Gravitational-wave versus binary-pulsar tests of strong-field gravity

TL;DR

This paper compares the effectiveness of binary pulsar and gravitational-wave observations in testing strong-field gravity within tensor-scalar theories, incorporating realistic nuclear matter models and more general theories.

Contribution

It generalizes previous analyses by including realistic equations of state and broader tensor-scalar theories, enhancing the understanding of strong-field gravity tests.

Findings

Binary pulsar tests provide strong constraints on tensor-scalar theories.

Gravitational-wave observations offer complementary probing power.

Finite-size effects influence the interpretation of tests.

Abstract

Binary systems comprising at least one neutron star contain strong gravitational field regions and thereby provide a testing ground for strong-field gravity. Two types of data can be used to test the law of gravity in compact binaries: binary pulsar observations, or forthcoming gravitational-wave observations of inspiralling binaries. We compare the probing power of these two types of observations within a generic two-parameter family of tensor-scalar gravitational theories. Our analysis generalizes previous work (by us) on binary-pulsar tests by using a sample of realistic equations of state for nuclear matter (instead of a polytrope), and goes beyond a previous study (by C.M. Will) of gravitational-wave tests by considering more general tensor-scalar theories than the one-parameter Jordan-Fierz-Brans-Dicke one. Finite-size effects in tensor-scalar gravity are also discussed.