Inflaton decay and reheating in nonminimal derivative coupling

Understand

We investigate the inflaton decay and reheating period after the end of inflation in the non-minimal derivative coupling (NDC) model with chaotic potential.

• In general, this model is known to provide an enhanced slow-roll inflation caused by gravitationally enhanced friction.
• We find violent oscillations of Hubble parameter which induces oscillations of the sound speed squared, implying the Lagrangian instability of curvature perturbation $\zeta$ under the comoving gauge $\varphi=0$.
• Also, it is shown that the curvature perturbation blows up at $\dot{\phi}=0$, leading to the breakdown of the comoving gauge at $\dot{\phi}=0$.