Four dimensional loop-erased random walk

The loop-erased random walk (LERW) in ${\mathbb{Z}}^4$ is the process obtained by erasing loops chronologically for simple random walk. We prove that the escape probability of the LERW renormalized by $(\log n{)}^{\frac{1}{3}}$ converges almost surely and in $L^p$ for all $p>0$. Along the way, we extend previous results by the first author building on slowly recurrent sets. We provide two applications for the escape probability. We construct the two-sided LERW, and we construct a $\pm 1$ spin model coupled with the wired spanning forests on ${\mathbb{Z}}^4$ with the bi-Laplacian Gaussian field on ${\mathbb{R}}^4$ as its scaling limit.