Phase dynamics and particle production in preheating

Abstract

We study a simple model of a massive inflaton field $\varphi$ coupled to another scalar filed $\chi$ with interaction term $g^2{\varphi }^2{\chi }^2$. We use the theory developed by Kofman {\em et al.} (Phys. Rev. D {\bf 56} (1997) 3258 [arXiv:hep-ph/9704452])for the first stage of preheating to give a full description of the dynamics of the $\chi$ field modes, including the behaviour of the phase, in terms of the iteration of a simple family of circle maps. The parameters of this family of maps are a function of time when expansion of the universe is taken into account. With this more detailed description, we obtain a systematic study of the efficiency of particle production as a function of the inflaton field and coupling parameters, and we find that for $g\lesssim 3\times 10^{-4}$ the broad resonance ceases during the first stage of preheating.

14 pages, 12 figures, accepted for publication in Phys. Rev. D. Correct Figure 9, results unchanged. Added references and corrected misprints/misspellings