Cosmological Evolution on Self-Tuned Branes and the Cosmological Constant

TL;DR

This paper investigates the cosmological evolution in brane-world models with bulk scalar fields, ruling out self-tuned potentials and proposing a supergravity framework that naturally leads to late-time acceleration consistent with observations.

Contribution

It introduces a supergravity-based brane-world model with a run-away potential that explains late-time cosmic acceleration without rapid oscillations.

Findings

Self-tuned potentials cause rapid oscillations incompatible with current cosmology.

Supergravity in singular spaces provides a natural framework for late-time acceleration.

The model predicts an acceleration parameter q_0=-4/7 and equation of state omega=-5/7.

Abstract

We consider the cosmological evolution of a bulk scalar field and ordinary matter living on the brane world in the light of the constraints imposed by the matter dominated cosmological evolution and a small cosmological constant now. We rule out models with a self-tuned minimum of the four dimensional potential as they would lead to rapid oscillations of the Hubble parameter now. A more natural framework is provided by supergravity in singular spaces where the brane coupling and the bulk potential are related by supersymmetry leading to a four dimensional run-away potential. For late times we obtain an accelerating universe due to the breaking of supersymmetry on the brane with an acceleration parameter of q_0=-4/7 and associated equation of state omega=-5/7.