Biological Physics · Cross-listed from cond-mat.soft
Multiscale order, flocking and phenotypic hysteresis in the cellular Potts model of epithelia
Calvin C. Bakker, Marc Durand, François Graner et al. (+1 more)
In epithelia, how do collective
cell migration and tissue spatial organization feedback on each other? We address this question through large-scale numerical simulations of the cellular Potts model. By accounting for both
cell morphology and cytoskeletal activity, we uncover a remarkably rich phase diagram featuring multiple types of orientational order, either as distinct phases or coexisting across length scales. We identify a specific pathway in parameter space along which a gradual increase in the actin polymerization rate drives a phase transition into a long-range flocking state. Simultaneously, quasi-long-range nematic order emerges at length scales much larger than the
cell size due to the combined effects of directed motion and lateral
cell-
cell interactions. At length scales comparible to
cell size, however,
cells adopt an approximatively hexagonal morphology, resulting in hexanematic order, similar to that observed in reconstituted Madin-Darby Canine Kidney (MDCK)
cell monolayers. With further increases in actin polymerization, nematic order becomes fully long-range, while hexatic order remains quasi-long-range and confined to short length scales, but independent of cytoskeletal activity. When noise is sufficiently low to allow crystallization at finite actin polymerization rate, cycling the
cell-monolayer across the melting transition yields an example of phenotypical hysteresis, reminiscent of that observed across the epithelial-mesenchymal transition.
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All authors Calvin C. Bakker, Marc Durand, François Graner, Luca Giomi
Optics
Single-Device VOC Fingerprinting via Polarization-Selective Anisotropic BeS-Clad Silicon Microring Resonator
Sudipta Saha, Shoumik Debnath and Md Kawsar Alam
A silicon microring resonator with an anisotropic beryllium sulfide (BeS) cladding is proposed for polarization-selective detection of exhaled-breath volatile organic compound biomarkers. The anisotropic dielectric response of BeS enables the transverse-electric (TE) and transverse-
magnetic (TM) modes to probe orthogonal components of the cladding permittivity tensor, generating two independent optical observables from a single device. Five clinically relevant biomarkers are investigated: acetone, isoprene, 4-hydroxyhexenal, 2-propenal, and benzene. First-principles optical constants are incorporated into three-dimensional finite-difference time-domain simulations to evaluate the sensing response. The TE mode exhibits a uniform resonance shift of 0.263 nm across all analytes and serves as a concentration reference channel, while the TM mode produces analyte-specific shifts ranging from 0.200 to 0.426 nm. A unique TM amplitude inversion is observed for benzene, enabling additional discrimination. The resulting dual-polarization response forms a two-dimensional optical fingerprint that distinguishes all five biomarkers without requiring a sensor array or multiple functionalized resonators. The device achieves quality factors of 4520 and 3151 for the TE and TM modes, respectively, with sensitivities up to 6.5 nm/RIU, figures of merit up to 14.9 RIU^-1, and detection limits as low as 1.5 mRIU. Cross-sensitivity analysis further shows that CO2 and H2O produce negative TM resonance shifts, separating interferents from target biomarkers in the fingerprint plane. The proposed platform demonstrates a compact route toward array-free photonic breath analysis using intrinsic cladding anisotropy.
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Applied Physics
Mid-infrared Assisted THz Phonon Amplification in a 2D Semiconductor for Room Temperature Detection
Christopher Sumner, Jakob Ziewer, Anju Sajan et al. (+2 more)
Efficient and selective excitation of
lattice vibrations is central to controlling energy flow at the nanoscale, yet remains challenging under conventional optical excitation. Here, we introduce a mid-infrared-assisted
phonon amplification approach, termed MIRAPA, that enables efficient energy injection directly into vibrational bonds. Using surface-enhanced resonant Raman scattering in few-layer $\mathrm{MoS_2}$, we exploit strong
exciton–
phonon coupling to monitor
phonon populations. When mid-infrared (MIR) light is introduced, it couples directly to out-of-plane
lattice vibrations, leading to room-temperature
phonon amplification exceeding $80\%$. Crucially, MIRAPA bypasses electronic excitation pathways, allowing the MIR power density to be nearly $300\times$ lower than that required for visible excitation to achieve comparable enhancement. The resulting
phonon modulation is robust, persisting over more than $2800$ on/off cycles and exceeding $15$ hours of continuous-wave
laser illumination without degradation. Quantitative analysis yields an effective noise-equivalent power of approximately $0.3\,\mathrm{nW}/\sqrt{\mathrm{Hz}}$ for MIR detection, highlighting the sensitivity of the approach. By combining vibrational selectivity, low-power operation, and long-term stability, MIRAPA provides a robust platform for probing and amplifying
phonons in two-dimensional
semiconductors. These results open new opportunities for nanoscale vibrational sensing, mid-infrared detection, and
phonon-based coherent devices, including routes toward
phonon lasing.
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All authors Christopher Sumner, Jakob Ziewer, Anju Sajan, Fumin Huang, Rohit Chikkaraddy
Atomic Physics
Rovibrational structure and electric dipole moments of the AcOCH$_3$+ ion
Anna Zakharova
The possibility of
laser cooling and the presence of closely spaced rovibrational doublets make polyatomic molecules an attractive platform for the $\mathcal{P}$, $\mathcal{T}$-violation searches. We study the spectrum of the lowest rovibrational state of the AcOCH$_3+$ symmetric top molecule. The electronic structure full-electron computation was performed within a relativistic coupled cluster method with double and perturbative triple excitations. The rovibrational wavefunctions are obtained using a coupled channel technique, taking into account all rovibrational effects and anharmonicities of the potential. As a result, the vibrational frequencies, as well as the values of the electric dipole moments for the rovibrational states, were computed.
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Optics · Cross-listed from cond-mat.mtrl-sci
The Emergence of Photonic Crystalline Order and Time-Series Dynamics in NaCl Droplet Deposition
Grzegorz S. Żmija, Grzegorz Cios and Benedykt R. Jany
Crystallization during droplet evaporation gives rise to complex, self-organized structures, yet the mechanisms underlying the emergence of ordered functional phases remain poorly understood. In this study, we present a comprehensive, multi-scale investigation into the crystallization dynamics of NaCl during droplet evaporation on a germanium (001) substrate, relevant for its IR applications. Through systematic microscopic characterization, we identify the formation of diverse microstructures, including 1D photonic
crystal nanostructures formed within hybrid
crystal-glass photonic system. To enable quantitative comparison across experimental conditions, we introduce the NaCl equivalent height as a unified metric to describe and classify the
evolution of crystalline morphology. Our results reveal that
diffusion anisotropy, rather than growth kinetics, primarily governs the maximal attainable structure size. Quantitative thin film interference analysis demonstrates the presence of discrete thickness layers in the film. Controlled evaporation experiments yield homogeneous crystallization patterns across the entire droplet area, facilitating the emergence of ordered photonic structures. Time-series dynamics analysis of height profiles uncovered the spatiotemporal
evolution of the crystallization front, providing insights into the details of underlying physical mechanisms. Together, these results establish a robust experimental framework for understanding and predicting crystallization behavior in evaporating droplets, with potential applications in materials synthesis, photonics, and microscale pattern formation.
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Chemical Physics
Two Protons, Two Positrons, and Four Electrons: Covalent Bond with van der Waals Characteristics
Jorge Charry and Alexandre Tkatchenko
Classifying interactions is key in the physical sciences, and bonding mechanisms in matter-antimatter systems remain particularly enigmatic. Here we focus on a paradigmatic example of positronium hydride (PsH) dimer composed of two
protons, two positrons, and four electrons, whose bonding nature has been previously described as either ionic, covalent, or van der Waals-like. Accurate
quantum Monte Carlo calculations show that the two positrons occupy a delocalized molecular orbital that envelopes the two hydrogen anions and responds as a collective dipole to an applied electric field. This positronic bonding stems from
quantum correlations that resemble a single covalent bond formed between negatively charged pseudo-
nuclei, but with a bond strength commensurate with the traditional van der Waals interaction. Our findings suggest that the ability to form delocalized proto-bonds is a more general property of
quantum systems, and could be present in a broader class of particles, antiparticles, and quasi-particles interacting with matter.
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Computational Physics · Cross-listed from math.NA
Homotopy continuation of viscoelastic waveguide dispersion curves: from intra-manifold tracking to inter-manifold transport
Dong Xiao, Zahra Sharif Khodaei and M. H. Aliabadi
Conventional mode tracking operates in the dark: it traces dispersion branches on the non-Hermitian
eigenvalue manifold using only local continuity, unaware of the global Riemann-sheet
topology. When exceptional points (EPs) lie close to the real frequency axis, the eigenvector similarity that local trackers rely on degrades, and mode tracking becomes unreliable, failing silently. This paper replaces blind intra-
manifold tracking with inter-
manifold transport. A material attenuation parameter s in [0,1] continuously maps the target lossy problem to an auxiliary lossless one whose Hermitian
eigenvalue problem yields a well-posed anchor
manifold on which each dispersion branch possesses a globally unique and continuous identity. These identities are defined once on the elastic anchor and then transported to the viscoelastic target via predictor-corrector homotopy continuation; as long as the path avoids all EPs, branch identity is preserved throughout the transport. For any mode pair whose EPs have not crossed the real frequency axis (Type I), the transported identities are inherited automatically. In contrast, when an EP crosses the real axis and becomes Type II, the
topology differs from the elastic anchor and a label swap is required. The framework is validated on symmetric and unsymmetric laminates, with most cases at loss factors of 0.003 to 0.02; for all Type I pairs in these cases the identities are inherited without alteration. For a challenging unsymmetric laminate at 0.05, several EP pairs have become Type II, yet the homotopy transport still produces numerically accurate solutions. Two diagnostic signatures–an extremely sharp imaginary-part crossing and a marked discrepancy between spectral group velocity and energy flux velocity–identify where the underlying EP
topology demands a label swap.
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Atomic Physics · Cross-listed from quant-ph
Transient dynamics of parametric driving for single-electron image current detection in a Paul trap
Baiyi Yu, Andris Huang, Isabel Sacksteder et al. (+1 more)
Nondestructive detection of single-electron motion is crucial for
quantum information processing with electrons trapped in Paul traps. The standard approach in Penning traps is to detect the image current induced on the trap electrodes by the electron's oscillatory motion. However, applying this approach in Paul traps for single electrons is currently hindered by motional frequency fluctuations arising from trap anharmonicities and instabilities in the rf trapping field. In this work, we propose a robust detection scheme exploiting the transient dynamics of parametric driving to overcome these limitations. Distinct from traditional steady-state approaches, our method focuses on the transient regime to break the temporal constraints imposed by steady-state assumptions, thereby enabling fast readout. We show that a controlled ramp of the parametric drive effectively locks the frequency of the electron motion in the transient regime, rendering the signal highly resilient to realistic experimental noise and inherent micromotion. This work paves the way for the experimental realization of nondestructive detection of single-electron motion in Paul traps.
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All authors Baiyi Yu, Andris Huang, Isabel Sacksteder, Hartmut Haeffner
Computational Physics
Fast contracted Clebsch–Gordan tensor products for equivariant graph neural networks
Anton Bochkarev, Yury Lysogorskiy and Ralf Drautz
We present an $\mathcal{O}(L^3)$
algorithm for evaluating contracted Clebsch–Gordan tensor products in $\mathrm{O}(3)$-equivariant machine learning potentials at fixed Canonical Polyadic (CP) rank. Mapping the angular integral to a structured Gauss–Legendre and
Fourier tensor-product grid decouples the radial channel contractions from the angular transforms. The antisymmetric parity-odd Clebsch–Gordan channels, unreachable by the symmetric pointwise product on a scalar $S^2$ grid, are recovered through the surface-curl pairing $\hat r \cdot [\nabla_{S^2} A \times \nabla_{S^2} B]$, the spherical Poisson bracket, which supplies the $L=1$ angular momentum on the grid while preserving rotational equivariance. The construction extends to parity-aware equivariant message passing in atomic-cluster-expansion-style architectures and is verified by direct numerical quadrature. The full uncontracted Clebsch–Gordan tensor product remains subject to the $\mathcal{O}(L^4)$ output-size lower bound. A
benchmark shows wall-clock scaling empirically as $L^2$ across the practical $l_{\max}$ range. For the on-site contraction this is pre-asymptotic, giving way to $L^3$ at large $l_{\max}$. For message passing it is structural and the runtime is
memory-bandwidth bound on $L^2$-sized grid tensors.
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Plasma Physics · Cross-listed from astro-ph.SR
The Role of Magnetic Reconnection in Energizing Protons and Heavier Ions at the Heliospheric Current Sheet
Giulia Murtas, Xiaocan Li, Fan Guo et al. (+3 more)
During near-Sun crossings of the heliospheric current sheet (HCS), Parker
Solar Probe (PSP) observed populations of high-energy
protons and heavier ions indicating possible energization by
magnetic reconnection up to 10s – 100s keV nucleon$^{-1}$. Here we study ion acceleration by
magnetic reconnection at the HCS. To estimate ion energization, we solve the Parker transport equation coupled to a large-scale 2D MHD reconnection simulation. We find that multiple ion species develop power-law distributions with both spectral index and high-energy cutoff $E_{\text{max}}$ consistent with in-situ data. By accounting for the injection physics determined by kinetic simulations, we confirm that the charge-to-mass ratio scales as $E_{\text{max}} \propto (Q/M)^{\alpha}$ with $\alpha \sim 0.8-1.1$, approximately consistent with PSP measurements in the broader range $\alpha \sim 0.6-1.7$. In the limit where ions are injected at the same energy per nucleon, $\alpha$ can be as low as $\sim 0.3$. These findings further support the role of
magnetic reconnection in producing high-energy heavy ions at the HCS.
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All authors Giulia Murtas, Xiaocan Li, Fan Guo, Giuseppe Arrò, Jeongbhin Seo, Colby Haggerty
Optics
Multifunctional Barophotonic Control of Resonators and Metasurfaces
Ping-Chun Chen, Mashnoon Alam Sakib, Mariia Stepanova et al. (+2 more)
Actively tunable nanophotonic platforms that control light-matter interactions enable reconfigurable optical systems and programmable photonic integrated
circuits. Hydrostatic pressure provides a noninvasive and material-agnostic mechanism for modulating the refractive index and resonance conditions without introducing free carriers or structural damage. Here, we demonstrate multiple pressure-dependent functionalities in silicon nitride nanostructures, including resonance tuning, refractive index modulation, and polarization state conversion. Applying a pressure of up to 5 GPa, we observe a Fabry-Pérot resonance shift of up to 30 nm and a relative refractive index decrease of up to 4%. Based on the results, we design and examine, to the best of our knowledge, the first extreme-pressure-tunable, polarization-converting metasurface, which tunes the ellipticity and orientation angle of the output light. These findings establish pressure-controllable silicon nitride as a viable platform for reconfigurable photonics and extreme-environment nanophotonic systems, including deep-ocean exploration, planetary interiors, and space applications.
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All authors Ping-Chun Chen, Mashnoon Alam Sakib, Mariia Stepanova, Melika Momenzadeh, Maxim R. Shcherbakov
Plasma Physics
Numerical simulations of waves and turbulence in coronal loops: observables and spectra
Fabio Feraco, Francesco Pucci, Claudio Meringolo et al. (+11 more)
We investigate numerically the time
evolution of velocity and
magnetic field fluctuations in a coronal loop, focusing on the dynamics due to both phase mixing and turbulent cascade. The intensity, doppler velocity and non-thermal broadening are synthesized from numerical results in order to establish if the upcoming Multi-slit
Solar Explorer (MUSE) mission could reveal the presence of those phenomena in the
solar corona through its unprecedented high-resolution spectroscopic observations. The loop is represented by a cylindrical pressure-balanced
magnetic structure with a transverse density and
magnetic field inhomogeneity. The initial perturbation is a superposition of a torsional Alfvén wave and a transverse turbulent component with different tunable weights. In order to reconstruct
plasma emission features we calculate moments of the Fe IX 171 Å\ spectral line. 2D maps obtained by integrating the emission along the assumed line of sight are calculated for the emission intensity $I_0$, the Doppler shift $I_1$ and the non-thermal broadening $I_2$, for several values of the model parameters. Finally, we simulate MUSE spectrograph by considering a resolution of $312$ km $\times$ $312$ km. We observe how intensity maps show the formation of longitudinal threads. The generation of small-scale fluctuations mainly takes place in the inhomogeneity region at the loop boundary, where the effects of phase mixing and non-thermal broadening are stronger. 1D power spectra of intensity and Doppler shift maps are calculated and compared with the corresponding spectra of density and line-of-sight velocity component. The agreement observed between the spectral indexes of the intensity power spectra at MUSE resolution and the one computed from the full 3D density field indicates that spectra of $I_0$ can be used to infer information on the spectrum of density inside a loop.
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All authors Fabio Feraco, Francesco Pucci, Claudio Meringolo, Giuseppe Nisticò, Fabio Reale, Paolo Pagano, Gabriele Cozzo, Tom Van Doorsselaere, Bart De Pontieu, Paola Testa, Sergio Servidio, Oreste Pezzi, Francesco Valentini, Francesco Malara
Atomic Physics
The PairInteraction Toolkit for Modeling Rydberg Physics in Alkali and Alkaline-Earth-Like Atoms
Johannes Mögerle, Frederic Hummel, Alicia Keil et al. (+8 more)
Rydberg atoms provide a powerful platform for exploring strongly interacting
quantum systems, both in free space and in structured electromagnetic environments, with growing applications in
quantum technology. Accurately modeling their single-atom properties and mutual interactions is essential for interpreting experiments and designing new architectures. We present a unified theoretical framework for Rydberg atoms and their interactions based on multi-channel
quantum defect theory (MQDT) and static electromagnetic Green's tensors. MQDT provides a precise description of Rydberg states of divalent atoms such as strontium and ytterbium, while the Green's tensor formalism provides a general and flexible approach for calculating interactions between two Rydberg atoms in arbitrary geometries, including modifications induced by nearby surfaces. We implement this framework in an updated version of the open-source toolkit PairInteraction [Weber et al., J.~Phys.~B~50 (2017)]. The implementation leverages high-performance libraries and achieves speedups of one order of magnitude for pair-potential calculations compared to prior software. We demonstrate the capabilities of the toolkit through example applications to divalent atoms and show excellent agreement with experimental data for an exemplary Stark map of $^{174}$Yb. The modular software architecture enables the community to extend it further.
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All authors Johannes Mögerle, Frederic Hummel, Alicia Keil, Tangi Legrand, Eduard J. Braun, Henri Menke, Jonathan King, Beatriz Olmos, Sebastian Hofferberth, Hans Peter Büchler, Sebastian Weber
Optics
Hybrid Nanophotonic Scintillators for Enhanced X-ray Absorption, Emission, and Time Resolution
Seou Choi, Sachin Vaidya, Avner Shultzman et al. (+3 more)
Scintillators convert ionizing radiation into visible
photons, enabling applications from
cosmic ray detection to medical imaging. Two independent strategies for improving scintillator performance via nanoscale patterning have recently been demonstrated: engineering material properties to enhance absorption of ionizing radiation and integrating nanophotonic structures to enhance the spontaneous emission rate ("nanophotonic scintillators"). Here, we propose a nanophotonic scintillator that simultaneously enhances both the initial energy conversion and the spontaneous emission rate, by periodically stacking a fast-emitting scintillator and a visible-light-transparent material with strong X-ray attenuation ("stopping layer") to form a one-dimensional (1D) photonic
crystal (PhC) scintillator. Photoelectric absorption in the stopping layer increases the number of photoelectrons that deposit energy in neighboring scintillator layers and contribute to scintillation. At the same time, the spontaneous emission rate is enhanced by the nanophotonic structuring itself. We design a 1D PhC comprising an organic scintillator and indium tin
oxide (ITO) as the stopping layer and numerically simulate the enhancement in scintillation yield and decay rate. The total detected light output is enhanced by up to a factor of 700 compared to a bulk organic scintillator of equal thickness. We further investigate a 1D PhC structure integrating inorganic and organic scintillators for time-of-flight positron emission
tomography (TOF-PET): replacing the non-scintillating stopping layer with an inorganic scintillator further increases the light yield, and the coincidence time resolution (CTR) is enhanced up to 3.5 times compared to a bulk inorganic scintillator of equal thickness. Our work presents a unified approach to improve key scintillation parameters within a single nanophotonic structure.
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All authors Seou Choi, Sachin Vaidya, Avner Shultzman, Charles Roques-Carmes, Ido Kaminer, Marin Soljačić
Medical Physics
A Monte Carlo positronium decay source model with multiple annihilation channels in GATE
Wojciech Krzemien, Mateusz Bala, Kamil Dulski et al. (+7 more)
Positronium-based imaging requires realistic modelling of positronium (Ps) decay in matter. We introduce a modular Ps decay model implemented in GATE 9.4 and GATE 10, enabling the definition of an arbitrary number of decay channels characterised by lifetime, branching fraction, annihilation multiplicity (2g/3g), and optional
prompt photon emission. The model is validated through analytical and numerical
benchmarks, including lifetime distributions, branching fraction consistency,
photon kinematics, and
prompt photon emission. Its practical applicability is demonstrated using simulations of mixed annihilation scenarios and the NEMA IEC phantom with a large field-of-view PET system. The proposed model accurately reproduces input lifetime distributions as weighted sums of exponential components and correctly samples decay channel fractions. Simulated two- and three-
photon annihilation kinematics are consistent with theoretical expectations. Complex mixtures of decay channels, including varying 3g-to-2g ratios and multi-component ortho-positronium lifetimes, are correctly modelled, with observable signatures reflected in both temporal and energy distributions. Phantom simulations demonstrate the capability to generate realistic positronium-sensitive
datasets. This work provides the first general-purpose, multi-channel positronium decay model integrated into GATE, enabling realistic simulations of positronium behaviour in complex media. The model supports the development and optimisation of positronium-based imaging techniques, including PLI and multi-
photon PET, and applies to medical imaging, industrial
tomography, and fundamental physics studies. Its public availability and compatibility with standard GATE workflows make it a valuable tool for the broader research community.
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All authors Wojciech Krzemien, Mateusz Bala, Kamil Dulski, Wojciech Zdeb, Aurélien Coussat, Beatrix C. Hiesmayr, Konrad Klimaszewski, Michał Obara, Lech Raczyński, Roman Y. Shopa
Chemical Physics
Categorification of Chemical Reactions: a bottom-up tower from stoichiometry to quantum structure
Kyunghoon Han
Chemistry's rules carry exceptions: the octet rule, Hess's Law, detailed balance, orbital
symmetry selection rules, all with disclaimers memorised separately. Their cause: a question from a richer structural level posed in the vocabulary of a simpler one, i.e. level incompleteness. This monograph makes the levels explicit, constructing a canonical tower of nine categorical levels from stoichiometry through thermochemistry,
equilibrium, kinetics, electron-pushing mechanisms, stereochemistry, potential energy surfaces, and electronic structure to all-particle
quantum mechanics. Each level emerges from pairs of reactions distinct yet indistinguishable at the previous level; the minimal extension resolving each ambiguity is provably unique, certified by a non-trivial cokernel in an
automorphism exact sequence, and recovers Feinberg's deficiency
theorems as homological corollaries. A perpendicular dimension: every ML model for chemistry (yield predictors, neural kinetic networks, equivariant force fields, learned wavefunctions) is a morphism in the Para-enrichment of one tower level, with equivariance and thermodynamic consistency as universal properties. Three incompleteness results (Eyring, Wegscheider, topological output gaps) apply to the current literature. The framework descends to code: an operational functor from a Para-enriched product of the first four levels into the Kleisli category of the probabilistic sub-monad of Haskell IO, instantiated as a simulator of the Briggs-Rauscher oscillating reaction: the first Kleisli semantics of Gillespie's next-reaction method and first Para application outside ML. The passage to all-particle
quantum mechanics, Born-Oppenheimer as the classical limit of a continuous field of C*-
algebras, remains the deepest open construction; four candidate
conjectures including Woolley-Primas have obstructions the framework makes specific.
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Chemical Physics
THEMol dataset: Torsion, Hessian, and Energy of Molecules
Jiashu Liang, Tianze Zheng, Yu Xia et al. (+13 more)
We present THEMol (Torsion, Hessian, Energy of Molecules), a massive open-source collection of
quantum mechanical properties tailored for closed-shell organic molecules, with up to 50 heavy atoms. THEMol includes a Hessian subset with more than 3 million relaxed geometries with Hessian
matrices, a TorsionScan subset with nearly 100 million constrained relaxed geometries with energies and forces, and relaxation-trajectory subsets (HessianRelax and TorsionScanRelax) that together comprise about 3 billion DFT calculations. The chemical space sampling is comprehensive, spanning twelve essential elements and diverse molecular architectures relevant to drug discovery, electrolytes, ionic
liquids, and beyond. The
dataset also features exhaustive conformational sampling through the TorsionScan and TorsionScanRelax subsets, including comprehensive in-ring and non-ring torsional scans. Furthermore, it contains an extensive library of Hessian
matrices, computed at relaxed geometries, to capture critical second-derivative information of the potential energy landscape. Additionally, we supply electron density-derived atomic multipoles computed via the Minimal Basis Iterative Stockholder partition scheme. Organized into five distinct subsets (Hessian, TorsionScan, HessianRelax, TorsionScanRelax, and MBIS), the data encompasses optimized geometries, relaxation trajectories, and derived molecular properties. We anticipate that this massive and diverse
dataset will significantly empower the development of highly accurate and transferable molecular potentials.
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All authors Jiashu Liang, Tianze Zheng, Yu Xia, Xingyuan Xu, Xu Han, Zhi Wang, Siyuan Liu, Ailun Wang, Yu Liu, Shiqian Tan, Dongfei Liu, Zhichen Pu, Yuanheng Wang, Qiming Sun, Xiaojie Wu, Wen Yan
Optics
Quantum-Secure Physical Unclonable Function enabled by Silicon Photonics Integrated Circuits
G. Sarantoglou, N. Tzekas, G. Moustakas et al. (+8 more)
Physical Unclonable Functions (PUFs) are hardware security primitives whose inherent physical complexity can be exploited for secure authentication and cryptographic key generation. Silicon photonic devices, owing to their suitability for
quantum and artificial intelligence applications alongside standard CMOS fabrication processes, constitute a highly promising substrate for integrated multifunctional PUFs. Despite the advanced security guarantees offered by
quantum cryptographic protocols and the central role of silicon photonics in
quantum technologies,
quantum readout strategies based on single-
photon states for photonic PUFs remain largely unexplored. In this work, we experimentally demonstrate a silicon nitride (SiN) programmable photonic Mach Zehnder interferometer mesh that implements a
unitary transformation and operates as a PUF, whose secret physical signature arises from uncontrollable waveguide variations during fabrication. Using experimentally derived parameters from the SiN integrated mesh, we further introduce and numerically evaluate a
quantum readout protocol that combines single-
photon states with PUFs. Maximally mixed
quantum states are employed to conceal the underlying
unitary transformation from passive eavesdropping. Security against adversaries possessing devices fabricated under similar conditions is assessed, with authentication performance quantified through Monte Carlo analysis of the false acceptance and false rejection rates as a function of the number of detected events and corrected errors. The results indicate exceptional performance with equal error rates as low as 10 to the minus 14, highlighting the potential of
quantum secure PUFs for high security authentication applications.
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All authors G. Sarantoglou, N. Tzekas, G. Moustakas, G.A. Karydis, V. Kaminski, E. Protsenko, K. Gradkowski, A. Bazin, C. Vigliar, A. Bogris, C. Mesaritakis
Biological Physics
A developmental switch from capillary rectification to elastic catapult enables honeydew ejection in the spotted lanternfly
Nami Ha, Elio J. Challita, Jacob S. Harrison et al. (+4 more)
Plant sap-feeding insects must dispose of excess fluid, yet at millimeter scales droplet release is constrained by capillary adhesion and contact-line pinning. How phloem-feeding insects solve this puzzle, particularly as the excretory apparatus changes in size and form from nymph to adult, has remained unclear. Combining micro-CT, high-speed imaging, measurements of honeydew properties, and reduced-order modeling, we show that the spotted lanternfly (Lycorma delicatula) uses distinct release mechanics across ontogeny. Nymphs release honeydew with an anal stylus that acts as a capillary rectifier, imposing a
curvature asymmetry that biases the attached droplet toward detachment through a Laplace-pressure difference. Adults use a longer stylus associated with an elastic basal region, maintain stylus-droplet contact through a finite compression phase, and release droplets with greater translational and rotational momentum. In both stages, stylus rotation is ultrafast, with peak angular accelerations of order $10^7$ rad/s$^{-2}$ and release unfolding on millisecond timescales, yet droplet ejection speed remains below stylus tip speed. Weber-Bond scaling based on measured honeydew properties places both stages at $We_d<1$ and $Bo_d<1$ at the outlet, but distinguishes their post-release states: nymphal droplets remain surface-tension dominated, whereas adult droplets enter deformation- and
spin-influenced regimes. Development therefore maintains waste clearance across ontogeny under the same outlet-scale capillary constraint by changing how stylus motion is coupled to the droplet at release, linking life-stage biomechanics to honeydew placement in this invasive phloem feeder and suggesting bioinspired strategies for droplet ejection, antifouling, and self-cleaning surfaces.
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All authors Nami Ha, Elio J. Challita, Jacob S. Harrison, Elizabeth G. Clark, Kendall E. Larson, Miriam F. Cooperband, Saad Bhamla
Fluid Dynamics
Effect of startup modes on cold start performance of PEM fuel cells with different cathode flow fields
Wenzhe Zhang, Xingxiao Tao, Qifeng Li et al. (+4 more)
Proton Exchange Membrane Fuel
Cell (PEMFC) is widely recognized for its cleanliness and high efficiency, but is still facing challenges in cold environments. At low temperatures, the formation of ice and repeated freezing/thawing cycles may cause
cell performance reduction and irreversible degradation. The cathode flow field of PEMFCs has a significant effect on the performance. In contrast to the conventional “channel-ridge” flow field, the metal foam has the advantages of excellent pre-distribution of gases and water drainage, which make it a promising candidate for the cold start. This paper examines the cold start of PEMFCs with metal foam flow field (MFFF) and serpentine flow field (SFF), and the influence of constant current mode, constant voltage mode, and ramping current mode is investigated experimentally through performance test and electrochemical characterization. The results show that lowering the voltage and increasing the current can enhance the cold-start performance of fuel
cells. The MFFF fuel
cell has superior cold start performance compared to the SFF fuel
cell under the constant voltage mode of 0.3 V. Furthermore, the variable current mode is developed by considering the distinct properties of heat and water production during various phases, and the results indicate that increasing the current density at the unsaturated stage leads to an elevated rate of heat production and a reduced rate of water production, which can improve the cold start of PEMFCs.
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All authors Wenzhe Zhang, Xingxiao Tao, Qifeng Li, Kai Sun, Rui Chen, Zhizhao Che, Tianyou Wang
Atmospheric and Oceanic Physics
From Particles to Policy: Technical Building Blocks for Multi-State SAI Coordination
R. Yahav, A. Spector, D. Kushnir et al. (+1 more)
Stratospheric aerosol injection (SAI) is a
solar radiation modification technique, proposed as an interim measure to offset warming while greenhouse gas (GHG) emissions are reduced. This paper discusses a possible SAI implementation route - an alternative to sulfate aerosols formed in situ - based on engineered solid particles having dedicated properties such as size, composition, surface chemistry, and traceable origin, supporting safety, controllability, and functionality needed for SAI systems. These engineered properties also open up options for any future multi-state coordination of SAI through two technical building blocks: (1) the SAI-induced radiative forcing (SRF) - the magnitude of the cooling effect attributable specifically to the SAI layer - as an operator-independent quantity, derivable from direct aerosol-layer measurements; and (2) particle traceability through identifying signatures embedded at production. Both could feed into a shared, publicly accessible monitoring database open to independent interrogation, addressing several governance challenges by anchoring compliance assessments in measurable parameters. Drawing on precedents from the Montreal Protocol, IAEA safeguards, and other regimes, we show that shared technical metrics have historically enabled multi-state cooperation, and we argue the same could apply to SAI. We describe a phased pathway in which the technical capabilities and coordination practices that would use them are developed and tested together, at scales orders of magnitude below operational deployment. To be clear - we regard SAI deployment as premature; the conditions under which it might be considered have not been met. The paper does not propose a governance framework; rather, it identifies technical infrastructure that could support a wide range of such frameworks.
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All authors R. Yahav, A. Spector, D. Kushnir, M. C. Waxman
Applied Physics
Radioactive Source Seeking using Bayesian Optimisation with Movement Penalty
Lysander Miller, Joshua Keene, Jeremy M. C. Brown et al. (+1 more)
The use of mobile robotics in radioactive source seeking has become an important part of modern radiation-safety practices, supporting timely mitigation of contamination risks and helping protect public health. However, measuring radiation is often time-consuming, rendering traditional gradient-based source-seeking methods less effective due to lower sample efficiency. This paper proposes a sample-efficient
Bayesian-Optimisation source-seeking strategy that utilises a heteroscedastic Gaussian process surrogate to balance exploration and exploitation. Excessive inter-sample travel is discouraged through a movement switching cost. The strategy is shown to generate sublinear regret in the source-seeking task, while simulations demonstrate its effectiveness in localising radioactive sources.
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All authors Lysander Miller, Joshua Keene, Jeremy M. C. Brown, Airlie Chapman
Plasma Physics
Real-time virtual circuits for plasma shape control via neural network emulators
Alasdair Ross, George K. Holt, Kamran Pentland et al. (+7 more)
Reliable position and shape control in tokamak
plasmas requires accurate real-time regulation of several strongly coupled shape parameters. The control vectors that disentangle these couplings, referred to as virtual
circuits (VCs), enable independent shape parameter control for a specific Grad–Shafranov (GS)
equilibrium. Numerical calculation of VCs is not currently feasible in real time, therefore VCs are usually computed prior to each experiment, using a small number of reference GS
equilibria sampled along the desired scenario trajectory, with each VC used to control the
plasma within a preset time interval. While effective near the reference
equilibrium, this approach can lead to degraded performance as the
plasma departs from the reference
equilibrium and/or from the desired trajectory, and it complicates the design of robust control strategies for rapidly evolving
plasma configurations. In this paper, we construct neural-network-based emulators of
plasma shape parameters from which VCs can be derived, to provide the MAST Upgrade (MAST-U)
plasma control system with state-aware VCs in real-time. To do this, we develop an extensive library of over a million simulated GS
equilibria, covering a substantial portion of the MAST-U operational space. These emulators provide differentiable functions whose gradients can be rapidly computed, enabling the derivation of accurate VCs for real-time shape control. We perform extensive verification of the emulated VCs by testing whether they disentangle the control problem. The neural-network-based approach delivers high accuracy and orthogonality across a diverse range of
equilibria. This work establishes the physical validity of emulated VCs as a scalable and general alternative to schedules of precomputed VCs.
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All authors Alasdair Ross, George K. Holt, Kamran Pentland, Adriano Agnello, Nicola C. Amorisco, Pedro Cavestany, Aran Garrod, Timothy Nunn, Charles Vincent, Graham McArdle
Plasma Physics
Generation of period-tunable MeV few-attosecond electron pulse trains via counter-propagating lasers
Qi Huang, Qing Jia, Zhongxuan Wang et al. (+1 more)
Attosecond electron pulses permit real-time probing of ultrafast material dynamics. However, generating few-attosecond electron pulses with MeV energies and low energy spread remains an enduring challenge for conventional beam-modulation techniques. Here we propose a compact dual-
laser scheme to modulate readily accessible electron beams into few-attosecond pulse trains, leveraging a stable parametric-resonance regime coupled with direct
laser acceleration. An accompanying theoretical framework is developed, yielding closed-form expressions for the tunable pulse period, duration, energy modulation and formation time, enabling flexible customization of the produced attosecond pulse trains. Consistent with these theoretical predictions, simulations verify the generation of ~ 1 as pulses with a Lorentz factor up to 15 and a relative energy spread below 0.02%. This work offers an experimentally feasible pathway toward high-quality, tunable MeV few-attosecond electron pulses.
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All authors Qi Huang, Qing Jia, Zhongxuan Wang, Jian Zheng
Computational Physics · Cross-listed from cond-mat.stat-mech
Lévy-like flights and fractal geometry of finite point sets
Konstantinos Chalas, F. K. Diakonos and A. S. Kapoyannis
We study Lévy-like and truncated Lévy-like flights with step probability distribution of the form $r^{-1+\nu}$ for negative, positive, and zero $\nu$, focusing on the appearance of fractal geometry characteristics in the generated point sets. Forming ensembles of such point sets with fixed multiplicity, we develop simulation techniques leading to the desired value of correlation dimension in a vast continuous interval of scales. In particular, we demonstrate the possibility to produce ensembles of data sets with a low number of points with the needed properties. Furthermore, we show that the positive $\nu$ distributions, apart from a region near the upper scale limit, show fractal behaviour that extends to infinitesimally low scales. As an example, we apply our findings to producing simulations relevant to the search for critical fluctuations, related to QCD critical endpoint, in heavy-ion collision experiments.
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Optics
Superconducting single-photon detectors for integrated quantum photonics
Ilya A. Stepanov, Oksana I. Shmonina, Evgeniy V. Sergeev et al. (+7 more)
Single-
photon detection possibility is a fundamental requirement for
quantum technologies, including communication, computing and sensing. To achieve scalability and practical deployment, increasing
attention is being directed toward integration of detectors with photonic integrated
circuits, which offer compactness and compatibility with mass production. Superconducting nanowire single-
photon detectors have emerged as the leading solution, combining near-unity efficiency, high temporal performance and the ability to be embedded across a wide range of photonic material platforms. In this review we trace the development of integrated superconducting nanowire single-
photon detectors from early demonstrations to recent advances, outlining the progress in device architectures, material engineering and integration strategies. We also discuss performance
benchmarks, emerging alternative designs, the future opportunities and challenges for this rapidly evolving field.
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All authors Ilya A. Stepanov, Oksana I. Shmonina, Evgeniy V. Sergeev, Aleksandr S. Baburin, Danila Yu. Ulyanov, Kirill A. Buzaverov, Sergey S. Avdeev, Aleksey B. Kramarenko, Yuri V. Panfilov, Ilya A. Rodionov
Chemical Physics
Uptake of stratospheric species on minerals proposed for stratospheric aerosol injection
Anais Lostier, Yair Segev, Tzemah Kislev et al. (+3 more)
Solid mineral-based particles have been proposed as alternatives to sulfates for
climate intervention by stratospheric aerosol injection, as a means for improving optical or chemical characteristics and thereby minimize risks and uncertainties. However, the heterogeneous reactivity of solid particles with stratospheric trace gases, and possible implications to the ozone layer, is currently not fully constrained, particularly at stratospheric concentrations. We present a systematic comparative study of the uptake of HNO3, HCl, and NO2 on calcite, alumina, crystalline silica (quartz), and amorphous silica, using complementary Knudsen
cell and flow reactor techniques. We find that NO2 uptake is weak on all surfaces, with estimated removal timescales indicating negligible impact on stratospheric nitrogen chemistry. Conversely, HCl uptake is substantial, with a pronounced concentration dependence consistent with surface site limited Langmuir adsorption. Extracting adsorption isotherms, we find that HCl surface coverage at stratospheric concentrations differs by four orders of magnitude between the surfaces, with calcite adsorbing the most and amorphous silica the least, suggesting a dominant role of surface acid-base character. Using HCl surface coverage as a proxy for ClONO2 reactive uptake, we estimate that amorphous silica could deplete substantially less ozone than calcite or alumina under equivalent injection scenarios. We find a marked difference between crystalline and amorphous silica, underscoring the sensitivity of heterogeneous chemistry to surface microstructure and the importance of selecting particles with low-reactivity surfaces in addition to considering bulk characteristics. Our findings motivate the development of particles with surfaces tailored for minimizing SAI risks and uncertainties, including minimal reactivity with stratospheric gases and background sulfate aerosols.
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All authors Anais Lostier, Yair Segev, Tzemah Kislev, Gal Schwartz Roitman, Nadine Locoge, Manolis N. Romanias
Optics
Stokes-anti-Stokes correlations of light propagating through weakly guiding optical fiber
Ivan V. Panyukov and Evgeny S. Andrianov
Statistical properties of light produced in spontaneous Raman scattering on an ensemble of molecules indicate the
quantum nature of this phenomenon. The scattered light is non-classical and has high non-classical intensity correlations between Stokes and anti-Stokes components. The temporal coherence of this light is well investigated, while many questions related to spatial coherence remain open. Recent experiments reveal two peculiar features of the spatial coherence of the Stokes and anti-Stokes light. First, the intensity correlations between Stokes and anti-Stokes light remain non-classical even for macroscopic samples containing many molecules. Second, these correlations decrease when signal propagates through a multi-mode optical fiber: the more propagating fiber modes at Stokes and anti-Stokes frequencies the less the correlations. Moreover, the second-order autocorrelation function of Stokes and anti-Stokes light also decreases with the number of propagating modes in multi-mode fiber. In this paper, we build a model of spontaneous Raman scattering correlations of light produced by an ensemble of molecules and propagating through weakly guiding optical fiber that quantitatively explains all these observations. We show that spacial orthogonality of the fiber modes makes the light propagating through these modes uncorrelated in the standard detection scheme. This leads to suppression of non-classical intensity correlations of the total field in the multi-mode fiber. We find the degree of non-classical correlations on fiber parameters. The obtained results pave the way for engineering of non-classical Stokes – anti-Stokes correlations.
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Optics · Cross-listed from quant-ph
The influence of strong coupling between single-photon source and spectral filter on photon statistics
Ivan V. Panyukov and Evgeny S. Andrianov
One of the most common approaches for coupling optical single-
photon sources and photonic integrated
circuits is to use a cavity. The cavity acts as a spectral filter that distorts the light spectrum and changes its statistical properties. But in the general case one should take into account not only spectral filtering of light but also the spectral filter influence on the single-
photon source dynamics. We build an effective analytical model for description of the cavity influence on the
photon statistics of light emitted by the single-
photon source as spectral filtering only. We show that this model correctly describes the
photon statistics even in a strong-coupling regime between the single-
photon source and the spectral filter. Our results can be useful for analytical modeling of
photon statistics of
quantum emitters strongly coupled to various electromagnetic interfaces.
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Fluid Dynamics
Evolution of lean hydrogen-air premixed flames under high-frequency acoustic forcing: flame morphology and displacement speed
Xinyi Chen, Frederick W. Young, Umair Ahmed et al. (+1 more)
Fully compressible numerical simulations of two-dimensional laminar lean hydrogen-air premixed flames have been performed, with the flame front subjected to acoustic forcing through the specification of a monopole-type sound source at the inflow. Simulations have been performed for acoustic frequencies ranging from 35~kHz to 500~kHz at two equivalence ratios, $\phi = 0.4$ and $\phi = 0.7$. During the flame-acoustic interaction, the flame evolves from an initially weakly stretched state to exponential perturbation growth, wrinkle interaction, and the formation of non-linear cellular structures, with distinct linear and non-linear stages identified from
Fourier mode analysis. The instability dynamics depend strongly on both forcing frequency and equivalence ratio. In the case of $\phi=0.4$, the flame behaviour is strongly influenced by thermodiffusive instability, with a characteristic sequence of uniform
cells,
cell splitting, and
cell merging. For $\phi=0.7$, weaker thermodiffusive effects result in a response more strongly governed by hydrodynamic instability and large-scale wrinkle growth. At low forcing frequencies, flame corrugations remain relatively uniform, whereas at high frequencies the flame front becomes increasingly modulated and develops envelope-like structures, which can be interpreted as the interaction between an intrinsic standing cellular mode and the imposed acoustic disturbance. In the linear growth regime, the density-weighted displacement speed, $S_d^*$, shows a linear correlation with total stretch rate, $K$, for all forcing frequencies. While in the non-linear growth regime, two distinct branches appear, corresponding to weakly stretched flame segments and strongly negatively curved segments associated with flame pinch-off.
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All authors Xinyi Chen, Frederick W. Young, Umair Ahmed, Robert Stewart Cant