• Milestone

Equation of state of nucleon matter and neutron star structure

A. Akmal, V. R. Pandharipande, and D. G. Ravenhall
Phys. Rev. C 58, 1804 – Published 1 September 1998
An article within the collection: Physical Review C 50th Anniversary Milestones
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Abstract

Properties of dense nucleon matter and the structure of neutron stars are studied using variational chain summation methods and the new Argonne v18 two-nucleon interaction, which provides an excellent fit to all of the nucleon-nucleon scattering data in the Nijmegen database. The neutron star gravitational mass limit obtained with this interaction is 1.67M. Boost corrections to the two-nucleon interaction, which give the leading relativistic effect of order (v/c)2, as well as three-nucleon interactions, are also included in the nuclear Hamiltonian. Their successive addition increases the mass limit to 1.80 and 2.20 M. Hamiltonians including a three-nucleon interaction predict a transition in neutron star matter to a phase with neutral pion condensation at a baryon number density of 0.2fm3. Neutron stars predicted by these Hamiltonians have a layer with a thickness on the order of tens of meters, over which the density changes rapidly from that of the normal to the condensed phase. The material in this thin layer is a mixture of the two phases. We also investigate the possibility of dense nucleon matter having an admixture of quark matter, described using the bag model equation of state. Neutron stars of 1.4M do not appear to have quark matter admixtures in their cores. However, the heaviest stars are predicted to have cores consisting of a quark and nucleon matter mixture. These admixtures reduce the maximum mass of neutron stars from 2.20 to 2.02 (1.91) M for bag constant B=200(122)MeV/fm3. Stars with pure quark matter in their cores are found to be unstable. We also consider the possibility that matter is maximally incompressible above an assumed density, and show that realistic models of nuclear forces limit the maximum mass of neutron stars to be below 2.5M. The effects of the phase transitions on the composition of neutron star matter and its adiabatic index Γ are discussed.

  • Received 14 April 1998

DOI:https://doi.org/10.1103/PhysRevC.58.1804

©1998 American Physical Society

Collections

This article appears in the following collection:

Physical Review C 50th Anniversary Milestones

This collection of milestone papers from PRC highlights research that remains central to current developments in nuclear physics.

Authors & Affiliations

A. Akmal*, V. R. Pandharipande, and D. G. Ravenhall

  • Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801

  • *Electronic address: akmal@rsm1.physics.uiuc.edu
  • Electronic address: vrp@uiuc.edu
  • Electronic address: ravenhal@uiuc.edu

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Vol. 58, Iss. 3 — September 1998

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