The physical acceptability conditions and the strategies to obtain anisotropic compact objects

TL;DR

This paper explores methods to incorporate anisotropy into relativistic compact objects, establishing acceptability criteria, and analyzing observational data to identify viable models consistent with NICER measurements.

Contribution

It introduces effective strategies for adding anisotropy with simple density profiles and proposes a practical rule relating boundary and central densities.

Findings

Most effective anisotropy method identified

A rule of thumb for density relation established

Observed radii are consistent with multiple models

Abstract

We studied five methods to include anisotropy, or unequal stress distributions, in general relativistic matter configurations. We used nine acceptability conditions that the metric and physical variables must meet to determine if our models were astrophysically viable. Our analysis found the most effective way to introduce anisotropy while keeping a simple density profile. We also found a practical "rule of thumb" that relates the density at the boundary to the density at the centre of relativistic matter distributions. Additionally, we calculated the configuration radius and encountered that values observed by NICER for PSR J0740+6620 are consistent with several acceptable matter configurations, both isotropic and anisotropic.