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In this paper we consider a model for the diffusion of a population in a strip-shaped field, where the growth of the species is governed by a Fisher-KPP equation and which is bounded on one side by a road where the species can have a…

Analysis of PDEs · Mathematics 2015-06-30 Andrea Tellini

We consider a family of exact solutions to a nonlinear reaction-diffusion model, constructed using nonclassical symmetry analysis. In a particular limit, the mathematical model approaches the well-known Fisher-KPP model, which means that it…

Exactly Solvable and Integrable Systems · Physics 2022-02-21 Scott W McCue , Bronwyn H Bradshaw-Hajek , Matthew J Simpson

We establish rigorous lower bounds on the speed of traveling fronts and on the bulk burning rate in reaction-diffusion equation with passive advection. The non-linearity is assumed to be of either KPP or ignition type. We consider two main…

Analysis of PDEs · Mathematics 2015-06-26 Alexander Kiselev , Leonid Ryzhik

We consider a Fisher-KPP equation with density-dependent diffusion and advection, arising from a chemotaxis-growth model. We study its behavior as a small parameter, related to the thickness of a diffuse interface, tends to zero. We…

Analysis of PDEs · Mathematics 2011-04-20 Matthieu Alfaro , Elisabeth Logak

The system under study is a reaction-diffusion equation in a horizontal strip, coupled to a diffusion equation on its upper boundary via an exchange condition of the Robin type. This class of models was introduced by H. Berestycki, L. Rossi…

Analysis of PDEs · Mathematics 2016-03-16 Laurent Dietrich , Jean-Michel Roquejoffre

We propose here a new model to describe biological invasions in the plane when a strong diffusion takes place on a line. We establish the main properties of the system, and also derive the asymptotic speed of spreading in the direction of…

Analysis of PDEs · Mathematics 2012-10-17 Henri Berestycki , Jean-Michel Roquejoffre , Luca Rossi

This paper is concerned with spreading properties of space-time heterogeneous Fisher--KPP equations in one space dimension. We focus on the case of everywhere favorable environment with three different zones, a left half-line with slow or…

Analysis of PDEs · Mathematics 2025-11-07 Thomas Giletti , Léo Girardin , Hiroshi Matano

In this paper we focus on three problems about the spreading speeds of nonlocal dispersal Fisher-KPP equations. First, we study the signs of spreading speeds and find that they are determined by the asymmetry level of the nonlocal dispersal…

Analysis of PDEs · Mathematics 2020-07-31 Wen-Bing Xu , Wan-Tong Li , Shigui Ruan

We report on recent progress in the study of nonlinear diffusion equations involving nonlocal, long-range diffusion effects. Our main concern is the so-called fractional porous medium equation, $\partial_t u +(-\Delta)^{s}(u^m)=0$, and some…

Analysis of PDEs · Mathematics 2014-01-16 Juan Luis Vázquez

We consider Fisher-KPP-type reaction-diffusion equations with spatially inhomogeneous reaction rates. We show that a sufficiently strong localized inhomogeneity may prevent existence of transition-front-type global in time solutions while…

Analysis of PDEs · Mathematics 2015-05-20 James Nolen , Jean-Michel Roquejoffre , Lenya Ryzhik , Andrej Zlatos

Our investigation focuses on the asymptotic spreading behavior of the Fisher-KPP equation with a mixed local-nonlocal operator in the diffusion (see the work by X. Cabr\'e and J.-M. Roquejoffre, 2013, ref.[8]) to the setting of mixed…

Analysis of PDEs · Mathematics 2025-09-01 Begoña Barrios , Bryan Pichucho , Alexander Quaas

This paper deals with the large time dynamics of bounded solutions of reaction-diffusion equations with unbounded initial support in $\mathbb{R}^N$. We prove a variational formula for the spreading speeds in any direction, and we also…

Analysis of PDEs · Mathematics 2023-07-08 François Hamel , Luca Rossi

A linear growth-diffusion equation is studied in a time-dependent interval whose location and length both vary. We prove conditions on the boundary motion for which the solution can be found in exact form, and derive the explicit expression…

Analysis of PDEs · Mathematics 2022-10-20 Jane Allwright

The goal of this paper is to find the homogenized equation of a heterogenous Fisher-KPP model in a periodic medium. The solutions of this model are pulsating travelling fronts whose \emph{speeds} are superior to a parametric minimal speed…

Analysis of PDEs · Mathematics 2012-02-01 Mohammad El Smaily

Reaction-diffusion equations describe various spatially extended processes that unfold as traveling fronts moving at constant velocity. We introduce and solve analytically a model that, besides such fronts, supports solutions advancing as…

Biological Physics · Physics 2026-02-13 Louis Brezin , Kyle J. Shaffer , Kirill S. Korolev

The Fisher-KPP equation is a reaction-diffusion equation originally proposed by Fisher to represent allele propagation in genetic hosts or population. It was also proposed by Kolmogorov for more general applications. A novel method for…

Mathematical Physics · Physics 2021-08-25 Luisiana Cundin

We expand on a previous study of fronts in finite particle number reaction-diffusion systems in the presence of a reaction rate gradient in the direction of the front motion. We study the system via reaction-diffusion equations, using the…

Statistical Mechanics · Physics 2009-11-11 Elisheva Cohen , David A. Kessler , Herbert Levine

We provide an asymptotic analysis of a fractional Fisher-KPP type equation in periodic non-connected 1-dimensional media with Dirichlet conditions outside the domain. After demonstrating the existence and uniqueness of a non-trivial bounded…

Analysis of PDEs · Mathematics 2019-10-28 Alexis Léculier , Sepideh Mirrahimi , Jean-Michel Roquejoffre

We treat a model of population dynamics in a periodic environment presenting a fast diffusion line. This phenomenon is modelled via a "road-field" system, which is a system of coupled reaction-diffusion equations set in domains of different…

Analysis of PDEs · Mathematics 2020-10-01 Elisa Affili

We provide an asymptotic analysis of a non-local Fisher-KPP type equation in periodic media and with a non-local stable operator of order $\alpha$ $\in$ (0, 2). We perform a long time-long range scaling in order to prove that the stable…

Analysis of PDEs · Mathematics 2018-12-14 Alexis Léculier