Facilitated exclusion process

TL;DR

This paper analyzes the Facilitated TASEP, revealing Tracy Widom GSE statistics for the rightmost particle and GUE in the bulk, using a solvable mapping to half-quadrant last-passage percolation, and explores model-dependent fluctuation behaviors.

Contribution

It demonstrates that the Facilitated TASEP exhibits cube-root time fluctuations with model-dependent statistics, expanding understanding of exclusion processes with density discontinuities.

Findings

Rightmost particle follows Tracy Widom GSE statistics.

Bulk particles exhibit GUE statistics.

Fluctuation behaviors are model-dependent, with GSE and GUE observed.

Abstract

We study the Facilitated TASEP, an interacting particle system on the one dimensional integer lattice. We prove that starting from step initial condition, the position of the rightmost particle has Tracy Widom GSE statistics on a cube root time scale, while the statistics in the bulk of the rarefaction fan are GUE. This uses a mapping with last-passage percolation in a half-quadrant which is exactly solvable through Pfaffian Schur processes. Our results further probe the question of how first particles fluctuate for exclusion processes with downward jump discontinuities in their limiting density profiles. Through the Facilitated TASEP and a previously studied MADM exclusion process we deduce that cube-root time fluctuations seem to be a common feature of such systems. However, the statistics which arise are shown to be model dependent (here they are GSE, whereas for the MADM exclusion process they are GUE). We also discuss a two-dimensional crossover between GUE, GOE and GSE distribution by studying the multipoint distribution of the first particles when the rate of the first one varies. In terms of half-space last passage percolation, this corresponds to last passage times close to the boundary when the size of the boundary weights is simultaneously scaled close to the critical point.