Superfluid Gap in Neutron Matter from a Microscopic Effective Interaction

Correlated basis function (CBF) perturbation theory and the formalism of cluster expansions have been recently employed to obtain an effective interaction from a nuclear Hamiltonian strongly constrained by phenomenology. We report the results of a study of the superfluid gap in pure neutron matter, associated with the formation of Cooper pairs in the (^1S_0) channel. The calculations have been carried out using an improved version of the CBF effective interaction, in which three-nucleon forces are taken into account using a microscopic model. Our results show that a non-vanishing superfluid gap develops at densities in the range (2 times 10^{-4} lesssim rho /rho _0 lesssim 0.1), where (rho _0 = 2.8 times 10^{14}~mathrm{g~cm}^{-3}) is the equilibrium density of isospin-symmetric nuclear matter, corresponding mainly to the neutron-star inner crust.