@MISC{Chen08thecosmological, author = {Jia-zhong Chen and Duoje Jia}, title = {The Cosmological Constant in Brane Cosmology}, year = {2008} }

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Abstract

We propose, based on brane cosmology, an explicit relation of the radius of the observed brane Universe and the extra dimensions:R = MPlR 2 extra for simultaneously solving both hierarchy problem and the cosmological constant problem without fine-tuning. This relation associates the dark energy (i.e., cosmic acceleration) in the cosmological physics with the electroweak scale in particle physics. We assumed that the supersymmetry on our Standard-Model brane is broken near the TeV energy scale, and the curvature induced by the resulted cosmological constant occurs only in the extra dimension. As a result, the effective cosmological constant (zero-point energy in higher dimensions) observed in our brane—dark energy—is a natural consequence of the breaking of supersymmetry in brane near the TeV. The smoothness of the dark energy is due to the fact that each space-time point of the flat brane corresponds to the dimensions with definite radius, and that the inverse of the extra-dimension radius corresponds to the dark energy (in natural unit). PACS number(s): 12.38.-t, 11.15.Tk, 12.38.Aw The discovery [1] that the expansion of the Universe is speeding up has presented cosmologists and particle physicists with a number of profound puzzles. In the context of general relativity (GR), the acceleration can be accounted for by simply assuming the existence of a smooth component of energy with large negative pressure (w ≡ p/ρ < −1/3), dubbed dark energy (cosmological constant), which account for about 73 % of the Universe energy. The one of these