Observational discrimination of Eddington-inspired Born-Infeld gravity from general relativity

TL;DR

This paper demonstrates that by combining neutron star radius measurements with terrestrial neutron skin thickness experiments, it is possible to distinguish Eddington-inspired Born-Infeld gravity from general relativity and estimate its coupling constant.

Contribution

It introduces a method to differentiate EiBI gravity from GR using neutron star radii and neutron skin thickness, overcoming EOS uncertainties.

Findings

Neutron star radii with 0.5 solar masses correlate with neutron skin thickness independently of EOS.

The correlation depends on the EiBI coupling constant.

Combined observations can discriminate EiBI from GR and estimate the coupling constant.

Abstract

Direct observations of neutron stars could tell us an imprint of modified gravity. However, it is generally difficult to resolve the degeneracy due to the uncertainties in equation of state (EOS) of neutron star matter and in gravitational theories. In this paper, we are successful to find the observational possibility to distinguish Eddington-inspired Born-Infeld gravity (EiBI) from general relativity. We show that the radii of neutron stars with $0.5M_{sun}$ are strongly correlated with the neutron skin thickness of ${}^{208}$Pb independently of EOS, while this correlation depends on the coupling constant in EiBI. As a result, via the direct observations of radius of neutron star with $0.5M_{sun}$ and the measurements of neutron skin thickness of ${}^{208}$Pb by the terrestrial experiments, one could not only discriminate EiBI from general relativity but also estimate the coupling constant in EiBI.