Fermi-surface instabilities in nuclear matter from angle-correlated particle-particle propagation

TL;DR

This paper investigates angular correlations in particle-particle propagation within nuclear matter, revealing new correlation structures that significantly affect the mass operator near the Fermi surface and may influence models of neutron stars and nuclear reactions.

Contribution

It introduces an exact treatment of the Pauli exclusion principle in the BBG equation, uncovering novel correlation features that alter the behavior of the mass operator and phase-space near the Fermi surface.

Findings

Correlation form factor emerges from the principal-value of the pp propagator

Imaginary part of the propagator is structurally different from traditional equations

Modified phase-space impacts nuclear matter saturation and neutron star models

Abstract

Angular correlations arising from particle-particle (pp) propagation in nuclear matter are investigated. Their account follows an exact treatment of the Pauli exclusion principle on intermediate states in the Bruekner-Bethe-Goldstone (BBG) equation. As a result, a correlation form factor emerges from the Cauchy principal-value of the pp propagator, while the imaginary part becomes structurally different from those in Lippmann-Schwinger-type equations. These novel features modify drastically the behaviour of the mass operator near the Fermi surface, reshaping the phase-space where its imaginary part vanishes and sliding down the saturation point of symmetric nuclear matter along the Coester band. The correlation structures found here --which go beyond angle-averaged (or effective-mass type) energy denominators-- may impact present day model predictions for neutron stars based on the BBG equation, and for scattering and reaction observables in full folding optical model calculations