The Cosmological Constant in Brane Cosmology

We propose, based on brane cosmology, an explicit relation R = MPlR 2 extra of the radius of the observed brane Universe and the extra dimensions for solving both the 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, thereby associates the cosmological observations (by WMAP, Planck satellite, SNAP, etc.) with the accelerators (such as LHC, Tevatron). 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 dimensions. 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. PACS number(s): 12.38.-t, 11.15.Tk, 12.38.Aw