Cosmic microwave background anisotropies from pre-big bang cosmology - art. no. 063501

We present an alternative scenario for cosmic structure formation where ini tial fluctuations are due to Kalb-Ramond axions produced during a pre-big b ang phase of inflation. We investigate whether this scenario, where the flu ctuations are induced by seeds and therefore are of isocurvature nature, ca n be brought in agreement with present observations by a suitable choice of cosmological parameters. We also discuss several observational signatures which can distinguish axion seeds from standard inflationary models. We fin ally discuss the gravitational wave background induced in this model and we show that it may be well within the range of future observations.