Neutron stars in Scalar-Tensor-Vector Gravity

TL;DR

This paper explores neutron star models within Scalar-Tensor-Vector Gravity (STVG), deriving solutions and modified TOV equations, revealing that STVG predicts heavier neutron stars than General Relativity and could explain recent mass observations.

Contribution

The work derives matter-sourced solutions and modified TOV equations in STVG, demonstrating its potential to model neutron stars with higher masses than GR.

Findings

STVG allows heavier neutron stars than GR.

Maximum neutron star masses depend on a deviation parameter.

STVG provides viable solutions for stellar structure in strong gravity.

Abstract

Scalar-Tensor-Vector Gravity (STVG), also referred as MOdified Gravity (MOG), is an alternative theory of the gravitational interaction. Its weak field approximation has been successfully used to described Solar System observations, galaxy rotation curves, dynamics of clusters of galaxies, and cosmological data, without the imposition of dark components. The theory was formulated by John Moffat in 2006. In this work, we derive matter-sourced solutions of STVG and construct neutron star models. We aim at exploring STVG predictions about stellar structure in the strong gravity regime. Specifically, we represent spacetime with a static, spherically symmetric manifold, and model the stellar matter content with a perfect fluid energy-momentum tensor. We then derive the modified Tolman-Oppenheimer-Volkoff equation in STVG and integrate it for different equations of state. We find that STVG allows heavier neutron stars than General Relativity (GR). Maximum masses depend on a normalized parameter that quantifies the deviation from GR. The theory exhibits unusual predictions for extreme values of this parameter. We conclude that STVG admits suitable spherically symmetric solutions with matter sources, relevant for stellar structure. Since recent determinations of neutron stars masses violate some GR predictions, STVG appears as a viable candidate for a new gravity theory.