Speaker
Description
We study the post-inflationary evolution of the equation of state from the end of inflation to the onset of radiation domination. Focusing on single-field inflation models, we consider an inflaton field that has a quadratic potential near the minimum and is coupled to a massless scalar field via a trilinear interaction. The early preheating phase — dominated by resonance processes and non-linear dynamics — is analysed using numerical lattice simulations. We then combine these results with an effective treatment of the late reheating stage by solving a set of Boltzmann equations to reconstruct the complete post-inflationary expansion history. This combined approach yields improved predictions for the inflationary CMB observables, the spectral index and the tensor-to-scalar ratio. We further compute the redshift of the stochastic gravitational wave background generated during preheating and find that its amplitude is suppressed by many orders of magnitude compared to previous estimates.