  We study the finite temperature free energy and fermion number for Dirac
fields in a one-dimensional spatial segment, under two different members of the
family of local boundary conditions defining a self-adjoint Euclidean Dirac
operator in two dimensions. For one of such boundary conditions, compatible
with the presence of a spectral asymmetry, we discuss in detail the
contribution of this part of the spectrum to the zeta-regularized determinant
of the Dirac operator and, thus, to the finite temperature properties of the
theory.
