Cosmology on Compact and Stable Supergravity Background
  We propose a cosmological model of D3-brane universe on compact and stable
supergravity background of wrapped D7-branes in type IIB string theory
previously argued to be dual to pure N=1 SU(N) gauge theory in four dimensions.
A model universe of order Planck size near the UV boundary dynamically flows
toward the IR with constant total energy density and accelerating expansion
followed by smooth transition to decelerating expansion and collides with the
wrapped D7-branes at the IR boundary. The model addresses the horizon and
flatness problems with most of the expansion produced during the decelerating
expansion phase. The inflationary scenario is used to generate sources of
inhomogeneities in the cosmic microwave background radiation and seeds for
large scale structure formation from quantum fluctuations which exit the Hubble
radius early during the accelerating expansion phase and the model addresses
the inhomogeneity problem with red tilt in the power spectrum. We propose that
the kinetic energy of the model universe is converted to matter and radiation
by the collision followed by formation of baryons that stabilizes the model
universe against gravitational force from the background at a finite distance
from the IR boundary with the wrapped D7-branes serving as sources of color.
Friedmann evolution then takes over with a positive cosmological constant term
coming from the remaining potential energy density which is interpreted as dark
energy. The magnitude of dark energy density is smaller than the total energy
density during the flow by a ratio of the scale factor when the model universe
appears in the UV to the scale factor at the moment of collision and stays
constant while the matter-radiation density falls during Friedmann expansion.
