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We derive a grey linear diffusion equation for photons with respect to inertial (or lab-frame) space and time, using asymptotic analysis in 1D planar geometry. The solution of the equation is the comoving radiation energy density. Our…

High Energy Astrophysical Phenomena · Physics 2026-02-12 Ryan T. Wollaeger , Jim E. Morel , Kendra P. Long , Mathew A. Cleveland , Robert B. Lowrie

In this work we propose a nonlinear stabilization technique for convection-diffusion-reaction and pure transport problems discretized with space-time isogeometric analysis. The stabilization is based on a graph-theoretic artificial…

Numerical Analysis · Computer Science 2019-11-18 Jesús Bonilla , Santiago Badia

We introduce a score-based generative sampling method for solving the nonlinear filtering problem with robust accuracy. A major drawback of existing nonlinear filtering methods, e.g., particle filters, is the low stability. To overcome this…

Optimization and Control · Mathematics 2023-06-16 Feng Bao , Zezhong Zhang , Guannan Zhang

We present an anisotropic extension of the isotropic osmosis model that has been introduced by Weickert et al.~(Weickert, 2013) for visual computing applications, and we adapt it specifically to shadow removal applications. We show that in…

Analysis of PDEs · Mathematics 2019-05-22 Simone Parisotto , Luca Calatroni , Marco Caliari , Carola-Bibiane Schönlieb , Joachim Weickert

We present an asymptotic preserving scheme based on a micro-macro decomposition for stochastic linear transport equations in kinetic and diffusive regimes. We perfom a mathematical analysis and prove that the scheme is uniformly stable with…

Numerical Analysis · Mathematics 2018-03-19 Nathalie Ayi , Erwan Faou

We derive a non-linear sigma-model for the transport of light (classical waves) through a disordered medium. We compare this extension of the model with the well-established non-linear sigma-model for the transport of electrons…

Disordered Systems and Neural Networks · Physics 2009-10-31 B. Elattari , V. Kagalovsky , H. A. Weidenmueller

In this work, we propose a new semi-Lagrangian (SL) finite difference scheme for nonlinear advection-diffusion problems. To ensure conservation, which is fundamental for achieving physically consistent solutions, the governing equations are…

Numerical Analysis · Mathematics 2025-11-05 Silvia Preda , Walter Boscheri , Matteo Semplice , Maurizio Tavelli

In this paper we construct numerical schemes to approximate linear transport equations with slab geometry by diffusion equations. We treat both the case of pure diffusive scaling and the case where kinetic and diffusive scalings coexist.…

Numerical Analysis · Mathematics 2015-05-18 Qin Li , Jianfeng Lu , Weiran Sun

Diffusion models have recently emerged as powerful generative priors for solving inverse problems. However, training diffusion models in the pixel space are both data-intensive and computationally demanding, which restricts their…

Computer Vision and Pattern Recognition · Computer Science 2024-04-17 Bowen Song , Soo Min Kwon , Zecheng Zhang , Xinyu Hu , Qing Qu , Liyue Shen

The aim of this paper is to provide a comprehensive study of some linear nonlocal diffusion problems in metric measure spaces. These include, for example, open subsets in $\mathbb{R}^N$, graphs, manifolds, multi-structures or some fractal…

Analysis of PDEs · Mathematics 2014-12-18 Aníbal Rodríguez-Bernal , Silvia Sastre-Gómez

This paper aims to develop and analyze a numerical scheme for solving the backward problem of semilinear subdiffusion equations. We establish the existence, uniqueness, and conditional stability of the solution to the inverse problem by…

Numerical Analysis · Mathematics 2025-05-07 Xu Wu , Jiang Yang , Zhi Zhou

We consider image denoising using a nonlinear diffusion process, where we solve unsteady partial differential equations with nonlinear coefficients. The noised image is given as an initial condition, and nonlinear coefficients are used to…

Numerical Analysis · Mathematics 2025-05-14 Maria Vasilyeva , Aleksei Krasnikov , Kelum Gajamannage , Mehrube Mehrubeoglu

In this work we first prove, by formal arguments, that the diffusion limit of nonlinear kinetic equations, where both the transport term and the turning operator are density-dependent, leads to volume-exclusion chemotactic equations. We…

Analysis of PDEs · Mathematics 2022-11-04 Gissell Estrada-Rodriguez , Diane Peurichard , Xinran Ruan

Planar wave trains are traveling wave solutions whose wave profiles are periodic in one spatial direction and constant in the transverse direction. In this paper, we investigate the stability of planar wave trains in reaction-diffusion…

Analysis of PDEs · Mathematics 2021-01-14 Björn de Rijk , Björn Sandstede

In this paper, we explore osmotic transport by means of molecular dynamics (MD) simulations. We first consider osmosis through a membrane, and investigate the reflection coefficient of an imperfectly semi-permeable membrane, in the dilute…

Mesoscale and Nanoscale Physics · Physics 2017-05-18 Hiroaki Yoshida , Sophie Marbach , Lydéric Bocquet

The dynamics of cross-diffusion models leads to a high computational complexity for implicit difference schemes, turning them unsuitable for tasks that require results in real-time. We propose the use of two operator splitting schemes for…

Numerical Analysis · Mathematics 2022-02-24 Diogo Lobo

We introduce a (linear) positive and asymptotic preserving method or solving the one-group radiation transport equation. The approximation in space is discretization agnostic: the space approximation can be done with continuous or…

Numerical Analysis · Mathematics 2019-05-10 Jean-Luc Guermond , Bojan Popov , Jean Ragusa

Recovering textures under shadows has remained a challenging problem due to the difficulty of inferring shadow-free scenes from shadow images. In this paper, we propose the use of diffusion models as they offer a promising approach to…

Computer Vision and Pattern Recognition · Computer Science 2025-05-13 Kangfu Mei , Luis Figueroa , Zhe Lin , Zhihong Ding , Scott Cohen , Vishal M. Patel

The inverse problem of backward diffusion is known to be ill-posed and highly unstable. Backward diffusion processes appear naturally in image enhancement and deblurring applications. It is therefore greatly desirable to establish a…

Numerical Analysis · Mathematics 2020-06-18 Leif Bergerhoff , Marcelo Cárdenas , Joachim Weickert , Martin Welk

We propose a nonlinear Discrete Duality Finite Volume scheme to approximate the solutions of drift diffusion equations. The scheme is built to preserve at the discrete level even on severely distorted meshes the energy / energy dissipation…

Analysis of PDEs · Mathematics 2017-05-31 Clément Cancès , Claire Chainais-Hillairet , Stella Krell