Relic Gravitational Waves from String Cosmology

A large class of string-cosmology backgrounds leads to a spectrum of relic stochastic gravitational waves, strongly tilted towards high frequencies, and characterized by two basic parameters of the cosmological model. We estimate the required sensitivity for detection of the predicted gravitational radiation and show that a region of our parameter space is within reach for some of the planned gravitational-wave detectors. -------------------------------- To appear in Phys. Lett. B 1 Introduction It is notoriously difficult to find accessible experimental signatures of fundamental strings because of their small Planckian size. Possibly, an interesting exception to this rule is represented by the cosmological predictions of string theory, since these originate from physics of the Early-Universe, when space-time curvatures may have been of Planckian strength. In order to arrive at some concrete, yet generic, predictions of string cosmology, we shall consider a large class of models in ..