The inflaton inevitably couples to all non-conformally coupled matters to gravity, through an oscillation in the Hubble parameter or the cosmic scale factor. This oscillation leads to particle production during the inflaton oscillation regime. In this talk, I first apply the analysis of scalar particle production to the case of minimally-coupled inflaton to gravity, and then extend the analysis to non-minimally coupled case, in which the Hubble parameter oscillates more violently. I also show the analysis of the graviton production by the inflaton in both minimal & non-minimal case.

Reference : 1. Gravitational Effects on Inflaton Decay, Yohei Ema, Ryusuke Jinno, Kyohei Mukaida, Kazunori Nakayama arXiv:1502:02475 2. Yohei Ema, Ryusuke Jinno, Kyohei Mukaida, Kazunori Nakayama, to appear