Level density of a Fermi gas with pairing interactions

The paper presents the level density for a Fermi gas with pairing interactions. First an approximate partition function is derived in terms of a universal function. Then a modified saddle-point method is used for the inverse Laplace transformation to obtain an algebraic expression which does not diverge for the ground state. This method was applied to the normal Fermi gas as well as to the paired Fermi gas. The results are compared to the standard and to the backshifted Fermi-gas level density.