Reviving Horndeski Theory using Teleparallel Gravity after GW170817
  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.
