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Abstract: We give detailed proofs of several new no-go theorems for constructing flatfour-dimensional accelerating universes from warped dimensional reduction.These new theorems improve upon previous ones by weakening the energyconditions, by including time-dependent compactifications, and by treatingaccelerated expansion that is not precisely de Sitter. We show that de Sitterexpansion violates the higher-dimensional null energy condition NEC if thecompactification manifold M is one-dimensional, if its intrinsic Ricci scalar Rvanishes everywhere, or if R and the warp function satisfy a simple limitcondition. If expansion is not de Sitter, we establish thresholdequation-of-state parameters w below which accelerated expansion must betransient. Below the threshold w there are bounds on the number of e-foldingsof expansion. If M is one-dimensional or R everywhere vanishing, exceeding thebound implies the NEC is violated. If R does not vanish everywhere on M,exceeding the bound implies the strong energy condition SEC is violated.Observationally, the w thresholds indicate that experiments with finiteresolution in w can cleanly discriminate between different models which satisfyor violate the relevant energy conditions.



Autor: Daniel H. Wesley

Fuente: https://arxiv.org/







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