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A particle with internal unobserved states diffusing in a force field will generally display effective advection-diffusion. The drift velocity is proportional to the mobility averaged over the internal states, or effective mobility, while…

Statistical Mechanics · Physics 2017-10-13 Erik Aurell , Stefano Bo

We formulate a scaling theory for the long-time diffusive motion in a space occluded by a high density of moving obstacles in dimensions 1, 2 and 3. Our tracers diffuse anomalously over many decades in time, before reaching a diffusive…

Statistical Mechanics · Physics 2024-10-22 H. Bendekgey , G. Huber , D. Yllanes

In this paper, we address a time-dependent one-dimensional linear advection-diffusion equation with Dirichlet homogeneous boundary conditions. The equation is solved both analytically, using separation of variables, and numerically,…

Analysis of PDEs · Mathematics 2023-12-12 Eeshwar Prasad Poudel , Pitambar Acharya , Jeevan Kafle , Shreeram Khadka

Sampling viable 3D structures (e.g., molecules and point clouds) with SE(3)-invariance using diffusion-based models proved promising in a variety of real-world applications, wherein SE(3)-invariant properties can be naturally characterized…

Machine Learning · Computer Science 2024-03-05 Zihan Zhou , Ruiying Liu , Jiachen Zheng , Xiaoxue Wang , Tianshu Yu

Behavior of the mixture of particles and dimers moving with different jump rates at reconstructed surfaces is described. Collective diffusion coefficient is calculated by the variational approach. Anisotropy of the collective particle…

Statistical Mechanics · Physics 2014-05-12 Marcin Mińkowski , Magdalena A. Załuska Kotur

We study a simple model of a random walker in d dimensions moving in the presence of a local heterogeneous attracting factor expressed in terms of an assigned space-dependent "attractiveness function", a situation frequently encountered in…

Statistical Mechanics · Physics 2017-06-21 Hardi Veermäe , Marco Patriarca

Asymptotic multiple scale homogenisation allows to determine the effective behaviour of a porous medium by starting from the pore-scale description, when there is a large separation between the pore-scale and the macroscopic scale. When the…

Classical Physics · Physics 2019-03-06 Pascale Royer

Diffusion in an evolving environment is studied by continuos-time Monte Carlo simulations. Diffusion is modelled by continuos-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional…

Soft Condensed Matter · Physics 2010-11-22 Janne Juntunen , Juha Merikoski

The diffusion in two dimensions of non-interacting active particles that follow an arbitrary motility pattern is considered for analysis. Accordingly, the transport equation is generalized to take into account an arbitrary distribution of…

Statistical Mechanics · Physics 2020-09-01 Francisco J. Sevilla

We study the scale dependence of effective diffusion of fluid tracers, specifically, its dependence on the P\'{e}clet number, a dimensionless parameter of the ratio between advection and molecular diffusion. Here, we address the case that…

Fluid Dynamics · Physics 2022-04-13 Yohei Kono , Yoshihiko Susuki , Takashi Hikihara

We propose a geometric perspective to describe the motion of self-propelled particles moving at constant speed in d dimensions. We exploit the fact that the vector that conveys the direction of motion of the particle performs a random walk…

Biological Physics · Physics 2016-05-30 Robert Großmann , Fernando Peruani , Markus Bär

In this work I show how a diffusion-advection equation in three space-dimensions may have its advection term weakly limited to a velocity field localized to a moving curve. This is rigorously accomplished through the technique of…

Analysis of PDEs · Mathematics 2021-06-24 Colin Klaus

We analyze a diffuse interface model for multi-phase flows of $N$ incompressible, viscous Newtonian fluids with different densities. In the case of a bounded and sufficiently smooth domain existence of weak solutions in two and three space…

Analysis of PDEs · Mathematics 2024-01-15 Helmut Abels , Harald Garcke , Andrea Poiatti

We introduce two discrete models of a collection of colliding particles with stored momentum and study the asymptotic growth of the mean-square displacement of an active particle. We prove that the models are superdiffusive in one dimension…

Probability · Mathematics 2020-01-08 Edward Crane , Sean Ledger , Balint Toth

We propose a seamless multiscale method which approximates the macroscopic behavior of the passive advection-diffusion equations with steady incompressible velocity fields with multi-spatial scales. The method uses decompositions of the…

Numerical Analysis · Mathematics 2016-06-22 Yoonsang Lee , Bjorn Engquist

We consider a spatially homogeneous advection-diffusion equation in which the diffusion tensor and drift velocity are time-independent, but otherwise general. We derive asymptotic expressions, valid at large distances from a steady point…

Chaotic Dynamics · Physics 2015-05-20 John Grant , Michael Wilkinson

Propagation of solitary waves in the presence of autocatalysis, diffusion, and symmetry breaking (differential) advection, is being studied. The focus is on drifting (propagating with advection) pulses that form via a convective instability…

Pattern Formation and Solitons · Physics 2010-02-08 Arik Yochelis , Moshe Sheintuch

The coupling between advection and diffusion in position space can often lead to enhanced mass transport compared to diffusion without flow. An important framework used to characterize the long-time diffusive transport in position space is…

Fluid Dynamics · Physics 2024-10-10 Zhiwei Peng

We study the steady laminar advective transport of a diffusive passive scalar released at the base of narrow three-dimensional longitudinal open channels with non-absorbing side walls and rectangular or truncated-wedge-shaped…

Fluid Dynamics · Physics 2020-02-14 Merlin A. Etzold , Julien R. Landel , Stuart B. Dalziel

The advection-diffusion equation is studied via a global Lagrangian coordinate transformation. The metric tensor of the Lagrangian coordinates couples the dynamical system theory rigorously into the solution of this class of partial…

Fluid Dynamics · Physics 2007-05-23 X. Z. Tang , A. H. Boozer
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