Large N Lattice QED

TL;DR

This paper investigates the phase transition behavior of non-compact QED with multiple fermion species, identifying two distinct transition lines with different physical origins, using a novel simulation method.

Contribution

It introduces a new method for unquenched simulations of lattice QED and analyzes the critical behavior for various N, revealing two phase transition lines with different physical mechanisms.

Findings

Existence of two phase transition lines: one second order, one first order.

The second order transition is driven by fermion effects.

The transition lines approach the $eta=0$ axis asymptotically.

Abstract

We study the $\beta, N$ critical behaviour of non compact QED with $N$ species of light fermions, using a method we have proposed for unquenched simulations. We find that there exist two phase transition lines: one, second order, and the other, first order, that approaches asymptotically the $\beta=0$ axis. These two lines have different physical origin, the second one being entirely due to fermions effects. We discuss the effect of the approximation used, in terms of an expansion of the effective action in powers of $N$, and conclude that the general features should not be affected by this approximation.