Non-vacuum initial states for the cosmological perturbations and the back-reaction problem of inflation

Abstract

In the framework of Inflationary theory, the assumption that the quantum state of the perturbations is a non-vacuum state leads to a difficulty: non-vacuum initial states imply, in general, a large energy density of inflaton field quanta, not of a cosmological term type, that could prevent the inflationary phase. In this short note, we discuss in detail why this is so, keeping an eye on possible non-Gaussian features due to considering generic non-vacuum initial states.

To appear in the Proceedings of the XXXVIIth Rencontres de Moriond on ``The Cosmological Model'', Les Arcs, France, March 16-23, 2002