Shortest spanning trees and a counterexample for random walks in random environments

Abstract

We construct forests that span ℤ^d, d≥2, that are stationary and directed, and whose trees are infinite, but for which the subtrees attached to each vertex are as short as possible. For d≥3, two independent copies of such forests, pointing in opposite directions, can be pruned so as to become disjoint. From this, we construct in d≥3 a stationary, polynomially mixing and uniformly elliptic environment of nearest-neighbor transition probabilities on ℤ^d, for which the corresponding random walk disobeys a certain zero–one law for directional transience.