arXiv Physics @arxiv_physics@qoto.org

In this paper, the ladder operators typical of quantum mechanics are used to construct an operatorial version of a model dubbed crimo-taxis. In a classical framework, the crimo-taxis model is described by reaction-diffusion partial differential equations describing a population divided into three interacting subgroups (ordinary citizens, drug users/dealers, and law enforcement personnel). By means of a quantum-like approach, these interacting subgroups are modeled using annihilation, creation, and number fermionic operators. Their dynamics is governed by a self-adjoint and time-independent Hamiltonian operator, emboding the interactions among the groups. Furthermore, a recent variant of the standard Heisenberg approach, namely $(\mathcal{H},ρ)$--induced dynamics, is also taken into account with the goal of enriching the dynamics. The results of some numerical simulations in a one--dimensional setting are presented and discussed.

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.

I proposed a unified model of particle physic and cosmology in \cite {1}, which can successfully account for many things of the inflation, dark energy, dark matter, neutrino mass and baryogenesis. Based on the model, I here focus on the fermion flavour issues. I introduce a realistic flavour symmetry to generate the fermion mass and mixing. From the model Lagrangian I derive a neutrino mass matrix with a special structure form and fewer parameters, its numerical solutions are precisely fitting to all the data of the neutrino mass spectrum and lepton mixing, and clearly show a stronger predicting power. In addition, I put forward to a new scenario of the leptogenesis, which is implemented through the two CP-asymmetric decay modes of a superheavy neutral Dirac-fermion, and also I establish its relationship with the neutrino mass and mixing. This mechanism can simply and elegantly account for the baryon asymmetry. In short, the model can address many issues of the fermion flavours, and it is very realistic, believable and measurable instead of an illusory theory, therefore we expect the ongoing and future experiments to test the model.

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.

We investigate the impact of network heterogeneity on synergistic contagion dynamics. By extending a synergistic contagion model to diverse heterogeneous network topologies, we uncover the emergence of novel dynamical regimes characterized by multiple stable states, separated by a rich set of bifurcations reaching up to codimension 4. Additionally, we demonstrate how synergy fundamentally reshapes the influence of nodes based on their degree. Unlike in non-synergistic epidemics, low-degree nodes can play a pivotal role in enabling network invasion at the onset of spread, while high-degree nodes can trigger explosive contagion. These findings challenge conventional control strategies, highlighting the need for new approaches to enhance or suppress synergistic contagion.

Experimental and numerical studies of incompressible turbulence suggest that the mean dissipation rate of kinetic energy remains constant as the Reynolds number tends to infinity (or the non-dimensional viscosity tends to zero). This anomalous behavior is central to many theories of high-Reynolds-number turbulence and for this reason has been termed the "zeroth law". Here we report a sequence of direct numerical simulations of incompressible Navier-Stokes in a box with periodic boundary conditions, which indicate that the anomaly vanishes at a rate that agrees with the scaling of third-moment of absolute velocity increments. Our results suggest that turbulence without boundaries may not develop strong enough singularities to sustain the zeroth law.

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.

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.

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.

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.

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.