Conventional and Unconventional Pairing and Condensates in Dilute Nuclear Matter

TL;DR

This paper reviews recent advances in understanding diverse pairing phenomena in dilute nuclear matter, highlighting various superfluid phases and their transitions relevant to astrophysical objects like supernovae and neutron stars.

Contribution

It provides a comprehensive survey of phase diagrams and pairing mechanisms, including unconventional phases and dineutron formation, using ab initio many-body techniques.

Findings

Identification of multiple superfluid phases in dilute nuclear matter

Characterization of BCS to BEC transition in terms of pairing gap and spectra

Conditions for emergence of unconventional pairing solutions and dineutron formation

Abstract

This contribution will survey recent progress toward an understanding of diverse pairing phenomena in dilute nuclear matter at small and moderate isospin asymmetry, with results of potential relevance to supernova envelopes and proto-neutron stars. Application of {\it ab initio} many-body techniques has revealed a rich array of temperature-density phase diagrams, indexed by isospin asymmetry, which feature both conventional and unconventional superfluid phases. At low density there exist a homogeneous translationally invariant BCS phase, a homogeneous LOFF phase violating translational invariance, and an inhomogeneous translationally invariant phase-separated BCS phase. The transition from the BCS to the BEC phases is characterized in terms of the evolution, from weak to strong coupling, of the pairing gap, condensate wave function, and quasiparticle occupation numbers and spectra. Additionally, a schematic formal analysis of pairing in neutron matter at low to moderate densities is presented that establishes conditions for the emergence of both conventional and unconventional pairing solutions and encompasses the possibility of dineutron formation.