A big bounce, slow-roll inflation and dark energy from conformal gravity

TL;DR

This paper explores a conformal gravity model that naturally produces a big bounce, slow-roll inflation, and dark energy, offering a unified explanation for early universe dynamics and late-time acceleration.

Contribution

It introduces a gauge theory of gravity based on the SO(4,2) conformal group that dynamically generates an effective cosmological constant and modifies early universe behavior.

Findings

Replaces the big bang with a big bounce due to weakened gravitational fields in the early universe.

Generates a period of slow-roll inflation following the bounce, explaining cosmic homogeneity.

Produces late-time acceleration consistent with dark energy observations.

Abstract

We examine the cosmological sector of a gauge theory of gravity based on the SO(4,2) conformal group of Minkowski space. We allow for conventional matter coupled to the spacetime metric as well as matter coupled to the field that gauges special conformal transformations. An effective cosmological constant is generated dynamically via solution of the equations of motion, and this allows us to recover the late time acceleration of the universe. Furthermore, gravitational fields sourced by ordinary cosmological matter (i.e. dust and radiation) are significantly weakened in the very early universe, which has the effect of replacing the big bang with a big bounce. Finally, we find that this bounce is followed by a period of nearly-exponential slow roll inflation that can last long enough to explain the large scale homogeneity of the cosmic microwave background.