Physics and Society · Cross-listed from econ.GN
Immigrant Residential Segregation in Europe: A Comparative Study of Spatial Segregation Patterns in Urban Areas across 30 Countries
Tobias Rüttenauer, Kasimir Dederichs and David Kretschmer
Immigrant residential segregation can profoundly shape access to opportunities, immigrant integration, and inter-group relations. Yet we lack systematic evidence on how segregation varies across Europe, and what structural factors are associated with these patterns. This study addresses the gap by focusing on two questions: (i) how does immigrant-native segregation vary across urban areas in Europe, and (ii) which urban area- and country-level characteristics are consistently linked to segregation? Using harmonised 1x1 km grid-level data from the 2021/22 census, we calculate spatially weighted Dissimilarity Indices for all 717 Functional Urban Areas (FUAs) across 30 European countries. We combine these measures with rich data on demographics, the economy, housing, immigrant populations, and policy. To identify robust correlates of segregation, we apply a Specification Curve Analysis across 16,164 regression models. Segregation is higher in Western and Northern Europe compared to most of Eastern and Southern Europe. Moreover, we show that segregation is heavily driven by macro-spatial dynamics between diverse urban cores and relatively homogeneous suburban areas. At the urban area level, segregation is systematically linked to the demographic composition and spatial distribution of the local population, economic conditions, housing
market characteristics, as well as the composition of the immigrant population. At the national level, established immigrant destinations are more segregated, while migration and integration policies are not consistently linked to segregation. These findings offer the most comprehensive comparative assessment of immigrant segregation across Europe to date, revealing how structural conditions relate to spatial integration.
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Optics · Cross-listed from quant-ph
Comparing Homodyne and Heterodyne Tomography of Quantum States of Light
Rhea P. Fernandes, Andrew J. Pizzimenti, Christos N. Gagatsos et al. (+1 more)
Non-Gaussian
quantum states are critical resources in photonic
quantum information processing, rendering their generation and characterization of increasing importance in
quantum optics. In this work, we theoretically and numerically analyze the relative efficiency of homodyne versus heterodyne measurements for reconstructing non-Gaussian states, a major outstanding question in continuous-variable
tomography. Combining a Fisher information-based formalism with simulated experiments, we find homodyne
tomography to outperform heterodyne measurements for all non-Gaussian states tested, although the separation between the two modalities proves significantly narrower than suggested by the asymptotic Cramer-Rao lower bound. Our results should find use for optimizing measurement strategies in practical continuous-variable
quantum systems.
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All authors Rhea P. Fernandes, Andrew J. Pizzimenti, Christos N. Gagatsos, Joseph M. Lukens
History and Philosophy of Physics · Cross-listed from quant-ph
Subsystems (in)dependence in GIE proposals
Nicolas Boulle and Guilherme Franzmann
Recent proposals suggest that detecting
entanglement between two spatially superposed masses would establish the
quantum nature of
gravity. However, these gravitationally induced
entanglement (GIE) experiments rely on assumptions about subsystem independence. We sharpen the theoretical underpinnings of such proposals by examining them through the lens of algebraic
quantum field theory (AQFT), distinguishing distinct operational and algebraic notions of independence. We argue that state and measurement independence of subsystems, essential to the experimental logic, is nontrivial in the presence of gauge constraints and gravitational dressing. Using gravitationally dressed fields, we recall that commutation relations between spacelike separated observables are nontrivial, undermining strict
Hilbert space factorization. We further explore the implications for
entanglement witnesses, investigating the Tsirelson bound when subsystem
algebras fail to commute, and showing that the Tsirelson bound persists for a suitably symmetrized CHSH observable even though the operational status of such "joint" observables becomes delicate when commensurability fails. Our analysis highlights how even within linearized covariant
quantum gravity, violations of microcausality may affect both the interpretation, modelling, and design of proposed laboratory tests of
quantum gravity, despite remaining negligible for current experimental regimes. Although we consider GIE-style protocols as a concrete case study, the subsystem-independence issues we highlight are generic to low-energy (perturbative)
quantum gravity. Finally, we derive estimates for dressing-induced microcausality violations, which suggest a complementary avenue to current proposals: in principle, bounding dressing-induced microcausality violations themselves as a probe of the
quantum nature of
gravity.
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Physics and Society
Irrelevant carrots and non-existent sticks: trust, governance, and security in the transition to quantum-safe systems
Ailsa Robertson, Siân Brooke, Sebastian De Haro et al. (+1 more)
Quantum computing poses an urgent and widely recognised threat to global cybersecurity, enabling encrypted government, financial, and healthcare data harvested today to be decrypted in the near future. Transitioning to
quantum-safe cryptography is therefore essential, demanding coordinated action across a complex, multi-actor innovation system. Drawing on insights from an expert workshop in Amsterdam, this study develops a socially informed
vision for a
quantum-safe future and analyses the current innovation landscape to identify critical gaps and the actions needed to address them. We map twelve key actor groups involved in the migration process, finding that regulators exert the strongest direct influence, while standardisation bodies play a crucial indirect role. This research provides one of the first system-level mappings of actors, influence pathways and governance responsibilities shaping the
quantum-safe transition, revealing several responsibilities with unclear ownership. Although centred on the Netherlands, our findings are applicable to other national contexts navigating
quantum-safe transitions.
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All authors Ailsa Robertson, Siân Brooke, Sebastian De Haro, Christian Schaffner
Physics and Society
Generating temporal networks with the Ascona model
Samuel Koovely
We introduce a queueing-based sampling framework for continuous-time temporal networks. We focus on a Markovian parametrization in which link start times follow a homogeneous Poisson process and link durations are exponentially distributed. We derive
stochastic properties of the resulting link streams and exploit them to generate synthetic temporal networks with controllable smoothness and prescribed event patterns, relevant for the validation and interpretation of methods for community, scale, change-point, and periodicity detection. By coupling this temporal mechanism with block-structured endpoint distributions, we obtain a continuous-time analogue of
stochastic block models. We also discuss extensions of the framework, including discrete-time and instantaneous-contact limits.
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Physics and Society
Fairness, Travel, and Market Potential: An Optimization Framework for NBA Expansion
Ali Hassanzadeh, Morteza Davari and Dries Goossens
The potential expansion of the National Basketball Association (NBA) to 32 teams raises the question of how to restructure its conferences and divisions while balancing travel efficiency,
fairness in team travel burdens, and commercial exposure. This study provides a quantitative framework for expansion planning. We develop two optimization models: one minimizing total travel distance and another following the Kalai-Smorodinsky (KS) proportional-improvement principle. The KS model maximizes the smallest normalized travel improvement between a team's fixed reference and individual ideal. Both models incorporate an opponent-exposure constraint to account for commercial considerations, and take into account road trips when measuring travel distance. Using data from all 30 current franchises and six candidate cities (Seattle, Las Vegas, Montreal, Vancouver, Tampa, and Mexico City), we evaluate 15 pairwise expansion scenarios under alternative season lengths and divisional formats. In the 30-team comparison, KS strikes a good balance between overall travel efficiency and
fairness across teams, giving greater
attention to individual travel burdens while keeping total travel close to the distance-minimizing solution. The expansion results show that travel requirements depend jointly on the candidate city pair and the competition format, highlighting the need to assess expansion and realignment together. Our study offers a flexible decision support framework for league executives, policymakers, and sports economists. It makes the trade-offs between total travel, individual gains, and opponent exposure explicit, providing evidence-based guidance for strategic league design.
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Atmospheric and Oceanic Physics · Cross-listed from cs.LG
Physics-Informed Lightweight Machine Learning for Aviation Visibility Nowcasting Across Multiple Climatic Regimes
Marcelo Cerda Castillo
Short-term prediction (nowcasting) of low-visibility and precipitation events is critical for aviation safety and operational efficiency. Current operational approaches rely on computationally intensive numerical weather prediction guidance and human-issued TAF products, which often exhibit conservative biases and limited temporal resolution. This study presents a lightweight gradient boosting framework (XGBoost) trained exclusively on surface observation data (METAR) and enhanced through physics-guided feature engineering based on thermodynamic principles. The framework is evaluated across 11 international airports representing distinct climatic regimes (including SCEL, KJFK, KORD, KDEN, SBGR, and VIDP) using historical data from 2000 to 2024. Results suggest that the model successfully captures underlying local physical processes without manual configuration. In a blind comparative evaluation against operational TAF forecasts, the automated model achieved substantially higher detection rates at tactical horizons (3 hours), with a 2.5 to 4.0 times improvement in recall while reducing false alarms. Furthermore, SHAP analysis reveals that the model performs an implicit reconstruction of local physical drivers (advection, radiation, and subsidence), providing actionable explainability for operational situational awareness. Keywords: aviation meteorology; physics-guided machine learning; explainable artificial intelligence; lightweight machine learning; nowcasting; METAR; TAF verification; edge computing
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Physics and Society
An evacuation simulator for pedestrian dynamics based on the Social Force Model
Julián López, Virginia Mazzone, M. Leticia Rubio Puzzo et al. (+1 more)
The evacuation of pedestrians from enclosed spaces represents a key problem in safety engineering and infrastructure design. Analyzing the collective dynamics that emerge during evacuation processes requires simulation tools capable of capturing individual interactions and spatial constraints realistically. In this work, we present SiCoBioNa, an open-source evacuation simulator based on the Social Force Model (SFM). The software provides an intuitive graphical interface that allows users to configure pedestrian properties, spatial geometries, and initial conditions without requiring prior expertise in numerical modeling techniques. The SFM framework enables the representation of goal-oriented motion, interpersonal interactions, and interactions with fixed obstacles. The simulator generates both quantitative data and visual outputs, facilitating the analysis of evacuation dynamics and the evaluation of different spatial configurations. Due to its modular and extensible design, SiCoBioNa serves as a reproducible research tool for studies on pedestrian dynamics providing practical support for evacuation planning.
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All authors Julián López, Virginia Mazzone, M. Leticia Rubio Puzzo, Juan Cruz Moreno
Chemical Physics
A Cartesian-3j Framework for Machine Learning Interatomic Potentials
Zemin Xu, Chenyu Wu, Wenbo Xie et al. (+1 more)
Machine learning interatomic potentials (MLIPs) have brought substantial gains in the extrapolation capability in computational chemistry. However, most equivariant models are typically built with spherical tensors (STs), while Cartesian tensor formulations remain less developed despite their natural
alignment with atomic coordinates and tensorial targets. In this work, we develop a Cartesian framework for irreducible Cartesian tensors (ICTs) by introduce the Cartesian-3j symbol and Cartesian Generalized Clebsch-Gordan Coefficients, which serve as direct analogues of the Wigner-3j symbol and Generalized Clebsch-Gordan coefficients defined for ST coupling. We extend the e3nn library to support ICT product, and use this framework to build Cartesian counterparts of MACE, NequIP, and Allegro, allowing the first controlled comparison where architectures are held fixed and only the tensor basis is changed. Our experiments show that irreducible Cartesian models can achieve accuracy comparable to spherical counterparts, but direct Cartesianization incurs unfavorable compute and
memory scaling, motivating dedicated Cartesian architectural choices. Leveraging ICTs and our framework, we introduce TACE-v1-OAM-M and demonstrate that it achieves competitive performance on Matbench Discovery compared to state-of-the-art ST models.
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All authors Zemin Xu, Chenyu Wu, Wenbo Xie, P. Hu
Chemical Physics
Multimer Embedding for Molecular Crystals Utilizing up to Tetramer Interactions
Alexander List, A. Daniel Boese and Johannes Hoja
Molecular
crystals possess a highly complex crystallographic landscape which in many cases results in the experimental observation of multiple
crystal structures for the same compound. Accurate results can often be obtained for such systems by employing periodic density functional theory using hybrid functionals; however, this is not always computationally feasible. One possibility to circumvent these expensive periodic calculations is the utilization of multimer
embedding methods. Therein, the fully periodic
crystal is described at a lower level of theory, and subsequently monomer energies, dimer interaction energies, etc. are corrected via high-level calculations. In this paper, we further extend such a multimer
embedding approach by one multimer order for all investigated properties, allowing us to compute
lattice energies up to the tetramer
embedding level, and atomic forces, the stress tensor, and harmonic
phonons up to the trimer level. We test the significance of including these higher-order multimers by
embedding PBE0+MBD multimers into periodic PBE+MBD calculations utilizing the X23
benchmark set of molecular
crystals and comparing the results to explicit periodic PBE0+MBD calculations. We show that tetramer interactions systematically improve the
lattice energy approximation and explore multiple possibilities for multimer selection. Furthermore, we confirm that trimer interactions are crucial for the description of the stress tensor, yielding
cell volumes within 1 % of those of PBE0+MBD. Subsequently, this also results in an improvement of the description of vibrational properties, giving on average gamma point frequencies within 1.3 wave numbers and vibrational free energies within 0.3 kJ/mol of the PBE0+MBD results.
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Applied Physics · Cross-listed from cond-mat.other
Photonics of topological magnetic textures
Vakhtang Jandieri, Ramaz Khomeriki, Daniel Erni et al. (+4 more)
Topological textures in magnetically ordered materials are important case studies for fundamental research with promising applications in data science. They can also serve as photonic elements to mold electromagnetic fields endowing them with features inherent to the
spin order, as demonstrated analytically and numerically in this work. A self-consistent theory is developed for the interaction of spatially structured electromagnetic fields with non-collinear, topologically non-trivial
spin textures. A tractable numerical method is designed and implemented for the calculation of the formed
magnetic/photonic textures in the entire simulation space. Numerical illustrations are presented for scattering from point-like singularities, i.e. Bloch points, in the magnetization vector fields, evidencing that the geometry and
topology of the
magnetic order results in photonic fields that embody orbital angular momentum, chirality as well as magnetoelectric densities. Features of the scattered fields can serve as a fingerprint for the underlying
magnetic texture and its dynamics. The findings point to the potential of topological
magnetic textures as a route to molding photonic fields.
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All authors Vakhtang Jandieri, Ramaz Khomeriki, Daniel Erni, Nicolas Tsagareli, Qian Li, Douglas H. Werner, Jamal Berakdar
Atomic Physics
Electric field diagnostics in a continuous rf plasma using Rydberg-EIT
Bineet Dash, Xinyan Xiang, Dingkun Feng et al. (+2 more)
We present a non-invasive spectroscopic technique to measure electric fields in
plasma, leveraging large polarizabilities and Stark shifts of Rydberg atoms. Rydberg Stark shifts are measured with high precision using narrow-linewidth
lasers via Electromagnetically Induced Transparency (EIT) of rubidium vapor seeded into a continuous, inductively coupled
radio-frequency (rf)
plasma in a few mTorr of argon gas. Without
plasma, the Rydberg-EIT spectra exhibit rf modulation sidebands caused by electric- and
magnetic-dipole transitions in the rf drive coil. With the
plasma present, the rf modulation sidebands vanish due to screening of the rf drive field from the
plasma interior. The lineshapes of the EIT spectra in the
plasma reflect the
plasma's Holtsmark microfield distribution, allowing us to determine
plasma density and collisional line broadening over a range of pressures and rf drive powers. The work is expected to have applications in non-invasive spatio-temporal electric-field diagnostics of low-pressure
plasma,
plasma sheaths, process
plasma and dusty
plasma.
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All authors Bineet Dash, Xinyan Xiang, Dingkun Feng, Eric Paradis, Georg Raithel
Classical Physics · Cross-listed from cond-mat.mes-hall
Signatures of real-space geometry, topology, and metric tensor in quantum transport in periodically corrugated spaces
Benjamin Schwager, Theresa Appel and Jamal Berakdar
The motion of a
quantum particle constrained to a two-dimensional non-compact Riemannian
manifold with non-trivial metric can be described by a flat-space Schroedinger-type equation at the cost of introducing local mass and metric and geometry-induced effective potential with no classical counterpart. For a metric tensor periodically modulated along one dimension, the formation of bands is demonstrated and transport-related quantities are derived. Using S-
matrix approach, the
quantum conductance along the
manifold is calculated and contrasted with conventional
quantum transport methods in flat spaces. The
topology, e.g. whether the
manifold is simply connected, compact or non-compact shows up in global, non-local properties such as the Aharonov-Bohm phase. The results vividly demonstrate emergent phenomena due to the interplay of reduced-dimensionality, particles
quantum nature, geometry, and
topology.
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Instrumentation and Detectors
A MAPS Detector for High Resolution Low Dose EBSD
Barnaby D.A. Levin, Kalani Moore, Nicolò M. Della Ventura et al. (+3 more)
The use of highly sensitive pixelated direct detectors has dramatically improved the performance of high energy instrumentation such as transmission electron microscopy. Here, we describe a recently developed monolithic active pixel sensor designed for low energy scanning electron microscopy applications. This detector enables electron backscatter diffraction (EBSD) at lower energies and dose than are accessible with existing scintillator-coupled detectors, expanding grain orientation mapping capabilities to materials such as ceramics that are poor electron conductors. The high detector sensitivity allows collection of rich diffraction information - providing dislocation defect contrast that is otherwise not accessible via EBSD. Indeed, even the energy of single electron interaction events can be measured with this detector, which we demonstrate to energy filter diffraction patterns revealing details of how diffraction occurs at low energy.
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All authors Barnaby D.A. Levin, Kalani Moore, Nicolò M. Della Ventura, McLean P. Echlin, Tresa M. Pollock, Daniel S. Gianola
Physics Education
Enhancing Kinematics Understanding Through a Real-Time Graph-Based Motion Video Game
Mateo Dutra, Marcos Abreu, Martín Monteiro et al. (+4 more)
Kinematics is a core topic in early physics courses, yet students often struggle to interpret motion and its graphical representations. To tackle these difficulties, we developed MissionMotion, a physical-computational videogame where students reproduce target motion graphs using real-time data from their own movements or from sensors connected through micro:bit or Arduino. The system displays both the target and the user-generated graph, providing immediate visual feedback and a score based on similarity. We piloted the environment with ninth-grade students in different school contexts and evaluated their experience using the MEEGA+ instrument. The results show strong engagement, positive perceptions of usability, and evidence that the game promotes reflection on motion graphs in ways that rarely emerge in traditional lessons. MissionMotion runs on any web-enabled device and all materials are openly available, offering teachers an accessible tool to integrate experimentation, computational thinking, and playful learning into physics classrooms.
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All authors Mateo Dutra, Marcos Abreu, Martín Monteiro, Silvia Sguilla, Cecilia Stari, Alvaro Suarez, Arturo C. Marti
Optics
Experimental Measurement of Enhanced Group Delay Silicon Photonic Waveguides Indicative of the Frozen Mode Regime Around the Stationary Inflection Point
Nathaniel Furman, Albert Herrero-Parareda, Anthony Rapp et al. (+6 more)
The dispersion engineering of periodic silicon photonic waveguides presents opportunities for significant group delay enhancement compared to uniform waveguides of comparable length. We describe the spectral response characteristics for measured devices and compare their properties to modeled data. These waveguides support the frozen mode regime (FMR) around near infrared wavelengths and are expected to show enhanced group delays around the FMR resonances. Measurements of fabricated devices provide evidence for enhanced delays and spectral properties associated with the FMR. We study how perturbations to the waveguide model impact agreement with measurements and its meaning for these devices operating in the FMR.
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All authors Nathaniel Furman, Albert Herrero-Parareda, Anthony Rapp, Ilya Vitebskiy, Ricky Gibson, Bradley J. Thompson, Dean P. Brown, Robert Bedford, Filippo Capolino
Fluid Dynamics
Rayleigh-Bénard thermal convection in emulsions: a short review
Francesca Pelusi, Andrea Scagliarini, Mauro Sbragaglia et al. (+2 more)
Thermally driven emulsions arise in a broad range of natural and industrial contexts, yet their fundamental physical understanding remains only partially established. Emulsions exhibit a complex, concentration-dependent rheology, ranging from Newtonian (dilute emulsions) to yield-stress (concentrated emulsions). In buoyancy-driven flows, the complex structure and rheology of the emulsion are strongly coupled to convective flows, giving rise to fascinating and non-trivial phenomena involving stability, transient dynamics, and morphological
evolution of the system. We review recent progress on thermally driven emulsions in the celebrated Rayleigh-Bénard configuration, offering new perspectives on the behaviour of soft materials in thermal convection.
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All authors Francesca Pelusi, Andrea Scagliarini, Mauro Sbragaglia, Massimo Bernaschi, Roberto Benzi
Physics and Society
The Colombian legislative process, 2014-2025: networks, topics, and polarization
Juan Sosa, Brayan Riveros and Emma J. Camargo-Díaz
The legislative output of Colombia's House of Representatives between 2014 and 2025 is analyzed using 4,083 bills. Bipartite networks are constructed between parties and bills, and between representatives and bills, along with their projections, to characterize co-sponsorship patterns, centrality, and influence, and to assess whether political polarization is reflected in legislative collaboration. In parallel, the content of the initiatives is studied through semantic networks based on co-occurrences extracted from short descriptions, and topics by party and period are identified using a
stochastic block model for weighted networks, with additional comparison using Latent Dirichlet Allocation. In addition, a
Bayesian sociability model is applied to detect terms with robust connectivity and to summarize discursive cores. Overall, the approach integrates relational and semantic structure to describe thematic shifts across administrations, identify influential actors and collectives, and provide a reproducible synthesis that promotes transparency and citizen oversight of the legislative process.
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Computational Physics · Cross-listed from cond-mat.mtrl-sci
Thermodynamical study of N$_2$ clathrate hydrate from DFT calculations
L. Martin-Gondre, V. Meko Fotso, C. Métais et al. (+3 more)
Thermodynamic stability of N$_2$ clathrate hydrates in the sI and sII structures is investigated using density functional theory with several exchange-correlation functionals, explicitly accounting for composition (cage occupancies) and pressure at T = 0 K. Among the tested functionals, revPBE-D3(0) best reproduces experimental
lattice parameters and bulk
moduli B$_0$ . Energetic analyses confirm the strong impact of large cage double occupancy on sI, whereas the convex-hull results show that sI with single occupancy remains thermodynamically stable up to $\sim$ 0.8 GPa alongside sII with single occupancy. Increasing pressure then stabilizes sII with double occupancy, consistent with its larger large-cage volume and lower framework strain. These results provide a coherent, first-principles thermodynamic framework for N$_2$ hydrate stability and a baseline for finite-temperature extension.
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All authors L. Martin-Gondre, V. Meko Fotso, C. Métais, A. Patt, J. Ollivier, A. Desmedt
Computational Physics · Cross-listed from cond-mat.stat-mech
Efficient Monte Carlo sampling of metastable systems using non-local collective variable updates
Christoph Schönle, Davide Carbone, Marylou Gabrié et al. (+2 more)
Monte Carlo simulations are widely used to simulate complex molecular systems, but standard approaches suffer from metastability. Lately, the use of non-local proposal updates in a collective-variable (CV) space has been proposed in several works. Here, we generalize these approaches and explicitly spell out an
algorithm for non-linear CVs and underdamped Langevin dynamics. We prove reversibility of the resulting scheme and demonstrate its performance on several numerical examples, observing a substantial performance increase compared to methods based on overdamped Langevin dynamics as considered previously. Advances in generative machine-learning-based proposal samplers now enable efficient sampling in CV spaces of intermediate dimensionality (tens to hundreds of variables), and our results extend their applicability toward more realistic molecular systems.
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All authors Christoph Schönle, Davide Carbone, Marylou Gabrié, Tony Lelièvre, Gabriel Stoltz
Medical Physics
A parallel, pipeline-based online analysis system for Interaction Vertex Imaging
Devin Hymers, Sebastian Schroeder, Olga Bertini et al. (+4 more)
Objective Interaction vertex imaging (IVI) is used for range monitoring in carbon ion radiotherapy, detecting depth differences between Bragg peak positions. Online range monitoring, which provides feedback during beam delivery, is particularly desirable, creating an opportunity to detect range errors before the treatment fraction is completed. Incorporating online range monitoring into clinical workflows may therefore improve the safety and consistency of radiotherapy. Approach The data analysis system was broken into a task-parallel pipeline approach, to allow multiple analysis stages to occur concurrently, beginning during acquisition. Computationally-expensive operations were further parallelized to reduce bottleneck effects. Data collected from irradiation of homogeneous plastic phantoms was replayed at the same rate it was initially acquired, to mimic data acquisition, and the time required to determine a range shift was measured. Main Results With an optimized pipeline, the delay between the end of irradiation and the determination of a range shift is consistently less than 200 ms. The majority of this time is associated with the final range shift determination, with a minor effect from the time required to analyze the last data packet. The most significant contribution to an optimized analysis workflow is the formation of clusters, requiring almost 50% of compute time. Significance This system is the first IVI implementation to achieve clinically-relevant online analysis times. The 200 ms time required to determine a range shift is less than the time required to accelerate a new spill in a synchrotron, and is comparable to the time required for reacceleration if multiple energies are delivered in the same spill. Clinical implementation of online range monitoring would allow treatment to be quickly paused or aborted if significant range errors are detected.
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All authors Devin Hymers, Sebastian Schroeder, Olga Bertini, Johann Heuser, Joerg Lehnert, Christian Joachim Schmidt, Dennis Mücher
Medical Physics
Clinical beam test of inter- and intra-fraction relative range monitoring in carbon ion radiotherapy
Devin Hymers, Sebastian Schroeder, Olga Bertini et al. (+5 more)
Interaction Vertex Imaging (IVI) is used for range monitoring (RM) in carbon ion radiotherapy. The purpose of RM is to measure the Bragg peak (BP) position for each contributing beam, and detect any changes. Currently, there is no consensus on a clinical RM method, the use of which would improve the safety and consistency of treatment. The prototype filtered IVI (fIVI) Range Monitoring System is the first system to apply large-area and high-rate-capable silicon detectors to IVI. Two layers of these detectors track
prompt secondary fragments for use in RM. This device monitored 16 cm and 32 cm diameter cylindrical plastic phantoms irradiated by clinical carbon ion beams at the Heidelberg Ion Beam Therapy Center. Approximately 20 different BP depths were delivered to each phantom, with a minimum depth difference of 0.8 mm and a maximum depth difference of 51.9 mm and 82.5 mm respectively. For large BP range differences, the relationship between the true depth difference and that measured by fIVI is quadratic, although for small differences, the deviation from a linear relationship with a slope of 1 is negligible. RM performance is strongly dependent on the number of tracked particles, particularly in the clinically-relevant regime. Significant performance differences exist between the two phantoms, with millimetric precision at clinical doses being achieved only for the 16 cm phantom. The performance achieved by the prototype fIVI Range Monitoring System is consistent with previous investigations of IVI, despite measuring at more challenging shallow BP positions. Further significant improvements are possible through increasing the sensitive area of the tracking system beyond the prototype, which will both allow an improvement in precision for the most intense points of a scanned treatment plan and expand the number of points for which millimetric precision may be achieved.
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All authors Devin Hymers, Sebastian Schroeder, Olga Bertini, Stephan Brons, Johann Heuser, Joerg Lehnert, Christian Joachim Schmidt, Dennis Mücher
Data Analysis and Statistics
Applying Gaussian Mixture Models to Track Reconstruction in Inelastic Scattering Experiments with Active Targets
A. Arokiaraj, M.B. Latif, R. Raabe et al. (+2 more)
Active targets such as ACTAR TPC are well suited for studying
giant resonances in unstable
nuclei via inelastic scattering in inverse kinematics. A key challenge in such measurements is the detection of low-energy ejectiles emitted at small angles relative to the beam direction. Accurate reconstruction of these tracks is essential for disentangling different resonance modes. Probabilistic models such as the Gaussian Mixture Model (GMM) are particularly effective in capturing the complex covariance structures characteristic of the beam-
recoil interface in narrow-angle events. In this work, we present a track reconstruction approach based on the GMM, specifically designed for inelastic scattering experiments with active targets. Special emphasis is placed on the treatment of low-energy tracks. The proposed method is demonstrated on simulated data of the $^{58}\mathrm{Ni}(\alpha,\alpha')^{58}\mathrm{Ni}$ reaction at an incident energy of $E=49$~MeV/nucleon, generated under conditions representative of the experiment carried out at GANIL for the same reaction.
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All authors A. Arokiaraj, M.B. Latif, R. Raabe, D. Thisse, M. Vandebrouck
Instrumentation and Detectors
Evaluation of a large-area double-sided silicon strip detector for quality assurance in ion-beam radiotherapy
Devin Hymers, Sebastian Schroeder, Olga Bertini et al. (+4 more)
Designed to provide quality assurance for ion-beam radiotherapy, the prototype fIVI (filtered Interaction Vertex Imaging) Range Monitoring System is a two-layer tracker which employs double-sided strip-segmented silicon detectors. To meet the high demands of a clinical environment, a large sensitive area is required, along with a fast and compact readout. As this device utilizes sensors and readout electronics adapted from particle physics, where the expected energy and count rate differ significantly from radiotherapy, validation was necessary to ensure that these sensors would function effectively at the order 100 MeV/u energies and order MHz count rates expected during clinical irradiation. Tests were conducted using scattered subclinical 19 MeV
protons at high intensity, and clinical 207 MeV/u carbon ions at low intensity to independently validate these variables. The detection system is found to operate at rates up to 1.3 MHz, with a negligible fraction of events being affected by pileup. The efficiency of hit reconstruction is high, with a timestamp resolution of 6.25 ns, and a coincidence window of 31.25 ns, as is required for clinical event rates. With these settings, over 90% of particle interactions are able to reconstruct unique hit positions and contribute to track formation. This device is the first system using large-area, high-resolution detectors which meets the demanding count rate requirements associated with clinical radiotherapy.
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All authors Devin Hymers, Sebastian Schroeder, Olga Bertini, Johann Heuser, Joerg Lehnert, Christian Joachim Schmidt, Dennis Mücher
Optics
Topology of the near field in enhanced transmission through subwavelength apertures
MA Ortiz-Ferreyro, J. Sumaya-Martinez and A. Esquivel-Navarrete
We analyze enhanced optical transmission through subwavelength apertures using a modal formulation for the two fundamental polarizations, transverse electric (TE) and transverse
magnetic (TM). Within this framework, the fields inside the aperture are described in terms of guided modes whose excitation and interference govern the transmission process. By examining the near-field energy transport through the time-averaged Poynting vector, we show that resonant transmission is accompanied by a pronounced reorganization of the energy flow in the vicinity of the aperture. As the wavelength is varied across resonance, the energy transport undergoes a topological transition characterized by vortical and saddle-type flow structures, localized backflow regions, and efficient energy funneling through the aperture. These features correlate with strong phase gradients and phase singularities associated with the excited modal fields. The modal approach provides a unified and physically transparent interpretation of enhanced transmission in both slits and channels, applicable to perfect conductors and beyond plasmonic regimes.
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Physics and Society
Unraveling persistent urban-rural gaps: A long-term provincial analysis of residential heating and cooling loads
Qinwen Tang, Ran Yan, Nan Zhou et al. (+1 more)
Climate change and rising thermal comfort demand make residential heating and cooling central to building-sector decarbonization. This study presents a bottom-up modeling framework to estimate residential heating and cooling loads across 30 Chinese provinces. The model, developed using EnergyPlus simulations of representative building prototypes, captures heating and cooling load patterns in both urban and rural housing over the period 1980-2024. The results indicate that: (1) In 2020, Guangdong recorded the highest cooling loads (76.5 TWh/a urban; 63.0 TWh/a rural). Henan exhibited the highest rural heating load (174.6 TWh/a), while urban heating loads were highest in Liaoning and Shandong. (2) Between 1980 and 2024, average urban cooling loads increased from 12.4 to 15.1 kWh/m2a, whereas rural cooling loads declined from 22.63 to 19.87 kWh/m2a. Urban heating loads decreased from 44.08 to 39.92 kWh/m2a, and rural heating loads declined more markedly from 100.15 to 72.42 kWh/m2a. (3) Urban residential floor area has exceeded rural stock in 22 provinces in recent years, compared with only four provinces in 2000. Moreover, the existence of 12 urban energy-efficiency standards versus a single rural standard reflects a persistent regulatory disparity. Counterfactual and factor-contribution analyses further indicate that the associated envelope-performance gap is a major contributor to urban-rural load-intensity differences, while building form has a more context-dependent influence. The proposed framework provides a replicable basis for region-specific clean heating strategies and differentiated building standards to support carbon neutrality.
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All authors Qinwen Tang, Ran Yan, Nan Zhou, Minda Ma
Optics
Model-Based Real-Time Synthesis of Acousto-Optically Generated Laser-Beam Patterns and Tweezer Arrays
Marcel Mittenbuehler, Lukas Sturm, Malte Schlosser et al. (+1 more)
Acousto-optic deflectors (AOD) enable spatiotemporal control of
laser beams through diffraction at an ultrasonic grating that is controllable by
radio-frequency (rf) waveforms. These devices are a widely used tool for high-bandwidth random-access scanning applications, such as optical tweezers in
quantum technology. A single AOD can generate multiple optical tweezers by multitone rf input in one dimension. Two-dimensional (2D) patterns can be realized with two perpendicularly oriented AODs. As the acousto-optical response depends nonlinearly on the applied frequency components, phases, and amplitudes, and in addition experiences dimensional coupling in 2D setups, intensity regulation becomes a unique challenge. Guided by coupled-wave theory and experimental observations, we derive a compute-efficient model which we implement on a graphics processing unit. Only one-time sampling of single-tone
laser-power calibration is needed for model parameter determination, allowing for straight-forward integration into optical instruments. We implement and experimentally validate an open-loop diffraction efficiency control system that enables programmable 2D multibeam trajectories with intensity control applied at every time step during digital signal generation, overcoming the limited flexibility, pattern-size constraints, and bandwidth limitations of methods using precalculation and precalibration of a predefined pattern set or closed-loop feedback. The system is capable of stable real-time waveform streaming of arrays with up to 50 x 50 tweezers with minimal time resolution of 1.4 ns (700 MS/s) and a peak latency below 257 microseconds for execution of newly requested patterns. Reactive, real-time 2D multibeam
laser patterning and scanning with strict intensity matching will substantially benefit parallelization and increasing data rates in materials processing, microscopy, and optical tweezers.
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All authors Marcel Mittenbuehler, Lukas Sturm, Malte Schlosser, Gerhard Birkl
Instrumentation and Detectors
Characterisation of silicon photomultipliers in a dilution refrigerator down to 9.4 mK towards a cryogenic cosmic-ray muon veto system
QUEST-DMC Collaboration: A. Kemp, S. Autti, E. Bloomfield et al. (+29 more)
We report the characterisation of a FBK NUV-HD-cryo silicon photomultiplier (SiPM) sensor operated in a 9.4 $\pm$ 0.2 mK environment inside a dilution refrigerator, towards the development of a cryogenic
cosmic ray
muon veto system to be operated internal to a dilution refrigerator required for low background experiments such as the QUEST-DMC dark matter search experiment. We characterise the single
photon response and the gain (the charge produced per detected
photon), the dark count noise rate, and correlated noise contributions as a function of operating voltage. This paper also reports first proof-of-concept measurements of using a SiPM coupled to scintillator internal to a dilution refrigerator, towards detecting high-energy events consistent with candidate
cosmic-ray
muon signals.
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All authors QUEST-DMC Collaboration: A. Kemp, S. Autti, E. Bloomfield, A. Casey, N. Darvishi, D. Doling, N. Eng, P. Franchini, R. P. Haley, P. J. Heikkinen, A. Jennings, S. Koulosousas, E. Leason, L. V. Levitin, J. March-Russell, A. Mayer, J. Monroe, D. Münstermann, M. T. Noble, J. R. Prance, X. Rojas, T. Salmon, J. Saunders, J. Smirnov, R. Smith, M. D. Thompson, A. Thomson, A. Ting, V. Tsepelin, S. M. West, L. Whitehead, D. E. Zmeev
Geophysics
Automatic Penalty Parameter Selection by Residual Whiteness Principle (RWP) and GCV for Full Waveform Inversion
Kamal Aghazade, Toktam Zand and Ali Gholami
Full-waveform inversion (FWI) is a powerful seismic imaging technique used to estimate high-resolution physical properties of subsurface structures by minimizing the misfit between observed and modeled seismic data. FWI is inherently a highly non-linear and ill-posed inverse problem. Extended-source approaches, such as the augmented Lagrangian (AL) method, are employed to improve solution convexity and robustness. A key component of this formulation is the penalty parameter, which controls the trade-off between data fitting and satisfaction of the wave-equation constraint, strongly influencing convergence in the presence of noise. The main challenge lies in selecting the penalty parameter. Traditional strategies such as the Discrepancy Principle (DP) require an accurate estimate of the noise level, which is often unknown or poorly characterized. Moreover, trial-and-error tuning requires repeatedly solving the inverse problem, making it computationally expensive. To overcome these limitations and develop a parameter-free, computationally efficient extended-source FWI
algorithm, we integrate two data-driven parameter-selection strategies–the Residual Whiteness Principle (RWP) and a stable variant of Generalized Cross-Validation (RGCV)–within a multiplier-oriented AL framework. Specifically, we adopt a dual-space AL formulation, which allows the background wave-equation operator to remain fixed and requires only a single LU factorization per frequency, significantly improving efficiency. This design enables dynamic adjustment of the parameter at negligible cost during iterations, making the
algorithm scalable for large-scale applications. Numerical experiments on acoustic and elastic FWI with white and colored noise show that, combined with the dual-space formulation, RWP provides strong noise robustness, resulting in a reliable automated solution for large-scale seismic inversion.
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Atomic Physics · Cross-listed from cond-mat.quant-gas
Structure of the mean-field yrast spectrum of a two-component Bose gas in a ring: role of interaction asymmetry
Hui Tang, Guan-Hua Huang, Shizhong Zhang et al. (+2 more)
The mean-field yrast spectrum of an SU(2)-symmetric two-component Bose gas confined to a ring geometry is known to exhibit an intricate nonanalytic structure that is absent in single-component systems. In particular, due to the interplay between the species concentration and the atomic interactions, a sequence of plane-wave states can emerge as yrast states at fractional values of the angular momentum per particle. This behavior stands in sharp contrast to the single-component case, where plane-wave states occur only at integer angular momenta. In this paper, we investigate how the structure of the yrast spectrum in a two-component Bose gas is modified by interaction asymmetry. By numerically solving the coupled Gross-Pitaevskii equations for propagating
soliton states, we compute the mean-field yrast spectrum and, in particular, determine the critical curves associated with the emergence of various plane-wave yrast states. We find that both the behavior of these critical curves and the mechanisms by which plane-wave yrast states arise depend sensitively on the relative strengths of the inter- and intra-component interactions. When the intra-component interaction is weaker, the plane-wave yrast states replace
soliton states through a continuous
evolution, as in the SU(2)-symmetric case, although the conditions for their existence become more restrictive. In contrast, when the intra-component interaction is stronger, plane-wave yrast states may emerge by overtaking
soliton states via branch crossings, and their stability is significantly enhanced. Our results have important implications for the existence and stability of persistent currents in asymmetric, two-component Bose gases.
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All authors Hui Tang, Guan-Hua Huang, Shizhong Zhang, Zhigang Wu, Eugene Zaremba