  Recently, Narayanan and Neuberger proposed that the fermion determinant for a
lattice chiral gauge theory be defined by an overlap formula. The motivation
for that formula comes from Kaplan's five dimensional lattice domain wall
fermions. In the case that the target continuum theory contains $4n$ chiral
families, we show that the effective action defined by overlap formula is
identical to the effective action of a modified waveguide model that has extra
bosonic ghost fields. This raises serious questions about the viability of the
overlap formula for defining chiral gauge theories on the lattice.
