Continuous Kasteleyn theory for the bead model

Abstract

Consider the semidiscrete torus ${\mathbb{T}}_n:=[0,1)\times \{0,1,\dots ,n-1\}$ representing $n$ unit length strings running in parallel. A bead configuration on ${\mathbb{T}}_n$ is a point process on ${\mathbb{T}}_n$ with the property that between every two consecutive points on the same string, there lies a point on each of the neighbouring strings. In this article we develop a continuous version of Kasteleyn theory to show that partition functions for bead configurations on ${\mathbb{T}}_n$ may be expressed in terms of Fredholm determinants of certain operators on ${\mathbb{T}}_n$. We obtain an explicit formula for the volumes of bead configurations on ${\mathbb{T}}_n$. The asymptotics of this formula confirm a recent prediction in the free probability literature. Thereafter we study random bead configurations on ${\mathbb{T}}_n$, showing that they have a determinantal structure which can be connected with exclusion processes. We use this machinery to construct a new probabilistic representation of TASEP on the ring.