Model nuclear matter calculations with a new fermion lowest order constrained variational method

A method of lowest order constrained variation for calculating the ground-state energy of dense systems, advanced previously by the present authors and shown to give excellent agreement for the Bethe homework problem is extended to deal with fermions. Using one state-independent correlation function in the new formalism, results with four different potentials that model various aspects of the real NN force are shown to be in excellent agreement with the other results available from various higher-order approximations, for densities up to and beyond nuclear matter density. The agreement is clearly superior to that obtained with any other lowest order approximation. When state dependence is introduced into the two-body correlation function in the new method, a considerable lowering of the energy is found in each case. It is suggested that this is a real effect which would be replicated in the other higher-order approximations, were they also extended to deal with state-dependent correlations. (Auth.)