Charge Screening in the Finite Temperature Schwinger Model

TL;DR

This paper analyzes charge screening and symmetry breaking in the finite temperature Schwinger model, revealing deconfinement in infinite volume due to nonlocal fermion effects, but confinement persists in finite volume.

Contribution

It demonstrates how nonlocal effects lead to spontaneous symmetry breaking and charge screening at finite temperature in the Schwinger model, with volume-dependent confinement properties.

Findings

Infinite volume exhibits charge screening and deconfinement.

Finite volume maintains confinement.

Nonlocal fermion effects cause symmetry breaking.

Abstract

We compute the effective action and correlators of the Polyakov loop operator in the Schwinger model at finite temperature and discuss the realization of the discrete symmetries that occur there. We show that, due to nonlocal effects of massless fermions in two spacetime dimensions, the discrete symmetry which governs the screening of charges is spontaneously broken even in an effective one-dimensional model, when the volume is infinite. In this limit, the thermal state of the Schwinger model screens an arbitrary external charge; consequently the model is in the deconfined phase, with the charge of the deconfined fermions completely screened. In a finite volume we show that the Schwinger model is always confining.