Light scalar field constraints from gravitational-wave observations of compact binaries

TL;DR

Gravitational-wave observations of neutron star-black hole binaries can constrain light scalar fields in scalar-tensor theories, providing bounds on scalar mass and coupling parameters with future detectors.

Contribution

This work demonstrates how gravitational-wave data can be used to set new bounds on light scalar fields in scalar-tensor theories, extending previous constraints.

Findings

Individual observations can set bounds on scalar parameters.

Future detectors will improve these bounds significantly.

Multiple observations can further tighten constraints.

Abstract

Scalar-tensor theories are among the simplest extensions of general relativity. In theories with light scalars, deviations from Einstein's theory of gravity are determined by the scalar mass m_s and by a Brans-Dicke-like coupling parameter \omega_{BD}. We show that gravitational-wave observations of nonspinning neutron star-black hole binary inspirals can be used to set lower bounds on \omega_{BD} and upper bounds on the combination m_s/\sqrt{\omega_{BD}}$. We estimate via a Fisher matrix analysis that individual observations with signal-to-noise ratio \rho would yield (m_s/\sqrt{\omega_{BD}})(\rho/10)<10^{-15}, 10^{-16} and 10^{-19} eV for Advanced LIGO, ET and eLISA, respectively. A statistical combination of multiple observations may further improve these bounds.