[Paper Review] Neutron Star Structure

C. J. Pethick, A. Akmal+2 more|arXiv (Cornell University)|May 14, 1999

Pulsars and Gravitational Waves Research3 citations

TL;DR

This paper reviews the structure of neutron stars using modern many-body theory to model dense nuclear matter, emphasizing tensor correlations, relativistic effects, and three-body forces. It demonstrates that three-body forces significantly influence neutron star properties, particularly equation of state and maximum mass, with implications for observable astrophysical behavior.

ABSTRACT

A review of properties of matter in the interior of neutron stars is given. Particular attention is paid to recent many-body theory calculations of the properties of dense matter. Among topics discussed are the strong increase of tensor correlations at relatively low densities, the "relativistic boost term" in the interaction, and the sensitivity of properties of neutron star models to three-body forces.

Motivation & Objective

• To understand the equation of state of dense nuclear matter in neutron star interiors using modern many-body theory.
• To investigate the role of tensor correlations in determining the properties of neutron-rich matter at moderate densities.
• To examine the impact of the relativistic boost term in the nucleon-nucleon interaction on neutron star models.
• To assess how three-body forces affect neutron star structure, including mass-radius relations and maximum mass constraints.
• To provide a theoretical foundation for interpreting astrophysical observations of neutron stars using nuclear many-body calculations.

Proposed method

• Employing modern many-body theory to calculate the equation of state of dense nuclear matter at high densities.
• Including tensor correlations in the nucleon-nucleon interaction to improve the description of short-range correlations.
• Incorporating the relativistic boost term in the effective interaction to account for relativistic corrections in dense matter.
• Using realistic two- and three-body nuclear interactions derived from free-space nucleon-nucleon scattering data.
• Solving the many-body problem self-consistently within the Brueckner-Hartree-Fock framework to determine energy per nucleon and pressure.
• Constructing neutron star equations of state from the calculated equation of state and solving the Tolman-Oppenheimer-Volkoff equations.

Experimental results

Research questions

• RQ1 How do tensor correlations in the nuclear interaction affect the equation of state of dense matter in neutron stars?
• RQ2 What is the role of the relativistic boost term in the nucleon-nucleon interaction for neutron star structure?
• RQ3 How sensitive are neutron star properties such as mass and radius to the inclusion of three-body forces?
• RQ4 What constraints do theoretical models place on the maximum mass of neutron stars?
• RQ5 How do modern many-body calculations reconcile with observational data on neutron star masses and radii?

Key findings

• Tensor correlations in the nuclear interaction lead to a strong increase in short-range correlations at relatively low densities, affecting the equation of state.
• The inclusion of the relativistic boost term in the interaction significantly modifies the energy per nucleon and pressure at high densities.
• Three-body forces are found to have a substantial impact on the equation of state, particularly in the density range relevant to neutron star cores.
• Neutron star models incorporating three-body forces predict a higher maximum mass than those without, consistent with observed massive neutron stars.
• Theoretical equations of state including many-body effects yield neutron star radii and masses that are in better agreement with recent astrophysical observations.
• The study highlights that uncertainties in three-body forces remain a key source of theoretical uncertainty in predicting neutron star properties.