Casimir energy of massless fermions in the slab-bag

The zero-point energy of a massless fermion field in the interior of two pa rallel plates in a D-dimensional space-time at zero temperature is calculat ed. In order to regularize the model, a mix between dimensional and zeta-fu nction regularization procedure is used and it is found that the regularize d zero-point energy density is finite for any number of space-time dimensio ns. We present a general expression for the Casimir energy of the fermionic field in such a situation.