Atmospheric and Oceanic Physics
FuXi-Nowcast: Environment-conditioned deep learning for severe convection nowcasting
Lei Chen, Zijian Zhu, Xiaoran Zhuang et al. (+4 more)
Severe convection produces localized hazards that often require warnings before radar echoes fully reveal storm development. Convective initiation and the maintenance of intense convection remain challenging for radar-only nowcasting because pre-convective signals may be absent from recent radar observations and strong echoes often decay rapidly in forecasts. Here we present FuXi-Nowcast, an environment-conditioned deep learning system that combines high-resolution observations with three-dimensional atmospheric forecasts to predict composite reflectivity, precipitation, wind gusts, and surface variables up to 12 h ahead. In April–July 2024 evaluations over East China, FuXi-Nowcast outperforms operational numerical, persistence and extrapolation baselines for reflectivity and precipitation. Case studies, diagnostics, and ablation experiments suggest that atmospheric moisture information and explicit preservation of strong convective signals contribute to forecasts of convective initiation and maintenance. These results show that environmental conditioning can mitigate important failure modes of radar-only nowcasting for high-impact convective weather.
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All authors Lei Chen, Zijian Zhu, Xiaoran Zhuang, Tianyuan Qi, Yuxuan Feng, Xiaohui Zhong, Hao Li
Plasma Physics
The effects of H blistering and ELMs on the thermal fatigue cracking of W by strikepoint sweeping
J. Hargreaves, J. Vernimmen, J. Scholten et al. (+1 more)
Cyclic thermal loads imposed on a W divertor by strikepoint sweeping may induce low-cycle thermal fatigue cracking of its
plasma-facing surfaces. This cracking may be accelerated by
plasma-material interactions such as H implantation, blistering, fuzz and void formation. Fatigue cracking may also synergise with ELM cracking. To explore these novel forms of environmentally assisted fatigue, FEA modelling was used to design a uniaxial fatigue experiment for Magnum-PSI that represents strikepoint sweeping at 1 Hz across a 100 mm span of a divertor target. Magnum-PSI was used to combine cyclic thermal loading of W with H implantation and two forms of ELM like pre-cracking. Quantitative SEM analysis of fatigue-cracked W revealed that H implantation significantly delayed crack initiation, with preimplanted targets requiring 450-600 cycles before failure compared to 150 cycles for non-implanted samples. This was attributed to hydrogen-induced dislocation pinning, which produces a case-hardening effect that inhibits persistent slip band formation. ELM-like pre-cracking combined with strikepoint sweeping was found to give rise to localised melting and the formation of 30 micromete diameter droplets, caused by thermal isolation of W regions by fatigue cracks. The implications for the fatigue lifetime of tokamak divertors are also discussed.
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All authors J. Hargreaves, J. Vernimmen, J. Scholten, T.W Morgan
General Physics
Chukchi Myths perspective on Special Relativity
Zurab K. Silagadze
The teaching of special relativity still follows Einstein's original two-postulate approach and thus recreates the relativistic revolution in the minds of students again and again, with all its attendant shocking and mysterious aspects. As Hermann Bondi long ago noted, such an approach, which emphasizes the revolutionary aspects of a theory rather than its continuity with earlier thought, "is hardly conducive to easy teaching and good understanding". But what could be a better alternative? In 1923, the distinguished Russian ethnographer, linguist, and anthropologist Tan-Bogoraz described the striking similarities between the special theory of relativity and the mythology of Chukchi shamans. Inspired by this surprising observation, I assume that the basic concepts of relativity are not at all alien to our innate perception of time and space, and I propose an approach to the foundations of relativity that emphasizes absolute concepts such as proper time and causal cones rather than relative ones.
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Physics and Society
A few ideas to promote inclusion
Thibaut Paumard, Aurélie Guilbert-Lepoutre, Maïca Clavel et al. (+5 more)
Promoting diversity, equity, inclusion and accessibility (DEIA) is both a legal and professional responsibility in French research institutions. This paper presents practical strategies to foster inclusive work environments within French research units. We summarize the regulatory context, key findings from the INSU-AA prospective on discrimination, and fundamental principles for promoting equity. We discuss approaches to mitigate implicit biases across all career stages, from early education to retirement, and outline strategies for equitable recruitment and career advancement. Concrete initiatives in one of our units (LESIA/LIRA) are described, including internal communications, exhibitions, and accessible pedagogical activities. The creation of a dedicated commission within the unit council ensures coordinated DEIA efforts, legitimized by institutional support and methodical planning. By sharing these experiences, we provide actionable guidance for research units seeking to advance DEIA in science.
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All authors Thibaut Paumard, Aurélie Guilbert-Lepoutre, Maïca Clavel, Florence Cornu, Ludovic Petitdemange, François Dulieu, Léa Griton, Rhita-Maria Ouazzani
General Physics
Baryogenesis constraints and parameter bounds in $f(T,T_{G})$ modified gravity
Amit Samaddar and S. Surendra Singh
We investigate the generation of the observed
baryon asymmetry of the Universe within the framework of $f(T,T_{G})$
gravity, where $T$ is the torsion scalar and $T_{G}$ denotes its teleparallel Gauss–Bonnet counterpart. Two illustrative models, $f(T,T_{G})=\alpha T+\beta \sqrt{T_{G}}$ and $f(T,T_{G})=-T+\delta\, T_{G}\ln(T_{G})$, are examined in a power-law background $a(t)=a_{0} t^{m}$. For both models, we derive analytic expressions for the
baryon-to-
entropy ratio $\eta_{B}/s$ using the standard and generalized baryogenesis formalisms, adopting high-energy decoupling conditions with $g_{b}=1$, $g_{s}=106$, $T_{D}=2\times10^{16}\,\mathrm{GeV}$, and $M_{\star}=2\times10^{12}\,\mathrm{GeV}$. Consistency of the cosmological dynamics requires $m>1$, and the observed value $\eta_{B}/s \simeq 9.42\times10^{-11}$ is obtained for constrained intervals of the parameters $\alpha$, $\beta$, $\delta$, and $m$. Numerical results confirm that both models reproduce the measured
baryon asymmetry without invoking extra fields or exotic matter sources. These findings indicate that teleparallel
gravity with a Gauss–Bonnet torsion term provides a natural and viable mechanism for baryogenesis, offering a compelling alternative to
curvature-based descriptions of the early Universe.
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Optics
Detection and imaging of chemicals and hidden explosives using terahertz time-domain spectroscopy and deep learning
Xinghe Jiang, Yuhang Li, Yuzhu Li et al. (+3 more)
Detecting concealed chemicals and explosives remains a critical challenge in global security. Terahertz time-domain spectroscopy (THz-TDS) offers a promising non-invasive and stand-off detection technique owing to its ability to penetrate optically opaque materials without causing ionization damage. While many chemicals exhibit distinct spectral features in the terahertz range, conventional terahertz-based detection methods often struggle in real-world environments, where variations in sample geometry, thickness, and packaging can lead to inconsistent spectral responses. In this study, we present a chemical imaging system that integrates THz-TDS with deep learning to enable accurate pixel-level identification and classification of different explosives. Operating in reflection mode and enhanced with plasmonic nanoantenna arrays, our THz-TDS system achieves a peak dynamic range of 96 dB and a detection bandwidth of 4.5 THz, supporting practical, stand-off operation. By analyzing individual time-domain pulses with deep neural networks, the system exhibits strong resilience to environmental variations and sample inconsistencies. Blind testing across eight chemicals, including pharmaceutical excipients and explosive compounds, resulted in an average classification accuracy of 99.42% at the pixel level. Notably, the system maintained an average accuracy of 88.83% when detecting explosives concealed under opaque paper coverings, demonstrating its robust generalization capability. These results highlight the potential of combining advanced terahertz spectroscopy with neural networks for highly sensitive and specific chemical and explosive detection in diverse and operationally relevant scenarios.
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All authors Xinghe Jiang, Yuhang Li, Yuzhu Li, Che-Yung Shen, Aydogan Ozcan, Mona Jarrahi
Optics
Quantum-optimal nonlinear microscopy with classical light
Joshua L. Reynolds, Shaun C. Burd, Tzu-Chieh Yen et al. (+3 more)
Nonlinear optical processes are used in biological microscopy to surpass the diffraction limit on resolution, image deeper into
brain tissues, and identify biomolecules without exogenous labels. These techniques typically require high optical intensities to increase the strength of the nonlinear interactions, which can perturb native biochemistry and damage or kill living samples. Stimulated Raman scattering (SRS) microscopy visualizes the spatial distribution of molecules using a nonlinear interaction between light and chemically specific molecular vibrations. However, the detection of biomolecules at low concentrations is limited by the total
photon dose that can be applied before photodamage alters the sample, and
photon shot noise sets the minimum achievable noise floor for most microscopes. Here we demonstrate a cavity-enhanced SRS microscope that is more sensitive than an equivalent conventional SRS microscope by up to 8.3(7) dB in spectroscopy and 8.6(1) dB in
cell imaging. These results approach
quantum limits on sensitivity and demonstrate that
quantum states of light are sufficient but not necessary to enhance the sensitivity of microscopy techniques that are limited by photodamage.
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All authors Joshua L. Reynolds, Shaun C. Burd, Tzu-Chieh Yen, Samsuzzoha Mondal, Soichi Wakatsuki, Mark A. Kasevich
Chemical Physics
Quantum Chemistry Simulation of Dibenzothiophene for Asphalt Aging Analysis
Om Tailor
This paper presents the execution and analysis of a comprehensive
quantum chemistry pipeline for gathering actionable insight into asphalt aging mechanisms through the study of dibenzothiophene (DBT), a key sulfur-containing compound in asphalt binders. Using advanced
quantum algorithms, specifically Variational
Quantum Eigensolver (VQE) with k-UpCCGSD and ADAPT-VQE ansatze, we achieved ground state energy calculations with accuracies reaching -864.69 Ha. Our implementation demonstrates
quantum advantages in handling strongly correlated electron systems while providing actionable insights for designing oxidation-resistant asphalt formulations. The work also establishes a scalable framework for
quantum-enhanced materials design.
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Fluid Dynamics
Interactions Between Internal Solitary Waves and Floating Canopies
Jen-Ping Chu, Mitul Luhar and Patrick Lynett
Interactions between internal solitary waves and floating canopies of varying length and porosity are examined via laboratory experiments and complementary simulations for a miscible, two-layer system. In both approaches, internal solitary waves of varying amplitudes are generated by a jet-array mechanism that is driven by the nonlinear eKdV solution. Pycnocline displacements, phase speeds, and velocity fields are obtained using synchronized planar
laser-induced fluorescence and particle imaging velocimetry systems in the experiment. In the simulations, the canopy is represented as a porous zone with prescribed porosity and hydraulic conductivity determined by the Kozeny-Carman model, which is validated by comparing simulated and measured horizontal velocity profiles. The higher-porosity (transitional) canopy produces a nearly monotonic, albeit minor, amplitude reduction and negligible wave energy dissipation after the interaction. However, the shear layer developed at the bottom edge of the lower-porosity (dense) canopy grows to a comparable strength as the shear sustained by the internal solitary wave profile at the pycnocline. The
vortex pair generated by this shear accelerates the upper-layer fluid beneath the canopy, leading to complex nonlinear amplitude modulation and significant wave transformation. With an extended canopy length, the internal solitary waves settle to a quasi-steady state with a significant phase speed reduction. Upon the wave exiting the canopy, flow separation at the downstream edge of the canopy again pairs with the shear at the pycnocline, inducing an intensified jet. This complex interaction leads to energy transfer between kinetic and potential energy under the dense canopy.
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Optics
Universal Quantum Interconnects via Phase-Coherent Four-Wave Mixing
Hao Zhang, Yang Xu, Linshan Sun et al. (+3 more)
Quantum transduction, which enables the coherent conversion of
quantum information between disparate physical platforms, is a cornerstone for realizing scalable and interoperable
quantum networks. Among various approaches, parametric frequency mixing processes such as four-wave mixing (FWM) offer a promising pathway toward efficient and low-noise transduction. In this work, we demonstrate the feasibility of coherent
quantum state transfer by indirectly verifying high-fidelity wavefunction's phase mapping (>99%) from the input field to the generated output field wave. Using a gas-filled hollow-core capillary fiber, we systematically investigate spectral phase
evolution across a broad range, including infrared (IR) to ultraviolet (UV) transitions, as well as conversions from telecom-band (1550 nm) to visible (516 nm) and deep-UV (308 nm) wavelengths. Our results reveal that strong phase coherence can be maintained throughout these diverse conversion regimes. Because
quantum properties such as coherence and
entanglement are intrinsically encoded in both the amplitude and phase of a photonic wavefunction, preserving spectral phase is essential for faithful
quantum information transfer. We further show that efficient and phase-preserving transduction can be achieved by tuning system parameters, offering valuable insights into nonlinear coupling dynamics. These findings establish a promising foundation for advancing FWM-based
quantum transduction schemes and open new avenues for integrating heterogeneous
quantum systems across wide spectral domains within future
quantum communication networks.
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All authors Hao Zhang, Yang Xu, Linshan Sun, Wei Cui, Robert W. Boyd, Sergio Carbajo
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
More is different: How chemical complexity influences stability in high entropy oxides
Ksenia Khoroshun, Mario U. González-Rivas and Alannah M. Hallas
Tailoring the chemical composition of a high
entropy oxide (HEO) is a powerful approach to enhancing desirable material properties. However, the targeted synthesis of HEO materials is often hindered by competing stabilizing and destabilizing factors, which are difficult to predict. This work examines the effects of increased configurational
entropy on the phase formation and stability of four notable complex
oxide families: perovskite ($AB$O$_3$), pyrochlore ($A_2B_2$O$_7$), Ruddlesden-Popper ($A_2B$O$_4$), and zirconium tungstate ($AB_2$O$_8$). Each of these structures has a tetravalent cation site, which we attempt to substitute with an entropic mixture of four cations, benchmarked by the parallel synthesis of a non-disordered reference compound. While all four target high
entropy materials can be expected to form based on ionic radii criteria, only the high
entropy perovskite Ba(Ti,Zr,Hf,Sn)O$_3$ is successfully synthesized. In the case of the pyrochlore, an
entropy-stabilized defect fluorite is formed instead, while the Ruddlesden-Popper phase co-exists with multiple competing phases. For the tungstate, an unexpected deep eutectic point between the precursors results in melting that precedes the formation of a high
entropy phase. Our case studies therefore illustrate that the stability of HEOs cannot be straightforwardly predicted based on ionic radii,
lattice geometry, and charge-balancing considerations alone due to the underlying complexity of the interactions between the many chemical constituents.
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Instrumentation and Detectors
Mu2e Straw Tube Tracker Gas Flow Quality Control
Vishal Bharatwaj, Scott N. Israel, Mamta Jangra et al. (+14 more)
We present a tracker gas flow quality control method developed for the Mu2e straw tube tracker. Using time-dependent current measurements, we quantify the onset time of ionization gain induced by an 55Fe source during gas exchange, which is correlated to the gas conductance in the straw. This allows for the identification of channels with inadequate flow. This approach is broadly applicable to other gaseous detectors that require high-channel-count screening.
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All authors Vishal Bharatwaj, Scott N. Israel, Mamta Jangra, Minh Truong Nguyen, Joey Peck, Matthew Stortini, Nam H. Tran, Dan Ambrose, Andrew Edmonds, Hannah Hass, Emma R. Martin, Aseet Mukherjee, Klara Northrup, James L. Popp, Vadim L. Rusu, Robert S. Tschirhart, Robert L. Wagner
Plasma Physics
A simple procedure for generating a Kappa distribution in PIC simulation
Seiji Zenitani
For kinetic modeling of
plasma processes in space, a rejection-sampling procedure for generating a Kappa distribution in particle-in-
cell (PIC) simulation is proposed. A Pareto distribution is employed as an envelope distribution. The procedure only requires uniform variates, and its acceptance efficiency is $\approx 0.73$–$0.8$.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Enhancing solar cell efficiency of AlxIn1-xN/Si heterojunctions using an a-Si buffer: A study of material, interface and device properties
M. Sun, R. G. Cornejo, M. de la Mata et al. (+4 more)
This study explores the impact of an optimized amorphous silicon (a-Si) buffer layer on AlxIn1-xN-on-Si(100) heterojunction
solar cells, with Al content varying from 0% (InN) to 55%. The buffer layer improves the structural quality of the AlInN layer, as evidenced by reduced full width at half maximum values in X-ray diffraction rocking curves around the AlInN (0002) peak. Atomic force microscopy reveals that the buffer layer does not alter surface roughness. The effectiveness of the a-Si buffer is demonstrated by an enhancement of the conversion efficiency under AM1.5G illumination from 3.3 % to 3.9 % for devices with 35 % Al. Looking at the effect of the Al content in devices with the a-Si buffer, the device with 22% Al shows the best photovoltaic performance, with a conversion efficiency of 4.1 % and a VOC of 0.42 V, JSC of 15.4 mA/cm2, and FF of 63.3%. However, performance declines for Al contents above 36% due to increased resistivity and reduced carrier concentration. These findings highlight the critical role of the novel a-Si buffer layer developed by RF-sputtering and the Al content in optimizing AlInN/Si heterojunction
solar cell performance.
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All authors M. Sun, R. G. Cornejo, M. de la Mata, S. I. Molina, B. Damilano, S. Valdueza-Felip, F. B. Naranjo
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Characterizing Defect Dynamics in Silicon Carbide Using Symmetry-Adapted Collective Variables and Machine Learning Interatomic Potentials
Soumajit Dutta, Cunzhi Zhang, Gustavo Perez Lemus et al. (+4 more)
Silicon carbide (SiC) divacancies are attractive candidates for
spin defect
qubits possessing long coherence times and optical addressability. The high activation barriers associated with SiC defect formation and motion pose challenges for their study by first-principles molecular dynamics. In this work, we develop and deploy machine learning interatomic potentials (MLIPs) to accelerate defect dynamics simulations while retaining ab initio accuracy. We employ an active learning strategy comprising
symmetry-adapted collective variable discovery and enhanced sampling to compile configurationally diverse training data, calculation of energies and forces using density functional theory (DFT), and training of an E(3)-equivariant MLIP based on the Allegro model. The trained MLIP reproduces DFT-level accuracy in defect transition activation free energy barriers, enables the efficient and stable simulation of multi-defect 216-atom supercells, and permits an analysis of the temperature dependence of defect thermodynamic stability and formation/annihilation kinetics to propose an optimal annealing temperature to maximally stabilize VV divacancies.
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All authors Soumajit Dutta, Cunzhi Zhang, Gustavo Perez Lemus, Juan J. de Pablo, Francois Gygi, Giulia Galli, Andrew L. Ferguson
Physics and Society · Cross-listed from astro-ph.IM
LEBS Toolkit for Addressing Development Challenges through Astronomy
Joyful E. Mdhluli
The LEBS Toolkit provides a comprehensive framework for astronomers and natural scientists to address development challenges through their field. The toolkit aligns with the Sustainable Development Goals (SDGs) and offers practical actions to achieve development outcomes. It emphasises the importance of effective communication between astronomy and development, highlighting four key components: Leadership, Externalities, Break Barriers to Entry and Support Functioning
Markets & Institutions (LEBS). Using these components, scientists can promote accurate information dissemination, encourage positive community impacts, overcome monopolistic barriers, and improve
market efficiency and institutional settings. The LEBS Toolkit serves as a guide for the scientific community in bridging the gap between scientific knowledge and practical development actions, ultimately contributing to global development goals.
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Atmospheric and Oceanic Physics
High-Resolution Retrieval of Atmospheric Boundary Layers with Nonstationary Gaussian Processes
Haoran Xiong, Paytsar Muradyan and Christopher J. Geoga
The atmospheric boundary layer (ABL) plays a critical role in governing turbulent exchanges of momentum, heat moisture, and trace gases between the Earth's surface and the free atmosphere, thereby influencing meteorological phenomena, air quality, and
climate processes. Accurate and temporally continuous characterization of the ABL structure and height
evolution is crucial for both scientific understanding and practical applications. High-resolution
retrievals of the ABL height from vertical velocity measurements is challenging because it is often estimated using empirical thresholds applied to profiles of vertical velocity variance or related
turbulence diagnostics at each measurement altitude, which can suffer from limited sampling and sensitivity to noise. To address these limitations, this work employs nonstationary Gaussian process (GP) modeling to more effectively capture the spatio-temporal dependence structure in the data, enabling high-quality – and, if desired, high-resolution – estimates of the ABL height without reliance on ad-hoc parameter tuning. By leveraging Vecchia approximations, the proposed method can be applied to large-scale
datasets, and example applications using full-day vertical velocity profiles comprising approximately $5$M measurements are presented.
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Biological Physics · Cross-listed from nlin.CD
Bifurcation Analysis of the Driven FitzHugh-Nagumo Oscillator: Prediction and Experiment
Edward H. Hellen
Bifurcation analysis is applied to the FitzHugh-Nagumo oscillator driven by a sinusoidal source. A numerically generated 2d regime map showing the variety of oscillatory dynamics in the parameter space of source frequency and amplitude agrees well with a map created from analog
circuit measurements. Application of the sinusoidal source to the fast variable's first-order differential equation produces an island in the map in which oscillations at the source frequency are unstable and the behavior is dominated by two distinct families of subharmonic limit cycles and by chaos. Previously published maps are portions of the map shown here and are shown to be consistent with it. The more detailed and comprehensive regime map presented here should facilitate the understanding of this foundational system and thereby aid the ongoing research involving more complicated implementations of the Fitzhugh-Nagumo system.
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Computational Physics
Persistent-variable thermal compositional simulation of multiphase flow with phase separation in porous media
Veljko Lipovac, Omar Duran, Eirik Keilegavlen et al. (+1 more)
Thermal compositional multiphase flow in porous media with phase transitions involves complex nonlinear interactions among flow, transport, and phase
equilibrium. This paper presents a persistent-variable formulation for thermal compositional flow using enthalpy to formulate the energy balance and the local
equilibrium problem.
Equilibrium conditions are derived from a thermodynamically consistent minimization problem using a persistent set of variables, allowing for seamless integration of
equilibrium calculations into a fully coupled flow and transport model. This formulation does not require phase stability tests and provides a continuous and full mathematical description of the multiphysics system, suitable for challenging non-isothermal scenarios. To tackle the nonlinearities arising from phase transitions, we embed a local solver for the thermodynamic subproblem within a global Newton solver for the fully implicit system. The local solver exploits the locality of the subproblem for parallelization and leverages the modularity of the persistent-variable formulation for both isothermal and isenthalpic
equilibrium conditions locally. We demonstrate the capability of our approach to simulate complex high-enthalpy systems, including narrow-boiling phenomena. The impact of the embedded local solver is analyzed through numerical experiments, demonstrating a reduction in global nonlinear iterations of up to 23 % with increased use of the local solver. The number of local iterations is controlled with a local solver tolerance and no significant impact on the global iteration number was observed for local residual tolerances as high as $1e-3$. The persistent-variable approach using enthalpy and the modularity of the embedded local solver advance the usage of
equilibrium calculations in multiphase flow simulations and are suitable for high-enthalpy applications.
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All authors Veljko Lipovac, Omar Duran, Eirik Keilegavlen, Inga Berre
Data Analysis and Statistics · Cross-listed from hep-ph
Resummed Distribution Functions: Making Perturbation Theory Positive and Normalized
Rikab Gambhir and Radha Mastandrea
Fixed-order perturbative calculations for differential cross sections can suffer from non-physical artifacts: they can be non-positive, non-normalizable, and non-finite, none of which occur in experimental measurements. We propose a framework, the Resummed Distribution Function (RDF), that, given a perturbative calculation for an observable to some finite order in $\alpha_s$, will “resum” the expression in a way that is guaranteed to match the original expression order-by-order and be positive, normalized, and finite. Moreover, our ansatz parameterizes all possible finite, positive, and normalized completions consistent with the original fixed-order expression, which can include N$^n$LL resummed expressions. The RDF also enables a more direct notion of perturbative uncertainties, as we can directly vary higher-order parameters and treat them as nuisance parameters. We demonstrate the power of the RDF ansatz by matching to thrust to $\mathcal{O}(\alpha_s^3)$ and extracting $\alpha_s$ with perturbative uncertainties by fitting the RDF to ALEPH data.
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Data Analysis and Statistics · Cross-listed from hep-ph
Enhancing next token prediction based pre-training for jet foundation models
Joschka Birk, Anna Hallin, Gregor Kasieczka et al. (+3 more)
Next
token prediction is an attractive pre-training task for jet foundation models, in that it is simulation free and enables excellent generative capabilities that can transfer across
datasets. Here we study multiple improvements to next
token prediction, building on the initial work of OmniJet-$\alpha$. Instead of tokenizing particles and subsequently only using the
token-ID as the model input for both the generative and the classification task, we adopt a hybrid setup, which allows us to use continuous feature vectors as model input while only using
token-IDs in the next
token prediction target. Secondly, we explore a combined pre-training strategy that combines masked particle modeling and generative learning objectives. Taken together, these changes greatly improve the performance in downstream classification tasks without any loss in generative performance.
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All authors Joschka Birk, Anna Hallin, Gregor Kasieczka, Nikol Madzharova, Ian Pang, David Shih
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Double Perovskites K2NbTaO6 and Rb2NbTaO6 from First-Principles: Towards Efficient Materials for Green Energy
Ouendadji Salima, Aissani Ali, El Haj Hassan Fouad et al. (+1 more)
The structural flexibility and multifunctional nature of double perovskite
oxides make them attractive for applications requiring coupled optical, mechanical, and thermal performance. Using first-principles computations, this study examines the structural, electronic, elastic, optical, and thermoelectric stability of K2NbTaO6 and Rb2NbTaO6. The two compounds combine to form a cubic double perovskite structure with ordered Nb$^{5+}$ and Ta$^{5+}$ cations. The calculated elastic constants satisfy the Born stability criteria, confirming mechanical stability; however, both K2NbTaO6 and Rb2NbTaO6 exhibit brittle behavior according to Pugh's ratio, reflecting limited ductility. Semiconducting behavior is revealed by band structure analysis with energy gaps of 2.79 eV for K2NbTaO6 and 2.63 eV for Rb2NbTaO6. Optical spectra show noticeable absorption in the high-energy region near the UV, indicating relevance for theoretical studies of optoelectronic and photocatalytic processes, without implying practical device efficiency. Therm
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All authors Ouendadji Salima, Aissani Ali, El Haj Hassan Fouad, Benahmedi Lakhdar
Fluid Dynamics
Effective permeabilities for flow through anisotropic microscopic geometries
Loïc Balazi, Fabian Holzberger, Stephan B. Lunowa et al. (+3 more)
This work develops a computational and theoretical framework for determining effective permeabilities in anisotropic microscopic geometries containing dense, fibre-like obstacles, motivated by the need to model flow in coiled aneurysm domains accurately. Building on homogenisation theory and fully resolved simulations in Representative Elementary Volumes (REVs), we validate the permeability model introduced in [C. Boutin, Study of permeability by periodic and self-consistent homogenisation. Eur. J. Mech. A Solids, 19(4):603-632, 2000] and propose a systematic methodology for capturing the directional variations induced by fibre orientation. The resulting permeability tensors are incorporated into macroscopic flow simulations based on the Darcy equation, enabling direct comparison of anisotropic and isotropic permeability models across several
benchmark configurations. Our findings show that anisotropy has a significant impact on local flow direction and magnitude, generating directional permeability contrasts which cannot be reproduced by classical isotropic approximations. By integrating coil-induced microstructural effects into continuum-scale hemodynamic models, the proposed approach enables more realistic assessment of post-treatment aneurysm flow behaviour. Beyond this clinical application, the framework is broadly applicable to other biomedical and engineering systems involving fibrous or filamentous porous microstructures.
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All authors Loïc Balazi, Fabian Holzberger, Stephan B. Lunowa, Malte A. Peter, Daniel Peterseim, Barbara Wohlmuth
History and Philosophy of Physics
Questions related to the Deflection of Light by Gravity determined by Soldner, Einstein and Schwarzschild
Klaus Wilhelm, Bhola N. Dwivedi and Karsten Muller
Before we discuss the deflection of light in a gravitational field, we give a brief overview of some basic physical formulas on
photon properties, generation and propagation. The much debated problems of the
redshift and the
photon propagation in a gravitational field is then considered and applied to the calculation of the speed of light. Many citations are given in direct quotations to avoid any misunderstandings. If the quotations are in German, an English translation is provided. Based on this speed, calculated and measured results are recalled on the deflection of light, with emphasis on the deflection near the Sun. We conclude that the speed of light and the deflection angle can be determined by energy and momentum conservation principles.
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