Hostname: page-component-8678677fb7-h96qj Total loading time: 0 Render date: 2026-10-09T23:00:08.182Z Has data issue: false hasContentIssue false

Some dependence results between the spreading speed and the coefficients of the space–time periodic Fisher–KPP equation

Published online by Cambridge University Press:  28 February 2011

GRÉGOIRE NADIN*
Affiliation:
CNRS, UMR 7598, Laboratoire Jacques-Louis Lions, F-75005 Paris, France email: nadin@ann.jussieu.fr

Abstract

We investigate in this paper the dependence relation between the space–time periodic coefficients A, q and μ of the reaction–diffusion equation\begin{linenomath}\[
\partial_t u -\nabla \cdot (A(t, x)\nabla u)+q(t, x)\cdot \nabla u = \mu(t, x)u(1-u),
\]
\end{linenomath}and the spreading speed of the solutions of the Cauchy problem associated with compactly supported initial data. We prove in particular that (1) taking the spatial or temporal average of μ decreases the minimal speed, (2) if μ is not constant with respect to x, then increasing the amplitude of the diffusion matrix A does not necessarily increase the minimal speed and (3) if A = IN, μ is a constant, then the introduction of a space periodic drift term q = ∇Q decreases the minimal speed. In order to prove these results, we use a variational characterisation of the spreading speed that involves a family of periodic principal eigenvalues associated with the linearisation of the equation near zero. We are thus back to the investigation of the dependence relation between this family of eigenvalues and the coefficients.

Information

Type
Papers
Copyright
Copyright © Cambridge University Press 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)