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Dark Energy after GW170817 Revisited

Copeland, Edmund J.; Kopp, Michael; Padilla, Antonio; Saffin, Paul M.; Skordis, Constantinos


Edmund J. Copeland

Michael Kopp

Antonio Padilla

Paul M. Saffin

Constantinos Skordis


We revisit the status of scalar-tensor theories with applications to dark energy in the aftermath of the gravitational wave signal GW170817 and its optical counterpart GRB170817A. At the level of the cosmological background, we identify a class of theories, previously declared unviable in this context, whose anomalous gravitational wave speed is proportional to the scalar equation of motion. As long as the scalar field is assumed not to couple directly to matter, this raises the possibility of compatibility with the gravitational wave data, for any cosmological sources, thanks to the scalar dynamics. This newly “rescued” class of theories includes examples of generalized quintic Galileons from Horndeski theories. Despite the promise of this leading order result, we show that the loophole ultimately fails when we include the effect of large scale inhomogeneities.

Journal Article Type Article
Publication Date Feb 12, 2019
Journal Physical Review Letters
Print ISSN 0031-9007
Electronic ISSN 1079-7114
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 122
Issue 6
Article Number 061301
APA6 Citation Copeland, E. J., Kopp, M., Padilla, A., Saffin, P. M., & Skordis, C. (2019). Dark Energy after GW170817 Revisited. Physical Review Letters, 122(6), doi:10.1103/physrevlett.122.061301
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