Neutron rich matter, neutron stars, and their crusts

TL;DR

This paper explores neutron rich matter's properties, its role in neutron stars and astrophysics, and introduces new experimental and modeling tools to understand its structure, strength, and implications for gravitational waves.

Contribution

It presents new experimental measurements, modeling approaches, and an equation of state for neutron-rich matter relevant to neutron stars and astrophysical phenomena.

Findings

Neutron star crust is the strongest known material.

Crust can support mountains large enough for gravitational wave detection.

New equation of state improves supernova and merger simulations.

Abstract

Neutron rich matter is at the heart of many fundamental questions in Nuclear Physics and Astrophysics. What are the high density phases of QCD? Where did the chemical elements come from? What is the structure of many compact and energetic objects in the heavens, and what determines their electromagnetic, neutrino, and gravitational-wave radiations? Moreover, neutron rich matter is being studied with an extraordinary variety of new tools such as Facility for Rare Isotope Beams (FRIB) and the Laser Interferometer Gravitational Wave Observatory (LIGO). We describe the Lead Radius Experiment (PREX) that is using parity violation to measure the neutron radius in 208Pb. This has important implications for neutron stars and their crusts. Using large scale molecular dynamics, we model the formation of solids in both white dwarfs and neutron stars. We find neutron star crust to be the strongest material known, some 10 billion times stronger than steel. It can support mountains on rotating neutron stars large enough to generate detectable gravitational waves. Finally, we describe a new equation of state for supernova and neutron star merger simulations based on the Virial expansion at low densities, and large scale relativistic mean field calculations.