differential equations (PDEs) in cardiac electrophysiology simulations. However, fitting such models to measurement data to develop digital twins or patient-specific computer models is challenging. Here, we introduce differentiable cardiac electrophysiology simulations that can be fitted automatically to spatio-temporal measurement data of action potential waves in cardiac tissue. By comparing the simulated dynamics with the observation data, we define a loss function that is minimized via gradient-based optimization. Backpropagating the loss gradient through the differentiable PDE solver enables us to learn the parameters and recover the full dynamics, even with sparse, noisy, or partial observations. Implemented using both the finite-difference and smoothed particle hydrodynamics methods, our simulation framework can be applied to pixel-, voxel-, or point-based data, such as 2D or 3D slabs, or arbitrary shapes, such as the heart's ventricles. Using this methodology, we locate early activation sites inside a 3D bi-ventricular simulation geometry and fit a phenomenological model to imaging data of a voltage spiral wave in a cardiac monolayer cell culture. With experimental data, we employed a perceptual loss based on the Video Joint-Embedding Predictive Architecture, which enables fitting to noisy imaging data, and a generative diffusion model to estimate initial conditions and constrain solutions. Differentiable cardiac electrophysiology simulations could improve the diagnosis of rhythm abnormalities in patients and facilitate the development of personalized models or digital twins of the heart.
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All authors Adarsh Pashikanti, Shrey Chowdhary, Alex Ho, Weizhen Li, Emilia Entcheva, Jan Christoph

Fluid Dynamics

Circulation Statistics in Rayleigh-Bénard Convection

Giovanni Saisse, Roshan J. Samuel, Luca Moriconi et al. (+2 more)

Important statistical properties of velocity circulation in homogeneous isotropic turbulence (HIT) have been unveiled in recent years, raising the question of whether they persist, or are modified, in other classes of turbulent flows. Motivated by the dominant role of small-scale structures in the circulation fluctuations of HIT, we investigate their relevance in direct numerical simulations of Rayleigh-Bénard convection at a Rayleigh number of $10^9$ and Prandtl number of $O(1)$. Within the thermal boundary layer (TBL), the distribution of elementary vortices is found to be strongly correlated with the temperature field, while the statistics of their core aspect ratios is significantly altered. Additionally, the probability distribution functions of circulation, computed for planar contours which are parallel to the walls, display salient features closely akin to those observed in HIT, with the Area Rule (a connection between circulation statistics and minimal surfaces) remaining particularly well satisfied – except for a possible transitional region at a distance of a few TBL thicknesses. Away from the TBL, as expected, the overall statistical behavior of these structures likewise resembles that of HIT, where the intermittent spatial distribution of small vortex tubes is instead determined by the energy dissipation field.
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All authors Giovanni Saisse, Roshan J. Samuel, Luca Moriconi, Jörg Schumacher, Katepalli R. Sreenivasan

Plasma Physics

Dependence of Momentum Transport on the Dominant Turbulence Regime in the DIII-D Tokamak

C. F. B. Zimmermann, C. Chrystal, E. Perez et al. (+8 more)

Accurate prediction of toroidal plasma rotation is essential for optimizing confinement and stability in future fusion devices. This work investigates turbulent core momentum transport in the DIII-D tokamak across a transition from ion-temperature-gradient (ITG)- to trapped-electron-mode (TEM)-dominated turbulence. A momentum transport framework previously developed for ASDEX Upgrade is applied to modulated neutral beam injection experiments, separating diffusive, convective, and residual-stress contributions via Fourier analysis of the rotation response. The dataset spans low-rotation conditions, dominant electron heating, and background ExB shearing rates below turbulence growth rates, accessing more reactor-relevant conditions. Gyrokinetic CGYRO and gyrofluid TGLF calculations confirm the scan covers an ITG-to-TEM transition. The analysis yields Prandtl numbers near unity. The pinch number shows no explicit dependence on the transition, instead ordering roughly with the logarithmic density gradient. The normalized residual stress, in contrast, exhibits a non-monotonic, V-shaped dependence across the transition: co-current in deep ITG and deep TEM regimes, near-zero or counter-current in the intermediate mixed-mode regime. This trend collapses onto an approximately linear dependence against electron kinetic profile gradients, suggesting residual stress generation by profile-shearing effects. Weaker background ExB shearing further shifts residual stress toward counter-current values. Linear CGYRO simulations for representative ITG and TEM discharges yield Prandtl and pinch numbers in good agreement with experiment, supporting gyrokinetic momentum-transport predictions in TEM-dominated regimes. These results indicate residual stress plays an important role in core rotation prediction for low-torque plasmas and should be included in predictive models of future reactor scenarios.
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All authors C. F. B. Zimmermann, C. Chrystal, E. Perez, T. Tala, C. Angioni, S. Haskey, F. Khabanov, R. M. McDermott, G. McKee, A. Salmi, L. Schmitz

Computational Physics · Cross-listed from cond-mat.mtrl-sci

exa-PD: A scalable high-performance workflow for multi-element phase diagram construction

Zhuo Ye, Feng Zhang, Maxim Moraru et al. (+4 more)

Exa-PD is a highly parallelizable workflow designed for the construction of multi-element phase diagrams (PDs). It uses standard sampling techniques, molecular dynamics (MD) and Monte Carlo (MC) as implemented in the LAMMPS package, to simultaneously sample multiple phases over a fine temperature-composition mesh for free-energy calculations. Parsl serves as the global workflow engine, coordinating large ensembles of MD and MC tasks to achieve massive parallelization with strong scalability. The resulting free energies of liquid and solid phases are then fed to CALPHAD modeling via the PyCalphad package to construct multi-element PDs.
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All authors Zhuo Ye, Feng Zhang, Maxim Moraru, Weiyi Xia, Ying Wai Li, Yongxin Yao, Cai-Zhuang Wang

Biological Physics · Cross-listed from math.DS

Ptolemy's Equant Equates to a Universal Dynamical Clock via Machine Learning

Jingdong Zhang, Luan Yang, Murilo S. Baptista et al. (+4 more)

Oscillatory dynamics arise ubiquitously in nonlinear systems, yet identifying a physically interpretable phase and phase dynamics in nonlinear, high-dimensional oscillations remains a central unresolved problem. Here we establish the principle of a universal dynamical clock, a physical perspective in which oscillations of arbitrary dimensionality and geometry are equivalently represented as uniform rotation through an equant-induced nonlinear viewing coordinate, inspired by Ptolemy's equant and formalised through an areal-uniformity principle reminiscent of Kepler's second law. Using a machine-learning framework, we demonstrate the existence of such an equant for a broad class of oscillatory dynamics and construct the associated dynamical clock and phase dynamics under additive forces, including noise, periodic perturbations, and coupling. Its value in uncovering new physical rules and phenomena is demonstrated by four findings: (i) collective oscillations in Escherichia coli populations obey a previously unexplained superlinear scaling law, resolving a long-standing open problem posed in 2004; (ii) the response mechanisms of engineered genetic circuits to changes in gene expression and environmental conditions; (iii) a classical-mechanics counterpart of the Berry geometric phase emerges naturally from the phase of the dynamical clock; and (iv) optimal equant non-uniformity provides a geometric early-warning signal for critical transitions and enables prediction of critical parameters. By providing operational and system-agnostic phase dynamics that can be constructed directly from data, the dynamical clock enables principled classification, comparison, and control of oscillatory systems, and offers a new route to understanding how specific dynamical regimes support distinct functional behaviours in networked systems.
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All authors Jingdong Zhang, Luan Yang, Murilo S. Baptista, Zefeng Zhang, Qunxi Zhu, Wei Lin, Celso Grebogi