Extended Brueckner-Hartree-Fock theory with pionic correlation in finite nuclei

Abstract

An extended Brueckner-Hartree-Fock (EBHF) theory is constructed for the description of nuclear structure in order to use a bare interaction among constituent particles. The nuclear interaction is characterized by the strong tensor force induced by pion exchange interaction. To handle the strong tensor force based on the single-particle picture, the Hartree-Fock variational model space is extended to include 2-particle 2-hole (2p-2h) states with all possible configurations, which are able to describe high momentum components originating from pseudo-scalar nature of the pion. We take a variational principle of the total energy in this extended model space. We obtain an equation for single-particle states in the Fermi sea with inclusion of the effect of the pion exchange and short-range repulsive interaction. We elucidate the nature of the EBHF theory by comparing with the Brueckner-Hartree-Fock (BHF) theory and the Feshbach projection operator method. The EBHF theory has a similar structure as the BHF theory except for the inclusion of the concept of the energy of the total system. The Feshbach projection operator method completely agrees with our framework when the P-space projection corresponds to the Hartree-Fock state and the Q-space projection corresponds to 2p-2h states with all possible configurations.