Dynamical Phase Transition of ASEP in the KPZ regime

TL;DR

This paper studies a dynamical phase transition in ASEP on the integer lattice, showing that at large times and specific initial conditions, the process converges to a mixture of pure states, revealing a new type of phase transition in the KPZ regime.

Contribution

It demonstrates that ASEP with deterministic initial data exhibits a mixture of pure states at large times, characterized by the behavior of a second class particle related to GUE distributions.

Findings

ASEP converges to a mixture of pure states at large times.

The mixture parameter is linked to the position of a second class particle.

The second class particle's distribution relates to differences of GUEs.

Abstract

We consider the asymmetric simple exclusion process (ASEP) on $\mathbb{Z}$. For continuous densities, ASEP is in local equilibrium for large times, at discontinuities however, one expects to see a dynamical phase transition, i.e. a mixture of different equilibriums. We consider ASEP with deterministic initial data such that at large times, two rarefactions come together at the origin, and the density jumps from $0$ to $1$. Shifting the measure on the KPZ $1/3$ scale, we show that the law of ASEP converges to a mixture of the Dirac measures with only holes resp. only particles. The parameter of that mixture is the probability that the second class particle, which is distributed as the difference of two independent GUEs, stays to the left of the shift. This should be compared with the results of Ferrari and Fontes from 1994 \cite{FF94b}, who obtained a mixture of Bernoulli product measures at discontinuities created by random initial data, with the GUEs replaced by Gaussians.