Instrumentation and Detectors
Ultra-trace analysis of U and Th in organic liquid scintillators with high sensitivity
A. Barresi, D. Chiesa, D. Merli et al. (+63 more)
Rare event searches demand extremely low background levels, necessitating ever-advancing screening techniques to enhance sensitivity.
Liquid scintillators are highly attractive as detector media due to their inherent radiopurity and scalability in mass. In this work, we present a screening procedure to measure ultra-trace concentrations of natural contaminants – $^{238}$U and $^{232}$Th – with sensitivities at the \qty{E-15}{g/g} level. Our method combines
neutron activation analysis with radiochemical techniques, followed by \bg\ coincidence spectroscopy to minimize interference backgrounds. This approach achieves sensitivities of \qty{0.65E-15}{g/g} for $^{238}$U and \qty{2.3E-15}{g/g} for $^{232}$Th, among the best reported worldwide. Potential pathways for further sensitivity improvements are outlined in the conclusions.
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All authors A. Barresi, D. Chiesa, D. Merli, M. Nastasi, S. Nisi, E. Previtali, M. Sisti, M. Borghesi, A. Cammi, C. Coletta, G. Ferrante, L. Loi, G. Andronico, V. Antonelli, D. Basilico, M. Beretta, A. Bergnoli, A. Brigatti, R. Brugnera, R. Bruno, A. Budano, B. Caccianiga, V. Cerrone, R. Caruso, C. Clementi, L.V. D'Auria, S. Dusini, A. Fabbri, G. Felici, A. Garfagnini, M.G. Giammarchi, N. Giudice, A. Gavrikov, M. Grassi, N. Guardone, F. Houria, C. Landini, L. Lastrucci, I. Lippi, P. Lombardi, F. Mantovani, S.M. Mari, A. Martini, L. Miramonti, M. Montuschi, D. Orestano, F. Ortica, A. Paoloni, L. Pelicci, E. Percalli, F. Petrucci, G. Ranucci, A.C. Re, B. Ricci, A. Romani, P. Saggese, A. Serafini, C. Sirignano, L. Stanco, E. Stanescu Farilla, V. Strati, M.D.C Torri, C. Tuve', C. Venettacci, G. Verde, L. Votano
Geophysics
Calendar Time Local Earthquake Forecasts from Earthquake Nowcasts: A Do-It-Yourself (DIY) Ensemble Method
John B Rundle, Ian Baughmann, Andrea Donnellan et al. (+3 more)
This paper presents a new technical method for computing calendar time forecasts in a local area for large earthquakes of a target magnitude MT using a count small earthquakes MS < MT in the area, together with the Gutenberg-Richter (GR) magnitude-frequency relation. The GR relation states that for every large target earthquake of magnitude greater than MT , there are on average NGR small earthquakes of magnitude MT > M >= MS. The only assumption is that the GR statistics of the local area are the same as in the larger surrounding regions. This assumption is used to construct an ensemble of earthquakes in larger surrounding regions to be used in computing the forecast. The method has significant skill, as defined by the Receiver Operating Characteristic (ROC) test, which improves as time since the last major earthquake increases. The probability is conditioned on the number of small earthquakes n(t) that have occurred since the last large earthquake. There is no need to assume a probability model, as the probability is instead computed directly as the Positive Predictive Value (PPV) associated with the ROC curve. The method is validated by comparison to the UCERF3 forecasts for the UCERF3-defined geographic boxes centered on Los Angeles and San Francisco. The method is then applied to a 125-KM radius circular area around Los Angeles, California, following the January 17, 1994 magnitude M6.7 Northridge earthquake, and short term forecasts (1 year and 5 year ) are computed.
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All authors John B Rundle, Ian Baughmann, Andrea Donnellan, Lisa Grant Ludwig, Geoffrey C Fox, Kazuyoshi Nanjo
Geophysics
Mount Rainier and Liberty Cap Elevation Survey 2025
Eric Gilbertson, Larry Signani, Branden Joy et al. (+5 more)
In 2024, we discovered that Columbia Crest, the historical summit of Mount Rainier, was no longer the highest point on the mountain. Instead, a point 133 m (436 ft) to the south along the southwest rim (SW Rim) was determined to be the new highest point on Mount Rainier. The Columbia Crest icecap melted down 6.64 m (21.8 ft) since 1998. A nearby peak, Liberty Cap, melted down 8.02 m (26.3 ft) since 2007. For this report, updated elevation measurements were taken in late summer 2025 of Columbia Crest and Liberty Cap. Columbia Crest melted an additional 0.37 m (1.2 ft) and Liberty Cap melted 0.67 m (2.2 ft) over the last year. To understand how Mount Rainier's summit may continue to evolve, we used ground-penetrating radar (GPR) to measure the thickness of the Columbia Crest icecap and Liberty Cap. As of 2025, ice is approximately 2 m - 5 m (6.6 ft - 16.5 ft) thick near the summit of Columbia Crest and 10 m - 13 m (32.8 ft - 42.7ft) thick near the summit of Liberty Cap. Using recent measurements by our team and other surveyors, melt rates for Columbia Crest have been -0.27 m/year (-0.9 ft/year) since 1998 (R squared = 0.990) and -0.49 m/year (-1.6 ft/year) for Liberty Cap since 2007 (R squared = 0.998). Based on the elevation of the nearest high-elevation visible rock, Liberty Cap will lose its status as an ice-capped peak by 2041. Assuming recent rates of change continue, it will melt to bedrock by 2047. Columbia Crest is already no longer the highest point on Mount Rainier, and it will likely melt to bedrock by 2045. As of 2025, our results indicate that the summit of Mount Rainier on the SW Rim is at an elevation of 4391.04 m (14406.3 ft +/- 0.1 ft) (NAVD88).
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All authors Eric Gilbertson, Larry Signani, Branden Joy, Daniel McGrath, Darin Loucks, Ethan O'Connor, Shannon Cheng, Scott Hotaling
Fluid Dynamics
An Euler-Lagrangian Multiphysics Coupling Framework for Particle-Laden High-Speed Flows
Hyeon Woo Nam, Tae Woong Jeong and Sung Min Jo
Particle-laden effects in high-speed flows require a coupled Euler and Lagrangian prediction technique with varying fidelity of thermochemical models, depending on the simulation conditions of interest. This requirement makes the development of a conventional monolithic solver challenging to manage the different fidelity of the thermochemical models within a single computational framework. To address this, the present study proposes a multi-solver framework for the coupled Euler-Lagrangian predictions applicable to various particle-laden high-speed flow conditions. Volumetric and surface couplings are established between a particle solver ORACLE (OpenFOAM-based lagRAngian CoupLEr) and a thermochemical nonequilibrium flow solver based on an adaptable data exchange
algorithm. The developed framework is then validated by predicting particle-laden supersonic nozzle flows and aerothermal heating around a hypersonic Martian atmospheric entry capsule. Finally, a quasi-1D approximation is proposed in conjunction with a surrogate method to efficiently and accurately predict particle-laden surface erosion, with quantified parametric uncertainty, for hypersonic aerothermal characterization.
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Optics
Observed enhanced emission at higher-order exceptional points in RF circuits
Nicolas Wyszkowski, Arunn Suntharalingam, Max Vitek et al. (+3 more)
The Purcell effect – stemming directly from the celebrated
Fermi's Golden Rule – links the enhanced emissivity of an emitter to the local density of states (LDoS) of a surrounding cavity. Under typical circumstances the LDoS is assumed to have a Lorentzian lineshape. Here, we go beyond the traditional Purcell framework by designing RF cavities with non-Lorentzian LDoS caused by higher-order non-Hermitian exceptional point degeneracies (EPDs) where $N\geq 2$ eigenfrequencies and their associated eigenmodes coalesce. We experimentally demonstrate a non-conventional emissivity enhancement (as compared to the isolated resonance regime) that increases with the EPD order $N$. The theoretical analysis traces its origin to an $N$-th power Lorentzian LDoS line shape that dominates under judicious spatially designed cavity losses. Our results reveal a new route to design cavities that do not rely on ultrahigh $Q$-factor resonators or small modal volumes.
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All authors Nicolas Wyszkowski, Arunn Suntharalingam, Max Vitek, Arkady Kurnosov, Lucas J. Fernández-Alcázar, Tsampikos Kottos
History and Philosophy of Physics
A result from the thesis of the french astronomer Alexandre Véronnet: critical latitudes
Hervé Le Ferrand
We are interested in a result found in the thesis of the astronomer Alexandre Véronnet (1876-1951) : "Precession of a fluid ring rotating along a parallel axis. Zone of maximum crustal compression at 35$^\circ$. A cause of earthquakes". In 1912, Alexandre Véronnet hypothesizes that the Earth's rotation influences the occurrence of earthquakes in the 35th parallel zone. Has this hypothesis been taken up by other authors, geophysicists, seismologists, etc.? Has it been confirmed or refuted? What is the literature on this subject? Our aim is not to draw a conclusion on this hypothesis but to examine the dissemination of a scientific result.
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Fluid Dynamics
Concentration Matters: Enhancing Particle Settling in Narrow Tilted Channels
Dipankar Kundu, Florencio Balboa Usabiaga, Adolfo Vázquez-Quesada et al. (+1 more)
Particles are known to sediment faster in containers with tilted walls than in vertical ones, a phenomenon known as the Boycott effect. In this work, we investigate how the tilt angle influences sedimentation in narrow channels across different particle volume fractions. Using particle-resolved computational fluid dynamics simulations, we reveal that there exists a concentration-dependent optimal tilt angle that maximizes sedimentation rates. Furthermore, at large tilt angles, the flow profiles across the channel deviate from the classical
parabolic shape. We show that these non-
parabolic profiles can be accurately captured by a one-dimensional Brinkman model, providing a predictive framework for understanding and tuning sedimentation in tilted geometries. Our findings demonstrate the potential to control and optimize particle settling by adjusting the channel tilt according to particle concentration, opening new possibilities for design in industrial and laboratory processes.
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All authors Dipankar Kundu, Florencio Balboa Usabiaga, Adolfo Vázquez-Quesada, Marco Ellero
Optics
Laser-written reconfigurable photonic integrated circuit directly coupled to a single-photon avalanche diode array
Giulio Gualandi, Simone Atzeni, Marco Gardina et al. (+8 more)
To date, most integrated
quantum photonics experiments rely on single-
photon detectors operating at cryogenic temperatures coupled to photonic integrated
circuits (PICs) through single-mode optical fibers. This approach presents significant challenges due to the detection complexity, as cryogenic conditions hinder the development of scalable systems. In addition, going towards fully-integrated devices or, at least, removing the optical fibers would be also advantageous to develop compact and cost-efficient solutions featuring a high number of optical modes. This work reports on the direct coupling of a PIC, fabricated by femtosecond
laser writing (FLW), and a silicon single-
photon avalanche diode (SPAD) array, fabricated in a custom planar technology and compatible with the operation at room temperature. The effectiveness of this solution is shown by achieving perfect coupling and a system detection efficiency as high as 41.0% at a wavelength of 561 nm, which is the highest value reported to date among both heterogeneous/hybrid integrated and directly coupled systems. We also show the robustness of the coupling to misalignments, demonstrating that costly
alignment procedures are not needed. Finally, we exploit the SPAD array to characterize a reconfigurable Mach-Zehnder interferometer, i.e., the basic building block of multimode reconfigurable PICs. This solution provides a new avenue to the design and implementation of
quantum photonics experiments, especially effective when compact and cost-efficient systems are needed.
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All authors Giulio Gualandi, Simone Atzeni, Marco Gardina, Antonino Caime, Giacomo Corrielli, Ivan Labanca, Angelo Gulinatti, Ivan Rech, Roberto Osellame, Giulia Acconcia, Francesco Ceccarelli
Computational Physics · Cross-listed from cs.LG
Hierarchical geometric deep learning enables scalable analysis of molecular dynamics
Zihan Pengmei, Spencer C. Guo, Chatipat Lorpaiboon et al. (+1 more)
Molecular dynamics simulations can generate atomically detailed trajectories of complex systems, but analyzing these dynamics can be challenging when systems lack well-established quantitative descriptors (features). Graph neural networks (GNNs) in which messages are passed between nodes that represent atoms that are spatial neighbors promise to obviate manual feature engineering, but the use of GNNs with biomolecular systems of more than a few hundred residues has been limited in the context of analyzing dynamics by both difficulties in capturing the details of long-range interactions with message passing and the
memory and runtime requirements associated with large graphs. Here, we show how local information can be aggregated to reduce
memory and runtime requirements without sacrificing atomic detail. We demonstrate that this approach opens the door to analyzing simulations of
protein-nucleic acid complexes with thousands of residues on single GPUs within minutes. For systems with hundreds of residues, for which there are sufficient data to make quantitative comparisons, we show that the approach improves performance and interpretability.
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All authors Zihan Pengmei, Spencer C. Guo, Chatipat Lorpaiboon, Aaron R. Dinner
Computational Physics · Cross-listed from cond-mat.dis-nn
Statistical physics for artificial neural networks
Zongrui Pei
The 2024 Nobel Prize in Physics was awarded for pioneering contributions at the intersection of artificial neural networks (ANNs) and
spin-glass physics, underscoring the profound connections between these fields. The topological similarities between ANNs and Ising-type models, such as the Sherrington-Kirkpatrick model, reveal shared structures that bridge statistical physics and machine learning. In this perspective, we explore how concepts and methods from statistical physics, particularly those related to glassy and disordered systems like
spin glasses, are applied to the study and development of ANNs. We discuss the key differences, common features, and deep interconnections between
spin glasses and neural networks while highlighting future directions for this interdisciplinary research. Special
attention is given to the synergy between
spin-glass studies and neural network advancements and the challenges that remain in statistical physics for ANNs. Finally, we examine the transformative role that
quantum computing could play in addressing these challenges and propelling this research frontier forward.
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Fluid Dynamics · Cross-listed from cond-mat.stat-mech
Convective Viscous Cahn-Hilliard/Allen-Cahn Equation with memory effects
P.O.Mchedlov-Petrosyan and L.N.Davydov
The combination of the well-known Cahn-Hilliard and Allen-Cahn equations is used to describe surface processes, such as simultaneous adsorption/desorption and surface
diffusion. In the present paper we have considered the convective-viscous Cahn-Hilliard/Allen-Cahn equation complemented by
memory effects. Exact solutions are obtained and the combined action of the applied field, dissipation and
memory are discussed.
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Instrumentation and Detectors
Observation of two nuclear recoil peaks induced by neutron capture on Al2O3
H. Abele, P. Ajello, B. Arnold et al. (+43 more)
We report the observation of two
nuclear recoil peaks induced by
neutron capture on aluminum in a cryogenic Al$_2$O$_3$ detector developed by the
NUCLEUS collaboration for the detection of reactor
neutrinos via coherent elastic
neutrino-
nucleus (CEvNS) process. Data collected at the Technical University of Munich in 2024 with a $^{252}$Cf source reveal a main
recoil line at 1145 eV from single-$\gamma$ de-excitation of $^{28}$Al and a newly observed structure near 575 eV originating from several two-$\gamma$ cascades. The latter constitutes the first direct measurement of a
nuclear recoil line induced by multi-$\gamma$ cascades. It is predicted by our simulations when the recoiling
nucleus has time to stop before the emission of the next $\gamma$-ray in the cascade. These results demonstrate the potential performance of the CRAB (Calibration
Recoil for Accurate Bolometry) method for in situ
nuclear recoil calibration and highlight the importance of accurately modeling
recoil stopping and
nuclear de-excitation times in cryogenic detectors of CEvNS and dark matter interactions.
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All authors H. Abele, P. Ajello, B. Arnold, E. Bossio, J. Burkhart, F. Cappella, N. Casali, R. Cerulli, J-P. Crocombette, G. del Castello, M. del Gallo Roccagiovine, P. de Marcillac, S. Dorer, C. Doutre, A. Erhart, S. Fichtinger, M. Friedl, C. Goupy, D. Hauff, E. Jericha, M. Kaznacheeva, H. Kluck, T. Lasserre, D. Lhuillier, O. Litaize, S. Marnieros, R. Martin, E. Namuth, T. Ortmann, L. Peters, D.V. Poda, F. Reindl, W. Reindl, J. Rothe, N. Schermer, J. Schieck, S. Schönert, C. Schwertner, G. Soum-Sidikov, R. Strauss, R. Thalmeier, L. Thulliez, M. Vignati, M. Vivier, P. Wasser, A. Wex
Optics
Giant optical anisotropy and visible-frequency epsilon-near-zero in hyperbolic van der Waals MoOCl2
Georgy Ermolaev, Adilet Toksumakov, Aleksandr Slavich et al. (+13 more)
The realization of extreme optical anisotropy is foundational to nanoscale light manipulation. Van der Waals (vdW)
crystal MoOCl2 has emerged as a promising candidate for this quest, hosting
hyperbolic plasmon polaritons in the visible and near-infrared wavelengths. However, the fundamental anisotropic dielectric tensor governing this behavior has remained elusive. Here, we resolve this problem by providing the first experimental determination of the full dielectric tensor of
hyperbolic vdW MoOCl2. Via spectroscopic ellipsometry, Mueller
matrix, and reflectance measurements, we quantify the material's optical duality: a metallic optical response ({\epsilon}_1 < 0) along the crystallographic a-axis and a dielectric response ({\epsilon}_1 > 0) along the orthogonal directions. This dichotomy drives an epsilon-near-zero (ENZ) condition at \approx 512 nm and results in
giant in-plane birefringence of \delta n \approx 2.2 for MoOCl2. As a result, our work provides the critical missing experimental parameters for MoOCl2, establishing it as a
benchmark hyperbolic and ENZ material.
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All authors Georgy Ermolaev, Adilet Toksumakov, Aleksandr Slavich, Anton Minnekhanov, Gleb Tselikov, Arslan Mazitov, Ivan Kruglov, Gleb Tikhonowski, Mikhail Mironov, Ilya Radko, Dmitriy Grudinin, Andrey Vyshnevyy, Zdeněk Sofer, Aleksey Arsenin, Kostya S. Novoselov, Valentyn Volkov
Applied Physics
Study on Improving Microwave Heating Uniformity Based on Phase-Frequency Simultaneous Modulation Technique
Xu Zhu, Shaoyue Wang, Da He et al. (+3 more)
Conventional microwave heating techniques are limited due to inherent thermal point residency effects and inadequate control over the heating process. A novel method is proposed to enhance microwave heating uniformity using the injection-pulling technique. In this method, the injection-pulling technique is used to achieve simultaneous modulation of both the output phase and frequency of the magnetron, thereby extending the locking bandwidth of the injection-locking technique. The output characteristics of the injection-pulled magnetron were validated through numerical calculations and experiments. Microwave heating experiments were conducted under both a five-cup water load and an absorbent paper load. Compared with conventional injection-locking frequency sweeping, the proposed method not only expands the sweeping bandwidth from 8 to 18 MHz but also further improves heating uniformity, offering more options for magnetron applications in microwave heating.
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All authors Xu Zhu, Shaoyue Wang, Da He, Liping Yan, Jianan Hu, Changjun Liu
Physics Education
Earth radius from a single sunrise image: a classroom-ready activity
Florian Dubath and Maria Alice Gasparini
We present a classroom based activity using a sunrise photograph of Mont Blanc shadow taken from Geneva to estimate the Earth radius. By determining the direction of
solar rays relative to the local vertical and accounting for atmospheric refraction, students can derive an upper bound approximately 70 percent above the accepted value. The discrepancy provides a concrete illustration of modelling assumptions and observational limitations. The activity combines
geometric reasoning, basic trigonometry, and order of magnitude estimation, allowing students to obtain a physically meaningful result from simple observations. Beyond its quantitative aspects, the approach highlights essential elements of the scientific method, including hypothesis formulation, model construction, uncertainty analysis, and comparison with external data, offering a structured introduction to Nature of Science concepts within upper secondary STEM curricula.
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Data Analysis and Statistics · Cross-listed from q-fin.ST
Detrended cross-correlations and their random matrix limit: an example from the cryptocurrency market
Stanisław Drożdż, Paweł Jarosz, Jarosław Kwapień et al. (+2 more)
Correlations in complex systems are often obscured by nonstationarity, long-range
memory, and heavy-tailed fluctuations, which limit the usefulness of traditional covariance-based analyses. To address these challenges, we construct scale and fluctuation-dependent correlation
matrices using the multifractal detrended cross-correlation coefficient $\rho_r$ that selectively emphasizes fluctuations of different amplitudes. We examine the spectral properties of these detrended correlation
matrices and compare them to the spectral properties of the
matrices calculated in the same way from synthetic Gaussian and $q$Gaussian signals. Our results show that detrending, heavy tails, and the fluctuation-order parameter $r$ jointly produce spectra, which substantially depart from the random case even under absence of cross-correlations in time series. Applying this framework to one-minute returns of 140 major cryptocurrencies from 2021-2024 reveals robust collective modes, including a dominant
market factor and several sectoral components whose strength depends on the analyzed scale and fluctuation order. After filtering out the
market mode, the empirical
eigenvalue bulk aligns closely with the limit of random detrended cross-correlations, enabling clear identification of structurally significant outliers. Overall, the study provides a refined spectral baseline for detrended cross-correlations and offers a promising tool for distinguishing genuine interdependencies from noise in complex, nonstationary, heavy-tailed systems.
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All authors Stanisław Drożdż, Paweł Jarosz, Jarosław Kwapień, Maria Skupień, Marcin Wątorek
Applied Physics · Cross-listed from cond-mat.mes-hall
Phase-Factor-Controlled Surface Spirals in the Magnetic Conical Phase: The Role of In-Plane Directionality
Haijun Zhao, Tae-Hoon Kim, Lin Zhou et al. (+1 more)
In
chiral magnets, the
magnetic textures surrounding domain walls exhibit a rich variety of structures, offering insights into fundamental physics and potential applications in spintronic devices. Conical spirals and related structures possess intrinsic in-plane directionalities governed by phase factors $\phi_0$, which are often obscured in long spirals due to cylindrical
symmetry but become prominent in short spirals or thin films. Using micromagnetic simulations, we systematically studied
magnetic textures at
ferromagnetic-conical interfaces (FCI), including 1D and 2D FCIs with various shapes. Surface spirals (SS) emerge adjacent to these FCIs, closely linked to the cone's in-plane reorientation. In 1D FCIs, reorientation controls the presence, shape, and topological charge of the SS, with a discontinuity point observed where spirals with opposite charges form on opposite sides. In 2D FCIs, eyebrow-like SS are evident. The reorientation angle between top and bottom SS is controlled by the film thickness, similar to stacked spirals reported previously. We further demonstrate that SSs form at the facets of skyrmion clusters within the conical phase, as confirmed by both simulations and Lorentz transmission electron microscopy observations in Co$_8$Zn$_{10}$Mn$_2$ thin films. The experiments specifically reveal two distinct formation pathways: thermally activated co-growth and field-driven transformation from residual helices. These findings establish $\phi_0$ as a fundamental control parameter for
magnetic states, enabling promising spintronic functionalities such as multi-state
memory through SS polymorphism and energy-efficient neuromorphic computing via controlled topological transitions.
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All authors Haijun Zhao, Tae-Hoon Kim, Lin Zhou, Liqin Ke
Fluid Dynamics
A Coupled CFD Framework for Combustor Turbine Interaction in a Research Aeroengine
Federico Lo Presti, Pierre Vauquelin, Jan Donndorf et al. (+3 more)
This work presents a fully coupled combustor turbine simulation framework applied to the MYTHOS aeroengine, developed within the Horizon Europe project MYTHOS, aimed at assessing the impact of Sustainable Aviation Fuels (SAFs) and hydrogen on next generation propulsion systems. The numerical setup features a dynamic, bidirectional coupling between a pressure-based solver with detailed finite rate chemistry, deployed in the combustor, and a density-based turbomachinery solver employing tabulated thermochemistry for efficiency, used for the turbine. The coupling is realised through a flux-averaging methodology that ensures conservative exchange of flow quantities and allows flow in arbitrary directions across the interface. Previous validation steps of presented methodology have shown the viability of the approach and are also shortly reviewd. The paper focuses on the chemistry handling strategy that guarantees thermochemical consistency between the two solvers. Coupled reacting simulations at cruise operating conditions demonstrate the capability of the framework to capture combustor generated hot streaks transport and their influence on turbine aerothermal loading. Comparison with segregated simulations of the two components shows that coupling captures the highly unsteady temperature and flow distributions at the turbine inlet and across the blade rows. Whilst mean aerodynamic loading are essentially unchanged, a realistic circumferential variability in blade thermal loading can be observed in the coupled simulations, thus establishing a consistent foundation for future studies on the effects of alternative fuels on core engine components.
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All authors Federico Lo Presti, Pierre Vauquelin, Jan Donndorf, Francesca di Mare, Xue-Song Bai, Christer Fureby
Fluid Dynamics
Characteristic Bending in Incompressible Flows
Matthew Blomquist, Stéphane Gaudreault and Maxime Theillard
We present the Characteristic Bending (CB) method, a general framework for advecting quantities under incompressible velocity fields. The method builds on standard semi-Lagrangian advection by interpreting the backward-in-time characteristic reconstruction as the construction of a reference map, a diffeomorphism between the current and initial geometries of the advected space. From this viewpoint, the CB method applies a volume-preserving projection to the map, systematically removing spurious compressible errors arising from time integration, interpolation, or from velocity fields that are only approximately divergence-free. This projection bends the characteristics toward the divergence-free space, preserving mass and
geometric features of the advected fields, even in the presence of significant error. We demonstrate the method in both two and three dimensions using
benchmark problems and for multiphase flows governed by the incompressible Navier-Stokes equations. The results show that the CB method serves as a drop-in replacement for traditional semi-Lagrangian schemes and as an augmentation of reference map formulations, offering improved robustness and accuracy in incompressible flow simulations.
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Fluid Dynamics
Model of incompressible turbulent flows via a kinetic theory
Ziyang Xin, Zhaoli Guo and Hudong Chen
Kinetic theory offers a promising alternative to conventional
turbulence modelling by providing a mesoscopic perspective that naturally captures non-
equilibrium physics such as non-Newtonian effects. In this work, we present an extension and theoretical analysis of the recent kinetic model for incompressible turbulent flows developed by Chen et al. (Atmos. 14(7), 1109, 2023), constructed for unbounded flows. The first extension is to reselect a relaxation time such that the turbulent transport coefficients are obtained more consistently and better align with well-established
turbulence theory. The Chapman-Enskog (CE) analysis of the kinetic model reproduces the traditional linear eddy viscosity and gradient
diffusion models for Reynolds stress and turbulent kinetic energy flux at the first order, and yields nonlinear eddy viscosity and closure models at the second order. Particularly, a previously unreported CE solution for turbulent kinetic energy flux is obtained. The second extension is to enable the model for wall-bounded turbulent flows with preserved near-wall asymptotic behaviours. This involves developing a low-Reynolds number kinetic model incorporating wall damping effects and viscous
diffusion, with boundary conditions enabling both viscous sublayer resolution and wall function application. Comprehensive validation against experimental and DNS data for turbulent plane Couette flow demonstrates excellent agreement in predicting mean velocity profiles, skin friction coefficients, and Reynolds stress distributions. It reveals that an averaged turbulent flow behaves similarly to a rarefied gas flow at a finite Knudsen number, capturing non-Newtonian effects inaccessible to linear eddy viscosity models. This kinetic model provides a physics-based foundation for
turbulence modelling with reduced empirical dependence.
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Atomic Physics · Cross-listed from quant-ph
Hybrid qubit-oscillator module from motional states of two interacting atoms
Jaeyong Hwang, Tianrui Xu, Sean R. Muleady et al. (+5 more)
We propose a
qubit-oscillator platform based on the motional states of two interacting atoms in an optical tweezer. By stroboscopically modulating an engineered trap with tunable anharmonicity, we implement a complete set of bosonic operations and their
qubit-controlled counterparts with high fidelity. This motional control enables accurate detection of
magnetic dipolar interactions with $\sim10$ Hz sensitivity in one second, reaching sub-Hz resolution within a few minutes in a $20\times20$ tweezer array under realistic experimental imperfections. Our approach establishes a versatile platform for motional
quantum control of two atoms, with applications to
spin-
boson physics and precision sensing of interaction potentials and trapping environments.
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All authors Jaeyong Hwang, Tianrui Xu, Sean R. Muleady, Steven K. Pampel, Gur Lubin, Dawson P. Hewatt, Cindy A. Regal, Ana Maria Rey
Physics and Society · Cross-listed from cond-mat.stat-mech
Thermodynamic description of world GDP distribution over countries
Klaus M. Frahm and Dima L. Shepelyansky
We apply the concept of Rayleigh-Jeans thermalization of classical fields for a description of the world Gross Domestic Product (GDP) distribution over countries. The thermalization appears due to a variety of interactions between countries with conservation of two integrals being total GDP and probability (norm). In such a case there is an emergence of Rayleigh-Jeans condensation at states with low GDP. This phenomenon has been studied theoretically and experimentally in multimode optical fibers and we argue that it is at the origin of emergence of poverty and oligarchic phases for GDP of countries. A similar phenomenon has been discussed recently in the framework of the Wealth Thermalization Hypothesis to explain the high inequality of wealth distribution in human society and companies at Stock Exchange
markets. We show that the Rayleigh-Jeans thermalization well describes the GDP distribution during the last 50 years.
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Geophysics
Toward Trustworthy Earthquake Catalogs in the Era of Automated Detection: A Probabilistic Framework for Robust Earthquake Location
Ziye Yu, Jinqing Sun, Yuqi Cai et al. (+4 more)
The rapid proliferation of deep-learning-based detection and association methods has greatly expanded automatically generated earthquake catalogs, but has also introduced false detections, mis-associated arrivals, and poorly constrained events, making rigorous uncertainty quantification essential. We present a fully probabilistic earthquake location framework that jointly infers hypocenters, origin times, phase-dependent noise scales, and contamination levels within a unified
Bayesian formulation. Robustness is achieved through a two-level hierarchical strategy: arrival-time residuals are modeled using a Student-$t$ scale-mixture to accommodate heavy-tailed noise, while an explicit two-component contamination model probabilistically classifies each phase pick as an inlier or outlier, with phase-specific contamination rates inferred from the data. This formulation avoids heuristic data rejection and manual thresholding. Posterior sampling is accelerated using a neural-network travel-time surrogate, enabling scalable inference for large catalogs. Synthetic tests demonstrate well-calibrated posterior uncertainties, and application to the 2022 Luding $M_s$~6.8 aftershock sequence shows that uncertainty-based screening reduces the catalog from 10{,}590 to 6{,}562 events without loss of recall. This framework provides a principled pathway toward statistically trustworthy earthquake catalogs in the era of automated seismic monitoring.
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All authors Ziye Yu, Jinqing Sun, Yuqi Cai, Zemin Liu, Pingping Wu, Xin Liu, Jiayan Tan
Chemical Physics · Cross-listed from cs.AI
GENIUS: An Agentic AI Framework for Autonomous Design and Execution of Simulation Protocols
Mohammad Soleymanibrojeni, Roland Aydin, Diego Guedes-Sobrinho et al. (+4 more)
Predictive atomistic simulations have propelled materials discovery, yet routine setup and debugging still demand computer specialists. This know-how gap limits Integrated Computational Materials Engineering (ICME), where state-of-the-art codes exist but remain cumbersome for non-experts. We address this bottleneck with GENIUS, an AI-agentic workflow that fuses a smart
Quantum ESPRESSO knowledge graph with a tiered hierarchy of large
language models supervised by a finite-state error-recovery machine. Here we show that GENIUS translates free-form human-generated
prompts into validated input files that run to completion on $\approx$80% of 295 diverse
benchmarks, where 76% are autonomously repaired, with success decaying exponentially to a 7% baseline. Compared with LLM-only baselines, GENIUS halves inference costs and virtually eliminates
hallucinations. The framework democratizes electronic-structure DFT simulations by intelligently automating protocol generation, validation, and repair, opening large-scale screening and accelerating ICME design loops across academia and industry worldwide.
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All authors Mohammad Soleymanibrojeni, Roland Aydin, Diego Guedes-Sobrinho, Alexandre C. Dias, Maurício J. Piotrowski, Wolfgang Wenzel, Celso Ricardo Caldeira Rêgo
Instrumentation and Detectors · Cross-listed from cond-mat.mtrl-sci
Measuring the buried interphase between solid electrolytes and lithium metal using neutrons
Andrew S. Westover, Katie L. Browning, Antonino Cannavo et al. (+6 more)
Interfaces are the key to next generation high energy batteries including solid state Li metal batteries. In solid state batteries, the buried nature of solid solid electrolyte electrode interfaces makes studying them difficult.
Neutrons have significant potential to non destructively probe these buried solid solid interfaces. This work presents a comparative study using both
neutron depth profiling (NDP) and
neutron reflectometry (NR) to study a model lithium metal-lithium phosphorus oxynitride (LiPON) solid electrolyte system. In the NDP data, no distinct interphase is observed at the interface. NR shows a difference between electrodeposited, and vapor deposited LiPON -Li interfaces but finds both are gradient interphases that are less than 30 nm thick. Additional simulations of the LiPON-Li2O-Li system demonstrate that NDP has an excellent resolution in the 50 nm-1 mm regime while NR has an ideal resolution from 0.1 - 200 nm with different sample requirements. Together NDP and NR can provide a complementary understanding of interfaces between Li metal and solid electrolytes across relevant length scales.
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All authors Andrew S. Westover, Katie L. Browning, Antonino Cannavo, Ralph Gilles, Jiri Vacik, James F. Browning, Neelima Paul, Giovanni Ceccio, Vasyl Lavrentiev
Optics · Cross-listed from quant-ph
Mitigating the Transition of SiV$^-$ in Diamond to an Optically Dark State
Manuel Rieger, Rubek Poudel, Tobias Waldmann et al. (+7 more)
Negatively charged silicon vacancy centers in diamond (SiV$^-$) are promising for
quantum photonic technologies. However, when subject to resonant optical excitation, they can inadvertently transfer into a zero-
spin optically dark state. We show that this unwanted change of charge state can be quickly reversed by the resonant
laser itself in combination with static electric fields. By defining interdigitated metallic contacts on the diamond surface, we increase the steady-state SiV$^-$ photoluminescence under resonant excitation by a factor $\ge3$ for most emitters, making it practically constant for certain individual emitters. We electrically activate single \sivs near the positively biased electrode, which are entirely dark without applying local electric fields. Using time-resolved 3-color experiments, we show that the resonant
laser not only excites the SiV$^-$, but also creates free holes that convert SiV$^{2-}$ to SiV$^-$ on a timescale of milliseconds. Through analysis of several individual emitters, our results show that the degree of electrical charge state controllability differs between individual emitters, indicating that their local environment plays a key role. Our proposed electric-field-based stabilization scheme enhances deterministic charge state control in group-IV color centers and improves its understanding, offering a scalable path toward
quantum applications such as
entanglement generation and
quantum key distribution.
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All authors Manuel Rieger, Rubek Poudel, Tobias Waldmann, Lina M. Todenhagen, Stefan Kresta, Nori N. Chavira Leal, Viviana Villafañe, Martin S. Brandt, Kai Müller, Jonathan J. Finley