Neutron Stars in f(R)-Gravity and Its Extension with a Scalar Axion Field

TL;DR

This paper reviews non-rotating neutron stars within R-square gravity and its extension with a scalar axion field, analyzing how modifications to Einstein's equations affect their mass-radius relations and structure.

Contribution

It introduces the effects of R-square gravity and scalar axion fields on neutron star properties, extending previous models in general relativity.

Findings

Modified mass-radius relations compared to GR

Dependence of mass on central density varies with equations of state

Extension with scalar axion field influences neutron star structure

Abstract

We present a brief review of general results about non-rotating neutron stars in simple R-square gravity and its extension with a scalar axion field. Modified Einstein equations are presented for metrics in isotropical coordinates. The mass-radius relation, mass profile and dependence of mass from central density on various equations of state are given in comparison to general relativity.