Neutron Matter from Low to High Density

Abstract

Neutron matter is an intriguing nuclear system with multiple connections to condensed matter and astrophysics. Considerable progress has been made over the past 20 years in exploring the properties of pure neutron fluids. We begin by reviewing research exploring the behavior of very low density neutron matter, which forms a strongly paired superfluid and is thus similar to cold Fermi atoms, although at energy scales that differ by many orders of magnitude. We then review the behavior of higher-density neutron matter, discussing research that ties the study of neutron matter to the determination of the properties of neutron-rich nuclei and neutron star crusts. Finally, we review the impact that neutron matter at even higher densities has on the mass–radius relation of neutron stars, thereby making contact with astrophysical observations.