## New no-go theorems for cosmic acceleration with extra dimensions

##### Authors
Wesley, Daniel H.
##### Description
We describe new no-go theorems for producing four-dimensional accelerating universes from warped dimensional reduction. The new theorems improve upon previous results by including dynamical extra dimensions and by treating four-dimensional universes that are not precisely de Sitter. The theorems show there exists a threshold four-dimensional equation-of-state parameter w below which the number of e-foldings of expansion is bounded, and give expressions for the maximum number of allowed e-foldings. In the generic case, the bound must be satisfied if the higher-dimensional theory satisfies the strong energy condition. If the compactification manifold M is one-dimensional, or if its (intrinsic) Ricci scalar R is identically zero, then the bound must be satisfied if the higher-dimensional theory satisfies the null energy condition.
Comment: v1: 4pp v2: references added v3: minor typo in (12a,b) corrected v4: minor corrections v5: re-organized
##### Keywords
High Energy Physics - Theory, Astrophysics, General Relativity and Quantum Cosmology