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We present a unified framework for solving partial differential equations (PDEs) using video-inpainting diffusion transformer models. Unlike existing methods that devise specialized strategies for either forward or inverse problems under…

Machine Learning · Computer Science 2025-06-18 Edward Li , Zichen Wang , Jiahe Huang , Jeong Joon Park

In this paper, we propose a space-time GMsFEM for transport equations. Multiscale transport equations occur in many geoscientific applications, which include subsurface transport, atmospheric pollution transport, and so on. Most of existing…

Numerical Analysis · Mathematics 2018-04-27 Eric T. Chung , Yalchin Efendiev , Yanbo Li

We develop novel numerical methods and perturbation approaches to determine the mean first passage time (MFPT) for a Brownian particle to be captured by either small stationary or mobile traps inside a bounded 2-D confining domain. Of…

Numerical Analysis · Mathematics 2019-11-20 Sarafa Iyaniwura , Tony Wong , Michael J. Ward , Colin B. Macdonald

We derive an approximate formula for the mean first-passage time (MFPT) to a small absorbing target of arbitrary shape inside an elongated domain of a slowly varying axisymmetric profile. For this purpose, the original Poisson equation in…

Chemical Physics · Physics 2022-05-06 Denis S. Grebenkov , Alexei T. Skvortsov

Diffusion is the macroscopic manifestation of disordered molecular motion. Mathematically, diffusion equations are partial differential equations describing the fluid-like large-scale dynamics of parcels of molecules. Spatially…

Fluid Dynamics · Physics 2018-10-26 F. Sattin , A. Bonato , L. Salasnich

A common scenario in a variety of biological systems is that multiple particles are searching in parallel for an immobile target located in a bounded domain, and the fastest among them that arrives to the target first triggers a given…

Statistical Mechanics · Physics 2025-07-15 Denis S. Grebenkov , Ralf Metzler , Gleb Oshanin

We discuss the derivation and the solutions of integro-differential equations (variable-order time-fractional diffusion equations) following as continuous limits for lattice continuous time random walk schemes with power-law waiting-time…

Statistical Mechanics · Physics 2020-07-22 Philipp Roth , Igor M. Sokolov

The phenomenon of distribution shift (DS) occurs when a dataset at test time differs from the dataset at training time, which can significantly impair the performance of a machine learning model in practical settings due to a lack of…

We present a one-dimensional model for diffusion in a fluctuating lattice; that is a lattice which can be in two or more states. Transitions between the lattice states are induced by a combination of two processes: one periodic…

Statistical Mechanics · Physics 2007-05-23 Jorge A. Revelli , Carlos. E. Budde , Horacio S. Wio

In this paper, we first present the general propagation multiple-relaxation-time lattice Boltzmann (GPMRT-LB) model and obtain the corresponding macroscopic finite-difference (GPMFD) scheme on conservative moments. Then based on the Maxwell…

Numerical Analysis · Mathematics 2023-08-24 Ying Chen , Xi Liu , Zhenhua Chai , Baochang Shi

We propose a unifying theoretical framework for the analysis of first-passage time distributions in two important classes of stochastic processes in which the diffusivity of a particle evolves randomly in time. In the first class of…

Statistical Mechanics · Physics 2019-11-05 D. S. Grebenkov

We introduce the concept of Randomly Modulated Gaussian Processes as a unifying framework for modeling, analyzing and classifying anomalous diffusion models in heterogeneous media. This formulation incorporates correlations in the…

Biological Physics · Physics 2026-03-16 Yann Lanoiselée , Denis S. Grebenkov , Gianni Pagnini

We present a general phase-space kinetic model for charged particle transport through combined localised and delocalised states, capable of describing scattering collisions, trapping, detrapping and losses. The model is described by a…

Statistical Mechanics · Physics 2016-09-14 Peter W. Stokes , Bronson Philippa , Daniel Cocks , Ronald D. White

The movement of organisms and cells can be governed by occasional long distance runs, according to an approximate L\'evy walk. For T cells migrating through chronically-infected brain tissue, runs are further interrupted by long pauses, and…

Biological Physics · Physics 2020-03-06 Gissell Estrada-Rodriguez , Heiko Gimperlein , Kevin J. Painter , Jakub Stocek

This paper considers the two-dimensional narrow escape problem in a domain which is composed of a relatively big head and several thin necks. The narrow escape problem is to compute the mean first passage time(MFPT) of a Brownian particle…

Mathematical Physics · Physics 2023-12-05 Xiaofei Li , Shengqi Lin

From the smallest biological systems to the largest cosmological structures, spatial domains undergo expansion and contraction. Within these growing domains, diffusive transport is a common phenomenon. Mathematical models have been widely…

Populations and Evolution · Quantitative Biology 2023-06-27 Stuart T. Johnston , Matthew J. Simpson

By using a time-dependent operator converting a distribution function (statistical operator) of a total system under consideration into the relevant form, new exact nonlinear generalized master equations (GMEs) are derived. The…

Statistical Mechanics · Physics 2007-05-23 Victor F. Los

The study of first passage times for diffusing particles reaching target states is foundational in various practical applications, including diffusion-controlled reactions. In this work, we present a bi-scaling theory for the probability…

Statistical Mechanics · Physics 2025-03-21 Talia Baravi , David A. Kessler , Eli Barkai

Consider a network embedded in the 2D plane, where a particle diffuses along the edges of the network. It is clear that over short length scales a particle moves along a single edge and thus undergoes one-dimensional diffusion. However, on…

Statistical Mechanics · Physics 2021-08-23 D. B. Wilson , C. H. L. Beentjes

In this work, a two-dimensional time-fractional subdiffusion model is developed to investigate the underlying transport phenomena evolving in a binary medium comprised of two sub-domains occupied by homogeneous material. We utilise an…

Numerical Analysis · Mathematics 2021-02-05 Libo Feng , Ian Turner , Patrick Perre , Kevin Burrage