An Application of Feynman-Kleinert Approximants to the Massive Schwinger Model on a Lattice

TL;DR

This paper explores the use of Feynman-Kleinert approximants to analyze the lattice Schwinger model, finding success in interpolating between different mass regimes but limited convergence in the continuum limit.

Contribution

It applies Feynman-Kleinert approximants to the lattice Schwinger model and corrects previous errors in continuum series coefficients.

Findings

Good results in interpolating between large and small fermion masses

Poor convergence when extrapolating to the weak-coupling continuum limit

Rectified an earlier derivation error in continuum series coefficients

Abstract

A trial application of the method of Feynman-Kleinert approximants is made to perturbation series arising in connection with the lattice Schwinger model. In extrapolating the lattice strong-coupling series to the weak-coupling continuum limit, the approximants do not converge well. In interpolating between the continuum perturbation series at large fermion mass and small fermion mass, however, the approximants do give good results. In the course of the calculations, we picked up and rectified an error in an earlier derivation of the continuum series coefficients.