  We compute the one loop graviton contribution to the self-energy of a very
light fermion on a locally de Sitter background. This result can be used to
study the effect that a small mass has on the propagation of fermions through
the sea of infrared gravitons generated by inflation. We employ dimensional
regularization and obtain a fully renormalized result by absorbing all
divergences with BPHZ counterterms. An interesting technical aspect of this
computation is the need for two noninvariant counterterms owing to the breaking
of de Sitter invariance by our gauge condition.
