M/String Theory, S-branes and Accelerating Universe
Abstract
Recently it was observed that the hyperbolic compactification of M/string theory related to S-branes may lead to a transient period of acceleration of the universe. We argue that this period can be associated with the present stage of the cosmological acceleration only if the 11d Planck length is exponentially smaller than the 4d Planck length. We study the time evolution of the corresponding effective 4d cosmological model supplemented by cold dark matter. By fine tuning the initial conditions, it is marginally possible to describe observational data for the late-time cosmic acceleration. We propose a possible explanation of this fine tuning and a resolution of the cosmological coincidence problem due to relation between the dark energy density and the effective dimensionality of the universe in this scenario.Keywords
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