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Paper   IPM / Physic / 7273
School of Physics
  Title:   An Accelerating Universe and Dynamical Compactification of Extra Dimensions
  Author(s):  F. Darabi
  Status:   Published
  Journal: Classical Quant. Grav.
  No.:  15
  Vol.:  20
  Year:  2003
  Pages:   3385-3402
  Supported by:  IPM
We study a (4 + D)-dimensional KaluzaKlein cosmology with a RobertsonWalker type metric having two scale factors a and R, corresponding to a D-dimensional internal space and four-dimensional universe, respectively. By introducing exotic matter as the spacetime part of the higher dimensional energymomentum tensor, a four-dimensional decaying cosmological term appears as   R-2, playing the role of an evolving dark energy in the universe. The resulting field equations yield the exponential solutions for the scale factors. These exponential behaviours may account for the dynamical compactification of extra dimensions and the accelerating expansion of the four-dimensional universe in terms of the Hubble parameter. The acceleration of the universe may be explained by the negative pressure of the exotic matter. It is shown that the rate of compactification of higher dimensions depends on the dimension, D. We then obtain the WheelerDeWitt equation and find the general exact solutions in D dimensions. A good correspondence between the classical solutions and the WheelerDeWitt solutions in any dimension, D, is obtained.

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