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## Reviving Horndeski Theory using Teleparallel Gravity after GW170817

Bahamonde, S; Dialektopoulos, KF; Gakis, V; Said, JL; (2020) Reviving Horndeski Theory using Teleparallel Gravity after GW170817. Physical Review D , 101 , Article 084060. 10.1103/PhysRevD.101.084060.

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## Abstract

Horndeski gravity was highly constrained from the recent gravitational wave observations by the LIGO Collaboration down to $|c_{g}/c-1|\gtrsim 10^{-15}$. In this Letter we study the tensorial perturbations in a flat cosmological background for an analogue version of Horndenki gravity which is based in Teleparallel Gravity constructed from a flat manifold with a nonvanishing torsion tensor. It is found that in this approach, one can construct a more general Horndeski theory satisfying $c_T=c_g/c=1$ without eliminating the coupling functions $G_5(\phi,X)$ and $G_4(\phi,X)$ that were highly constrained in standard Horndeski theory. Hence, in the Teleparallel approach one is able to restore these terms, creating an interesting way to revive Horndeski gravity.

Type: Article Reviving Horndeski Theory using Teleparallel Gravity after GW170817 An open access version is available from UCL Discovery 10.1103/PhysRevD.101.084060 http://dx.doi.org/10.1103/PhysRevD.101.084060 English This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. UCLUCL > Provost and Vice Provost OfficesUCL > Provost and Vice Provost Offices > UCL BEAMSUCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences https://discovery.ucl.ac.uk/id/eprint/10096948