title: Cosmology of a Friedmann-Lamaître-Robertson-Walker 3-brane, late-time cosmic acceleration, and the cosmic coincidence.
abstract: A late epoch cosmic acceleration may be naturally entangled with cosmic coincidence--the observation that at the onset of acceleration the vacuum energy density fraction nearly coincides with the matter density fraction. In this Letter we show that this is indeed the case with the cosmology of a Friedmann-Lamaître-Robertson-Walker (FLRW) 3-brane in a five-dimensional anti-de Sitter spacetime. We derive the four-dimensional effective action on a FLRW 3-brane, from which we obtain a mass-reduction formula, namely, M(P)(2) = ρ(b)/|Λ(5)|, where M(P) is the effective (normalized) Planck mass, Λ(5) is the five-dimensional cosmological constant, and ρ(b) is the sum of the 3-brane tension V and the matter density ρ. Although the range of variation in ρ(b) is strongly constrained, the big bang nucleosynthesis bound on the time variation of the effective Newton constant G(N) = (8πM(P)(2))(-1) is satisfied when the ratio V/ρ ≳ O(10(2)) on cosmological scales. The same bound leads to an effective equation of state close to -1 at late epochs in accordance with astrophysical and cosmological observations.
authors.affiliation: Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand.
authors.forename: Ciaran
authors.initials: C
authors.lastname: Doolin
authors.affiliation: Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand and Centre for Cosmology and Theoretical Physics (CCTP), Tribhuvan University, Kathmandu 44618, Nepal and Theory Department, CERN, CH-1211 Geneva 23, Switzerland.
authors.forename: Ishwaree P
authors.initials: IP
authors.lastname: Neupane