Pre-Big Bang, vacuum and noncyclic cosmologies
WMAP and Planck open the way to unprecedented Big Bang phenomenology, not only for the standard Big Bang model but also for less conventional approaches including pre-Big Bang patterns. An example is provided by the recent claim (Gurzadyan et al.) that the cosmological sky is a weakly random one with mostly regular signal. If confirmed, this situation would have significant implications not only for cyclic cosmologies following the analyses recently proposed by Gurzadyan and Penrose, but also for noncyclic cosmologies incorporating a new fundamental scale beyond Planck scale and, possibly, new ultimate constituents of matter with unconventional basic properties as compared to conventional particles. More generally and in all cases, new alternatives to standard physics can be considered from a cosmological point of view concerning vacuum structure, the nature of space-time, the origin of our Universe, the validity of quantum field theory, solutions to the cosmological constant problem, inflationary scenarios, dark matter and dark energy, a new approach to string-like theories... Lorentz-like symmetries (standard or superbradyonic) can then be naturally stable space-time configurations produced in general cosmological scenarios including the formation and evolution of the present vacuum. We discuss basic ideas and phenomenological issues for non-cyclic pre-Big Bang cosmologies in the present context.