The Extent and Observable Properties of Nuclear Pasta in Neutron Star Crusts

A layer of nuclear soft condensed matter called nuclear pasta is predicted to mediate the crust-core transition in neutron stars. We present detailed 3D quantum calculations of nuclear pasta in neutron star crusts and proto-neutron stars. We find that nuclear pasta occurs at lower densities than predicted in semi-classical or classical models, and we predict that over 50% of the mass of a neutron star crust is taken up by nuclear pasta independent of uncertainties in the nuclear equation of state. We show that nuclear pasta likely co-exists with spherical nuclei at the lowest densities, and that multiple phases of pasta likely coexist at higher densities. We explore a number of consequences for observables. As a proto-neutron star cools, nuclear pasta tends to keep the outer layers of the star hotter for longer, resulting in an observable imprint on the late-time neutrino signal from supernovae. When the neutron star crust condenses, pasta likely forms microscopic domains characterized by different nuclear geometries, enhancing the disorder of the inner crust and contributing to an observable signal in the cooling of older accreting neutron stars in quiescence.