Complexity and neutron stars with crust and hyperon core

Abstract

Abstract Continuing the work of K. Ch. Chatzisavvas and others [1], a measure of complexity proposed by R. López-Ruiz, H.L Mancini, and X. Calbet [2] is used to study a model of neutron star (NS) with crust and hyperon core. We employed the relativistic-mean-field approximation theory to build the Lagrangian density model of the neutron star’s core and from it, obtained the equation of state (EoS), ∈(ρ). This ∈(ρ) was then put into the complexity equation and the complexity-values were obtained using numerical methods. Plotted against the corresponding mass values, the results show that neutron star’s complexity-mass curves behave very similarly to an isolated-system phase complexity diagram, which was not apparent in the previous work by Chatzisavvas et al.. The reason for this is that the crust EoS put an upper limit to the complexity value and it follows that the crust itself is an ordered system of low complexity. We also show that NS have the properties of a perfect crystal although they are modeled as liquid.