Microscopic structure of shocks and antishocks in the ASEP conditioned on low current

TL;DR

This paper analyzes the microscopic structure of shocks and antishocks in the ASEP conditioned on low current, revealing how shocks perform biased random walks and how antishocks remain stable under certain conditions.

Contribution

It provides explicit descriptions of shock dynamics, invariant measures, and stability properties in the ASEP under low current conditioning, including transition rates and measure decompositions.

Findings

Shock position performs a biased random walk.

Invariant measure from the shock position remains unchanged.

Antishock stability under local conditioning is proven.

Abstract

We study the time evolution of the ASEP on a one-dimensional torus with $L$ sites, conditioned on an atypically low current up to a finite time $t$. For a certain one-parameter family of initial measures with a shock we prove that the shock position performs a biased random walk on the torus and that the measure seen from the shock position remains invariant. We compute explicitly the transition rates of the random walk. For the large scale behaviour this result suggests that there is an atypically low current such that the optimal density profile that realizes this current is a hyperbolic tangent with a travelling shock discontinuity. For an atypically low local current across a single bond of the torus we prove that a product measure with a shock at an arbitrary position and an antishock at the conditioned bond remains a convex combination of such measures at all times which implies that the antishock remains microscopically stable under the locally conditioned dynamics. We compute the coefficients of the convex combinations.