The equation of state for the nuclear matter and the properties of the neutron star

TL;DR

This paper calculates the nuclear matter equation of state and models neutron star structure, revealing how different assumptions affect maximum mass and radius, and discusses the negligible impact of the cosmological constant.

Contribution

It introduces a modified nuclear potential energy formula incorporating causality and analyzes its effects on neutron star properties.

Findings

Maximum neutron star mass of 1.932 solar masses with original equation of state.

Modified equation of state yields a maximum mass of 1.440 solar masses.

Cosmological constant has negligible influence on neutron star structure.

Abstract

The equation of state for the beta stable nuclear matter is calculated numerically, and then the Tolman-Oppenheimer-Volkov equation for the structure of the neutron star is solved in the fourth-order Runge-Kutta algorithm. It shows the mass and radius of the neutron star are functions of the central density of the neutron star and a maximum mass of 1.932 solar masses with a corresponding radius of 9.340km is obtained. Considering the equation of state of the nuclear matter must obey the causality, a new factor c is added in the nuclear potential energy formula. Therefore, with a new equation of state for the beta stable nuclear matter when c=0.15, a new maximum mass of 1.440 solar masses with a radius of 9.765km for the neutron star is obtained. Finally, the contribution of the cosmological constant to the structure of the neutron star is discussed, and we find the cosmological constant has minimal or negligible influence on the properties of the neutron star.