The periodic Schur process and free fermions at finite temperature

TL;DR

This paper simplifies the correlation function derivation of the periodic Schur process using free fermion formalism, explores its edge scaling limit at finite temperature, and extends the model to strict partitions, revealing universal crossover behaviors.

Contribution

It provides a new simpler derivation of correlation functions, analyzes the finite-temperature edge behavior, and extends the model to strict partitions with related correlation functions.

Findings

Correlation functions become determinantal via grand canonical ensemble.

Edge behavior described by universal finite-temperature Airy kernel.

Extreme value statistics interpolate between Tracy-Widom GUE and Gumbel distributions.

Abstract

We revisit the periodic Schur process introduced by Borodin in 2007. Our contribution is threefold. First, we provide a new simpler derivation of its correlation functions via the free fermion formalism. In particular, we shall see that the process becomes determinantal by passing to the grand canonical ensemble, which gives a physical explanation to Borodin's "shift-mixing" trick. Second, we consider the edge scaling limit in the simplest nontrivial case, corresponding to a deformation of the poissonized Plancherel measure on partitions. We show that the edge behavior is described, in a certain crossover regime different from that for the bulk, by the universal finite-temperature Airy kernel, which was previously encountered by Johansson and Le Doussal et al. in other models, and whose extreme value statistics interpolates between the Tracy-Widom GUE and the Gumbel distributions. We also define and prove convergence for a stationary extension of our model. Finally, we compute the correlation functions for a variant of the periodic Schur process involving strict partitions, Schur's P and Q functions, and neutral fermions.