  We analyze the normal phase of the attractive Hubbard model within dynamical
mean-field-theory. We present results for the pair-density, the
spin-susceptibility, the specific heat, the momentum distribution, and for the
quasiparticle weight. At weak coupling the low-temperature behavior of all
quantities is consistent with Fermi liquid theory. At strong coupling all
electrons are bound pairs, which leads to a spin gap and removes fermionic
quasi-particle excitations. The transition between the Fermi liquid phase and
the pair phase takes place at a critical coupling of the order of the
band-width and is generally discontinuous at sufficiently low temperatures.
