On the absence of zero-temperature limit of equilibrium states for finite-range interactions on the lattice $\mathbb{Z}^2$

TL;DR

This paper constructs finite-range lattice interactions in two dimensions where equilibrium states do not converge as temperature approaches zero, answering a previously open question about zero-temperature limits.

Contribution

It demonstrates the existence of finite-range interactions on $\

Findings

Equilibrium states fail to converge at zero temperature in 2D lattice models.

Constructs explicit examples of non-converging Gibbs states.

Addresses a previously unresolved question in statistical mechanics.

Abstract

We construct finite-range interactions on $\mathcal{S}^{\mathbb{Z}^2}$, where $\mathcal{S}$ is a finite set, for which the associated equilibrium states (i.e., the shift-invariant Gibbs states) fail to converge as temperature goes to zero. More precisely, if we pick any one-parameter family $(\mu_\beta)_{\beta>0}$ in which $\mu_\beta$ is an equilibrium state at inverse temperature $ \beta$ for this interaction, then $\lim_{\beta\to\infty}\mu_\beta$ does not exist. This settles a question posed by the first author and Hochman who obtained such a non-convergence behavior when $d\geq 3$, $d$ being the dimension of the lattice.