Detailed analysis of the curvature bounce: background dynamics and imprints in the CMB

TL;DR

This paper investigates a non-singular bounce scenario in a positively curved universe, analyzing its background dynamics, primordial power spectrum, and imprints on the CMB, showing compatibility with observations and potential deviations at large scales.

Contribution

It provides a detailed analysis of the curvature bounce, including background evolution and CMB signatures, highlighting its insensitivity to initial conditions and distinguishing bounce effects from vacuum choices.

Findings

Primordial power spectrum computed for various inflaton potentials.

CMB temperature anisotropies compatible with current data.

Potential large-scale deviations from standard cosmology identified.

Abstract

If the spatial sections of the Universe are positively curved, extrapolating the inflationary stage backward in time inevitably leads to a classical bounce. This simple scenario, non-singular and free of exotic physics, deserves to be investigated in details. The background dynamics exhibits interesting features and is shown to be mostly insensitive to initial conditions as long as observational consequences are considered. The primordial scalar power spectrum is explicitly computed, for different inflaton potentials, and the subsequent CMB temperature anisotropies are calculated. The results are compatible with current measurements. Some deviations with respect to the standard paradigm can however appear at large scales and we carefully disentangle what is associated with the vacuum choice with what is more fundamentally due to the bounce itself.