Neutron Stars in a Varying Speed of Light Theory

TL;DR

This paper explores how neutron star properties are affected in a varying speed of light (VSL) gravity theory where the speed of light depends on a scalar field, revealing strong dependence on coupling parameters and potential for arbitrarily small maximum masses.

Contribution

It introduces a VSL gravity model applied to neutron stars, analyzing their structure, mass-radius relations, and cosmological evolution, which is a novel approach in alternative gravity theories.

Findings

Neutron star masses and radii depend strongly on scalar field coupling.

Maximum neutron star mass can be arbitrarily small for certain parameters.

Derived a relation linking star energy change to scalar field evolution.

Abstract

We study neutron stars in a varying speed of light (VSL) theory of gravity in which the local speed of light depends upon the value of a scalar field $\phi$. We find that the masses and radii of the stars are strongly dependent on the strength of the coupling between $\phi$ and the matter field and that for certain choices of coupling parameters, the maximum neutron star mass can be arbitrarily small. We also discuss the phenomenon of cosmological evolution of VSL stars (analogous to the gravitational evolution in scalar-tensor theories) and we derive a relation showing how the fractional change in the energy of a star is related to the change in the cosmological value of the scalar field.