Has the Universe always expanded ?

Abstract

We consider a cosmological setting for which the currently expanding era is preceded by a contracting phase, that is, we assume the Universe experienced at least one bounce. We show that scalar hydrodynamic perturbations lead to a singular behavior of the Bardeen potential and/or its derivatives (i.e. the curvature) for whatever Universe model for which the last bounce epoch can be smoothly and causally joined to the radiation dominated era. Such a Universe would be filled with non-linear perturbations long before nucleosynthesis, and would thus be incompatible with observations. We therefore conclude that no observable bounce could possibly have taken place in the early universe if Einstein gravity together with hydrodynamical fluids is to describe its evolution, and hence, under these conditions, that the Universe has always expanded.

11 pages, LaTeX-ReVTeX, no figures, submitted to PRD

References in corpus (3)

• Cosmological implications of the MAXIMA-I high resolution Cosmic Microwave Background anisotropy measurement
• A Brief Comment on "The Pyrotechnic Universe"
• Graceful exit from inflation using quantum cosmology

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