  We apply strong-coupling perturbation theory to gauge theories containing
domain-wall fermions in Shamir's surface version. We construct the effective
Hamiltonian for the color-singlet degrees of freedom that constitute the
low-lying spectrum at strong coupling. We show that the effective theory is
identical to that derived from naive, doubled fermions with a mass term, and
hence that domain-wall fermions at strong coupling suffer both doubling and
explicit breaking of chiral symmetry. Since we employ a continuous fifth
dimension whose extent tends to infinity, our result applies to overlap
fermions as well.
