Improving the Lattice QED Action

TL;DR

This paper investigates the universality of features in lattice QED simulations by formulating a quenched model with different lattice spacings for photons and fermions, analyzing critical exponents.

Contribution

It introduces a quenched lattice QED model with variable blocking parameters to study the universality of critical behavior in strong coupling regimes.

Findings

Critical exponents delta and beta are independent of blocking parameters.

Critical exponents are unaffected by the choice of gauge-invariant photon action.

The model demonstrates universality in the chiral phase transition features.

Abstract

Strongly coupled QED is a model whose physics is dominated by short-ranged effects. In order to assess which features of numerical simulations of the chiral phase transition are universal and which are not, we have formulated a quenched version of the model in which photon degrees of freedom are defined on a lattice of spacing a, but fermions only on a lattice of spacing 2a. The fermi-photon interaction is then obtained via a blocking procedure, whose parameters allow a degree of control over the relative importance of short wavelength modes. Results from a variety of models are presented; the critical exponents delta and beta governing the transition appear to be independent of the blocking, or even of whether a gauge-invariant action is used for the photons.