Physics and Society
Noise-induced stop-and-go traffic dynamics: Modelling and control
Raphael Korbmacher, Parthib Khound, Antoine Tordeux et al. (+1 more)
Stop-and-go waves in traffic flow are captivating collective phenomena with important safety and environmental consequences. While classical theories attribute these oscillations to linear instabilities caused by reaction delays and inertia, this study explores an alternative
stochastic perspective. Using a linearly stable car-following model, we show that white Gaussian noise in the measurement of the inter-vehicle distance can destabilise the flow, inducing a phase transition to periodic stop-and-go dynamics via a nonlinear instability mechanism. Furthermore, we demonstrate that a simple linear transformation of the model, which amplifies the system response while introducing a positive acceleration bias, can counteract noise-induced effects and restores the stability of uniform traffic flow. These findings, supported by numerical simulations, aim to provide new insights into the modelling and control of oscillatory traffic dynamics.
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All authors Raphael Korbmacher, Parthib Khound, Antoine Tordeux, Frank Gronwald
History and Philosophy of Physics
Post-Cold War Diaspora of Russian Particle Physicists
Vladimir Shiltsev
While the migration of scientists from the Soviet Union to the West occurred at a modest pace during the 1970s and 1980s, the dissolution of the USSR in 1991 and the ensuing economic and social hardships precipitated a massive exodus that amounted to a true
brain drain. The international physics community, particularly in Europe and the United States, absorbed a substantial influx of specialists in
nuclear, high-energy, and accelerator physics, including both seasoned scientists and engineers as well as promising graduate students and postdoctoral fellows. Many of these emigre researchers went on to assume leadership positions, drive major experimental and theoretical initiatives, and achieve scientific distinction that equaled or even surpassed their accomplishments at home. In this article we explore the defining features of this post Cold War scientific diaspora, assess its impact on Russia research infrastructure and capabilities, and evaluate its enduring contributions to global particle physics collaborations and discoveries.
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Applied Physics
Demonstration of KV-Class e̱ta}-Ga2O3 Trench Junction Barrier Schottky Diodes with SpaceModulated Junction Termination Extension
Advait Gilankar, Julian Gervassi-Saga, Martha R. McCartney et al. (+4 more)
In this work, we report on the design and fabrication of p-NiO/Ga2O3 trench junction barrier schottky diodes (JBSD) integrated with space-modulated junction termination extension (SM-JTE) and compare the performance with planar Ni/Ga2O3 schottky diodes (SBDs) and p-NiO/Ga2O3 heterojunction diodes (HJDs). The JBSDs achieved breakdown voltages exceeding 1.8 kV along with low leakage currents (<10-2 A/cm2), while displaying low turn on voltage (VON) of ~1V, which is similar to that of planar Ni/Ga2O3 SBDs. The fabricated devices showed excellent forward characteristics with low differential on-resistance (Ron,sp) ranging from 4-10.5 m{\Omega}-cm2, for fin width between 0.6- 1.25 microns. Best performing device with fin width of 0.85{\mu}m showed a unipolar figure of merit (FOM) of ~0.7GW/cm2. This work showcases the benefits of trench JBS design along with SM-JTE edge-termination for efficient high-performance kilovolt-class e̱ta}- Ga2O3 diodes.
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All authors Advait Gilankar, Julian Gervassi-Saga, Martha R. McCartney, Nabasindhu Das, David Malcolm McComas, David J. Smith, Nidhin Kurian Kalarickal
Physics Education
Teaching Using Immersion – Explaining Magnetism and Eclipses in a Planetarium Dome
Patricia H Reiff and Carolyn Sumners
Previously we have shown that three-dimensional concepts are more readily learned in a three-dimensional context. Although VR headsets are growing in popularity, they only provide a quite limited field of view, and each person in a group may be viewing a different direction or a different time in the visualization. By using instead a fullsphere movie (VR360) in a planetarium dome instead of a headset, you can "share the VR"(TM) and specify which half of the sphere your audience is looking at. You can pause the movie, ask questions using a clicker system, display the results, and move on if the subject is mastered or explain more if items are not understood. This paper shows the results of teaching magnetism in a dome theater, showing that both students and teachers nearly double their understanding of magnetism topics after one viewing. We also created seven animations explaining eclipses that were distributed free to nearly 200 planetariums. Listing of concepts learned by teachers in our live eclipse program are shown.
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Computational Physics
Predicting parameters of a model cuprate superconductor using machine learning
V. A. Ulitko, D. N. Yasinskaya, S. A. Bezzubin et al. (+2 more)
The computational complexity of calculating phase diagrams for multi-parameter models significantly limits the ability to select parameters that correspond to experimental data. This work presents a machine learning method for solving the inverse problem -
forecasting the parameters of a model
Hamiltonian for a cuprate
superconductor based on its phase diagram. A comparative study of three deep learning architectures was conducted: VGG, ResNet, and U-Net. The latter was adapted for regression tasks and demonstrated the best performance. Training the U-Net model was performed on an extensive
dataset of phase diagrams calculated within the mean-field approximation, followed by validation on data obtained using a semi-classical heat bath
algorithm for Monte Carlo simulations. It is shown that the model accurately predicts all considered
Hamiltonian parameters, and areas of low prediction accuracy correspond to regions of parametric insensitivity in the phase diagrams. This allows for the extraction of physically interpretable patterns and validation of the significance of parameters for the system. The results confirm the promising potential of applying machine learning to analyze complex physical models in condensed matter physics.
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All authors V. A. Ulitko, D. N. Yasinskaya, S. A. Bezzubin, A. A. Koshelev, Y. D. Panov
Optics
Respiration Rate Sensor Based on Fiber Cavity Attenuated Phase Shift Spectroscopy
Muhammad Fahd Ibrahim, Shazreen Rashid, Noor-ul-Amin Nazir et al. (+1 more)
Respiratory rate (RR) is a vital sign with significant diagnostic value. Existing RR monitors often suffer from baseline drift over time, breaths can be occluded by limb or body movements, and many systems struggle to resolve shallow or extreme thoracic motion. Here, we propose a novel RR-monitoring sensor based on fiber-cavity attenuated phase-shift spectroscopy~(CAPS). The sensor comprises a fiber cavity whose portion is embedded into a flexible chest binder in a sinusoidal-like pattern, which the patient wears. Thoracic expansion and contraction during breathing modulate the cavity, and RR is extracted through CAPS measurements. Our sensor exhibits high reproducibility, strong sensitivity to strain and pressure induced by chest movements, inherent resistance to baseline drift, and the ability to detect body movements. The system achieves a root-mean-square error of 0.91 breaths per minute relative to the ground truth, across RR values ranging from 8 to 44 breaths per minute, when tested on multiple subjects in various postures, including sitting, supine, prone, and lateral positions. We anticipate that this work will contribute to the development of comprehensive optical fiber-based sleep monitoring systems.
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All authors Muhammad Fahd Ibrahim, Shazreen Rashid, Noor-ul-Amin Nazir, M. Imran Cheema
Accelerator Physics
Comment on "Monochromatization interaction region optics design for direct s-channel Higgs production at FCC-ee"
Dmitry Shatilov
The original article [1] can be logically divided into two parts: 1) the selection of main parameters for monochromatization and 2) interaction region optics design; the comment pertains only to the first part. The authors of [1] state that "The purpose of this paper is to report on the development of realistic IR optics designs for monochromatization at the FCC-ee". However, the proposed parameters do not seem very realistic and raise many questions; due to space limitations, we will only consider the most important ones.
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Optics
Needle beams and structured space-time wavepackets
Ruediger Grunwald and Martin Bock
Recent research on needle beams and space-time wavepackets (STWPs) is presented. Quasi-nondiffracting STWPs propagate at stable spatial and temporal localization over extended distances. In a simple model, STWPs are interpreted as being composed of differential needle beams. Simulations indicate that pulsed Bessel-like needle beams can reach higher spectral and temporal homogeneity compared to spatio-spectrally shaped focused Gaussian beams. The interference of femtosecond needle beam arrays leads to nondiffracting self-imaging in space and time. High-speed switching of STWPs with combined optical systems, orbital angular momentum generation with self-torque and other emerging fields of research are addressed
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Applied Physics · Cross-listed from eess.SY
Applied Neural Network-Based Active Control for Vortex-Induced Vibrations Suppression in a Two-Degree-of-Freedom Cylinder
Soha Ilbeigi, Ashkan Bagherzadeh and Alireza Sharifi
Vortex-Induced Vibrations (VIVs) of cylindrical structures present significant challenges in various engineering applications, including marine risers, tall buildings, and renewable energy systems. Hence, it is vital to control
Vortex-Induced Vibrations of cylindrical structures. For this purpose, in this study a novel approach is introduced to VIV control, based on a model-based active control strategy integrated with a Neural Network (NN) in the presence of uncertainty modeling. The proposed method utilizes a closed-loop control system, where feedback from the system's dynamic state is used to generate adaptive control commands, enabling the system to respond to changing flow conditions and nonlinearities. Then, the controllability analysis is conducted to assess the efficiency of the control strategy in mitigating VIV. Two control approaches are implemented: simple learning and composite learning. Both strategies significantly enhance vibration suppression, achieving up to 99% reduction in vibrations despite uncertainties in the system. The results demonstrate the potential of the proposed method to enhance the efficiency, stability, and lifespan of structures subject to VIV.
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Optics
Negative Index Makes a Perfect Time-Domain Lens, Generating Slow Playback of Ultrafast Events
Oded Schiller, Yonatan Plotnik, Guy Bartal et al. (+1 more)
We explore the effects of incorporating negative index materials into the physics of time-varying media and find that changing the refractive index from positive to negative creates a perfect time-reversed wave: a perfect time-domain lens. Unlike other mechanisms of phase conjugation, the perfect time-domain lens time-reverses both the propagating waves and the evanescent part of the spectrum. Moreover, we find that the time-reversed wave can be slowed down or accelerated, depending on the refractive index ratio. We show that this effect remains strong even when the refractive index varies arbitrarily slow, in sharp contradistinction to time-reflection which necessitates large index changes at sub-cycle rates. This is the first avenue found to yield significant negative-frequency waves using a temporal interface without the need for sub-cycle modulation or impedance matching. The effect can be used to record extreme ultrafast information and subsequently play it backwards at a slow rate, and vice-versa.
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All authors Oded Schiller, Yonatan Plotnik, Guy Bartal, Mordechai Segev
Physics and Society
Quantum Diplomacy within the Southeast Asia Quantum Ecosystem
Pak Shen Choong, Nurisya Mohd Shah and Yung Szen Yap
Amid the International Year of
Quantum Science and Technology 2025 (IYQ 2025), a significant portion of global funding has been dedicated to various
quantum initiatives, with over 30 countries announcing their respective
quantum strategies. Within the Southeast Asia context, Singapore, Thailand, and the Philippines have launched their respective
quantum strategies and roadmaps. Meanwhile, six out of eleven Southeast Asia countries have expressed interest in formulating a regional
quantum ecosystem to pursue a set of common goals.
Quantum technologies, though still in their infancy within the second
quantum revolution, have advanced rapidly in recent years. Due to their dual-use nature,
quantum technologies are considered emerging and disruptive, often raising concerns from the cybersecurity perspective. While several discussions regarding Malaysia's
quantum initiative and strategy are ongoing, it is vital to broaden the conversation and position Malaysia within the regional ecosystem. This paper provides an overview of Malaysia's
quantum landscape and a summary of the regional initiatives since the establishment of Southeast Asia
Quantum Network. We then analyse Malaysia's strengths in
quantum research and provide four recommendations to strengthen the regional ecosystem.
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Computational Physics
Refining Machine Learning Potentials through Thermodynamic Theory of Phase Transitions
Paul Fuchs and Julija Zavadlav
Foundational Machine Learning Potentials can resolve the accuracy and transferability limitations of classical force fields. They enable microscopic insights into material behavior through Molecular Dynamics simulations, which can crucially expedite material design and discovery. However, insufficiently broad and systematically biased reference data affect the predictive quality of the learned models. Often, these models exhibit significant deviations from experimentally observed phase transition temperatures, in the order of several hundred kelvins. Thus, fine-tuning is necessary to achieve adequate accuracy in many practical problems. This work proposes a fine-tuning strategy via top-down learning, directly correcting the wrongly predicted transition temperatures to match the experimental reference data. Our approach leverages the Differentiable Trajectory Reweighting
algorithm to minimize the free energy differences between phases at the experimental target pressures and temperatures. We demonstrate that our approach can accurately correct the phase diagram of pure Titanium in a pressure range of up to 5 GPa, matching the experimental reference within tenths of kelvins and improving the
liquid-state
diffusion constant. Our approach is model-agnostic, applicable to multi-component systems with solid-solid and solid-
liquid transitions, and compliant with top-down training on other experimental properties. Therefore, our approach can serve as an essential step towards highly accurate application-specific and foundational machine learning potentials.
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Fluid Dynamics
Vortex Dynamics from Burst-and-Coast Motion of Anguilliform and Carangiform Swimmers
Zahra Maleksabet, Maham Kamran, Ali Tarokh et al. (+1 more)
Fish perform various propulsive maneuvers while swimming by generating traveling waves along their bodies and producing thrust through tail strokes. Anguilliform swimmers spread motion along the body, while carangiform swimmers' motion is more prominent near their tails. Many species also switch between continuous undulation and intermittent swimming, such as burst-and-coast maneuver, which can save energy but can also change the wake structure and hydrodynamic forces. Our current study aims at explaining} how duty cycle (DC), undulatory gaits, and Strouhal number (St), shape the near-body
vortices, overall wakes, and the hydrodynamic forces. We carry out three-dimensional simulations at Re = 3000 for flows around an eel (anguilliform) and a Jack Fish (carangiform) for DC = 0.2-1.0 and St = 0.30 and 0.40. Our results reveal that the burst-and-coast motion for both swimmer produce bow-shaped wakes, the two rows of which on the sides approach each other to form a more coherent wake as DC is increased to 1.0 that corresponds to the wake of continuously undulating swimmers. It is also found that the intermittent motion at a higher Strouhal number produces more drag, contrary to the continuous undulatory kinematics. We further investigate this behavior by quantifying the strengths of
vortices produced around the two swimmers and their instantaneous kinematic metrics. A detailed analysis for the role of different body sections in the production of unsteady streamwise forces is also presented. These insights provide important connections between the swimmers' physiologies, their kinematics, and the governing
vortex dynamics to attain certain hydrodynamic metrics for designing next-generation autonomous bio-inspired
underwater robots.
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All authors Zahra Maleksabet, Maham Kamran, Ali Tarokh, Muhammad Saif Ullah Khalid
Applied Physics
A CMOS+X Spiking Neuron With On-Chip Machine Learning
Steven Louis, Matthew Blake Abramson, Hannah Bradley et al. (+8 more)
We present the design and numerical simulation of a spiking
neuron in a proof-of-concept model of on-chip machine learning. Built within the CMOS+X framework, the spiking
neuron consists of an NMOS transistor combined with a
magnetic tunnel junction (MTJ). This NMOS+MTJ unit, when simulated in the industry-standard
circuit simulation software “LTspice”, reproduces multiple functions of a biological
neuron, including threshold spiking, latency, refractory periods, synaptic integration, and inhibition. These behaviors arise from the intrinsic magnetization dynamics of the MTJ and do not require any additional control circuitry. By interconnecting the NMOS+MTJ
neurons, we construct a model of an analog multilayer network that learns through spike-timing-dependent weight updates derived from a gradient-descent rule, with both training and inference modeled in the analog domain. The simulated network demonstrates spike propagation and successful training on the XOR task under the modeled conditions.
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All authors Steven Louis, Matthew Blake Abramson, Hannah Bradley, Cody Trevillian, Gene David Nelson, Andrei Slavin, Artem Litvinenko, Jason Gorski, Ilya N. Krivorotov, Darrin Hanna, Vasyl Tyberkevych
Space Physics
Accounting for Solar Radiation Pressure in the Hamiltonian Normal Form of the Elliptic Restricted Three-Body Problem
Carson Hunsberger, David Schwab, Roshan Eapen et al. (+1 more)
Hamiltonian normal forms allow for the analytical approximation of center
manifold trajectories and their invariant
manifolds through the separation of the saddle and center subspaces that make up the dynamics at the collinear libration points within the
elliptic restricted three-body problem. The circular restricted three-body problem is a special case of the
elliptic problem– one that does not take into account the eccentricity of the true orbits of the primaries and thus provides a dynamical model of varying accuracy depending on the true anomaly of the primaries. This paper first shows that the normal forms of the
elliptic problem offer nearly identical trajectory characterization capabilities to those of the circular problem and then demonstrates the difference in fidelity by comparing the circular and
elliptic normal form representations of ephemeris data for the James Webb Space
Telescope. Furthermore, methodology for including
solar radiation pressure within the normal form is introduced, and the same ephemeris data is used to demonstrate the resulting increase in fidelity of the dynamical model.
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All authors Carson Hunsberger, David Schwab, Roshan Eapen, Puneet Singla
Computational Physics · Cross-listed from cs.LG
Quantum-Classical Physics-Informed Neural Networks for Solving Reservoir Seepage Equations
Xiang Rao, Yina Liu and Yuxuan Shen
Solving reservoir seepage partial differential equations (PDEs) is critical for hydrocarbon development optimization and production
forecasting. Conventional numerical solvers suffer from mesh errors and high computational cost. Standard Physics-Informed Neural Networks (PINNs) are limited by inefficient parameters. They also face weak high-dimensional representation and poor nonlinear fitting ability. We adapt the Discrete Variable (DV)-
Circuit Quantum-Classical Physics-Informed Neural Network (QCPINN) to tackle these drawbacks. This work applies the method to four representative reservoir seepage models. The models cover heterogeneous single-phase pressure
diffusion. They also include nonlinear Buckley-Leverett two-phase waterflooding. Another case is adsorption-coupled convection-
diffusion compositional flow. The last one refers to fully coupled pressure-saturation two-phase flow with exponential permeability heterogeneity. The QCPINN combines classical preprocessing and postprocessing networks with a DV
quantum core. It leverages
quantum entanglement and superposition to boost high-dimensional feature mapping. Physical constraints are embedded within the framework to guarantee physically consistent solutions. We evaluate three
quantum circuit topologies including Cascade, Cross-mesh and Alternate. Numerical tests prove QCPINNs outperform classical PINNs in prediction accuracy, and the
circuit topologies show case-specific performance with clear applicable ranges. This work verifies QCPINN's practicability for reservoir engineering. It bridges
quantum computing research with oilfield industrial applications.
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Atomic Physics
Demonstration of a Raman Velocity Filter in Collinear Laser Spectroscopy: Towards Applications for sub-ppm High-Voltage Measurements
Julien Spahn, Hendrik Bodnar, Kristian König et al. (+1 more)
Raman transitions have a wide range of applications in atomic physics and have recently been proposed as a means for improving high-precision high-voltage measurements. Here, we present a theoretical analysis and a first experimental demonstration of $5s\,^2\mathrm{S}_{1/2} \rightarrow 4d\,^2\mathrm{D}_{3/2,5/2}$ Raman transitions in $^{88}$Sr$^+$ ions in collinear
laser spectroscopy. For the theoretical description the three-level system is reduced to an effective two-level system, in order to estimate the experimental parameters, while the role of the spatial
laser intensity distribution in combination with the radial extension of the ion beam are elucidated by performing simulations of the full four-level system. Experimentally, we realized the first velocity-selective Raman transition in collinear
laser spectroscopy. Using a $^{88}$Sr$^+$ ion beam, we demonstrate a reduction in the energy width to less than $200\,$meV, which is about an order of magnitude reduction compared to the usage of an optical dipole transition as in previous works. We also investigate two-
photon Rabi oscillations and show that their observed collapse is consistent with the simulations.
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All authors Julien Spahn, Hendrik Bodnar, Kristian König, Wilfried Nörtershäuser
Optics
Passive Silicon Nitride On-Chip Polarimetry: Precise Polarization Detection with Imperfect Components
Christoph Stockinger, Natale G. Pruiti, Isaac Tribaldo et al. (+3 more)
Polarization is a fundamental property of light that carries distinct and valuable information. Consequently, its precise measurement is crucial for numerous applications, including biomedical imaging, remote sensing, and optical communication. Since polarization cannot be measured directly, it is typically inferred by converting it into intensity signals using dedicated optical elements. Conventional approaches, however, predominantly rely on bulky optical components, leading to considerably high fabrication costs and limited integration density. Here, we introduce a passive photonic integrated
circuit capable of precisely determining the polarization state of visible free-space light. An silicon nitride on-chip architecture employing a compact polarization-splitting grating coupler and a set of passive interferometers encodes the polarization information into intensity signals, allowing conventional detectors to accurately reconstruct the polarization state. With increasing compactness of photonic components, however, susceptibility to fabrication tolerances as well as intrinsic design constraints increases, potentially leading to non\-/ideal behaviour. To address this, we introduce a robust calibration procedure that enables precise measurements even in the presence of imperfections. The chip design, combined with the calibration procedure, offers a robust, small-footprint, and high-speed approach to polarimetry, enabling a wide range of applications.
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All authors Christoph Stockinger, Natale G. Pruiti, Isaac Tribaldo, Jörg S. Eismann, Marc Sorel, Peter Banzer
Plasma Physics
Integrating High Performance In-Memory Data Streaming and In-Situ Visualization in Hybrid MPI+OpenMP PIC MC Simulations Towards Exascale
Jeremy J. Williams, Stefan Costea, Daniel Medeiros et al. (+11 more)
Efficient simulation of complex
plasma dynamics is crucial for advancing fusion energy research. Particle-in-
Cell (PIC) Monte Carlo (MC) simulations provide insights into
plasma behavior, including
turbulence and confinement, which are essential for optimizing fusion reactor performance. Transitioning to exascale simulations introduces significant challenges, with traditional file input/output (I/O) inefficiencies remaining a key bottleneck. This work advances BIT1, an electrostatic PIC MC code, by improving the particle mover with OpenMP task-based parallelism, integrating the openPMD streaming API, and enabling in-
memory data streaming with ADIOS2's Sustainable Staging Transport (SST) engine to enhance I/O performance, computational efficiency, and system storage utilization. We employ profiling tools such as gprof, perf, IPM and Darshan, which provide insights into computation, communication, and I/O operations. We implement time-dependent data checkpointing with the openPMD API enabling seamless data movement and in-situ visualization for real-time analysis without interrupting the simulation. We demonstrate improvements in simulation runtime, data accessibility and real-time insights by comparing traditional file I/O with the ADIOS2 BP4 and SST backends. The proposed hybrid BIT1 openPMD SST enhancement introduces a new paradigm for real-time scientific discovery in
plasma simulations, enabling faster insights and more efficient use of exascale computing resources.
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All authors Jeremy J. Williams, Stefan Costea, Daniel Medeiros, Jordy Trilaksono, Pratibha Hegde, David Tskhakaya, Leon Kos, Ales Podolnik, Jakub Hromadka, Kevin A. Huck, Allen D. Malony, Frank Jenko, Erwin Laure, Stefano Markidis
Optics
Errors in PDH offset locking due to spurious spectral features
Roame A. Hildebrand, Wance Wang, Connor Goham et al. (+2 more)
The Pound-Drever-
Hall (PDH) technique is widely used to stabilize the frequency of
lasers. Here we report on a routinely underestimated source of error in PDH offset-locking: a shift in the lock point due to the unintended interaction between residual optical sidebands and higher-order spatial modes in misaligned Fabry-Perot cavities. Significant frequency deviations-up to 50% of the cavity linewidth-can arise when the optical offset is obtained from a sinusoidally driven EOM. We measure this deviation experimentally, find agreement with a simple model, and show how a spectrally-pure frequency offset can reduce the deviation by an order of magnitude. Our findings draw
attention to a systematic effect of importance to precision optical spectroscopy, optical clocks, and
quantum information science.
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All authors Roame A. Hildebrand, Wance Wang, Connor Goham, Alessandro Restelli, Joseph W. Britton
Space Physics
The May 2024 Storm: dayside magnetopause and cusps in simulated soft X-Rays
J. Ng, L.-J. Chen, B. Burkholder et al. (+10 more)
The coronal mass ejection (CME) arriving at Earth on May 10, 2024 caused the most intense geomagnetic storm in the last two decades, and resulted in highly unusual magnetopause and cusp dynamics. We simulate soft X-Ray emission due to
solar wind charge exchange with exospheric neutrals to image the global dayside dynamics, focusing on the impact of a dense CME current sheet during the storm main phase. The magnetopause moves inward to ~ 4 RE, and at the same time, the two cusps manifest as nearly parallel emission ridges in X-Ray. As the interplanetary
magnetic field reverses, the cusp ridges move to higher latitudes for ~ 10 minutes after the reversal. The X-Ray emission can be detected by imagers to be flown on future missions to provide a global picture of the magnetopause and cusps with quantitative determination of their locations
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All authors J. Ng, L.-J. Chen, B. Burkholder, D. Sibeck, F. S. Porter, K. H. Pham, V. G. Merkin, H. Connor, J. W. Bonnell, S. Petrinec, Y. Zou, B. Alterman, G. Cucho-Padin
History and Philosophy of Physics
Comparing land- and skyscapes in the three main manorial-conquered lands of the Canary Islands
Maria Florencia Muratore, Alejandro Gangui, Juan Antonio Belmonte et al. (+1 more)
This work is a study of the relationship between astronomy and landscape focused on the orientation of Christian churches of the three main Manorial (Señorío) Islands of the Canary archipelago (Spain): Lanzarote, La Gomera and Fuerteventura. As a background, we have the information provided by the texts of early Christian writers, which imposed that churches should be oriented towards the east [..]. The fieldwork that supports our comparative study is based on the measurement of the precise location coordinates, axis' azimuth and angular height of the horizon for most of the churches of the three islands, which amounts to about 120 sets of measurements. For the study of the sample, we have employed various analyses, both statistical, as well as calendric and orographic. Our results show that on all the islands, the pattern of double orientations is repeated, which contemplates the canonical tradition of orienting the altars of churches within the
solar range (pointing either eastward or westward). Very few cases also occur where it is possible to identify constructions whose orientation follows solstitial patterns, perhaps as imitation of aboriginal worship. But this double pattern also includes a high proportion of churches with orientations far from this range. An example is Lanzarote and Fuerteventura, both islands subjected to the same flow of the prevailing trade winds in the region, but each with its own characteristics. Another example is given by the particular orography of deep ravines of La Gomera, which determines the orientation of the temples located in those geographical accidents. In this paper we show how the combination of elements of the land- and skyscape can, with a high degree of probability, offer a satisfactory explanation to the particular orientation of these insular centres of worship, which were built during the first decades after the European conquest.
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All authors Maria Florencia Muratore, Alejandro Gangui, Juan Antonio Belmonte, Carmelo Cabrera
Plasma Physics · Cross-listed from nucl-th
Generalized Beth–Uhlenbeck entropy formula from the $\Phi-$derivable approach
David Blaschke, Gerd Röpke and Gordon Baym
We derive a generalized Beth-Uhlenbeck formula for the
entropy of a dense
fermion system with strong two-particle correlations, including scattering states and bound states. We work within the $\Phi-$derivable approach to the thermodynamic potential. The formula takes the form of an energy-momentum integral over a statistical distribution function times a unique spectral density. In the near mass-shell limit, the spectral density reduces, contrary to naïve expectations, not to a Lorentzian but rather to a "squared Lorentzian" shape. The relation of the Beth-Uhlenbeck formula to the $\Phi$-derivable approach is exact at the two-loop level for $\Phi$. The formalism we develop, which extends the Beth-Uhlenbeck approach beyond the low-density limit, includes Mott dissociation of bound states, in accordance with Levinson's
theorem, and the self-consistent back reaction of correlations in the
fermion propagation. We discuss applications to further systems, such as
quark matter and
nuclear matter.
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Fluid Dynamics
Stratification, turbulence organization, and pressure-strain effects on surface-layer turbulence anisotropy
Ivana Stiperski, Gabriel G. Katul, Elie Bou-Zeid et al. (+1 more)
At large scales, the Reynolds stress tensor exhibits notable anisotropy, a key feature of all wall-bounded turbulent flows. Yet, how the drivers of this anisotropy evolve with shearing and thermal stratification in the atmospheric surface layer (ASL) remains a daunting challenge for theory and models alike. Here, the velocity variance budgets are used to explore the
evolution of anisotropy in the daytime ASL close to the surface, region known to be problematic for large eddy simulations. A special focus is placed on the importance of slow and rapid pressure-strain correlations and the role of transport on partitioning the turbulent kinetic energy among the velocity components. Results obtained from near-surface observations of four
datasets over flat and horizontally homogeneous terrain show persistent anisotropy over a wide range of flux Richardson numbers $R_{if}$ and wall-normal distances, and highlight the importance of different processes in three distinct flow regimes, roughly related to dynamic ($|R_{if}|\ll1$), dynamic-convective ($|R_{if}|\sim1$) and convective ($|R_{if}|\gg1$) regimes of the ASL. In particular, close to the surface in the dynamic-convective regime, a drop in wall-normal velocity variance and a substantial increase of spanwise velocity variance are shown to result from the increasing role of pressure transport and rapid distortion, related to
turbulence organization. This behaviour is not captured by the classic Rotta closure but requires the inclusion of both rapid pressure-strain and transport terms. In all regimes wall blocking is found to influence
turbulence close to the surface, thus requiring the adoption of an anisotropic Rotta model to accommodate its effects.
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All authors Ivana Stiperski, Gabriel G. Katul, Elie Bou-Zeid, Marc Calaf
Computational Physics
Comparing time and frequency domain numerical methods with Born-Rytov approximations for far-field electromagnetic scattering from single biological cells
Cael Warner
The Born-Rytov approximation estimates effective refractive index of biological
cells from measurements of scattered light intensity, polarization and phase. Effective refractive index is useful for estimating a biological
cell's dry mass, volume, and internal morphology directly from its elastic light scattering pattern. This work compares the Born-Rytov approximation with analytical, Yee-
lattice finite-difference time-domain, and discrete-dipole approximations to Maxwell's equations in the cases of electromagnetic scattering from a sphere and a tomographic reconstruction of Saccharomyces cerevisiae. Practical advantages and limitations of each numerical method are compared for modeling electromagnetic scattering of both near-field intensity and the far-field projected intensity, in terms of accuracy,
memory, and compute time. When compared with a commercial software implementation of the Yee-
lattice finite-difference time domain method, the Born-Rytov scattering approximation and discrete dipole approximation show better agreement with the far-field light scattering pattern from Saccharomyces cerevisiae.
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Plasma Physics
Solar Wind Penetration into Dusty Magnetospheres creates Electrostatic Waves and Structures
Usman Saeed, Shaukat Ali Shan and Hamid Saleem
The low frequency electrostatic perturbations have been investigated in a bi ion
plasma in the background of static
dust. It is shown that the field aligned shear flow of both the ions produce low frequency electrostatic instabilities and create nonlinear structures, the double layers and the
solitons. The general theoretical model is applied to the magnetospheres of Jupiter (with positively charged
dust) and Saturn (with negatively charged
dust) which have oxygen ions in addition to
protons. This model predicts the existence of extremely low frequency electrostatic waves with real frequencies of the order of a milli Hertz (mHz) to several mHz and this range of frequencies have been reported in literature for these
plasma environments. The estimated width of the nonlinear structures vary from a few hundred meters to a few kilometers. These structures are similar to that observed in the oxygen and oxygen hydrogen
plasmas in Earth's upper ionosphere which is free from
dust.
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Fluid Dynamics
Intermittency from instanton calculus at the transition to turbulence and fusion rules
Timo Schorlepp and Rainer Grauer
Understanding intermittency of turbulent systems from the underlying differential equations is an outstanding problem in fluid dynamics. Here, in the example of Burgers
turbulence as a stringent test, we introduce a semi-analytical method that yields high-order structure function exponents by combining instanton calculus, fusion rule predictions, and low-order statistical inputs from direct numerical simulations (DNS). We use instanton predictions, calibrated by DNS, to evaluate high velocity gradient (VG) moments at the onset of intermittency, and then infer scaling exponents in fully developed
turbulence via fusion rules. We show that the method captures the crossover at $\mathrm{Re}_\lambda \approx 1$ in the VG moment scaling, highlight the necessity of including fluctuations around instantons, and discuss future extensions.
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Atomic Physics
Shell formation and two-dimensional nanofriction in three-dimensional ion Coulomb crystals
L.-A. Rüffert and T. E. Mehlstäubler
Self-organized three-dimensional (3D) ion Coulomb
crystals in linear Paul traps naturally form concentric shells that provide a curved, atomically resolved interface for studying two-dimensional (2D) nanofriction. Building on earlier studies of one-dimensional nanofriction and orientational melting in 2D ion
crystals, we extend friction studies from linear chains and planar rings to 3D shell structures. Using molecular-dynamics simulations, we map shell formation as a function of ion number N and trap aspect ratio and obtain a simple scaling relation that can aid ion-number estimation in experiments. We compute a Peierls-Nabarro-type potential for rotating the outer shell against a static inner core, using the rotation angle as a collective coordinate. Changing N by one can alter the effective rotational barrier by up to a factor of ~7, while changes by only a few ions can lead to variations up to a factor of ~60. Combining
geometric commensurability analysis with energy decomposition, we show that the barrier is governed by a system-dependent interplay between inter-shell interaction, outer-shell response and trap confinement. Dynamical simulations with applied torques reveal pinned, stick-slip and smooth-sliding regimes with depinning thresholds that depend on ion number, inner-shell geometry and trap aspect ratio. Some configurations show hysteresis due to torque-induced metastable states. We further find that spatially varying coupling to the inner-core corrugation can create coexisting fast and slow domains within the rotating outer shell, realizing multidimensional friction in which intra-shell shear and inter-shell nanofriction act simultaneously. Our results establish self-organized ion Coulomb
crystals as model systems for 2D nanofriction and suggest routes toward ion-based nanorotors, torque sensors and ultra-low-friction nanomechanical systems.
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Accelerator Physics
First Experimental Demonstration of Reinforcement Learning-Based Tuning on the PSI Injector 2 Cyclotron
M. Haj Tahar, W. Joho, E. Solodko et al. (+7 more)
Reliable operation of high-power
proton cyclotrons is a critical requirement for Accelerator Driven Systems (ADS) and other large-scale applications. Beam tuning in such machines is traditionally performed manually, a process that can be slow, non-optimal, and difficult to execute in the presence of faults or changing conditions. To address this, we developed and deployed a machine learning (ML) based tuning framework on the Injector 2 cyclotron at PSI, chosen as an ideal testbed for high-power operation. The system combined a tailored reinforcement learning (RL)
algorithm with real-time diagnostics and control, and incorporated accelerator-physics inspired adaptations such as an overshoot strategy that reduced
magnetic field settling times by nearly a factor of six. Over an extensive 12-day operational test campaign, relatively long in the context of real-time ML experiments, the RL
agent successfully tuned the machine across multiple operating points. For each investigated configuration, stable policies were obtained within a few hours of online training and subsequently demonstrated reliable low-loss operation during overnight evaluation runs. Crucially, the learned policy remained effective when transferred from low-current training to operation at beam currents up to 800 {\mu}A, demonstrating robust generalization under appropriately adapted operational constraints. These results constitute the first demonstration of RL-assisted tuning on a high-power cyclotron, with direct relevance to ADS-class drivers.
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All authors M. Haj Tahar, W. Joho, E. Solodko, M. Bocchio, S. Marquie, M. Busch, A. Barchetti, J. Grillenberger, J. Snuverink, M. Schneider
Applied Physics
Recent Developments of the VOXES Von Hamos X-ray Spectrometer for Laboratory XES and XAS Studies
Simone Manti, Alberto Clozza, Gabriel Moskal et al. (+5 more)
VOXES is a Von Hamos X-ray spectrometer developed at the INFN National Laboratories of Frascati for high-resolution laboratory X-ray spectroscopy in the 5–20~keV range. It uses curved mosaic
crystals and motorized positioning stages to perform wavelength-dispersive X-ray fluorescence (WD-XRF) with sub-10~eV tunable resolution for extended and dilute samples. Recent developments include the integration of an energy-dispersive X-ray fluorescence (ED-XRF) line based on a silicon pin-diode detector, which enables flux monitoring and simultaneous ED and WD measurements. In addition, a dedicated
liquid-sample holder has been introduced, and a Y-shaped support geometry, crucial for switching to a transmission layout, provides mechanical compatibility with laboratory XAS, now under implementation. These upgrades expand the versatility and automation of VOXES, strengthening its role as a table-top platform for laboratory X-ray spectroscopy.
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All authors Simone Manti, Alberto Clozza, Gabriel Moskal, Kristian Piscicchia, Diana Sirghi, Florin Sirghi, Catalina Curceanu, Alessandro Scordo