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

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.