Dark Energy in Light of Multi-Messenger Gravitational-Wave Astronomy

• Published in: Frontiers in astronomy and space sciences Vol. 5
• Main Authors: Ezquiaga, Jose María, Zumalacárregui, Miguel
• Format: Journal Article
• Language: English
• Published: United States Frontiers Media 21.12.2018; Frontiers Research Foundation; Frontiers Media S.A
• Subjects: ASTRONOMY AND ASTROPHYSICS; Astrophysics; dark energy; General Relativity and Quantum Cosmology; gravitational wave propagation; High Energy Physics - Phenomenology; High Energy Physics - Theory; modified gravity; multi-messenger astronomy; Physics; testing general relativity; gravitational radiation: emission; expansion: acceleration; graviton: massive; gravitational radiation: direct detection; general relativity; detector: upgrade; Einstein Telescope; dispersion relation; dark energy: equation of state; neutron star: binary; Multi-messenger astrophysics; Cosmology - Theory; Gravitation; violation: Lorentz; gravitational wave astronomy; detector: sensitivity; LISA; gravitational radiation detector; modified gravity; Dark energy (DE); gravitational radiation; Multi-messenger astronomy; Hubble constant; Dark energy and cosmology; graviton: excited state; gravitation: massive
• DOI: 10.3389/fspas.2018.00044
• ISSN: 2296-987X

Gravitational waves (GWs) provide a new tool to probe the nature of dark energy (DE) and the fundamental properties of gravity. We review the different ways in which GWs can be used to test theories of gravity and cosmology, emphasizing models for late-time cosmic acceleration. Lagrangian-based gravitational theories beyond general relativity (GR) are classified into those breaking fundamental assumptions, containing additional fields and massive graviton(s). In addition to Lagrangian based theories we present the effective theory of DE and the μ-Σ parametrization as general descriptions of cosmological gravity. Multi-messenger GW detections can be used to measure the cosmological expansion (standard sirens), providing an independent test of the DE equation of state and measuring the Hubble parameter. Several key tests of gravity involve the cosmological propagation of GWs, including anomalous GW speed, massive graviton excitations, Lorentz violating dispersion relation, modified GW luminosity distance and additional polarizations, which may also cause GW oscillations. We summarize present constraints and their impact on DE models, including those arising from the binary neutron star merger GW170817. Upgrades of LIGO-Virgo detectors to design sensitivity and the next generation facilities such as LISA or Einstein Telescope will significantly improve these constraints in the next two decades.