Domain wall fermions in a waveguide: the phase diagram at large Yukawa coupling

TL;DR

This paper analyzes the phase diagram of domain wall fermions in a waveguide at large Yukawa coupling, revealing that species doublers reappear and confirming the difficulty of formulating lattice chiral gauge theories with this method.

Contribution

The authors develop a systematic expansion for large Yukawa coupling, providing an analytic understanding of the phase diagram and fermion spectrum in the model.

Findings

Species doublers reappear at large Yukawa coupling

No lattice chiral gauge theory can be obtained from this approach

Analytic phase diagram elucidated at large coupling

Abstract

In this paper we return to a model with domain wall fermions in a waveguide. This model contains a Yukawa coupling $y$ which is needed for gauge invariance. A previous paper left the analysis for large values of this coupling incomplete. We fill the gap by developing a systematic expansion suitable for large $y$, and using this, we gain an analytic understanding of the phase diagram and fermion spectrum. We find that in a sense all the species doublers come back for large $y$. The conclusion that no lattice chiral gauge theory can be obtained from this approach therefore remains valid.