Preheating in multifield inflation

Abstract

The theory of cosmic inflation was proposed to address problems with Standard Big Bang cosmology. The theory suggests the existence of an epoch during which the universe underwent an exponential expansion, followed by an epoch of slower expansion. Realistic models of high-energy physics require multiple scalar fields. Renormalization of these fields in curved space-time requires these fields to be nonminimally coupled to the space-time Ricci scalar. These couplings induce a nontrivial field-space manifold when we move from the Jordan frame to the Einstein frame. In the Einstein frame, the potential becomes asymptotically flat, leading to ridges and valleys in field-space. The existence of these ridges and valleys results in a strong single-field attractor behavior of the fields. We study preheating in multifield models of inflation with nonminimal couplings. In this phase, we find an efficient transfer of energy from the oscillating background fields to the coupled fluctuations. We identify features of preheating that are not present in the minimally coupled case. In particular, we observe how the Fourier structure of the background field oscillations changes as the value of the dimensionless non-minimal coupling, [zeta]1 changes. We also observe how the resonance structure of perturbations changes as we tune [zeta]1.