Late Time Acceleration of the 3-Space in a Higher Dimensional Steady
  State Universe in Dilaton Gravity
  We present cosmological solutions for (1+3+n)-dimensional steady state
universe in dilaton gravity with an arbitrary dilaton coupling constant w and
exponential dilaton self-interaction potentials in the string frame. We focus
particularly on the class in which the 3-space expands with a time varying
deceleration parameter. We discuss the number of the internal dimensions and
the value of the dilaton coupling constant to determine the cases that are
consistent with the observed universe and the primordial nucleosynthesis. The
3-space starts with a decelerated expansion rate and evolves into accelerated
expansion phase subject to the values of w and n, but ends with a Big Rip in
all cases. We discuss the cosmological evolution in further detail for the
cases w=1 and w=1/2 that permit exact solutions. We also comment on how the
universe would be conceived by an observer in four dimensions who is unaware of
the internal dimensions and thinks that the conventional general relativity is
valid at cosmological scales.
