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Using test-particle simulations, we investigate the temporal dependence of the two-point velocity correlation function for charged particles scattering in a time-independent spatially fluctuating magnetic field derived from a…

High Energy Astrophysical Phenomena · Physics 2015-06-05 Federico Fraschetti , Joe Giacalone

Diffusion of electrons in two-dimensional disordered systems with spin-orbit interactions is investigated numerically. Asymptotic behaviors of the second moment of the wave packet and of the temporal auto-correlation function are examined.…

Condensed Matter · Physics 2009-10-28 Tohru Kawarabayashi , Tomi Ohtsuki

In a system of noisy self-propelled particles with interactions that favor directional alignment, collective motion will appear if the density of particles increases beyond a certain threshold. In this paper, we argue that such a threshold…

Soft Condensed Matter · Physics 2010-03-29 Chiu Fan Lee

We introduce a model of self-propelled particles carrying out a Brownian motion with a diffusion coefficient which depends on the local density of particles within a certain finite radius. Numerical simulations show that in a range of…

Statistical Mechanics · Physics 2009-11-11 Cristobal Lopez

The stochastic dynamics of an active particle undergoing a constant speed and additionally driven by an overall fluctuating torque is investigated. The random torque forces are expressed by a stochastic differential equation for the angular…

Statistical Mechanics · Physics 2011-12-22 Christian Weber , Paul K. Radtke , Lutz Schimansky-Geier , Peter Hänggi

Collective motion - or flocking - is an emergent phenomena that underlies many biological processes of relevance, from cellular migrations to animal groups movement. In this work, we derive scaling relations for the fluctuations of the mean…

Soft Condensed Matter · Physics 2023-02-13 Martino Brambati , Giuseppe Fava , Francesco Ginelli

We use confocal microscopy to directly visualize the spatial fluctuations in fluid flow through a three-dimensional porous medium. We find that the velocity magnitudes and the velocity components both along and transverse to the imposed…

Soft Condensed Matter · Physics 2013-08-07 Sujit S. Datta , Harry Chiang , T. S. Ramakrishnan , David A. Weitz

Active particles (i.e., self-propelled particles or called microswimmers), different from passive Brownian particles, possess more complicated translational and angular dynamics, which can generate a series of anomalous transport phenomena.…

Soft Condensed Matter · Physics 2022-01-05 Ze-Hao Chen , Zhi-Xi Wu

We investigate the dynamics of a single deformable self-propelled particle which undergoes a spinning motion in a two-dimensional space. Equations of motion are derived from the symmetry argument for three kinds of variables. One is a…

Soft Condensed Matter · Physics 2013-07-09 Mitsusuke Tarama , Takao Ohta

We discuss recent work on the static and dynamical properties of the asymmetric exclusion process, generalized to include the effect of disorder. We study in turn: random disorder in the properties of particles; disorder in the spatial…

Statistical Mechanics · Physics 2009-11-11 Mustansir Barma

We present a comprehensive study of Vicsek-style self-propelled particle models in two and three space dimensions. The onset of collective motion in such stochastic models with only local alignment interactions is studied in detail and…

Statistical Mechanics · Physics 2009-11-13 Hugues Chaté , Francesco Ginelli , Guillaume Grégoire , Franck Raynaud

We study the stochastic dynamics of a particle with two distinct motility states. Each one is characterized by two parameters: one represents the average speed and the other represents the persistence quantifying the tendency to maintain…

Statistical Mechanics · Physics 2021-07-16 M. Reza Shaebani , Heiko Rieger

We investigate the transport of a passive tracer in a two-dimensional stratified random medium with flow parallel and perpendicular to the strata. Assuming a Gaussian random flow with a Gaussian correlation function, it is not only possible…

Disordered Systems and Neural Networks · Physics 2009-11-07 M. Clincy , H. Kinzelbach

Motions of fluctuating Brownian particles in an incompressible viscous fluid have been studied by coupled simulations of Brownian particles and host fluid. We calculated the velocity autocorrelation functions of Brownian particles and…

Soft Condensed Matter · Physics 2012-11-22 Takuya Iwashita , Yasuya Nakayama , Ryoichi Yamamoto

A recently developed wavelet based approach is employed to characterize the scaling behavior of spectral fluctuations of random matrix ensembles, as well as complex atomic systems. Our study clearly reveals anti-persistent behavior and…

Chaotic Dynamics · Physics 2009-11-11 P. Manimaran , Prasanta K. Panigrahi , P. Anantha Lakshmi

We compare the fluctuations in the velocity and in the fraction of time spent at a given position for minimal models of a passive and an active particle: an asymmetric random walker and a run-and-tumble particle in continuous time and on a…

Statistical Mechanics · Physics 2019-10-03 Emil Mallmin , Richard A Blythe , Martin R Evans

Particles moving along curved trajectories will diffuse if the curvature fluctuates sufficiently in either magnitude or orientation. We consider particles moving at a constant speed with either a fixed or with a Gaussian distributed…

Soft Condensed Matter · Physics 2009-11-10 Andrew D. Rutenberg , Andrew J. Richardson , Claire J. Montgomery

Active fluids operate by constantly dissipating energy at the particle level to perform a directed motion, yielding dynamics and phases without any equilibrium equivalent. The emerging behaviors have been studied extensively, yet…

Statistical Mechanics · Physics 2020-02-03 Étienne Fodor , Takahiro Nemoto , Suriyanarayanan Vaikuntanathan

We study a process of anomalous diffusion, based on intermittent velocity fluctuations, and we show that its scaling depends on whether we observe the motion of many independent trajectories or that of a Liouville-like equation driven…

Statistical Mechanics · Physics 2009-11-07 M. Bologna , P. Grigolini , B. J. West

Velocity fluctuations of grains flowing down a rough inclined plane are experimentally studied. The grains at the free surface exhibit fluctuating motions, which are correlated over few grains diameters. The characteristic correlation…

Other Condensed Matter · Physics 2009-11-11 Olivier Pouliquen