Phase Structure of Compact $QED_3$ with Massless Fermions

TL;DR

This paper studies the phase structure of (2+1)-dimensional compact QED with massless fermions, revealing a single-phase behavior and introducing a new mechanism for understanding the critical phenomena related to the number of fermion flavors.

Contribution

The paper develops a new understanding of the N-critical phenomenon in compact QED3 and provides evidence for a single-phase structure using an N-expansion approach.

Findings

Only one phase exists in the model.

The qualitative phase structure remains unchanged with higher order N terms.

Strong evidence supports the single-phase conclusion.

Abstract

In the framework of (2+1)-dimensional compact lattice QED with light fermions, we investigate the phase diagram in the $(\beta, N)$ plane. The approximations involved are related to an expansion of the effective fermionic action as a power series of the flavor number $N$. We also develop a new mechanism for understanding the $N-$critical phenomenon in the full theory. Our results for the specific heat indicate that only one phase does exist. We give strong evidences that this qualitative result should not be changed with the inclusion of higher order terms in the $N$ expansion.