Effective Interactions in StronglyCoupled Quantum Systems
Abstract
In this thesis, we study the role of effective interactions in stronglycoupled Fermi systems where the shortrange correlations introduce difficulties requiring special treatment. The correlated basis function method provides the means to incorporate the shortrange correlations and generate the matrix elements of the Hamiltonian and identity operators in a nonorthogonal basis of states which are so important to our studies. In the first half of the thesis, the particlehole channel is examined to elucidate the effects of collective excitations. Proceeding from a leastaction principle, a generalization of the random phase approximation is developed capable of describing such stronglyinteracting Fermi systems as nuclei, nuclear matter, neutronstar matter, and liquid ('3)He. A linear response of dynamically correlated system to a weak external perturbation is also derived based on the same framework. In the second half of the thesis, the particleparticle channel is examined to elucidate the effects of pairing in nuclear and neutronstar matter. This begins a renewed attack on the problem of nucleonic superfluids, with a microscopic investigation of ('1)S(,0) neutron pairing in lowdensity neutronstar matter, i.e., in the inner crustal regime of neutron stars. The superfluid energy gap and condensation energy are calculated in the framework of secondorder correlatedbasis perturbation theory, thereby incorporating important effects of polarization of the medium on the effective pairing interaction. The energy gap and condensation energy are found to be emphatically suppressed, relative to the results of earlier variational treatments. The calculations are carried out for two "realistic" semiphenomenological nucleonnucleon potentials, based on the Reid and Bethe Johnson interactions. The dependence of the energy gap on the effective mass is studied, and the implications of proton contamination of neutron matter are addressed briefly. The accuracy of the standard BCS weakcoupling formulae is assessed. The consequences of the strong suppression of ('1)S(,0) neutron superfluidity in the innercrust region for observational properties of neutron stars (cooling and postglitch dynamics) are discussed.
 Publication:

Ph.D. Thesis
 Pub Date:
 1986
 Bibcode:
 1986PhDT.......102C
 Keywords:

 SUPER FLUIDITY;
 NEUTRON MATTER;
 Physics: Nuclear