Long-time dynamics of a competition model with nonlocal diffusion and free boundaries: Vanishing and spreading of the invader

Abstract

In this work, we investigate the long-time dynamics of a two species competition model of Lotka-Volterra type with nonlocal diffusions. One of the species, with density $v(t,x)$, is assumed to be a native in the environment (represented by the real line $\mathbb{R}$), while the other species, with density $u(t,x)$, is an invading species which invades the territory of $v$ with two fronts, $x=g(t)$ on the left and $x=h(t)$ on the right. So the population range of $u$ is the evolving interval $[g(t),h(t)]$ and the reaction-diffusion equation for $u$ has two free boundaries, with $g(t)$ decreasing in $t$ and $h(t)$ increasing in $t$, and the limits $h_{\infty }:=h(\infty )\le \infty$ and $g_{\infty }:=g(\infty )\ge -\infty$ thus always exist. We obtain detailed descriptions of the long-time dynamics of the model according to whether $h_{\infty }-g_{\infty }$ is $\infty$ or finite. In the latter case, we reveal in what sense the invader $u$ vanishes in the long run and $v$ survives the invasion, while in the former case, we obtain a rather satisfactory description of the long-time asymptotic limit for both $u(t,x)$ and $v(t,x)$ when a certain parameter $k$ in the model is less than 1. This research is continued in a separate work, where sharp criteria are obtained to distinguish the case $h_{\infty }-g_{\infty }=\infty$ from the case $h_{\infty }-g_{\infty }$ is finite, and new phenomena are revealed for the case $k\ge 1$. The techniques developed in this paper should have applications to other models with nonlocal diffusion and free boundaries.