Pre-Big Bang, vacuum and noncyclic cosmologies

Abstract

LAPP, Universite de Savoie, CNRS/IN2P3B.P. 110, 74941 Annecy-le-Vieux Cedex, FranceE-mail: lgm_sci@yahoo.frWMAP and Planck open the way to unprecedented Big Bang phenomenology, potentially allow-ingtotestthestandardBigBangmodelaswellaslessconventionalapproachesincludingpre-BigBang cosmologies. An illustration is provided by the recent claim (Gurzadyan et al. [1]) that thecosmological sky would be a weakly random one with mostly regular signal. This work has beenfollowed by an interesting and useful debate. Whatever the conclusion, it appears that a detailedstudyofWMAPandPlanckdatacanhavesignificantimplicationsforpre-BigBangtheories. Notonly for cyclic cosmologies following the analysis recently proposed by Gurzadyan and Penrose[2], but also for noncyclic approaches incorporating a new fundamental scale beyond the Planckscale and, possibly, new ultimate constituents of matter with unconventional basic properties ascompared to standard particles [3, 4]. Alternatives to standard physics can be considered from acosmological point of view concerning vacuum structure, the nature of space-time, the origin andevolution of our Universe, the validity of quantum field theory and conventional symmetries, so-lutions to the cosmological constant problem, inflationary scenarios, dark matter and dark energy,the interpretation of string-like theories... Lorentz-like symmetries for the properties of matter(standard or superbradyonic [5, 6]) can then be naturally stable space-time configurations result-ing from general cosmological scenarios that incorporate physics beyond the Planck scale anddescribe the formation and evolution of the present vacuum. But an even more primordial ques-tion seems to be that of the origin of half-integer spins, that cannot be generated through orbitalangular momentum in the usual real space-time. It turns out that the use of a spinorial space-time[7, 8] with two complex coordinates instead of the conventional four real ones presents severalattractive features. Taking the cosmic time to be the modulus of a SU(2) spinor leads by purelygeometric means to a naturally expanding universe [8, 9], with a ratio between cosmic relativevelocities and distances equal to the inverse of the age of the Universe. No reference to standardmatter, hidden fields, gravitation or relativity is required to get such a result that looks quite rea-sonablefromanobservationalpointofview. Wediscussbasicideasandphenomenologicalissuesfor noncyclic pre-Big Bang cosmologies in the present context.The 2011 Europhysics Conference on High Energy Physics-HEP 2011,July 21-27, 2011Grenoble, Rhone-Alpes, France