Disconnection and entropic repulsion for the harmonic crystal with random conductances

TL;DR

This paper investigates the phase transition and disconnection phenomena for the harmonic crystal with random conductances on high-dimensional lattices, revealing entropic effects and providing bounds related to homogenized capacity.

Contribution

It extends previous work on constant conductances to the case of random conductances, introducing novel solidification estimates for random walks and analyzing disconnection probabilities.

Findings

Identifies a non-trivial phase transition at a constant critical level.

Provides asymptotic bounds on disconnection probabilities in terms of homogenized capacity.

Shows that disconnection induces an entropic push-down of the field.

Abstract

We study level-set percolation for the harmonic crystal on $\mathbb{Z}^d$, $d \geq 3$, with uniformly elliptic random conductances. We prove that this model undergoes a non-trivial phase transition at a critical level that is almost surely constant under the environment measure. Moreover, we study the disconnection event that the level-set of this field below a level $\alpha$ disconnects the discrete blow-up of a compact set $A \subseteq \mathbb{R}^d$ from the boundary of an enclosing box. We obtain quenched asymptotic upper and lower bounds on its probability in terms of the homogenized capacity of $A$, utilizing results from Neukamm, Sch\"affner and Schl\"omerkemper, see arXiv:1606.06533. Furthermore, we give upper bounds on the probability that a local average of the field deviates from some profile function depending on $A$, when disconnection occurs. The upper and lower bounds concerning disconnection that we derive are plausibly matching at leading order. In this case, this work shows that conditioning on disconnection leads to an entropic push-down of the field. The results in this article generalize the findings of arXiv:1802.02518 and arXiv:1808.09947 by the authors which treat the case of constant conductances. Our proofs involve novel "solidification estimates" for random walks, which are similar in nature to the corresponding estimates for Brownian motion derived by Sznitman and the second author in arXiv:1706.07229.