Mixing time for the asymmetric simple exclusion process in a random environment

Hubert Lacoin, Shangjie Yang

Published 2021-02-04Version 1

We consider the simple exclusion process in the integer segment $ [1, N]$ with $k\le N/2$ particles and spatially inhomogenous jumping rates. A particle at site $x\in [ 1, N]$ jumps to site $x-1$ (if $x\ge 2$) at rate $1-\omega_x$ and to site $x+1$ (if $x \le N-1$) at rate $\omega_x$ if the target site is not occupied. The sequence $\omega=(\omega_x)_{ x \in \mathbb{Z}}$ is chosen by IID sampling from a probability law whose support is bounded away from zero and one (in other words the random environment satisfies the uniform ellipticity condition). We further assume $\mathbb{E}[ \log \rho_1 ]<0$ where $\rho_1:= (1-\omega_1)/\omega_1$, which implies that our particles have a tendency to move to the right. We prove that the mixing time of the exclusion process in this setup grows like a power of $N$. More precisely, for the exclusion process with $N^{\beta+o(1)}$ particles where $\beta\in [0,1)$, we have in the large $N$ asymptotic $$ N^{\max\left(1,\frac {1}{\lambda}, \beta+ \frac 1 {2\lambda}\right)+o(1)} \le t_{\mathrm{Mix}}^{N,k} \le N^{C+o(1)}$$ where $\lambda>0$ is such that $\mathbb{E}[\rho_1^{\lambda}]=1$ ($\lambda=\infty$ if the equation has no positive root) and $C$ is a constant which depends on the distribution of $\omega$. We conjecture that our lower bound is sharp up to sub-polynomial correction.