Accessing universal relations of binary neutron star waveforms in massive scalar-tensor theory

TL;DR

This study explores how universal relations in binary neutron star waveforms are affected in massive scalar-tensor gravity, revealing breaches of universality through numerical simulations with varying scalar couplings.

Contribution

It systematically analyzes the impact of massive scalar-tensor gravity on neutron star waveform relations, highlighting deviations from general relativity.

Findings

Universal relations are breached in scalar-tensor gravity.

Numerical simulations show significant deviations from general relativity.

Difficulties in establishing quasi-universal relations in alternative theories.

Abstract

We investigate how the quasi-universal relations connecting tidal deformability with gravitational waveform characteristics and/or properties of individual neutron stars that were proposed in the literature within general relativity would be influenced in the massive Damour-Esposito-Farese-type scalar-tensor gravity. For this purpose, we systematically perform numerical relativity simulations of ~120 binary neutron star mergers with varying scalar coupling constants. Although only three neutron-star equations of state are adopted, a clear breach of universality can be observed in the data sets. In addition to presenting difficulties in constructing quasi-universal relations in alternative gravity theories, we also briefly compare the impacts of non-general-relativity physics on the waveform features and those due to the first order or cross-over quantum chromodynamical phase transition.