A pure general relativistic non-singular bouncing origin for the Universe

Aurélien Barrau

doi:10.1140/epjc/s10052-020-8158-5

Abstract

In this article, we argue that the past of the Universe, extrapolated from standard physics and measured cosmological parameters, might be a non-singular bounce. We also show that, in this framework, quite stringent constraints can be put on the reheating temperature and number of inflationary e-folds, basically fixing T_{RH}sim T_{GUT} and Nsim 70. We draw some conclusions about the shape of the inflaton potential and raise the “naturalness” issue in this context. Finally, we argue that this could open a very specific window on the “pre big bounce" universe.

Highlights

Cosmological studies often mix the search for the correct theory required to described the World and the investigation of contingent phenomena occurring within a well defined paradigm
We take for granted the usual ingredients of the cosmic scenario, in particular the existence of an inflationary stage
We try to focus on the latter consideration even if we address the naturalness and fine-tuning issues. It is in itself a well known solution to the Einstein field equations in cosmology, it is in practice often forgotten than the Big Bang singularity does not appear anymore when taking into account the possible positive curvature of the Universe mixed with an effective cosmological constant. It is regularly argued – especially within the community of quantum gravity – that new physics is unavoidably required to avoid the dramatic breakdown of general relativity when going backward in time

Summary

Introduction

Cosmological studies often mix the search for the correct theory required to described the World and the investigation of contingent phenomena occurring within a well defined paradigm. The closedness of the Universe is quite strongly favored by recent data and new analysis, as explained It is in itself a well known solution to the Einstein field equations in cosmology, it is in practice often forgotten than the Big Bang singularity does not appear anymore when taking into account the possible positive curvature of the Universe mixed with an effective cosmological constant. It is regularly argued – especially within the community of quantum gravity – that new physics is unavoidably required to avoid the dramatic breakdown of general relativity (unless assuming very exotic contents) when going backward in time. This, opens unique observational features through modifications of the primordial power spectrum

The curvature of the Universe

Duration of inflation and reheating temperature

Fine-tuning and inflation potential

Consistency

Observational footprints

Conclusion