On cover times for 2D lattices

Abstract

We study the cover time $τ_{\mathrm{cov}}$ by (continuous-time) random walk on the 2D box of side length $n$ with wired boundary or on the 2D torus, and show that in both cases with probability approaching 1 as $n$ increases, $\sqrt{τ_{\mathrm{cov}}}=\sqrt{2n^2}[\sqrt{2/π} \log n + O(\log\log n)]$. This improves a result of Dembo, Peres, Rosen, and Zeitouni (2004) and makes progress towards a conjecture of Bramson and Zeitouni (2009).

21 pages, major revision upon previous version