Inflation and Oscillations of Universe in 4D Dilatonic Gravity

Abstract

We investigate the inflation of Universe in a model of four dimensional dilatonic gravity with a massive dilaton field $\Phi$. The dilaton plays simultaneously the roles of an inflation field and a quintessence field. It yields a sequential {\em hyper}-inflation with a graceful exit to asymptotic de Sitter space-time, which is an attractor, and is approached as $\exp (-\sqrt{3{\Lambda }^{obs}}ct/2)$. The time duration of the inflation is reciprocal to the the mass of the dilaton: $\Delta t_{infl}\sim m_{{}_{\Phi }}^{-1}$. The typical number of e-folds in the simplest model of this type is shown to be realistic without fine tuning.

Comments: 11 pages, latex, 9 figures. Accepted for publication in Physical Review D, 2003