From Microscopic to Macroscopic: The Effect of Relativistic Mean Field Parameter Sets on Neutron Star Structure

Abstract

Neutron stars, as extremely compact astrophysical objects, provide a unique natural laboratory for investigating the physics of compact matter. Neutron stars can be described from two complementary perspectives, namely microscopic and macroscopic states. The microscopic state is characterized through the relativistic mean-field (RMF) equation of state, which describes the dynamics of dense matter inside the star. The macroscopic state, on the other hand, is described by the Tolman–Oppenheimer–Volkoff (TOV) equations, which determine the global stellar structure. This study aims to examine how the microscopic properties of neutron stars influence their macroscopic behavior by varying the microscopic coupling constants encoded in different RMF parameter sets. The parameter sets employed in this work are taken from well-established and widely validated RMF models in the literature, including NL3, FSUGold, S271, and Z271. Through numerical modeling, the effects of variations in these parameter sets on the maximum mass, radius, energy density, and pressure of neutron stars are systematically investigated. The results demonstrate that the choice of parameter set has a significant impact on the maximum mass that a neutron star can support. In particular, stiffer parameter sets lead to larger maximum masses, whereas softer parameter sets result in smaller maximum masses.