Luis Gonzalez-Mestres
BICEP2, Planck, spinorial space-time, pre-Big Bang
(340K, PDF)
ABSTRACT. The field of Cosmology is currently undergoing a positive and constructive crisis. Controversies concerning inflation are not really new. But after the 2013-2014 Planck and BICEP2 announcements, the basic issues can involve more direct links between the Mathematical Physics aspects of cosmological patterns and the interpretation of experimental results. Open questions and new ideas on the foundations of Cosmology can emerge, while future experimental and observational programs look very promising. The BICEP2 result reporting a B-mode polarization of the cosmic microwave background (CMB) radiation inconsistent with the null hypothesis at a significance of > 5 sigma was initially presented as a signature of primordial gravitational waves from cosmic inflation. But polarized dust emission may be at the origin of the signal, and further measurements and analyses are required. Even assuming that part of the observed CMB B-mode polarization has indeed been generated by the early Universe, its theoretical and cosmological interpretation is far from obvious. Inflationary gravitational waves are not the onlypossible source of primordial CMB B-modes. Alternative cosmologies such as pre-Big Bang patterns and the spinorial space-time (SST) we introduced in 1996-97 can naturally produce this polarization. Furthermore, the SST automatically generates for each comoving observer a local privileged space direction (PSD) whose existence may have been confirmed by Planck data. If such a PSD exists, it seems normal to infer that vector perturbations have been strong in the early Universe leading to CMB B-modes in suitable scenarios. More generally, pre-Big Bang cosmologies can also generate gravitational waves in the early Universe without inflation. After briefly describing detectors devoted to the study of the CMB polarization, we discuss the results of the BICEP2 experiment as well as recent Planck results and analyses. Considering the experimental situation and prospects, we further analyse possible alternatives to the inflationary interpretation of a primordial B-mode polarization of cosmic microwave background radiation.