I will talk about our works (arXiv:1608.01213, arXiv:1710.06851,
arXiv:1902.06736) in which we calculate the equation of state of the inflaton field after inflation and provide an upper bound on the duration before radiation domination by taking the nonlinear dynamics of the fragmented inflaton field into account. For the models considered, I will discuss how our work significantly reduces the uncertainty in inflationary observables. I will also consider various aspects of the linear and nonlinear dynamics of the inflaton such as parametric self-resonance, the generation of scalar metric perturbations and gravitational waves. I will also review the recent progress in the understanding of the equation of state after inflation in models featuring gauge bosons.
