Largest-loop-first loop-erased random walk on $\mathbb{Z}^{4}$

TL;DR

This paper introduces the largest-loop-first (LLF) loop-erased random walk on , showing its expected length scales as n divided by a power of log n, and proves its convergence to Brownian motion in four dimensions.

Contribution

It defines a new loop-erasing procedure based on loop size and analyzes its properties, revealing differences from traditional chronological LERW.

Findings

Expected LLF LERW length is of order n (log n)^{-1/2+o(1)} in 4D.

LLF LERW and chronological LERW likely belong to different universality classes.

LLF LERW converges to Brownian motion in four dimensions.

Abstract

Let $S = (S(n))$ be a simple random walk on $\mathbb{Z}^{d}$ started at the origin. We study a loop-erasing procedure of $S[0,n]$ that differs from Lawler's chronological loop-erasure. Specifically, we remove loops from $S[0,n]$ in decreasing order of their lengths. The resulting random simple path is called the largest-loop-first (LLF) LERW. For $d=4$, we prove that the expected length of LLF LERW is of the order $n (\log n)^{-1/2 + o(1)}$. In particular, this suggests that chronological LERW and LLF LERW belong to different universality classes. Furthermore, we also prove the convergence of LLF LERW to Brownian motion in four dimensions.