Inflation and CMB anisotropy from quantum metric fluctuations

Abstract

We propose a model of cosmological evolution of the early and late Universe which is consistent with observational data and naturally explains the origin of inflation and dark energy. We show that the de Sitter accelerated expansion of the FLRW space with no matter fields (hereinafter, empty space) is its natural state, and the model does not require either a scalar field or cosmological constant or any other hypotheses. This is due to the fact that the De Sitter State is an exact solution of the rigorous mathematically consistent equations of one-loop quantum gravity for the empty FLRW space that are finite off the mass shell. Space without matter fields is not empty as it always has the natural quantum fluctuations of the metric, i.e. gravitons. Therefore, the empty (in this sense) space is filled with gravitons, which have the backreaction effect on its evolution over time forming a self-consistent de Sitter instanton leading to the exponentially accelerated expansion of the Universe. At the start and the end of cosmological evolution, the Universe is assumed to be empty, and this fact explains the origin of inflation and dark energy. The Universe starts and ends with de Sitter expansion but the evolutionary process runs in these cases in opposite directions. It leads to the prediction that the signs of the parameter 1 + w should be opposite in the two cases, which is consistent with observations. Fluctuations of the number of gravitons lead to fluctuations of their energy density which in turn leads to the observed CMB temperature anisotropy of the order of ∼10⁻⁵ and CMB polarization. Within this scenario, it is not a hypothetical scalar field that generates inflation and relic gravitational waves but on the contrary, gravitational waves (gravitons) generate inflation, CMB anisotropy and dark energy.