Chemical Physics
A Vector-Based Algorithm for Generating Complete Balanced Reaction Sets with Arbitrary Numbers of Reagents
Nataliia Yilmaz, Pavlo Kozub and Svitlana Kozub
We present a vector-based method to balance chemical reactions. The
algorithm builds candidates in a deterministic way, removes duplicates, and always prints coefficients in the lowest whole-number form. For redox cases, electrons and
protons/hydroxide are treated explicitly, so both mass and charge are balanced. We also outline the basic principles of the vector formulation of stoichiometry, interpreting reactions as integer vectors in composition space, this
geometric view supports compact visualizations of reagent-product interactions and helps surface distinct reaction families. The method enumerates valid balances for arbitrary user-specified species lists without special-case balancing rules or symbolic tricks, and it provides a clean foundation for developing new algorithmic variants (e.g., alternative objectives or constraints). On representative examples (neutralization, double displacement, decomposition, classical redox, small multicomponent sets) and a negative control, the method produced correct integer balances. When multiple balances exist, we report a canonical one - minimizing the total coefficient sum with a simple tie-breaker - without claiming global optimality beyond the solutions the search enumerates. The procedure applies per reaction and extends to reaction networks via consistent per-reaction application. We do not report runtimes, broader benchmarking and code/data release are planned.
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Chemical Physics · Cross-listed from cond-mat.soft
Associative and Segregative Liquid-Liquid Phase Separation in Macromolecular Solutions
Remco Tuinier and Alvaro Gonzalez Garcia
We investigate
liquid-
liquid phase separation (LLPS) and interfacial properties of two LLPS modes: associative (ALLPS) and segregative (SLLPS). Analytical expressions for the critical point (CP) and binodal boundaries are derived and show excellent agreement with self-consistent field (SCF)
lattice computations. Distinct thermodynamic features differentiate ALLPS from SLLPS: (1) in ALLPS,
polymers co-concentrate within a single dense phase coexisting with a solvent-rich phase, whereas in SLLPS each
polymer forms a separate phase; (2) the attractive interaction per monomer in ALLPS is strongly dependent on solvent quality, but solvent-independent in SLLPS; and (3) ALLPS binodals exhibit near-universal behavior, largely independent of solvent content. SCF results further show that interfacial tension increases and interfacial width decreases with distance from the CP. We provide scaling relations for both quantities are provided. Compared with SLLPS, ALLPS displays higher interfacial tension and a thinner interface, reflecting distinct molecular organization at the
liquid-
liquid boundary.
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Atmospheric and Oceanic Physics
Diagnostic vs dynamic representation of the inverse barometer effect in a global ocean model and its potential for probabilistic storm surge forecasting
Nils Melsom Kristensen, Kristian Mogensen, Sarah-Jane Lock et al. (+1 more)
The global ocean model NEMO is run in a series of stand-alone configurations (2015-2022) to investigate the potential for improving global medium-range storm surge forecasts by including the inverse barometer effect. The analysis focus on the residual water level, i.e. the water level variations not due to tides. Here, we compare a control experiment, where the inverse barometer effect was not included, against a run dynamically forced with mean sea level pressure. In the control experiment, the inverse barometer effect was then calculated diagnostically and added to the ocean model sea surface elevation, resulting in a total of three experiments to investigate. We compare against the global GESLA3 water level data set and find that the inclusion of the inverse barometer effect reduces the root-mean-square error by $\sim 1~cm$ on average. When we mask out all data where the observed residual water level is less than $\pm1$ or $\pm2$ standard deviations, including the inverse barometer effect reduces the RMS error by $4-5$ cm. While both methods reduce water level errors, there are regional differences in their performance. The run with dynamical pressure forcing is seen to perform slightly better than diagnostically adding the inverse barometer effect in enclosed basins such as the Baltic Sea. Finally, an ensemble forecast experiment with the Integrated Forecast System of the European Centre for Medium-range Weather Forecasts demonstrates that when the diagnostic inverse barometer effect is included for a severe storm surge event in the North Sea (Storm Xaver, December 2013), the ensemble spread of water level provides a stronger and earlier indication of the observed maximum surge level than the when the effect is excluded.
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All authors Nils Melsom Kristensen, Kristian Mogensen, Sarah-Jane Lock, Øyvind Breivik
Fluid Dynamics
Influence of surfactant kinetics on rapid interface creation via microjet impact on liquid pools
D. Fernández-Martínez, E. J. Vega, J. M. Montanero et al. (+2 more)
We experimentally investigate the influence of surfactant adsorption kinetics on cavity dynamics during the rapid formation of interfaces. For this purpose, we use a submillimeter jet impacting onto a surfactant-laden
liquid pool much larger than the jet dimensions. Cavity retraction and closure occur on a submillisecond timescale, posing a stringent test of the ability of surfactants to reduce surface tension dynamically. Our experiments reveal the difference between the effects of sodium dodecyl sulfate (SDS), a surfactant with moderately fast adsorption kinetics, and Surfynol 465, a surfactant with ultrafast adsorption kinetics. For SDS, the collapse pathway is nearly indistinguishable from that of pure water, suggesting negligible dynamic surface tension reduction. In contrast, Surfynol allows the emergence of deeper cavities that persist longer in the
liquid pool. The harmonic oscillator model accurately captures the cavity retraction in the deep seal regime. The fitted values of the damping ratios are consistent with the dynamic surface tensions.
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All authors D. Fernández-Martínez, E. J. Vega, J. M. Montanero, U.J. Gutiérrez-Hernández, D. Fernández Rivas
Chemical Physics
Vector-Based Approach to the Stoichiometric Analysis of Multicomponent Chemical Reactions: The Case of Black Powder
Pavlo Kozub, Nataliia Yilmaz and Svitlana Kozub
The study demonstrates the capabilities of a vector-based approach for calculating stoichiometric coefficients in chemical equations, using black powder as an illustrative example. A method is proposed for selecting and constraining intermediate interactions between reactants, as well as for identifying final products. It is shown that even a small number of components can lead to a large number of final and intermediate products. Through concrete calculations, a correlation is established between the number of possible chemical equations and the number of reactants. A methodology is proposed for computing all possible chemical equations within a reaction system for arbitrary component ratios, enabling the derivation of all feasible chemical reactions. Additionally, a method is developed for calculating the chemical composition for a fixed set of reactants, allowing for the evaluation of the set of products resulting from all possible chemical interactions given a specified initial composition.
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Computational Physics · Cross-listed from quant-ph
Variational quantum computing for quantum simulation: principles, implementations, and challenges
Lucas Q. Galvão, Anna Beatriz M. de Souza, Marcelo A. Moret et al. (+1 more)
This work presents a comprehensive overview of variational
quantum computing and their key role in advancing
quantum simulation. This work explores the simulation of
quantum systems and sets itself apart from approaches centered on classical data processing, by focusing on the critical role of
quantum data in Variational
Quantum Algorithms (VQA) and
Quantum Machine Learning (QML). We systematically delineate the foundational principles of variational
quantum computing, establish their motivational and challenges context within the noisy intermediate-scale
quantum (NISQ) era, and critically examine their application across a range of prototypical
quantum simulation problems. Operating within a hybrid
quantum-classical framework, these
algorithms represent a promising yet problem-dependent pathway whose practicality remains contingent on trainability and scalability under noise and barren-plateau constraints.This review serves to complement and extend existing literature by synthesizing the most recent advancements in the field and providing a focused perspective on the persistent challenges and emerging opportunities that define the current landscape of variational
quantum computing for
quantum simulation.
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All authors Lucas Q. Galvão, Anna Beatriz M. de Souza, Marcelo A. Moret, Clebson Cruz
Geophysics
Data-driven Exploration of Tropical Cyclone's Controllability
Yohei Sawada, Masashi Minamide, Yuyue Yan et al. (+2 more)
Although the chaotic nature of the atmosphere may enable efficient control of tropical cyclones (TCs) via small-scale perturbations, few studies have proposed data-driven optimization methods to identify such perturbations. Here, we apply the recently proposed Ensemble Kalman Control (EnKC) to a TC simulation. We show that EnKC finds small-scale perturbations that mitigate TC. An EnKC-estimated reduction in surface water vapor, located approximately 250km from the TC center, suppresses convective activity and latent heat release in the eye wall, leading to a reduction of TC intensity. To advance the discovery of feasible TC mitigation strategies, we discuss the potential of this data-driven method for leveraging chaos, as well as its remaining challenges.
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All authors Yohei Sawada, Masashi Minamide, Yuyue Yan, Kazumune Hashimoto, Le Duc
Fluid Dynamics
Confirming Wave Turbulence Predictions in Rotating Turbulence
Omri Shaltiel, Omri Gat and Eran Sharon
Though highly impacting our lives, rotating turbulent flows are not well understood. These anisotropic three-dimensional disordered flows are governed by different nonlinear processes, each of which can be dominant in a different range of parameters. More than 20 years ago, Galtier used weak wave
turbulence theory (WTT) to derive explicit predictions for the energy spectrum of rotating
turbulence. The spectrum is an outcome of forward energy transfer by inertial waves, the linear modes of rotating fluid systems. This spectrum has not yet been observed in freely evolving flows. In this work, we show that the predicted WTT field does exist in steady rotating
turbulence, alongside with the more energetic quasi two-dimensional turbulent field. By removing the 2D component from the steady state velocity field, we show that the remainder three-dimensional field consists of inertial waves and exactly obeys WTT predictions. Our analysis verifies the dependence of the energy spectrum on all four relevant parameters and provides limits, beyond which WTT predictions fail. These results provide a solid basis for new theoretical and experimental works focused on the coexistence of the quasi 2D field and the inertial waves field and on their interactions.
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Atmospheric and Oceanic Physics
The representation of Convectively Coupled Equatorial Waves and upscale energy transfer in models with explicit and parametrized convection
E. McKinnon-Gray, D. Shipley, J. Methven et al. (+4 more)
Convectively Coupled Equatorial Waves (CCEWs) dominate atmospheric variability on timescales of 2–30 days in the Tropics, bringing episodes of widespread heavy precipitation. This study compares the representation of CCEWs and their connection to upscale energy transfer in two Met Office Unified Model simulations of the full tropical channel with identical km-scale resolution for the DYAMOND Summer period. The principal difference between the simulations is that one parametrizes convection (GAL9), while the other (RAL3) is convection permitting. The GAL9 convection scheme acts to remove vertical instability without explicitly representing the resolved-scale circulation associated with convective plumes. We present the first quantitative diagnosis of interscale energy transfer and its relation to CCEWs. This diagnosis is important because upscale energy transfer between convection and large-scale waves may influence accurate simulation of tropical weather systems. The average upper-tropospheric upscale transfer simulated by RAL3 is approximately 50% higher than GAL9. CCEWs are more coherent in RAL3, with an average phase-speed variability 80% higher than observations, compared with 166% higher in GAL. RAL3 also simulates greater upscale energy transfer within waves than GAL9 with a stronger correlation between the interscale energy transfer and equatorial wave winds. Kelvin and Rossby waves are associated with upscale energy transfer from scales 4-8 times smaller than their wavelength, related to active deep convection within a particular sector of the wave phase. Our findings show that the explicit representation of convection has a significant impact on the simulation of upscale energy transfer, and is very likely to be a significant factor in the faithful simulation of convective coupling within CCEWs.
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All authors E. McKinnon-Gray, D. Shipley, J. Methven, T. H. A. Frame, C. Sanchez, A. McCabe, N. M. Roberts
Instrumentation and Detectors
On Improving Nuclear Fuel Imaging Using Position Sensitive Detectors
Erik Brücken, Peter Andersson, Mihaela Bezak et al. (+9 more)
Spent
nuclear fuel imaging before disposal is of utmost importance before long term disposal in dedicated storage facilities. Passive Gamma Emission
Tomography (PGET) is an approved method by the International Atomic Energy Agency. The present detection system is based on small CZT detectors behind a tungsten-based collimator consisting of a linear array of slits. Small scale CZT
crystals limit the detection efficiency of high energetic gamma rays from the fuel rods, mainly the 662 keV emissions from Cs-137. In our study based on full Monte-Carlo simulations as well as on experiments, we explore the capabilities of large pixelated CZT detectors to be used for PGET. We will discuss the theoretical advantages and practical challenges of the larger
crystals. We demonstrate that the larger
crystals, depending on their orientation, will increase the detection efficiency by a factor of 7 to 13. Due to the pixelated sensor signal readout we also explore the possibility to employ Compton imaging to improve the information on the location of origin of gamma rays. In addition we explore the usefulness of commercial gamma-ray imagers for waste characterisation and decommissioning. In particular we report on the performance of the GeGI imager from PHDS Co and the H420 imager from H3D Inc in measuring
nuclear waste drums at Svafo, Sweden.
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All authors Erik Brücken, Peter Andersson, Mihaela Bezak, Peter Dendooven, Sofia Godø, Stefan Holm, Matti Kalliokoski, Aage Kalsæg, Gustav Pettersson, Anders Puranen, Vikram Rathore, Santeri Saariokari
Data Analysis and Statistics · Cross-listed from stat.AP
Inferring Mobility Reductions from COVID-19 Disease Spread along the Urban-Rural Gradient
Sydney Paltra, Jonas Dehning, Viola Priesemann et al. (+1 more)
The COVID-19 pandemic reshaped human mobility through policy interventions and voluntary behavioral changes. Mobility adaptions helped mitigate pandemic spread, however our knowledge which environmental, social, and demographic factors helped mobility reduction and pandemic mitigation is patchy. We introduce a
Bayesian hierarchical model to quantify heterogeneity in mobility responses across time and space in Germany's 400 districts using anonymized mobile phone data. Decomposing mobility into a disease-responsive component and disease-independent factors (temperature, school vacations, public holidays) allows us to quantify the impact of each factor. We find significant differences in reaction to disease spread along the urban-rural gradient, with large cities reducing mobility most strongly. Employment sectors further help explain variance in reaction strength during the first wave, while political variables gain significance during the second wave. However, reduced mobility only partially translates to lower peak incidence, indicating the influence of other hidden factors. Our results identify key drivers of mobility reductions and demonstrate that mobility behavior can serve as an operational proxy for population response.
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All authors Sydney Paltra, Jonas Dehning, Viola Priesemann, Kai Nagel
Optics
Momentum-resolved reflectivity of a 2D photonic crystal in the near-infrared
Timon J. Vreman, Melissa J. Goodwin, Ad Lagendijk et al. (+1 more)
Two-dimensional (2D) photonic
crystals offer strong control over the propagation of light through their bands. Theoretical methods for computing the band structure in 2D are well-established and fast because 2D photonic
crystals are homogeneous in the third dimension. Experimental verification is scarce, however, especially in the telecom range, because real photonic
crystals and experimental methods inherently cannot be homogeneous in the third dimension. In this work, we report momentum-resolved reflectivity measurements on photonic
crystals that are periodic in two dimensions and homogeneous over a thickness of 5 {\mu}m. Using
Fourier spectroscopy, we carefully select wave vectors in the 2D plane of periodicity of the photonic
crystal. Our experiments agree excellently with 2D band structure calculations and with 2D finite-difference time-domain simulations, confirming that our experimental methods truly pertain to nanophotonics in 2D. Our results provide a robust bridge between theory and experiment, and our techniques can be readily extended to other 2D structures, including those with functional defects.
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All authors Timon J. Vreman, Melissa J. Goodwin, Ad Lagendijk, Willem L. Vos
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
The Microscopic Nature of Orbital Disorder in LaMnO$_{3}$
Bodoo Batnaran, Andrew L. Goodwin, Michael A. Hayward et al. (+1 more)
We present a revised atomistic picture of the order-disorder transition in the archetypal orbital-ordered perovskite material, LaMnO$_{3}$. Our study uses machine-learning-driven molecular-dynamics simulations which describe the temperature
evolution of pair distribution functions in close agreement with experiment. We find the orbital-disordered phase in LaMnO$_{3}$ to comprise a mixture of differing structural distortions with and without inversion
symmetry, implying a mixture of different orbital arrangements. These distortions are highly dynamic with an estimated lifetime of $\sim 40$ fs at 1,000 K, and their fluctuations converge with the timescales of conventional thermal motion in the high-$T$ phase - indicating that the electronic instability responsible for static Jahn-Teller distortions at low temperature instead drives
phonon anharmonicity at high temperatures. Beyond LaMnO$_{3}$, our work opens an avenue for studying a wider range of correlated materials.
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All authors Bodoo Batnaran, Andrew L. Goodwin, Michael A. Hayward, Volker L. Deringer
Optics
Radiative local density of states in three-dimensional photonic band-gap crystals to interpret time-resolved emission
Timon J. Vreman, Ad Lagendijk and Willem L. Vos
We investigate the spontaneous emission of light in three-dimensional (3D) photonic
crystals through theoretical calculations and simulations. It is well known that spontaneous emission depends on the radiative local density of states (RLDOS). Photonic band-gap
crystals radically modulate the RLDOS, thereby controlling spontaneous emission. We compare two different methods to calculate the RLDOS: the plane-wave expansion (PWE) method and the finite-difference time-domain (FDTD) method. The PWE method directly calculates the RLDOS of an infinite photonic
crystal, whereas the FDTD method simulates the RLDOS through the power emitted by a dipole in a finite photonic
crystal. We demonstrate that the methods yield similar frequency-dependent trends in the RLDOS, with relative differences of less than 12% that originate from the different boundary conditions. We employ the plane-wave expansion method to compute distributions of emission rates that are relevant to many optical experiments where
quantum emitters are distributed within a
crystal. Such distributions of emission rates enable us to compute and directly interpret the time-resolved decay as observed in experiments. We expect that our results promote the RLDOS to the realm of optical design and products.
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Chemical Physics
Cross Learning between Electronic Structure Theories for Unifying Molecular, Surface, and Inorganic Crystal Foundation Force Fields
Ilyes Batatia, Chen Lin, Joseph Hart et al. (+5 more)
Creating a single unified interatomic potential capable of attaining ab initio accuracy across all chemistry remains a long-standing challenge in computational chemistry and materials science. This work introduces a training protocol for foundation machine-learning interatomic potentials (MLIPs) that bridge molecular, surface, and materials chemistry through cross-domain learning. First, we introduce enhancements to the MACE architecture that improve its performance on chemically diverse databases by increasing weight sharing across chemical elements and introducing non-linear factors into the tensor decomposition of the product basis. Second, we develop a multi-head replay post-training methodology that enables efficient knowledge transfer across diverse chemical domains. By fine-tuning on
datasets at different levels of electronic structure theory, including inorganic
crystals, molecular systems, surface chemistry, and reactive organic chemistry, we demonstrate that a single unified model achieves state-of-the-art performance across several chemical domains. Comprehensive benchmarking reveals superior cross-domain transferability compared with existing specialised and multi-task models, with notable improvements in molecular and surface properties while maintaining state-of-the-art performance in materials-property prediction.
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All authors Ilyes Batatia, Chen Lin, Joseph Hart, Elliott Kasoar, Alin M. Elena, Sam Walton Norwood, Thomas Wolf, Gábor Csányi
Plasma Physics
Robust direct laser acceleration of electrons with flying-focus laser pulses
Talia Meir, Kale Weichman, Alexey Arefiev et al. (+2 more)
Direct
laser acceleration (DLA) offers a compact source of high-charge, energetic electrons for generating secondary radiation or
neutrons. While DLA in high-density
plasma optimizes the energy transfer from a
laser pulse to electrons, it exacerbates nonlinear propagation effects, such as filamentation, that can disrupt the acceleration process. Here, we show that superluminal flying-focus pulses (FFPs) mitigate nonlinear propagation, thereby enhancing the number of high-energy electrons and resulting x-ray yield. Three-dimensional particle-in-
cell simulations show that, compared to a Gaussian pulse of equal energy (1 J) and intensity (2x10^20 W/cm^2), an FFP produces 80x more electrons above 100 MeV, increases the electron cutoff energy by 20%, triples the high-energy x-ray yield, and improves x-ray collimation. These results illustrate the ability of spatiotemporally structured
laser pulses to provide additional control in the highly nonlinear, relativistic regime of
laser-
plasma interactions.
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All authors Talia Meir, Kale Weichman, Alexey Arefiev, John P. Palastro, Ishay Pomerantz
Optics · Cross-listed from cond-mat.mtrl-sci
Terahertz Time-Domain Spectroscopy and Density Functional Theory Analysis of Low-Frequency Vibrational Modes of a Benzoxazolium-Coumarin Donor-pi-Acceptor Chromophore
Sidhanta Sahu, Phalguna Krishna Das Vana, Anupama Chauhan et al. (+5 more)
To elucidate low-frequency vibrational modes, we investigate a benzoxazolium–coumarin (BCO+) donor-pi-acceptor derivative using transmission terahertz time-domain spectroscopy (THz-TDS). The retrieved complex refractive index reveals distinct modes at 0.62, 0.85, 1.30, 1.81, and 2.07 THz. Gas-phase density functional theory (DFT) agrees well with these features and enables assignment of specific intramolecular motions. Together, THz-TDS and DFT identify the characteristic low-frequency modes of BCO+ and suggest their connection to intramolecular charge transfer-relevant
nuclear motions, highlighting that THz-TDS can serve as a sensitive probe of vibrational signatures in donor-pi-acceptor systems.
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All authors Sidhanta Sahu, Phalguna Krishna Das Vana, Anupama Chauhan, Poulami Ghosh, Vijay Sai Krishna Cheerala, Sanyam, C. N. Sundaresan, N. Kamaraju
Fluid Dynamics
Model-Adaptive Simulation of Hierarchical Shallow Water Moment Equations in One Dimension
Rik Verbiest and Julian Koellermeier
Shallow free surface flows are often characterized by both subdomains that require high modeling complexity and subdomains that can be sufficiently accurately modeled with low modeling complexity. Moreover, these subdomains may change in time as the water flows through the domain. This motivates the need for space and time adaptivity in the simulation of shallow free surface flows. In this paper, we develop the first adaptive simulations using the recently developed Shallow Water Moment Equations, which are an extension of the standard Shallow Water Equations that allow for vertically changing velocity profiles by including additional variables and equations. The model-specific modeling complexity of a shallow water moment model is determined by its order. The higher the order of the model, the more variables and equations are included in the model. Shallow water moment models are ideally suited for adaptivity because they are hierarchical such that low-order models and high-order models share the same structure. To enable adaptive simulations, we propose two approaches for the coupling of the varying-order shallow water moment equations at their boundary interfaces. The first approach dynamically updates padded state variables but cannot be written in conservative form, while the second approach uses fixed padded state variable values of zero and reduces to conservative form for conservative moment equations. The switching procedure between high-order models and low-order models is based on a new set of model error
estimators, originating from a decomposition of the high-order models. Numerical results of a dam break and of the collision of a dam-break wave with a smooth wave for different friction parameter values yield accurate results, while achieving speedups up to 40 percent compared to a non-adaptive model with fixed modeling complexity.
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Optics
Illuminating the lantern: coherent, spectro-polarimetric characterisation of a multimode converter
Adam K. Taras, Barnaby R. M. Norris, Christopher Betters et al. (+4 more)
While photonic lanterns efficiently and uniquely map a set of input modes to single-mode outputs (or vice versa), the optical mode transfer
matrix of any particular fabricated device cannot be constrained at the design stage due to manufacturing imperfections. Accurate knowledge of the mapping enables complex sensing or beam control applications that leverage multimode conversion. In this work, we present a characterisation system to directly measure the electric field from a photonic lantern using digital off-axis holography, following its
evolution over a 73 nm range near 1550 nm and in two orthogonal, linear polarisations. We provide the first multi-wavelength, polarisation decomposed characterisation of the principal modes of a photonic lantern. Performance of our testbed is validated on a single-mode fibre then harnessed to characterise a 19-port, multicore fibre fed photonic lantern. We uncover the typical wavelength scale at which the modal mapping evolves and measure the relative dispersion in the device, finding significant differences with idealised simulations. In addition to detailing the system, we also share the empirical mode transfer
matrices, enabling future work in astrophotonic design, computational imaging, device fabrication feedback loops and beam shaping.
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All authors Adam K. Taras, Barnaby R. M. Norris, Christopher Betters, Andrew Ross-Adams, Peter G. Tuthill, Jin Wei, Sergio Leon-Saval
Medical Physics
Analytical Model of Prompt Gamma Timing for Spatiotemporal Emission Reconstruction in Particle Therapy
Julius Werner, Malte Schmidt, Francesco Pennazio et al. (+4 more)
Particle therapy relies on up-to-date knowledge of the stopping power of the patient tissues to deliver the prescribed dose distribution. The stopping power describes the average particle motion, which is encoded in the distribution of
prompt-gamma
photon emissions in time and space. We reconstruct the spatiotemporal emission distribution from multi-detector
Prompt Gamma Timing (PGT) data. Solving this inverse problem relies on an accurate model of the
prompt-gamma transport and detection including explicitly the dependencies on the time of emission and detection. Our previous work relied on Monte-Carlo (MC) based system models. The tradeoff between computational resources and statistical noise in the system model prohibits studies of new detector arrangements and beam scanning scenarios. Therefore, we propose here an analytical system model to speed up recalculations for new beam positions and to avoid statistical noise in the model. We evaluated the model for the MERLINO multi-detector-PGT prototype. Comparisons between the analytical model and a MC-based reference showed excellent agreement for single-detector setups. When several detectors were placed close together and partially obstructed each other, intercrystal scatter led to differences of up to 10 % between the analytical and MC-based model. Nevertheless, when evaluating the performance in reconstructing the spatiotemporal distribution and estimating the stopping power, no significant difference between the models was observed. Hence, the procedure proved robust against the small inaccuracies of the model for the tested scenarios. The model calculation time was reduced by 1500 times, now enabling many new studies for PGT-based systems.
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All authors Julius Werner, Malte Schmidt, Francesco Pennazio, Jorge Roser, Jona Kasprzak, Veronica Ferrero, Magdalena Rafecas
Optics · Cross-listed from cs.CV
Large-FOV RGBD Imaging via Structured PSF Coding in a Bio-inspired Monocentric System
Zongxi Yu, Xiaolong Qian, Shaohua Gao et al. (+4 more)
High-fidelity large-field-of-view (LFOV) 3D sensing, essential for autonomous platforms, is hindered by the coupling of anisotropic off-axis aberrations and the ill-posed nature of
monocular depth estimation. To address this fundamental physical bottleneck, we propose the Bio-inspired Monocentric Imaging (BMI) framework, a holistic co-design integrating a monocentric optical
topology with a physics-aware reconstruction network. By pairing a concentric spherical lens with a hemispherical sensor, our system structurally eliminates coma, astigmatism, and field
curvature. Instead of relying on external modulators or hardware redundancy, we exploit the intrinsic aberration as a deterministic, radially symmetric carrier for depth encoding. Theoretical analysis via the Cramér-Rao Lower Bound confirms that this
topology maintains superior depth sensitivity across the entire FOV. To decode these optical cues, our framework utilizes a dual-head network to jointly recover high-fidelity All-in-Focus images and dense metric depth maps from single-shot captures. The efficacy of this co-design is evaluated through physically-based simulations of field-dependent PSFs across the full optical FOV. On NYU Depth V2, our system achieves a superior balance of image fidelity (31.15dB PSNR) and depth precision (0.161m RMSE). It further maintains consistent reconstruction under spatially varying PSFs sampled across a 120{\deg} optical FOV, mitigating the peripheral degradation observed in conventional wide-field designs. The source code is publicly available at https://github.com/ZongxiYu-ZJU/BMI.
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All authors Zongxi Yu, Xiaolong Qian, Shaohua Gao, Qi Jiang, Yao Gao, Kailun Yang, Kaiwei Wang
Chemical Physics
Reactive capacitance of flat patches of arbitrary shape
Denis S. Grebenkov and Raphael Maurette
We investigate the capacity of a flat partially reactive patch of arbitrary shape to trap independent particles that undergo steady-state
diffusion in the three-dimensional space. We focus on the total flux of particles onto the patch that determines its reactive capacitance. To disentangle the respective roles of the reactivity and the shape of the patch, we employ a spectral expansion of the reactive capacitance over a suitable Steklov
eigenvalue problem. We derive several bounds on the reactive capacitance to reveal its monotonicity with respect to the reactivity and the shape. Two probabilistic interpretations are presented as well. An efficient numerical tool is developed for solving the associated Steklov spectral problem for patches of arbitrary shape. We propose and validate, both theoretically and numerically, a simple, fully explicit approximation for the reactive capacitance that depends only on the surface area and the electrostatic capacitance of the patch. This approximation opens promising ways to access various characteristics of
diffusion-controlled reactions in general domains with multiple small well-separated patches. Direct applications of these results in statistical physics and physical chemistry are discussed.
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Instrumentation and Detectors · Cross-listed from cond-mat.mtrl-sci
Advanced structural characterization of single-walled carbon nanotubes with 4D-STEM
Antonin Louiset, Daniel Förster, Vincent Jourdain et al. (+5 more)
Single wall carbon nanotubes (SWCNT) exhibit remarkable optical and electrical properties making them one of the most promising materials for next generation electronic and optoelectronic devices. Their electronic properties strongly depend on their chirality, i.e., their structural configuration, as well as on the presence and nature of atomic defects. Currently, the lack of versatile and efficient structural characterization techniques limits SWCNT applications. Here, we report how four-dimensional scanning transmission electron microscopy (4D-STEM) can address critical challenges in SWCNT structural analysis. Using modern fast pixelated electron detectors, we were able to acquire rapidly a large number of low noise electron diffraction patterns of SWCNTs. The resulting 4D-STEM data allow to precisely determine the local chirality of multiple nanotubes at once, with limited electron dose (down to 1750 e-/Å^2) and nanometric spatial resolution (down to 3.1 nm). We also show how this approach enables to track the chirality along a single nanotube, while giving access to the strain distribution. Then, we report how 4D-STEM data enable to reconstruct high-resolution images with electron ptychography. With this second approach, structural information can be obtained with atomic scale spatial resolution allowing atomic defect imaging. Finally, we investigate how multi-slice electron ptychography could provide even further insight on nanotube defect structures thanks to its close to 3D imaging capabilities at atomic resolution.
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All authors Antonin Louiset, Daniel Förster, Vincent Jourdain, Saïd Tahir, Nicola Vigano, Jean-Luc Rouvière, Christophe Bichara, Hanako Okuno
Instrumentation and Detectors
Characterization of the Li$_2$WO$_4$ crystal as a cryogenic scintillating calorimeter
D. L. Helis, A. Melchiorre, S. Nagorny et al. (+16 more)
A wide range of scintillating bolometers is under investigation for applications in the search for rare events and processes beyond the Standard Model. In this work, we report the first measurement of a natural, non-molybdenum-doped, lithium tungstate (LWO)
crystal operated underground as a scintillating cryogenic calorimeter. The detector achieved a baseline energy resolution of 0.5 keV RMS with a low-energy threshold of about 1.5 keV. The simultaneous readout of heat and light enabled particle identification, revealing a clear separation between $\beta/\gamma$, $\alpha$, and
nuclear recoil populations above 300 keV, with a light-yield-based particle discrimination better than $6\sigma$. These results, fully comparable with those achieved with other compounds in the field, demonstrate that LWO is a promising candidate for rare-event searches. In particular, the combination of excellent
radio-purity (with U/Th levels below 0.5 mBq/kg) and sensitivity to
neutron interactions via the $^6$Li(n,$\alpha$)$^3$H reaction makes this material an attractive option for next-generation experiments on dark matter, coherent elastic
neutrino-
nucleus scattering, and
spin-dependent interactions.
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All authors D. L. Helis, A. Melchiorre, S. Nagorny, M. Noia, L. Pagnanini, S. Pirro, A. Puiu, G. Benato, P. Carniti, R. Elleboro, P. Gambacorta, C. Gotti, V. D. Grigorieva, S. Nisi, E. Olivieri, G. Pessina, S. Piacentini, M. Shafiee, V. N. Shlegel
Optics
Femtosecond self-diffraction as a measure of the nonlinear response spectrum
Luca Assogna, Giovanna Salvitti, Matteo Silvestri et al. (+11 more)
Self diffraction is a four-wave mixing process proportional to the square modulus of third-order nonlinearity susceptibility $\chi^{(3)}$, which is related to the material's electronic and thermal properties. In this study, we investigate the wavelength dependence of the self-diffracted signal generated by a femtosecond pulsed
laser in a dye solution to directly evaluate the electronic third-order nonlinear susceptibility spectrum. By accounting for absorption effects and phase matching conditions, we determine the $\vert\chi^{(3)}\vert$ for different concentrations. Experimental results complemented with theoretical predictions, show that in the low absorption and thin sample limits, the signal reproduce the $\vert\chi^{(3)}\vert$ spectral profile. These findings demonstrate the feasibility of measuring nonlinear susceptibility spectra arising solely from the bound-electronic response across a wide spectral range and for various compounds.
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All authors Luca Assogna, Giovanna Salvitti, Matteo Silvestri, Federico Perrella, Riccardo Mincigrucci, Cristian Soncini, Elena Incerto, Armando Carlone, Majed Chergui, Claudio Masciovecchio, Paola Benassi, Andrea Marini, Davide Tedeschi, Carino Ferrante
Instrumentation and Detectors
Development of a new phase-retrieval algorithm from a single-shot image for X-ray schlieren microscopy
Ryutaro Nishimura, Yoshio Suzuki, Hiroshi Sugiyama et al. (+5 more)
In this paper, a new phase-
retrieval algorithm from an X-ray schlieren image is proposed. The schlieren method allows phase-contrast imaging with an objective lens and a knife-edge filter placed at the back focal plane of the objective. This method finds a wide range of applications in the visible-light region for transparent specimen visualization. The schlieren contrast does not directly correspond to the phase shift. However, the phase map can be reconstructed from a single-shot schlieren image of a transparent and weak-phase object using the filtered
Fourier transform method. A proof-of-principle experiment was performed in the hard-X-ray region at the AR-NE1A beamline of the
Photon Factory facility at the High Energy Accelerator Research Organization (KEK).
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All authors Ryutaro Nishimura, Yoshio Suzuki, Hiroshi Sugiyama, Daisuke Wakabayashi, Yuki Shibazaki, Keiichi Hirano, Noriyuki Igarashi, Nobumasa Funamori
Medical Physics
Photoacoustics on the go: An Embedded Photoacoustic Sensing Platform
Talia Xu, Caitlin Smith, Charles Lo et al. (+3 more)
Several centimeters below the skin lie multiple biomarkers, such as glucose, oxygenation, and blood flow. Monitoring these biomarkers regularly and in a non-invasive manner would enable early insight into metabolic status and vascular health. Currently, there are only a handful of non-invasive monitoring systems. Optical methods offer molecular specificity (i.e., multi-biomarker monitoring) but have shallow reach (a few millimeters); ultrasound penetrates deeper but lacks specificity; and MRI is large, slow, and costly. Photoacoustic (PA) sensing combines the best of optical and ultrasound methods. A
laser transmitter emits pulses that are absorbed by different molecules, providing specificity. These light pulses generate pressure changes that are captured by an ultrasound receiver, providing depth. Photoacoustic sensing is promising, but the current platforms are bulky, complex, and costly. We propose the first embedded PA platform. Our contributions are fourfold. First, inspired by
LiDAR technology, we propose a novel transmitter that emits pulses similar to those in the state-of-the-art (SoA), but instead of using high-voltage sources and complex electronic interfaces, we use a simple low-power microcontroller (MCU). Second, we carry out a thorough analysis of our custom transmitter and a commercial system. Third, we build a basic ultrasound receiver that is able to process the faint signal generated by our transmitter. Lastly, we compare the performance of our platform against a SoA commercial system, and show that we can detect glucose and (de)oxygenated hemoglobin in two controlled solution studies. The resulting signal characteristics indicate a plausible path toward noninvasive, real-time, at-home sensing relevant to diabetes care. More broadly, this platform lays the groundwork for translating the promise of PA sensing into a broader practical reality.
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All authors Talia Xu, Caitlin Smith, Charles Lo, Jami Shepherd, Gijs van Soest, Marco Zuniga
Atomic Physics · Cross-listed from quant-ph
Encoding computationally hard problems in triangular Rydberg atom arrays
Xi-Wei Pan, Huan-Hai Zhou, Yi-Ming Lu et al. (+1 more)
Rydberg atom arrays are a promising platform for
quantum optimization, encoding computationally hard problems by reducing them to independent set problems with unit-disk graph
topology. In Nguyen et al., PRX
Quantum 4, 010316 (2023), a systematic and efficient strategy was introduced to encode multiple problems into a special unit-disk graph: the King's subgraph. However, King's subgraphs are not the optimal choice in two dimensions. Due to the power-law decay of Rydberg interaction strengths, the approximation to unit-disk graphs in real devices is poor, necessitating post-processing that lacks physical interpretability. In this work, we develop an encoding scheme that can universally encode computationally hard problems on triangular
lattices, based on our innovative automated gadget search strategy. Numerical simulations demonstrate that
quantum optimization on triangular
lattices reduces independence-constraint violations by approximately two orders of magnitude compared to King's subgraphs, substantially alleviating the need for post-processing in experiments.
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All authors Xi-Wei Pan, Huan-Hai Zhou, Yi-Ming Lu, Jin-Guo Liu
Fluid Dynamics
Sub-cavity Induced Passive Control of Confined Supersonic Cavity Flows Across Varying Freestream Mach Numbers
Sreejita Bhaduri, Mohammed Ibrahim Sugarno and Ashoke De
The self-sustaining oscillations in cavity flows enhance fluid mixing and promote energy and momentum transport. However, the associated oscillation frequencies can amplify acoustic loading, potentially damaging surrounding structures. Hence, understanding cavity dynamics across geometries and freestream conditions and developing strategies to regulate these oscillations without compromising performance are essential. This study examines the influence of sub-cavities placed at the front and aft walls of a cavity confined by a top wall with a deflection angle of 2.29 degrees, under freestream Mach numbers 2 and 3. Large eddy simulations (LES) are performed using OpenFOAM, and unsteady pressure signals are analyzed through spectral methods. Results show that the aft-wall sub-cavity most effectively suppresses the dominant oscillation at Mach number 2, while the front-wall sub-cavity achieves greater suppression at Mach number 3. Density gradient (numerical Schlieren) and vorticity fields, normalized acoustic impedance, and global wavelet power reveal the mechanisms responsible for this attenuation. At Mach number 2, the aft-wall sub-cavity entrains mass and disrupts the convective feedback loop. At Mach number 3, the front-wall sub-cavity weakens the hydrodynamic-acoustic coupling near the leading edge, disrupting the compressibility-driven feedback. These configurations suppress dominant frequencies by 5.45 and 23.4 percent for Mach numbers 2 and 3, respectively. Cross-correlation between pressure probes and Dynamic Mode Decomposition (DMD) further confirm the mechanisms behind the observed frequency suppression
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Optics
Moire-enabled optical vortex with tunable topological charge in twisted bilayer photonic crystals
Tiancheng Zhang, Li Lei, Changhao Ding et al. (+11 more)
The orbital angular momentum (OAM) of light is a versatile degree of freedom with transformative impact across optical communication, imaging, and micromanipulation. These applications have motivated a growing demand for compact, reconfigurable
vortex arrays with tunable topological charge, yet integrating these functionalities into nanophotonic platforms remains elusive. Among possible strategies to meet this challenge is exploiting the twist degree of freedom in layered structures, which enables both emerging moire physics and unprecedented reconfigurability of photonic and electronic properties. Here, we harness these capabilities in twisted
bilayer moire photonic
crystals (TBMPCs) to realize
vortex array generation with tunable OAM, demonstrated both analytically and experimentally. Central to this advancement is a new class of quasi-bound state in the continuum: Bessel-type modes emerging from moire-induced interlayer coupling, which generate
vortex beams with tailored spiral phase distributions. We experimentally demonstrate
vortex beams spanning eight OAM orders, from -3 to 4, and achieve selective excitation of distinct topological charges at a fixed telecommunication wavelength by tuning the interlayer separation and twist angle. Furthermore, localized Bessel-type modes at AA stacking regions can be excited nonlocally across the moire superlattice, enabling
vortex array generation. Our work offers new insights into moire physics and introduces an innovative approach for future multiplexing technology integrating OAM, wavelength, and spatial division.
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All authors Tiancheng Zhang, Li Lei, Changhao Ding, Fanhao Meng, Qicheng Jiang, Lijie Li, Scott Dhuey, Jingze Yuan, Zhengyan Cai, Yi Li, Jingang Li, Costas P. Grigoropoulos, Haoning Tang, Jie Yao