Dark Energy After GW170817: Dead Ends and the Road Ahead.

By J. Ezquiaga, M. Zumalacárregui. Physical Review Letters, 2017

768 citations recorded by the source corpus.

Multimessenger gravitational-wave (GW) astronomy has commenced with the detection of the binary neutron star merger GW170817 and its associated electromagnetic counterparts. The almost coincident observation of both signals places an exquisite bound on the GW speed |c_{g}/c-1|≤5×10^{-16}. We use this result to probe the nature of dark energy (DE), showing that a large class of scalar-tensor theories and DE models are highly disfavored. As an example we consider the covariant Galileon, a cosmologically viable, well motivated gravity theory which predicts a variable GW speed at low redshift. Our results eliminate any late-universe application of these models, as well as their Horndeski and most of their beyond Horndeski generalizations. Three alternatives (and their combinations) emerge as the only possible scalar-tensor DE models: (1) restricting Horndeski's action to its simplest terms, (2) applying a conformal transformation which preserves the causal structure, and (3) compensating the different terms that modify the GW speed (to be robust, the compensation has to be independent on the background on which GWs propagate). Our conclusions extend to any other gravity theory predicting varying c_{g} such as Einstein-Aether, Hořava gravity, Generalized Proca, tensor-vector-scalar gravity (TEVES), and other MOND-like gravities.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/423da8303eac7be16aaad8e234a495caaacdd81c

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Citations in the corpus

Testing modified gravity at cosmological distances with LISA standard sirens (2019, background): “For example, the recent simultaneous detection of a gravitational and an electromagnetic signal from GW170817 [1–4], and the follow-up studies of the electromagnetic counterpart [5] impose severe constraints on theories predicting a different speed for gravitational and electromagnetic waves [6–10].”
Gravitational wave decay into dark energy (2018, background): “mplies that in general the speed of GWs may be dierent from the speed of light [3,4]. The recent observations put severe bounds on this possibility and therefore strong constraints on some DE models [5,6,7,8]. See also [9]|and references therein|for a review. In this paper we want to study another p”
Horndeski theory and beyond: a review (2019, background): “In light of GW170817, we have seen that some of free functions in DHOST Lagrangians can be strongly constrained upon imposing cGW = 1 [195, 196, 197, 198, 199, 200, 201, 202].”
Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA (2013, background): “An intuitive understanding of localization can be gained by considering triangulation using the observed time delays between sites (Fairhurst 2009, 2011).”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, background): “If we decide to be too conservative and ignore the presence of the higher order operators, that would enter naturally from the effective field theory point of view, we can then put very restrictive bounds on the modified gravity theories [275, 276, 277, 278, 279, 280, 281, 282].”