The Coulomb-Higgs phase transition in Z(8) and q=8 U(1)-Higgs models

TL;DR

This paper investigates the nature of the Coulomb-Higgs phase transition in Z(8) and q=8 U(1)-Higgs models, revealing it to be first order, contrary to previous beliefs of second order, with implications for the phase diagram.

Contribution

The study demonstrates that the Coulomb-Higgs transition in these models is first order, challenging prior assumptions of second order behavior and clarifying the phase transition line characteristics.

Findings

The transition is clearly first order, not second order.

The transition line is first order over a wide region with decreasing latent heat.

The transition approaches the 4D XY model limit with vanishing latent heat.

Abstract

The Coulomb-Higgs phase transition of the four dimensional Z$_8$ gauge model is studied. We find clear first order properties in contradiction with the previously stressed second order behavior. That transition point may be regarded as the end of a transition line of the U(1)-Higgs model with charge $q=8$, that has been also assumed of second order. We show that this line is first order in a wide region, with a decreasing latent heat that goes to zero when closing to the 4--$d$ XY model limit.