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Following Geroch, Traschen, Mars and Senovilla, we consider Lorentzian manifolds with distributional curvature tensor. Such manifolds represent spacetimes of general relativity that possibly contain gravitational waves, shock waves, and…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Philippe G. LeFloch , Cristinel Mardare

A $g$--subdiffusion equation with fractional Caputo time derivative with respect to another function $g$ is used to describe a process of a continuous transition from subdiffusion with parameters $\alpha$ and $D_\alpha$ to subdiffusion with…

Statistical Mechanics · Physics 2022-05-25 Tadeusz Kosztołowicz , Aldona Dutkiewicz

The modelling of linear and nonlinear reaction-subdiffusion processes is more subtle than normal diffusion and causes different phenomena. The resulting equations feature a spatial Laplacian with a temporal memory term through a time…

Analysis of PDEs · Mathematics 2021-08-24 Jichen Yang , Jens D. M. Rademacher

In this article, we present a Latent Diffusion Model (LDM) for the generation of brain Magnetic Resonance Imaging (MRI), conditioning its generation based on pathology (Healthy, Glioblastoma, Sclerosis, Dementia) and acquisition modality…

This paper develops an abstract theory for subdifferential operators to give existence and uniqueness of solutions to the initial-boundary problem (P) for the nonlinear diffusion equation in an unbounded domain $\Omega\subset\mathbb{R}^N$…

Analysis of PDEs · Mathematics 2018-05-09 Takeshi Fukao , Shunsuke Kurima , Tomomi Yokota

We investigate in this paper propagation phenomena for the heterogeneous reaction-diffusion equation $\partial_t u -\Delta u = f(t,u)$, $x\in R^N$, $t\in\R$, where f=f(t,u) is a KPP monostable nonlinearity which depends in a general way on…

Analysis of PDEs · Mathematics 2011-05-03 Grégoire Nadin , Luca Rossi

We study a class of semilinear diffusion equations on infinite, connected, weighted graphs, focusing on two types of nonlinearities: monotone decreasing and Lipschitz continuous. Under minimal structural assumptions on the graph, we…

Analysis of PDEs · Mathematics 2026-05-15 Elvise Berchio , Davide Bianchi , Alberto G. Setti , Maria Vallarino

We consider a diffusion problem on a network on whose nodes we impose Dirichlet and generalized, non-local Kirchhoff-type conditions. We prove well-posedness of the associated initial value problem, and we exploit the theory of…

Analysis of PDEs · Mathematics 2018-12-21 Delio Mugnolo

We investigate long-time behaviors of empirical measures associated with subordinated Dirichlet diffusion processes on a compact Riemannian manifold $M$ with boundary $\partial M$ to some reference measure, under the quadratic Wasserstein…

Probability · Mathematics 2022-06-09 Huaiqian Li , Bingyao Wu

We introduce a location statistic for distributions on non-linear geometric spaces, the diffusion mean, serving as an extension and an alternative to the Fr\'echet mean. The diffusion mean arises as the generalization of Gaussian maximum…

Statistics Theory · Mathematics 2022-12-06 Benjamin Eltzner , Pernille Hansen , Stephan F. Huckemann , Stefan Sommer

This paper considers particle propagation in a cylindrical molecular communication channel, e.g. a simplified model of a blood vessel. Emitted particles are influenced by diffusion, flow, and a vertical force induced e.g. by gravity or…

Computational Physics · Physics 2019-02-26 Maximilian Schäfer , Wayan Wicke , Rudolf Rabenstein , Robert Schober

We establish dimension-independent estimates related to heat operators e^{tL} on manifolds. We first develop a very general contractivity result for Markov kernels which can be applied to diffusion semigroups. Second, we develop estimates…

Differential Geometry · Mathematics 2014-12-12 Brian C. Hall , Matthew Cecil

We find a renormalized "time-dependent diffusion coefficient", D(t), for pulsed excitation of a nominally diffusive sample by solving the Bethe-Salpeter equation with recurrent scattering. We observe a crossover in dynamics in the…

Disordered Systems and Neural Networks · Physics 2009-11-10 S. K. Cheung , X. Zhang , Z. Q. Zhang , A. A. Chabanov , A. Z. Genack

The problem of diffusion in a time-dependent (and generally inhomogeneous) external field is considered on the basis of a generalized master equation with two times, introduced in [1,2]. We consider the case of the quasi Fokker-Planck…

Statistical Mechanics · Physics 2015-05-18 S. A. Trigger , G. J. F. van Heijst , O. F. Petrov , P. P. J. M. Schram

The main objective of this paper is analysis of the initial-boundary value problems for the linear time-fractional diffusion equations with a uniformly elliptic spatial differential operator of the second order and the Caputo type…

Analysis of PDEs · Mathematics 2023-04-18 Yuri Luchko , Masahiro Yamamoto

We consider the heat equation with Dirichlet boundary conditions on the tubular neighborhood of a closed Riemannian submanifold. We show that, as the tube radius decreases, the semigroup of a suitably rescaled and renormalized generator can…

Analysis of PDEs · Mathematics 2008-10-29 O. Wittich

The time-fractional diffusion-wave equation is revisited, where the time derivative is of order $2 \nu$ and $0 < \nu \le 1$. The behaviour of the equation is "diffusion-like" (respectively, "wave-like") when $0 < \nu \le \frac{1}{2}$…

Analysis of PDEs · Mathematics 2021-10-25 Marianito R. Rodrigo

We continue the study of Modica type gradient estimates for non-homogeneous parabolic equations initiated in \cite{BG}. First, we show that for the parabolic minimal surface equation with a semilinear force term if a certain gradient…

Analysis of PDEs · Mathematics 2015-03-10 Agnid Banerjee , Nicola Garofalo

Diffusion maps (DM) constitute a classic dimension reduction technique, for data lying on or close to a (relatively) low-dimensional manifold embedded in a much larger dimensional space. The DM procedure consists in constructing a spectral…

Machine Learning · Statistics 2022-03-08 Shan Shan , Ingrid Daubechies

We study the existence of Feller semigroups arising in the theory of multidimensional diffusion processes. We study bounded perturbations of elliptic operators with boundary conditions containing an integral over the closure of the domain…

Analysis of PDEs · Mathematics 2014-05-05 Pavel Gurevich