Braneworld Flattening by a Cosmological Constant

TL;DR

This paper introduces a braneworld model with a cosmological constant where the universe naturally evolves to a flat Minkowski spacetime, potentially causing Lorentz violations and offering a new perspective on the cosmological constant problem.

Contribution

The paper proposes a novel braneworld scenario with an infinite volume bulk that achieves a flat universe regardless of the sign of the cosmological constant, highlighting unique Lorentz-violating effects.

Findings

Universe evolves to Minkowski spacetime for positive energy densities.

The model allows a flat universe with arbitrary negative cosmological constant.

Potential Lorentz symmetry violations due to varying speed of light effects.

Abstract

We present a model with an infinite volume bulk in which a braneworld with a cosmological constant evolves to a static, 4-dimensional Minkowski spacetime. This evolution occurs for a generic class of initial conditions with positive energy densities. The metric everywhere outside the brane is that of a 5-dimensional Minkowski spacetime, where the effect of the brane is the creation of a frame with a varying speed of light. This fact is encoded in the structure of the 4-dimensional graviton propagator on the braneworld, which may lead to some interesting Lorentz symmetry violating effects. In our framework the cosmological constant problem takes a different meaning since the flatness of the Universe is guaranteed for an arbitrary negative cosmological constant. Instead constraints on the model come from different concerns which we discuss in detail.