Revisiting Einstein-Gauss-Bonnet Theories after GW170817

Understand

In this work we study the inflationary framework of Einstein-Gauss-Bonnet theories which produce a primordial gravitational wave speed that respects the constraint imposed by the GW170817 event, namely $\left| c_T^2 - 1 \right| < 6 \times 10^{-15}$ in natural units.

• For these theories in general, the scalar Gauss-Bonnet coupling function $\xi (\phi)$ is arbitrary and unrelated to the scalar potential.
• We develop the inflationary formalism of this theory, and present analytic forms for the slow-roll indices, the observational indices and the $e$-foldings number, assuming solely a slow-roll era and also that the constraints imposed by the GW170817 event hold true.
• We present in detail an interesting class of models that produces a viable inflationary era.