Physical properties of the massive Schwinger model from the nonperturbative functional renormalization group

TL;DR

This paper uses the nonperturbative functional renormalization group to analyze the massive Schwinger model, confirming the phase transition's universality class and exploring temperature and vacuum effects on physical quantities.

Contribution

It demonstrates how the functional renormalization group can be applied to derive comprehensive physical properties of the massive Schwinger model, including phase transition and temperature dependence.

Findings

Phase transition belongs to 2D Ising universality class.

Physical quantities match density matrix renormalization group results.

Screening of fractional charges occurs only at infinite temperature.

Abstract

We investigate the massive Schwinger model in $d=1+1$ dimensions using bosonization and the nonperturbative functional renormalization group. In agreement with previous studies we find that the phase transition, driven by a change of the ratio $m/e$ between the mass and the charge of the fermions, belongs to the two-dimensional Ising universality class. The temperature and vacuum angle dependence of various physical quantities (chiral density, electric field, entropy density) are also determined and agree with results obtained from density matrix renormalization group studies. Screening of fractional charges and deconfinement occur only at infinite temperature. Our results exemplify the possibility to obtain virtually all physical properties of an interacting system from the functional renormalization group.