  Realistic nucleon-nucleon interaction induce correlations to the nuclear
many-body system which lead to a fragmentation of the single-particle strength
over a wide range of energies and momenta. We address the question of how this
fragmentation affects the thermodynamical properties of nuclear matter. In
particular, we show that the entropy can be computed with the help of a
spectral function which can be evaluated in terms of the self-energy obtained
in the Self-Consistent Green's Function approach. Results for the density and
temperature dependences of the entropy per particle for symmetric nuclear
matter are presented and compared to the results of lowest order finite
temperature Brueckner--Hartree--Fock calculations. The effects of correlations
on the calculated entropy are small, if the appropriate quasi-particle
approximation is used. The results demonstrate the thermodynamical consistency
of the self-consistent T-matrix approximation for the evaluation of the Green's
functions.
