Implication of GW170817 for cosmological bounces
  The detection of GW170817 and its electromagnetic counterpart has revealed
the speed of gravitational waves coincides with the speed of light, $c_T=1$.
Inspired by the possibility that the physics implied by GW170817 might be
related with that for the primordial universe, we construct the spatially flat
stable (throughout the whole evolution) nonsingular bounce models in the beyond
Horndeski theory with $c_T=1$ and in the degenerate higher-order scalar-tensor
(DHOST) theory with $c_T=1$, respectively. Though it constricts the space of
viable models, the constraint of $c_T=1$ makes the procedure of building models
simpler.
