Neutron Star Mergers Chirp About Vacuum Energy

TL;DR

Gravitational wave observations from neutron star mergers can reveal the influence of vacuum energy on neutron star structure, offering a novel way to test fundamental physics and QCD effects.

Contribution

This paper proposes using gravitational wave data to detect the impact of vacuum energy on neutron star properties, a new approach linking astrophysics and quantum chromodynamics.

Findings

Vacuum energy affects neutron star tidal deformabilities at large chirp masses.

Measurable changes in gravitational wave signals can indicate vacuum energy contributions.

Potential to test gravitational properties of vacuum energy independently from cosmic acceleration.

Abstract

Observations of gravitational waves from neutron star mergers open up novel directions for exploring fundamental physics: they offer the first access to the structure of objects with a non-negligible contribution from vacuum energy to their total mass. The presence of such vacuum energy in the inner cores of neutron stars occurs in new QCD phases at large densities, with the vacuum energy appearing in the equation of state for a new phase. This in turn leads to a change in the internal structure of neutron stars and influences their tidal deformabilities which are measurable in the chirp signals of merging neutron stars. By considering three commonly used neutron star models we show that for large chirp masses the effect of vacuum energy on the tidal deformabilities can be sizable. Measurements of this sort have the potential to provide a first test of the gravitational properties of vacuum energy independent from the acceleration of the Universe, and to determine the size of QCD contributions to the vacuum energy.