Relic Gravitons And String Pre-Big-Bang Cosmology

In this paper, after discussing the mechanism of graviton production during an early phase of accelerated expansion, we will review the main features of the spectrum of primordial gravitational radiation for the class of string-inspired models called pre-big-bang models. Furthermore, we will also outline the implications on pre-big-bang models of current and future searches of gravitational waves with ground-based detectors.