A nonperturbative study of phase transitions in the multi-frequency sine-Gordon model

TL;DR

This paper investigates phase transitions in multi-frequency sine-Gordon models using a nonperturbative approach, identifying critical points, lines, and a tricritical point through numerical analysis.

Contribution

It provides the first substantial evidence for a tricritical point in the three-frequency sine-Gordon model and maps the critical and first-order transition lines.

Findings

Evidence for a tricritical point in the three-frequency model

Identification of the critical line and spectrum changes

Detection of first-order transition points

Abstract

The phase spaces of the two- and three-frequency sine-Gordon models are examined in the framework of truncated conformal space approach. The focus is mainly on a tricritical point in the phase space of the three-frequency model. We give substantial evidence that this point exists. We also find the critical line in the phase space and present TCSA data showing the change of the spectrum on the critical line as the tricritical endpoint is approached. We find a few points of the line of first order transition as well.