The Oscillating Universe: an Alternative to Inflation

The aim of this paper is to show, that the 'oscillating universe' is a viable alternative to inflation. We remind that this model provides a natural solution to the flatness or entropy and to the horizon problem of standard cosmology. We study the evolution of density perturbations and determine the power spectrum in a closed universe. The results lead to constraints of how a previous cycle might have looked like. We argue that most of the radiation entropy of the present universe may have originated from gravitational entropy produced in a previous cycle. We show that measurements of the power spectrum on very large scales could in principle decide whether our universe is closed, flat or open.