# Dynamical Wilson fermions and the problem of the chiral limit in compact lattice QED

## TL;DR

This paper investigates the chiral transition in compact lattice QED with Wilson fermions, comparing quenched and full theories, and finds that quenched approximation works well at strong coupling but not at weaker coupling.

## Contribution

It provides a detailed comparison of the chiral transition line in quenched and full lattice QED, highlighting the limitations of quenched approximation at different coupling strengths.

## Key findings

- Quenched theory approximates full theory well at strong coupling ($eta=0$).
- At larger $eta$, the full theory's transition does not align with the zero-mass pseudoscalar limit.
- The chiral limit cannot be defined at higher $eta$ due to transition inconsistencies.

## Abstract

We compare the approach to the chiral transition line $~\kappa_c(\bt)~$ in quenched and full compact lattice QED with Wilson fermions within the confinement phase, especially in the pseudoscalar sector of the theory. We show that in the strong coupling limit ($\beta =0$) the quenched theory is a good approximation to the full one, in contrast to the case of $\beta =0.8$. At the larger $\beta$-value the transition in the full theory is inconsistent with the zero--mass limit of the pseudoscalar particle, thus prohibiting the definition of a chiral limit.