  Fermion self-energy associated with wave function renormalization is studied
in a five-dimensional Yukawa theory on the orbifold S1/Z2. One-loop divergence
can be subtracted with only two renormalization constants in the bulk and on
the branes. We show that the bulk and brane parts of the self-energy are
uniquely determined with requiring physical conditions. With this procedure,
momentum-scale dependence of the renormalized self-energy is given and the
distribution of the bulk and brane parts can be found at low and high energies.
Despite possible higher degrees of divergence in higher dimensions, the
regularization scheme dependence does not arise. A viewpoint of the
regularization scheme dependence at higher-loop level is also discussed. We
find that the ratio of the bulk contribution to the brane contribution depends
on the momentum scale in a very mild way, so that the relative coefficient of
bulk and brane kinetic terms can be regarded as approximately constant for the
leading quantum effect. The physical conditions given here are applicable to
remove ambiguity in various orbifold models.
