String cosmology and the beginning-of-time myth

The myth according to which the Universe-and time itself-started with a big bang will be challenged. Classical and quantum gravitational instabilities, can, respectively, inflate and warm up a primordial pre-bangian Universe satisfying a superstring-motivated principle of "asymptotic past triviality". Properties of the pre-bangian Universe can be probed through its observable relics, which include: (i) a (possibly observable) stochastic gravitational-wave background; (ii) a (possible) new mechanism for seeding the galactic magnetic fields; (iii) a (possible) new source of large-scale structure and CMB anisotropy. (33 refs).