# Neutron stars in general relativity and scalar-tensor theory of gravity

## TL;DR

This paper compares neutron star properties in general relativity and scalar-tensor gravity, highlighting how current and future observations can constrain nuclear physics and alternative gravity theories.

## Contribution

It analyzes neutron star masses and radii within different gravity theories and discusses how observations can differentiate between them and constrain nuclear matter properties.

## Key findings

- Current radius measurements constrain nuclear equation of state.
- Future observations of massive neutron stars can test scalar-tensor gravity.
- Neutron star data can inform both nuclear physics and gravity theories.

## Abstract

The masses and radii of neutron stars are discussed in general relativity and scalar-tensor theory of gravity and the differences are compared with the current uncertainties stemming from the nuclear equation of state in the relativistic mean-field framework. It is shown that astrophysical and gravitational waves observations of radii of neutron stars with masses $M \lesssim 1.4 M_{\odot}$ constrain only the nuclear equation of state, and in particular the density dependence of the nuclear symmetry energy. Future observations of massive neutron stars may constrain the coupling parameters of the scalar-tensor theory provided that a general consensus on the dense nuclear matter equation of state is reached.