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Contrail, or not contrail, that is the question: the "feasibility" of climate-optimal routing arxiv.org/abs/2504.13907

Where do local markets fit in the current European Electricity Market structures? arxiv.org/abs/2504.13919

Parenthood Penalties in Academia: Childcare Responsibilities, Gender Role Beliefs and Institutional Support arxiv.org/abs/2504.13923

Modeling transport in weakly collisional plasmas using thermodynamic forcing arxiv.org/abs/2504.14000

Modeling transport in weakly collisional plasmas using thermodynamic forcing

How momentum, energy, and magnetic fields are transported in the presence of macroscopic gradients is a fundamental question in plasma physics. Answering this question is especially challenging for weakly collisional, magnetized plasmas, where macroscopic gradients influence the plasma's microphysical structure. In this paper, we introduce thermodynamic forcing, a new method for systematically modeling how macroscopic gradients in magnetized or unmagnetized plasmas shape the distribution functions of constituent particles. In this method, we propose to apply an anomalous force to those particles inducing the anisotropy that would naturally emerge due to macroscopic gradients in weakly collisional plasmas. We implement thermodynamic forcing in particle-in-cell (TF-PIC) simulations using a modified Vay particle pusher and validate it against analytic solutions of the equations of motion. We then carry out a series of simulations of electron-proton plasmas with periodic boundary conditions using TF-PIC. First, we confirm that the properties of two electron-scale kinetic instabilities -- one driven by a temperature gradient and the other by pressure anisotropy -- are consistent with previous results. Then, we demonstrate that in the presence of multiple macroscopic gradients, the saturated state can differ significantly from current expectations. This work enables, for the first time, systematic and self-consistent transport modeling in weakly collisional plasmas, with broad applications in astrophysics, laser-plasma physics, and inertial confinement fusion.

arXiv.org

Adaptive Diffusion Models for Motion-corrected Cone-beam Head CT arxiv.org/abs/2504.14033

A thermodynamically consistent and robust four-equation model for multi-phase multi-component compressible flows using ENO-type schemes including interface regularization arxiv.org/abs/2504.14063

A Binary Collision Method for Screened Coulomb Collisions in weakly and moderately coupled Plasmas arxiv.org/abs/2504.14067

Understanding the Optical Theorem of Scattering: Scattering Surface Area against Scattering Cross Section, an Example with Ellipsoidal Scattering arxiv.org/abs/2504.13184

High-Precision Phase Control of an Optical Lattice with up to 50 dB Noise Suppression arxiv.org/abs/2504.13264

High-Precision Phase Control of an Optical Lattice with up to 50 dB Noise Suppression

An optical lattice is a periodic light crystal constructed from the standing-wave interference patterns of laser beams. It can be used to store and manipulate quantum degenerate atoms and is an ideal platform for the quantum simulation of many-body physics. A principal feature is that optical lattices are flexible and possess a variety of multidimensional geometries with modifiable band-structure. An even richer landscape emerges when control functions can be applied to the lattice by modulating the position or amplitude with Floquet driving. However, the desire for realizing high-modulation bandwidths while preserving extreme lattice stability has been difficult to achieve. In this paper, we demonstrate an effective solution that consists of overlapping two counterpropagating lattice beams and controlling the phase and intensity of each with independent acousto-optic modulators. Our phase controller mixes sampled light from both lattice beams with a common optical reference. This dual heterodyne locking method allows exquisite determination of the lattice position, while also removing parasitic phase noise accrued as the beams travel along separate paths. We report up to 50dB suppression in lattice phase noise in the 0.1Hz - 1Hz band along with significant suppression spanning more than four decades of frequency. When integrated, the absolute phase diffusion of the lattice position is only 10Å over 10 s. This method permits precise, high-bandwidth modulation (above 50kHz) of the optical lattice intensity and phase. We demonstrate the efficacy of this approach by executing intricate time-varying phase profiles for atom interferometry.

arXiv.org

The influence of wetting effects on the stability of spanwise-confined liquid films arxiv.org/abs/2504.13300

The influence of wetting effects on the stability of spanwise-confined liquid films

We investigate the influence of side-walls wetting effects on the linear stability of falling liquid films confined in the spanwise direction. Building upon our previous stability framework, which was developed to analyze the effect of spanwise confinement on the stability, we now incorporate wetting phenomena to develop a more comprehensive theoretical model. This extended model captures the interplay of gravity, inertia, surface tension, viscous dissipation, static meniscus, and moving contact lines. The base state exhibits two key features: a curved meniscus and a velocity overshoot near the side walls. A biglobal linear stability analysis is conducted based on the linearized Navier-Stokes equations. Unlike classical stability theory, our results reveal that surface tension, when strong, suppresses the long-wave instability ($k \rightarrow 0$), significantly increasing the critical Reynolds number as it increases. Notably, this effect is more pronounced for smaller contact angles. Moreover, stabilization is present across all wavenumbers at small Reynolds numbers, however, at large Reynolds numbers, the stabilization effect weakens, even for small contact angles. Furthermore, this stabilization is governed by the ratio of the capillary length to channel width, where complete stabilization occurs when this ratio exceeds a critical value dependent on the contact angle. We attribute this behavior to a capillary attenuation mechanism that dominates at smaller contact angles. No destabilization due to velocity overshoot was observed in the linear regime. Additionally, the introduction of wetting effects results in vortical structures in the vicinity of the side walls. These vortices dissipate the perturbation energy, thereby stabilizing the flow.

arXiv.org

Harnessing Leading-Edge Vortices for Improved Thrust Performance of Wave-Induced Flapping Foil Propulsors arxiv.org/abs/2504.13309

Harnessing Leading-Edge Vortices for Improved Thrust Performance of Wave-Induced Flapping Foil Propulsors

This study employs high-fidelity fluid-structure interaction simulations to investigate design optimizations for wave-assisted propulsion (WAP) systems using flapping foils. Building on prior work that identified the leading-edge vortex (LEV) as critical to thrust generation for these flapping foil propulsors, this work explores pitch control mechanisms and foil geometries to improve performance across varying sea states. Two pitch-limiting strategies $\unicode{x2014}$ a spring-limiter and an angle-limiter $\unicode{x2014}$ are evaluated. Results show that while both perform similarly at higher sea states, the angle-limiter yields superior thrust at sea-state 1, making it the preferred mechanism due to its simplicity and effectiveness. Additionally, foil geometry effects are analyzed, with thin elliptical and flat plate foils outperforming the baseline NACA0015 shape. The elliptical foil offers marginally better performance and is recommended for WAP applications. A fixed pitch amplitude of 5° provides thrust across all sea states, offering a practical alternative to more complex adaptive systems. These findings demonstrate how insights into the flow physics of flapping foils can inform the design of more efficient WAP systems.

arXiv.org

Machine-learning Closure for Vlasov-Poisson Dynamics in Fourier-Hermite Space arxiv.org/abs/2504.13313

Machine-learning Closure for Vlasov-Poisson Dynamics in Fourier-Hermite Space

Accurate reduced models of turbulence are desirable to facilitate the optimization of magnetic-confinement fusion reactor designs. As a first step toward higher-dimensional turbulence applications, we use reservoir computing, a machine-learning (ML) architecture, to develop a closure model for a limiting case of electrostatic gyrokinetics. We implement a pseudo-spectral Eulerian code to solve the one-dimensional Vlasov-Poisson system on a basis of Fourier modes in configuration space and Hermite polynomials in velocity space. When cast onto the Hermite basis, the Vlasov equation becomes an infinitely coupled hierarchy of fluid moments, presenting a closure problem. We exploit the locality of interactions in the Hermite representation to introduce an ML closure model of the small-scale dynamics in velocity space. In the linear limit, when the kinetic Fourier-Hermite solver is augmented with the reservoir closure, the closure permits a reduction of the velocity resolution, with a relative error within two percent for the Hermite moment where the reservoir closes the hierarchy. In the strongly-nonlinear regime, the ML closure model more accurately resolves the low-order Fourier and Hermite spectra when compared to a naïve closure by truncation and reduces the required velocity resolution by a factor of sixteen.

arXiv.org

Prototype acoustic positioning system for the Pacific Ocean Neutrino Experiment arxiv.org/abs/2504.13323

Prototype acoustic positioning system for the Pacific Ocean Neutrino Experiment

We present the design and initial performance characterization of the prototype acoustic positioning system intended for the Pacific Ocean Neutrino Experiment. It comprises novel piezo-acoustic receivers with dedicated filtering- and amplification electronics installed in P-ONE instruments and is complemented by a commercial system comprised of cabled and autonomous acoustic pingers for sub-sea installation manufactured by Sonardyne Ltd. We performed an in-depth characterization of the acoustic receiver electronics and their acoustic sensitivity when integrated into P-ONE pressure housings. These show absolute sensitivities of up to $-125\,$dB re V$^2/μ$Pa$^2$ in a frequency range of $10-40\,$kHz. We furthermore conducted a positioning measurement campaign in the ocean by deploying three autonomous acoustic pingers on the seafloor, as well as a cabled acoustic interrogator and a P-ONE prototype module deployed from a ship. Using a simple peak-finding detection algorithm, we observe high accuracy in the tracking of relative ranging times at approximately $230-280\,μ$s at distances of up to $1600\,$m, which is sufficient for positioning detectors in a cubic-kilometer detector and which can be further improved with more involved detection algorithms. The tracking accuracy is further confirmed by independent ranging of the Sonardyne system and closely follows the ship's drift in the wind measured by GPS. The absolute positioning shows the same tracking accuracy with its absolute precision only limited by the large uncertainties of the deployed pinger positions on the seafloor.

arXiv.org
Metamaterial two-sphere Newton's cradle

Locally resonant metamaterials are among the most studied types of elastic/acoustic metamaterials, with significant research focused on wave propagation in a continuum of "meta-atoms" Here we investigate the collision dynamics of two identical pendulum-suspended mass-in-mass resonators, essentially a two-sphere Newton's cradle, emphasizing the readily realizable scenario where the internal resonator frequency is much greater than the pendulum frequency. We first show that the dynamics of a collision can be described using effective parameters, similar to how previous metamaterials research has characterized wave propagation through effective material properties. Non-conventional collision dynamics -- observed in two colliding mass-in-mass systems where one is initially at rest -- include behaviors such as the moving sphere rebounding as if from a fixed wall while the other remains essentially stationary, the spheres coupling and moving forward in near-unison, and the spheres recoiling in opposite directions. These responses can be achieved by tuning the effective parameters. We demonstrate that these parameters can take on values that differ significantly from those in a conventional Newton's cradle. Additionally, we investigate multiple collisions of the two spheres, revealing complex dynamics. This work paves the way for the development and study of new "collision-based metamaterial" structures.

arXiv.org
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