Tidal Deformability of Neutron Stars in Unimodular Gravity

TL;DR

This paper investigates how unimodular gravity, a modified theory of gravity, affects the tidal deformability of neutron stars, revealing observable signatures that differ from general relativity.

Contribution

It introduces the study of neutron star tidal deformability within unimodular gravity considering non-conserved energy-momentum, and calculates the electric and magnetic tidal Love numbers.

Findings

Electric-type tidal Love numbers increase with non-conservation parameter.

Magnetic-type tidal Love numbers decrease with non-conservation parameter.

Observational data favors a small negative non-conservation parameter.

Abstract

Unimodular gravity is a modified theory with respect to general relativity by an extra condition that the determinant of the metric is fixed. Especially, if the energy-momentum tensor is not imposed to be conserved separately, a new geometric structure appears with potentially observational signatures. In this paper, we study tidal deformability of compact star in the unimodular gravity under the assumption of non-conserved energy-momentum tensor. Both the electric-type and magnetic-type quadrupole tidal Love numbers are calculated for neutron stars with polytrope model. It is found that the electric-type tidal Love numbers are monotonically increasing, but the magnetic-type ones are decreasing, with the increase of the non-conservation parameter. Compared with the observational data from detected gravitational-wave events, a small negative non-conservation parameter is favored.