Journal of Functional Analysis ( IF 1.7 ) Pub Date : 2020-08-06 , DOI: 10.1016/j.jfa.2020.108723 Xing Liang , Tao Zhou
In this paper, we investigate the spreading phenomena of the general nonlocal KPP equation in almost periodic media where μ is a probability measure on and a is a positive almost periodic function with .
Two constants and are called the spreading speeds of in the positive and negative directions respectively provided the following two statements hold:
(i) For any nonnegative initial function with a compact support, ;
(ii) There is some such that for any nonnegative initial function , if on an interval longer than L, then
In this paper, we show that if the heterogeneity of the media can be averaged by the diffusion, then has spreading speeds. Precisely, let be the support of μ, be the closed additive subgroup generated by and , we have the following theorem: Theorem 0.1 Let a be an almost periodic function with . Then has spreading speeds and provided .
Let be an at most countable set of real numbers. Suppose that for any , for any and . Set Theorem 0.2 If the support of μ for any , then for any almost periodic function a with and being a basis of frequencies of a, has spreading speeds. If for some , then there is some almost periodic function a with and being a basis of frequencies of a such that has no spreading speeds.
中文翻译:
非局部KPP方程在几乎周期介质中的传播速度
在本文中,我们研究了一般非局部KPP方程在几乎周期介质中的扩散现象其中μ是对并且a是一个正的几乎周期函数,具有。
两个常数 和 被称为传播速度 分别在以下两个方面保持正向和负向:
(i)对于任何非负初始函数 在紧凑的支撑下, ;
(ii)有一些 这样对于任何非负初始函数 如果 间隔大于L,则
在本文中,我们表明,如果可以通过扩散将介质的异质性平均化,则 传播速度快。准确地,让是μ的支持, 是由生成的封闭加法子组 和 ,我们有以下定理:
定理0.1
设a是一个几乎周期性的函数 。然后 传播速度快 和 提供 。
让 是最多可数的实数集。假设对于任何, 对于任何 和 。组
定理0.2
如果支持μ 对于任何 ,则对于任何几乎周期函数a 和 作为a频率的基础, 传播速度快。
如果 对于一些 ,然后有一些几乎周期性的函数 和 作为频率的基础 没有传播速度。