Plasma Physics · Cross-listed from astro-ph.HE
Closure models for the feedback of energetic particles on plasma turbulence
J. Pratt
Energetic particles interact with the
plasma surrounding them, resonating with certain
plasma waves to stabilize them while destabilizing others, and changing the character of the background
turbulence in ways that have not been fully quantified or understood. Interaction with the turbulent background
plasma is key to the acceleration of many types of energetic particles including high-energy
cosmic rays,
solar energetic particles, and pick-up ions. This is a process that would ideally be described by a kinetic model, a type of model that follows a probability distribution function (PDF) for all particles in 7-dimensional space. Because of the high dimensionality of a kinetic model, such simulations use the largest computational resources available, and are yet unable to simulate a realistic number of particles, reach the large scales necessary for astrophysical problems, or use high-precision numerical methods. Two available alternatives to kinetic
plasma models have been explored: a multi-fluid model, and a hybrid fluid/Fokker-Planck model. These methods are hampered by the physical modeling of the coupling. We develop a new model, which follows the PDF for all particles; this can be viewed as a step toward physical realism above a multi-fluid MHD model, while also being more computationally efficient than a kinetic model. The equations we develop model both the background
plasma and the energetic particles self-consistently. Over the last decade, similar PDF methods have been developed to a high level of sophistication to model reactive flows and turbulent combustion for engineering applications. For treatment of the feedback of the energetic particles on a background
plasma, a PDF closure approach should evaluate the mean characteristics, including the density, with better statistical quality than will particle-sampling procedures.
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Computational Physics · Cross-listed from cs.LG
Physics-Informed Uncertainty Enables Reliable AI-driven Design
Tingkai Xue, Chin Chun Ooi, Yang Jiang et al. (+5 more)
Inverse design is a central goal in much of science and engineering, including frequency-selective surfaces (FSS) that are critical to microelectronics for telecommunications and optical metamaterials. Traditional surrogate-assisted optimization methods using deep learning can accelerate the design process but do not usually incorporate uncertainty quantification, leading to poorer optimization performance due to erroneous predictions in data-sparse regions. Here, we introduce and validate a fundamentally different paradigm of Physics-Informed Uncertainty, where the degree to which a model's prediction violates fundamental physical laws serves as a computationally-cheap and effective proxy for predictive uncertainty. By integrating physics-informed uncertainty into a multi-fidelity uncertainty-aware optimization workflow to design complex frequency-selective surfaces within the 20 - 30 GHz range, we increase the success rate of finding performant solutions from less than 10% to over 50%, while simultaneously reducing computational cost by an order of magnitude compared to the sole use of a high-fidelity solver. These results highlight the necessity of incorporating uncertainty quantification in machine-learning-driven inverse design for high-dimensional problems, and establish physics-informed uncertainty as a viable alternative to quantifying uncertainty in surrogate models for physical systems, thereby setting the stage for autonomous scientific discovery systems that can efficiently and robustly explore and evaluate candidate designs.
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All authors Tingkai Xue, Chin Chun Ooi, Yang Jiang, Luu Trung Pham Duong, Pao-Hsiung Chiu, Weijiang Zhao, Nagarajan Raghavan, My Ha Dao
Data Analysis and Statistics · Cross-listed from astro-ph.CO
Constraining reionization morphology and source properties with 21cm galaxy cross-correlation surveys
Yannic Pietschke, Anne Hutter and Caroline Heneka
Cross-correlations between 21cm observations and
galaxy surveys provide a powerful probe of reionization by providing robustness against foreground contamination while linking ionization morphology to
galaxies. We quantified the constraining power of 21cm
galaxy cross-power spectra for inferring the neutral hydrogen fraction, $x_\mathrm{HI}(z),$ and mean overdensity, $\langle 1+\delta_\mathrm{HI} \rangle(z)$, exploring dependence on the field of view;
redshift precision, $\sigma_z$; and minimum
halo mass, $M_\mathrm{h,min}$. We employed our simulation-based inference framework EoRFlow for likelihood-free parameter estimation. Mock observations include thermal noise for 100h of SKA-Low with foreground avoidance and realistic
galaxy-survey effects. For a fiducial survey ($\mathrm{FOV}=100\,\mathrm{deg}^2$, $\sigma_z=0.001$, $M_\mathrm{h,min}=10^{11}\mathrm{M}_\odot$), cross-power spectra yield unbiased constraints with posterior volumes (PVs) of $\sim$10% relative to priors. Cross-power measurements reduce the PV by 20-30% versus 21cm auto-power alone. With foreground avoidance, spectroscopic
redshift precision is essential; photometric
redshifts render cross-correlations uninformative. Notably, cross-power spectra constrain ionizing source properties, the escape fraction $f_\mathrm{esc,}$ and the
star formation efficiency $f_*$, which remain degenerate in auto-power (PV >60%). Tight constraints require either deep surveys detecting faint
galaxies ($M_\mathrm{h,min} \sim 10^{10}\mathrm{M}_\odot$) with moderate foregrounds (PV~11%) or conservative mass limits with optimistic foreground removal (PV~19%). 21cm
galaxy cross-correlations enhance morphology constraints beyond auto-power while enabling previously inaccessible source property constraints. Realizing full potential requires precise
redshifts and either faint
galaxy detection limits or improved 21cm foreground cleaning.
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Optics
Spin-redirection Berry phase with planar rays
Aymeric Braud and Renaud Gueroult
Geometric or Berry phases are fundamental manifestations that appear in many areas of physics. They arise from the geometry of the space describing the properties of multi-component wave fields. An important example for electromagnetic waves is the
spin-redirection Berry phase associated with the
evolution of the
spin direction. Because this effect has traditionally been studied in isotropic media where the
spin is aligned with the ray trajectory, it has become commonly assumed that this
spin-redirection Berry phase requires nonplanar rays. Here we show that a
spin-redirection phase can in fact arise along a planar ray if the
spin evolves along the ray. We expose this effect through the singular example of a moving unmagnetized
plasma, and demonstrate how this behavior can more generally arise from a finite transverse
spin. In identifying this new
spin-redirection mechanism our work not only provides the tools to discover additional manifestations of SOIs in nature, but also uncovers supplemental degrees of freedom to harness SOIs to control light.
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Optics
Broadband tunable narrow-linewidth laser based on scattering-enhanced fiber covering E-S-C-L bands
Minzhi Xu, Zechun Geng, Da Wei et al. (+9 more)
This work demonstrates a broadband tunable narrow-linewidth
laser based on scattering-enhanced fiber, covering the E-S-C-L wavelength bands from 1337.47 nm to 1631.39 nm, with a total tuning span of 293.92 nm. The
laser employs two
semiconductor optical amplifiers (SOAs) centered at 1420 nm and 1550 nm, which are connected into a single ring resonator via polarization multiplexing. Wavelength selection and tunability is realized using an ultra-broadband tunable filter based on a blazed grating. To suppress side longitude modes, an 18-meter-long femtosecond-
laser-empowered random scattering fiber is utilized inside the cavity as a feedback medium, yielding an output linewidths between 1.54 kHz and 2.61 kHz. Benefited from the fast response of the galvanometer mirror and short relaxation time of SOAs, wavelength switching time is less than 1 ms under different tuning channels among the wavelength range of near 300 nm. The stable single-longitude-mode operation is maintained across the entire tuning range. The exceptionally broad tuning range and high spectral purity of the
laser endow it with significant application potentials across a wide range of fields.
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All authors Minzhi Xu, Zechun Geng, Da Wei, Yujia Li, Juntao He, Chaoze Zhang, Wei Du, Lei Gao, Leilei Shi, Ligang Huang, Jindong Wang, Tao Zhu
Optics
Hybrid integrated narrow linewidth laser with external distributed optical feedback from a silicon strip waveguide
Da Wei, Leilei Shi, Yujia Li et al. (+8 more)
External optical feedback via Rayleigh scattering from an integrated microresonator or an optical fiber has been demonstrated to significantly narrow the intrinsic linewidth of
semiconductor lasers. Wavelength matching between the lasing cavity and the external high-Q microresonator is required to accumulate Rayleigh scattering based optical feedback. Optical fiber can provide Rayleigh scattering based optical feedback for any lasing wavelength. However, optical fibers hundreds of meters or even kilometers long are required for the accumulation of Rayleigh scattering based optical feedback, hindering the integration of narrow linewidth
lasers. Here, we present an integrated scheme that collects distributed feedback signal with weak wavelength dependence by exploiting surface radiation in a silicon waveguide. The effects of waveguide width on the intensities of the surface radiation and distributed optical feedback signal are first numerically analyzed by introducing a collection coefficient. Numerical calculations show that a 1 {\mu}m-wide strip waveguide yields optimal performance for excitation and collection of distributed optical feedback, which is also experimentally verified by measuring the feedback signal with an optical frequency-domain reflectometry. Benefitting from the enhanced distributed optical feedback that is 34.72 dB higher than that in a single-mode fiber, the hybrid integrated
laser demonstrates an intrinsic linewidth of 1.52 kHz, a side-mode suppression ratio (SMSR) of 74.71 dB, and a frequency noise of 24.44 Hz2/Hz. Furthermore, within a maximum allowable wavelength tuning range of 2.342 nm, the linewidth narrowing ratio depends little on the wavelength for all the waveguides with different widths.
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All authors Da Wei, Leilei Shi, Yujia Li, Minzhi Xu, Chaoze Zhang, Xianming Huang, Jianxian Yu, Lei Zhai, Wenxuan Huang, Huan Tian, Tao Zhu
Applied Physics · Cross-listed from cond-mat.soft
Role of transfer films and interfacial cracking in metallic sliding wear
R.Xu and B.N.J. Persson
The origin of wear particles in metallic sliding contacts remains debated. Classical views based on cold-welded junctions suggest that plastic yielding of the real contact area should lead to large wear coefficients, in apparent contradiction with the small values typically measured for metals. Here we argue that this discrepancy can be resolved if most junctions do not directly produce wear particles, but instead cause metal transfer and the formation of a weakly bound transfer film. Wear then occurs intermittently when fragments of this film detach due to crack propagation at the interface between the transfer film and the underlying bulk metal. We perform unlubricated reciprocating sliding experiments on nominally smooth stainless steel, brass, and aluminum. For steel on steel, the wear mass loss shows an initial stage with negligible mass change up to a sliding distance of $\sim 2.4 \ {\rm m}$, followed by a linear regime. Transfer-film formation in dissimilar-metal contacts is evidenced by optical imaging, net mass gain of the steel slider, and energy-dispersive X-ray spectroscopy, and the collected debris is flake-like. These observations support a transfer-film-controlled wear mechanism associated with cold-welded junctions.
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Optics
Uncooled Poisson Bolometer for High-Speed Event-Based Long-wave Thermal Imaging
Mohamed A. Mousa, Leif Bauer, Utkarsh Singh et al. (+3 more)
Event-based
vision provides high-speed, energy-efficient sensing for applications such as autonomous
navigation and motion tracking. However, implementing this technology in the long-wave infrared remains a significant challenge. Traditional infrared sensors are hindered by slow thermal response times or the heavy power requirements of cryogenic cooling. Here, we introduce the first event-based infrared detector operating in a Poisson-counting regime. This is realized with a spintronic Poisson bolometer capable of broadband detection from 0.8-14$\mu\text{m}$. In this regime, infrared signals are detected through statistically resolvable changes in
stochastic switching events. This approach enables room-temperature operation with high timing resolution. Our device achieves a maximum event rate of 1,250 Hz, surpassing the temporal resolution of conventional uncooled microbolometers by a factor of 4. Power consumption is kept low at 0.2$\mu$W per pixel. This work establishes an operating principle for infrared sensing and demonstrates a pathway toward high-speed, energy-efficient, event-driven thermal imaging.
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All authors Mohamed A. Mousa, Leif Bauer, Utkarsh Singh, Ziyi Yang, Angshuman Deka, Zubin Jacob
Optics
Hierarchical self-organization of highly-ordered granular ensemble of optical solitons through collective motions
Xiaocong Wang, Benhai Wang, Haochen Lin et al. (+6 more)
Self-organizations of ordered patterns in far-from-
equilibrium many-body systems host fundamental importance in many disciplines. Meanwhile, complex systems often feature hierarchical structures with distinct scales for different layers, enabling high-level effective dynamics without exhaustive tracking of all possible degrees of freedoms. In this work, we report a study of the self-organization dynamics of highly-ordered
soliton ensembles in a high-harmonic mode-locked fiber
lasers through collective motions driven by nonlocal optomechanical interactions and local collisions, which exhibit a series of universal characteristics reminiscent of phase transitions. Moreover, the multi-
soliton laser-field can be coarsely grained as a granular ensemble of limit-cycle oscillators with simple interaction rules derived from fine-scale physics. The self-organization of the multitude of
solitons in the mode-locked
laser cavity can then be mapped into a low-dimensional dynamic model that essentially reproduced the emergent process. Our work affords a conceptual framework for understanding the complex structure formation in nonlinear
laser systems, and may help to design ultrafast
lasers by exploiting universal principles of collective motions.
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All authors Xiaocong Wang, Benhai Wang, Haochen Lin, Wenbin He, Yu Jiang, Qi Huang, Xintong Zhang, Long Zhang, Meng Pang
Atomic Physics · Cross-listed from cond-mat.quant-gas
Supersolid phases and collective excitations in two-dimensional Rashba spin-orbit coupled spin-1 condensates
Sanu Kumar Gangwar, Sayan Chatterjee, Rajamanickam Ravisankar et al. (+3 more)
We investigate the collective excitation spectrum and dynamics of a quasi two-dimensional
spin-1 Bose-Einstein condensate with Rashba type
spin-orbit (SO) coupling. Employing Bogoliubov-de-Gennes analysis, we analytically compute the excitation spectra across a wide range of interaction strengths and coupling parameters. By systematically varying the SO and Rabi couplings, we uncover distinct dynamical signatures of
quantum phase transitions, including mode softening, the appearance of roton-like minima, and miscibility-driven instabilities in both
ferromagnetic and
antiferromagnetic interaction regimes. In the
antiferromagnetic case, these instabilities lead to a dynamically unstable supersolid phase characterized by the coexistence of density modulation and global phase coherence. To corroborate the analytical predictions, we numerically solve the coupled Gross-Pitaevskii equations and analyze the dynamical stability of the condensate. Our results provide experimentally accessible signatures for spinor condensates with tunable
spin-orbit coupling and demonstrate the rich interplay between
spin-dependent interactions and synthetic couplings in nonequilibrium
quantum fluids.
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All authors Sanu Kumar Gangwar, Sayan Chatterjee, Rajamanickam Ravisankar, Henrique Fabrelli, Paulsamy Muruganandam, Pankaj Kumar Mishra
Space Physics · Cross-listed from astro-ph.SR
Different Transient Phenomena at the Edges of Traveling Foreshocks
Primoz Kajdic, Xóchitl Blanco-Cano, Diana Rojas-Castllo et al. (+1 more)
Past kinetic simulations and spacecraft observations have shown that traveling foreshocks (TFs) are bounded by either foreshock compressional boundaries (FCBs) or foreshock bubbles (FBs). Here we present four TFs with a different kind of structure appearing at one of their edges. Two of them, observed by the Cluster mission, are bounded by a hot flow anomaly (HFA). In one case, the HFA was observed only by the spacecraft closest to the bow shock, while the other three probes observed an FCB. In addition, two other TFs were observed by the MMS spacecraft to be delimited by a structure that we call HFA-like FCB. In the spacecraft data, these structures present signatures similar to those of HFAs: dips in
magnetic field magnitude and
solar wind density, decelerated and deflected
plasma flow and increased temperature. However, a detailed inspection of these events reveals the absence of heating of the SW beam. Instead, the beam almost disappears inside these events and the
plasma moments are strongly influenced by the suprathermal particles. We suggest that HFA-like FCBs are related to the
evolution and structure of the directional discontinuities of the interplanetary
magnetic field whose thickness is larger than the gyroradious of suprathermal ions. We also show that individual TFs may appear together with several different types of transient upstream mesoscale structures, which brings up a question about their combined effect on regions downstream of the bow shock.
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All authors Primoz Kajdic, Xóchitl Blanco-Cano, Diana Rojas-Castllo, Nojan Omidi
Optics
An exploration of lateral optical forces from a triangular periodic motif
Bo Gao, Henkjan Gersen and Simon Hanna
This computational study investigates lateral optical forces in asymmetric dielectric nanostructures, focusing on their connection to resonant light-matter interactions. We examine isosceles triangular motifs that exhibit two distinct types of optical force response under plane wave illumination. Through parameter-space analysis, we identify stable zones where optical forces remain consistent and switching bands where forces change abruptly as parameters are altered. The observed force spectra show characteristic asymmetric lineshapes, suggesting Fano-resonance behavior. Eigenfrequency analysis confirms these effects arise from interference between discrete eigenmodes and continuum propagation states, with the eigenmode Q-factors correlating with transition sharpness. These findings provide insights into how structural geometry influences optical forces through resonant effects, offering guidance for designing optically-driven systems where controlled optical force responses are desired.
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Chemical Physics
Nucleophilic substitution at silicon under vibrational strong coupling: Refined insights from a high-level ab initio perspective
Niels-Ole Frerick, Michael Roemelt and Eric W. Fischer
We study the bimolecular nucleophilic substitution (S$_\mathrm{N}$2) reaction of 1-phenyl-2-trimethylsilylacetylene (PTA) under vibrational strong coupling (VSC) from the perspective of high-level ab initio
quantum and polaritonic chemistry. Specifically, we address conflicting mechanistic proposals, cavity-induced electronic corrections under VSC and the relevance of a previously debated Si-C-stretching motion of PTA for vibrational polariton formation. We first provide computational evidence for a two-step mechanism based on density functional theory and high-level coupled cluster results, identify new encounter and products complexes and illustrate the relevance of diffuse basis functions for a qualitatively correct description of anionic reactive systems. We subsequently show that cavity-induced dipole fluctuation corrections of electronic energies can be significant on the level of cavity Born-Oppenheimer coupled cluster theory and discuss their qualitative impact on the proposed two-step mechanism taking into account cavity-induced molecular reorientation. We finally show that the Si-C-stretching contribution to the experimentally relevant double-peak feature of PTA exhibits a dominant dipole character, which renders it central for linear IR response and vibrational polariton formation despite the presence of CH$_3$-rocking contributions. The dipole character along the cleaving Si-C-bond is eventually shown to rationalize Rabi splittings throughout the proposed two-step mechanism. Our work refines the microscopic perspective on the S$_\mathrm{N}$2 reaction of PTA under VSC and highlights recent developments in ab initio polaritonic chemistry for the VSC regime.
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Fluid Dynamics
N.E.O.N.-Bridge Geometry Determination: Turbulence Modeling of Individual N.E.O.N.-Bridge Segment
Arturo Rodriguez, Dominic Alexander, Nicolas J. Torres et al. (+4 more)
The N.E.O.N.-Bridge is a capstone project being developed by students at TAMUCC, under the oversight of Los Alamos National Laboratory. The project requires the development of a hull geometry for an autonomous bridge segment optimized to support onboard electronics and camera systems while maintaining stability in a dynamic water environment. Traditional ribbon bridge systems typically do not experience intense hydrodynamic loading due to current transportation and assembly methods, whereas the N.E.O.N-Bridge must continuously withstand forces from dynamic flow patterns. The requirement for a hull geometry to have both hydrodynamic design and
rigidity, as in current ribbon bridges, has posed unique challenges. The current hull designs were evaluated through turbulent water-flow simulations performed with ANSYS Discovery. Boundary conditions were determined based on the forward motion of the bridge segment, simulating inlet and outlet flows, and the resulting pressure distribution. A waterline-based
geometric constraint derived from the camera system's elevation enabled the simulation to model flow characteristics in an operational scenario. Velocity fields, pressure contours, and turbulent flow patterns were analyzed to identify areas of high loading and hydrodynamic inefficiencies. The findings will provide essential performance metrics that could be used to make design adjustments to the overall hull geometry. The simulation results will support improvements in stability, structural
rigidity, and overall effectiveness of the hull geometry, advancing the development of the N.E.O.N-Bridge segments.
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All authors Arturo Rodriguez, Dominic Alexander, Nicolas J. Torres, Benay Ozcelik, Omar Escudero, Ty Reitzel, Pablo Rangel
Atmospheric and Oceanic Physics
Livestock, Methane and Climate
D. Alexander, J. D. Ferguson, A. Glatzle et al. (+2 more)
Methane emissions by livestock have a negligible effect on Earth's temperature. For example, killing all of the approximately 1.6 billion cattle on Earth in the year 2025, when this paper was written, would only reduce atmospheric methane concentrations enough to change the temperature by -0.04 C. Killing all 1.3 billion sheep would lead to a temperature change of -0.004 C. New Zealand's pledge to reduce methane emissions of their livestock by 14% to 24% from those in the year 2017 would change the temperature by -0.000005 to -0.000008 C, far too small to measure. These are maximum temperature savings where methane emissions from domestic livestock are not replaced by other sources (such as wild ruminants and termites) during the inevitable rewilding of managed grasslands and rangelands.
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All authors D. Alexander, J. D. Ferguson, A. Glatzle, W. Happer, W. A. van Wijngaarden
Atomic Physics · Cross-listed from quant-ph
Imperfect blockade in Rydberg superatoms
Valentin Magro, Sébastien Garcia and Alexei Ourjoumtsev
Ensembles of atoms interacting via their Rydberg levels, known as "superatoms" for their ability to encode
qubits and to emit single
photons, attract increasing
attention as building blocks for
quantum network nodes. Assessing their performance requires an accurate, physically informative and numerically scalable description of interactions in a large and disordered ensemble. We derive such a description from first principles and successfully test it against brute-force numerics and experimental data. This model proves essential to make quantitative predictions about gate fidelities or
photon emission efficiencies, and to guide experiments towards large-scale superatom-based systems.
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Optics
Gravitational wave detectors from an experimental perspective
Marina Trad-Nery, Margherita Turconi and Walid Chaibi
This chapter introduces the fundamental principles of gravitational wave detectors in a simple and comprehensive manner. Because these instruments aim for extremely high sensitivity, it is essential to understand their various noise sources, how such noise couples to the detector output, and the strategies used to mitigate them. These noises contributions are computed in the frame of the Virgo detector and a sensitivity curve is calculated. Although a simplified layout of a gravitational wave detector is considered, it takes into account the most dominant effects and yields in a sensitivity estimate close to the what is observed in real detectors.
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Plasma Physics
Evidence of Langmuir/$\mathcal{Z}$-mode Wave Decay into $\mathcal{Z}$-mode Electromagnetic Radiation in the Solar Wind
F. J. Polanco-Rodríguez, C. Krafft and P. Savoini
The nonlinear decay of Langmuir/$\mathcal{Z}$-mode waves into electromagnetic $\mathcal{Z}$-mode wave radiation at the
plasma frequency is observed for the first time in the
solar wind. This finding was enabled by the unprecedented high-resolution electric and
magnetic field measurements provided by the
Radio Plasma Waves (RPW) instrument aboard the
Solar Orbiter spacecraft, which encountered an electron beam associated with a Type III
radio burst. The decay process is definitively identified through multiple lines of evidence: satisfaction of frequency and wavevector resonance conditions, strong phase coherence and temporal coincidence between the interacting waves, exclusion of competing mechanisms, and full agreement with theoretical predictions. Particle-in-
cell simulations, conducted under close beam-
plasma conditions, successfully reproduce the key features of the observations. Notably, they suggest that the wave packet observed by
Solar Orbiter may be trapped within an extended, nearly flat-bottomed density well, where the decay process is not overcome by wave scattering on random density fluctuations and subsequent mode conversion effects.
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Accelerator Physics
Design and modeling of a liquid-lead dump concept for beamstrahlung radiation absorption in the CERN Future Circular e$^+$e$^-$ Collider
Silvio Candido, Rui Franqueira Ximenes, Anton Lechner et al. (+13 more)
The electron-positron Future Circular
Collider (FCC-ee) being developed at CERN will generate intense beamstrahlung radiation, thus requiring
photon absorbers downstream of the interaction points. This work presents the conceptual design of flowing-
liquid-lead absorbers capable of dissipating around 370 kW of
photon power, with a mean
photon energy of 62 MeV. Two configurations are investigated: an inclined-flow geometry, developed to increase the
photon interaction length to maximize absorption, and a compact upstream slope with an additional pool, in which a free-surface lead flow intercepts the power peak before a downstream pool dissipates the remaining load.
Photon-matter interactions are modeled using Monte Carlo simulations in fluka, while conjugate heat-transfer and free-surface dynamics are analyzed through computational-fluid-dynamics simulations using ansys fluent. Design refinements are introduced based on the simulated thermal and hydraulic performance and to mitigate secondary effects such as
photon backscattering. Both configurations demonstrate stable operation within the 300 kg/s flow limit and maintain
liquid-lead and structural temperatures within the operational range of 450–500 $^{\circ}$C. The results establish circulating
liquid lead as a feasible and thermally robust baseline technology for beamstrahlung absorption in FCC-ee.
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All authors Silvio Candido, Rui Franqueira Ximenes, Anton Lechner, Alessandro Frasca, Giuseppe Lerner, Antonio Perillo Marcone, Regis Seidenbinder, Markus Widorski, Louise Jorat, Giacomo Lavezzari, Davide Bozzato, Gabriel Banks, Marco Calviani, Luca Tricarico, Carlo Carrelli, Mariano Tarantino
Fluid Dynamics
Spontaneous epicuticular charging affects droplet dynamics on living leaves
Mihir Durve, Serena Armiento, Benham Kamare et al. (+3 more)
How water droplets move and slide on leaves influences plant ecophysiological and abiotic interactions, as well as the design of advanced bio-inspired wetting materials. Despite cross-disciplinary relevance, current descriptions of the in situ dynamics of droplets on living leaves focus almost exclusively on surface structure and chemistry, treating the leaf as a static, electrically neutral substrate. Here, three decades after the mechanistic discovery of the Lotus effect, we show that a yet 'hidden' force due to instantaneous electrical phenomena affect the dynamic droplet motion on living leaves. Using high-speed motion tracking and precision charge measurements, we show that droplets sliding on the pristine epicuticular wax layer on superhydrophobic Colocasia esculenta leaves strongly charge affecting its dynamics, previously observed only on synthetic (highly electronegative fluorinated) surfaces. Droplets accumulate charges of Qp,D1 = -0.02 to -0.15 nC per 30 uL droplet on pristine leaves. However, we specifically demonstrate the crucial role of the epicuticular wax layer plasticity: by a structural modification that decreases its roughness amplitude, the same leaves gain an impressive 30-40 fold enhancement in charge transfer (reaching Qt,D1 = -2.8 to -5.2 nC) slowing the droplet by half due to an estimated electrostatic force of 11 uN dominating the resistive forces. The charge accumulation is surface-history-dependent and charge quantities per droplet are surprisingly similar or even exceeding those recently reported from artificial surfaces. Our findings prove that electrostatic charging is a fundamental component of droplet-leaf interactions, opening new research directions from charge-affected leaf ecology to sustainable materials for droplet-based energy harvesting by tuning surface treatments and, moreover,...
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All authors Mihir Durve, Serena Armiento, Benham Kamare, Sauro Succi, Barbara Mazzolai, Fabian Meder
Optics
Phase conjugated master oscillator fiber power amplifier
Tingwei Gu, Xin Zeng, Huawei Jiang et al. (+4 more)
High-power narrow-linewidth fiber
lasers are fundamentally limited by stimulated Brillouin scattering (SBS), which constrains further power scaling while maintaining spectral linewidth. Traditional mitigation techniques, such as active phase modulation, often introduce trade-offs among complexity, cost, and spectral brightness. In this study, we propose and experimentally demonstrate a novel all-optical approach for spectral linewidth manipulation and SBS suppression using optical phase conjugation (OPC). By leveraging nonlinear spectral broadening followed by phase conjugation, this method enables sophisticated linewidth narrowing in fiber amplifier, resulting in narrow linewidth output and enhanced SBS threshold. Using a low-cost fiber oscillator as the seed source, we achieve a spectral compression ratio exceeding 3 times. This method not only eliminates the need for complex electro-optic modulation systems but also provides a pathway toward simpler, high-brightness fiber
laser systems. Our findings underscore the viability of OPC as a transformative tool for nonlinearity management and power scaling in high-performance fiber
laser architectures.
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All authors Tingwei Gu, Xin Zeng, Huawei Jiang, Suming Luo, Maokai Yang, Xuezong Yang, Yan Feng
Fluid Dynamics
Enhanced Wall Boundary Modeling for Turbulent Flows Using the Lattice Boltzmann Method with Adaptive Cartesian Grids
Jorge Ponsin and Carlos Lozano
We propose an enhanced wall-boundary treatment for the
lattice Boltzmann method (LBM), designed for high-Reynolds-number turbulent flows on adaptively refined Cartesian grids. The method improves the slip-velocity bounce-back scheme by coupling it with a near-wall
turbulence model based on an analytical wall function. The Spalart-Allmaras (negative)
turbulence model is solved using a second-order finite-difference scheme and integrated within the LBM framework to statistically represent the Reynolds-Averaged Navier-Stokes (RANS) equations (LBM-RANS). The approach is validated on two
benchmark configurations: the National Advisory Committee for Aeronautics (NACA) 0012 airfoil and the McDonnell Douglas (MD)-30P30N multi-element high-lift configuration. LBM-RANS results show good agreement with conventional finite-volume RANS solutions and experimental data for key aerodynamic quantities, including pressure and skin-friction distributions, as well as turbulent boundary layer velocity profiles and eddy-viscosity fields. The method delivers smooth and accurate predictions of skin friction, which are often challenging for immersed-boundary approaches on Cartesian grids. The auxiliary
geometric data required for enforcing the turbulent boundary condition are minimal, making the method potentially well-suited for graphics processing unit (GPU)-based implementations. Moreover, no ad-hoc near-wall treatments are needed, as the boundary condition is applied naturally via the link-wise bounce-back scheme. These results illustrate that the proposed LBM-RANS framework can robustly and accurately simulate high-Reynolds-number turbulent two-dimensional (2D) flows over complex aerodynamic geometries under
equilibrium or near-
equilibrium conditions.
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Chemical Physics
Refinement and Performance Benchmark for Range-Separated Water Force Field
Qian Gao, Junmin Chen and Kuang Yu
In our previous work, we developed a CCSD(T)-level range-separated water force field that combines the power of physics-driven and machine learning models. However, it was found that expensive CCSD(T)/CBS calculations lead to limited number of QM data as well as the missing of force labels, both of which lead to training instability issues. Bulk properties show large variations that cannot be resolved by simply reducing the fitting error in small cluster QM
dataset. Such instability in bulk phase simulation is a universal problem in the training of machine learning potentials (MLPs), and is particularly severe at CCSD(T) level of theory.In this work, using our range-separated water model as an example, we aim to overcome these limitations by developing a new training workflow. It is composed by several techniques including: 1. an active learning protocol that ensures more thorough sampling in different temperatures and densities; 2. an intermediate force label technique employing machine learning density functional; and 3. an ensemble knowledge
distillation (EKD) method. These techniques significantly stabilize the resulting water model, consistently achieving sub-chemical accuracies in both cluster energies and experimental properties.
Benchmarks are carried out for various properties including densities, radial distribution functions (RDFs), dielectric constants, diffusivity, and infrared spectra, all showing state-of-the-art (SOTA) performances and proving the effectiveness of the training protocol.
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Fluid Dynamics
Flash evaporation Riemann Problem: Formulation and its Exact Solution
Haotong Bai, Ping Yi, Yixin Yang et al. (+3 more)
Flash evaporation, a
liquid-to-gas phase transition phenomenon in real fluids, is prevalent in aerospace propulsion systems. To elucidate the physical mechanisms of such complex flows and provide theoretical
benchmarks for Computational Fluid Dynamics simulations, this paper formalizes the Flash evaporation Riemann problem (FeRP) characterized by the expansion branch crossing the saturation line, within the framework of Homogeneous
Equilibrium and Vapor-
Liquid Equilibrium assumptions. An exact solution framework that analytically resolves all thermodynamic derivatives of
equilibrium two-phase fluids is established for arbitrary two-parameter equations of state. By evaluating the Landau fundamental derivative, the non-classical wave structures arising in the FeRP are analyzed, for which a stable iterative solution strategy incorporating the Chapman-Jouguet condition as an outer constraint is proposed. Furthermore, an exact solution for the FeRP based on Wood's mechanical
equilibrium speed of sound is developed, enabling a comprehensive evaluation of its thermodynamic implications. Results indicate that Wood's model alters the definition of the two-phase mixture
entropy in the Euler equations, introducing an isentropic path characterized by a "density lag" effect and non-physical
entropy decrease. Comparative analysis of the FeRP under typical scramjet fuel injection conditions reveals that, although Wood's model captures the general trend of the Riemann solution curve, it significantly underestimates intermediate pressure, velocity, and the extent of vaporization relative to the complete
equilibrium model.
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All authors Haotong Bai, Ping Yi, Yixin Yang, Guoyan Zhao, Wenjia Xie, Mingbo Sun
Fluid Dynamics
Seeing through water: diffuse image-based depth measurements in three-dimensional dam-break flows
Elia Buono, Roberto Bosio, Andrea Cagninei et al. (+1 more)
In this work we present a dedicated experimental facility and an image-based method for measuring water depth in a radially spreading dam-break wave propagating over a horizontal plane. The facility consists of a prismatic reservoir containing a known volume of water dyed with a soluble colorant and equipped with a removable vertical breach whose geometry can be varied, and a 6.4 m x 3.4 m plane that can be inclined from 0{\deg} to 30{\deg}. The plane is enclosed within a light box providing highly uniform illumination through an array of 60 LED floodlights. Wave propagation is captured by two scientific CMOS cameras mounted on the ceiling of the light box, which record the spatial and temporal
evolution of the dye-induced color intensity associated with the advancing water layer. Preliminary dry calibration tests were conducted to assess the spectral compatibility between the broadband white-LED emission, the CMOS sensor sensitivity, and the absorption properties of several dyes at different concentrations. This analysis identified the dye providing the highest attenuation within the effective spectral band of the imaging system, ensuring sensitivity to very small optical path lengths. Based on this characterization, a bi-exponential model is introduced to relate the normalized gray level to the optical path length. A series of dam-break experiments with five initial reservoir levels was performed to assess statistical repeatability. The high consistency observed across the repeated tests confirms the robustness of the measurement procedure. The validity of the reconstructed depth fields is further supported by independent estimates of the water volume released from the reservoir, obtained from an array of ultrasonic level sensors and from a calibrated analytical emptying model. Together, these comparisons confirm the reliability and accuracy of the proposed methodology.
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All authors Elia Buono, Roberto Bosio, Andrea Cagninei, Davide Poggi
Applied Physics
On the relation between time-reversed acoustics and Green's function retrieval in space-variant and in time-variant materials
Kees Wapenaar, Johannes Aichele and Dirk-Jan van Manen
The methods of time-reversed acoustics and Green's function
retrieval are traditionally deployed for classical inhomogeneous, time-invariant materials. The mutual relation between these methods is well-established. Recently, similar methods have been proposed for homogeneous, time-variant materials. Here we investigate their mutual relation and their relation with the corresponding methods in classical materials. For this analysis we make use of the fact that the wave equations for both classes of material are similar, with the roles of time and space interchanged. However, the principle of causality holds for both classes of material, hence, here the roles of time and space are not interchanged. We find that: (1) whereas classical time-reversed acoustics involves emission of a time-reversed single-component wave field from a (ideally closed) boundary into the inhomogeneous material, its idealized counterpart involves emission of a sign-reversed two-component wave field, recorded in a time-reversed material, from a single time instant into the actual time-variant material; (2) whereas classical Green's function
retrieval involves temporal crosscorrelation of wave fields at two space locations in response to single-component sources on a (ideally closed) boundary, its counterpart involves spatial crosscorrelation of wave fields at two time instants in response to two-component sources at a single time instant.
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Physics and Society
Socioeconomic Determinants of the COVID-19 Infodemic
Anna Bertani, Alessandro Cortese, Federico Pilati et al. (+2 more)
The COVID-19 pandemic has been accompanied by an infodemic of misinformation that impedes effective public health responses. This study examines relationships between socioeconomic factors and infodemic risk patterns across 37 OECD countries using Twitter data from 2020-2022. Employing dimensionality reduction techniques on 20 socioeconomic indicators, we identify complex correlations with infodemic measures that evolve throughout the pandemic. Countries exhibit distinct clustering in their infodemic profiles that transcend conventional socioeconomic categorizations. We find that dynamic information behaviors dominate initial crisis responses, while stable socioeconomic conditions become more influential as the pandemic progresses. News media diet diversity emerges as a significant protective factor, with pluralistic information ecosystems demonstrating greater resilience against misinformation. Additionally, institutional stability correlates strongly with reduced infodemic
volatility over time. These findings highlight how infodemics are embedded within broader socioeconomic contexts, providing foundations for targeted interventions to build societal resilience against misinformation during future health emergencies.
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All authors Anna Bertani, Alessandro Cortese, Federico Pilati, Pierluigi Sacco, Riccardo Gallotti
Atomic Physics · Cross-listed from quant-ph
Atom-light hybrid interferometer for atomic sensing with quantum memory
Xingchang Wang, Xinyun Liang, Dasen Yang et al. (+7 more)
Quantum memories feature a reversible conversion of optical fields into long-lived atomic
spin waves, and are therefore ideal for operating as sensitive atomic sensors. However, up to now, atom-light interferometers have lacked an efficient approach to exploit their ultimate atomic sensing performance, since an extra optical delay line is required to compensate for the
memory time. Here, we report a new protocol that records the photocurrent via heterodyne mixing with a stable local oscillator. The obtained complex quadrature amplitude that carries information imprinted on its phase by an external
magnetic field, is successfully recovered from the interference patterns between the light and the atomic
spin wave, without the stringent requirement of having them overlap in time. Our results reveal that the sensitivity scales favorably with the lifetime of the
quantum memory. Our work may have important applications in building distributed
quantum networks through
quantum memory-assisted atom-light interferometers.
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All authors Xingchang Wang, Xinyun Liang, Dasen Yang, Liang Dong, Ying Zuo, Jianmin Wang, Linyu Chen, Georgios A. Siviloglou, Z. Y. Ou, J. F. Chen
Applied Physics · Cross-listed from cond-mat.mes-hall
Potential of Graphene/AlGaN/GaN heterostructures to study the drag and two-stream instability effects
A. Rehman, D.B. But, P. Sai et al. (+6 more)
Graphene/AlGaN/GaN
heterostructures are proposed to investigate the drag and two-stream instability effects. In this study,
graphene grown by chemical vapor deposition was transferred from copper onto the top of the standard AlGaN/GaN wafer, forming a
heterostructure with two conducting layers separated by an AlGaN barrier layer. Contacts fabricated to the two-dimensional electron gas and
graphene allowed us to study the drag current induced in
graphene by passing the drive current through the two-dimensional electron gas. At low temperatures, the
graphene drag current exhibited
quantum oscillations as a function of the drive voltage. As temperature increases,
quantum oscillations disappear, and the magnitude of the drag current increases.
Graphene/AlGaN/GaN
heterostructures are a promising platform for studying drag and two-stream instability effects, especially if the AlGaN barrier layer thickness can be reduced to a few nanometers.
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All authors A. Rehman, D.B. But, P. Sai, M. Dub, P. Prystawko, A. Krajewska, G. Cywinski, W. Knap, S. Rumyantsev
Instrumentation and Detectors
Precision Light Yield and Crosstalk Characterization for the SuperFGD scintillator cubes
I. Alekseev, A. Chvirova, M. Danilov et al. (+12 more)
A detailed study of a $5\times5\times5$ cube prototype of the SuperFGD detector was performed using a 730 MeV/$c$ pion beam at the SC-1000 synchrocyclotron (PNPI, Gatchina, Russia). The detector, based on plastic scintillation cubes with orthogonal wavelength-shifting (WLS) fiber readout and silicon photomultipliers (SiPMs), was tested to evaluate its performance in terms of light yield, spatial uniformity, and optical crosstalk. Using high-resolution tracking, the spatial distribution of light yield was mapped with a granularity of 0.5 mm. An average light response map was obtained by combining data from 27 cubes. Optical crosstalk between adjacent cubes was also measured and characterized in four directions (left, right, up, down). Position-dependent crosstalk values ranged from 2% to 6%, with the highest levels observed near cube interfaces. These results confirm the excellent performance and scalability of the SuperFGD design, and provide valuable input for simulation tuning and reconstruction
algorithms in the ND280 upgrade of the T2K experiment. The obtained result on the response uniformity and crosstalk are reasonably well described by simple MC model of the setup.
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All authors I. Alekseev, A. Chvirova, M. Danilov, S. Fedotov, A. Khotjantsev, M. Kolupanova, N. Kozlenko, A. Krapiva, Y. Kudenko, A. Mefodiev, O. Mineev, D. Novinsky, E. Samigullin, N. Skrobova, D. Svirida