  Cosmology motivated by string theory has been studied extensively in the
recent literature. String theory is promising because it has interesting
features such as unifying gravity, electromagnetic, weak and strong nuclear
forces. However, even the energy scale of the experiments at the Large Hadron
Collider (~TeV) is too low to detect any strong evidence for string theory. The
energy scale of inflation can be above ~10^9 TeV. Therefore, it is expected to
find some signature of string theory in cosmology.
  String theory predicts ten space-time dimensions. In the brane world
scenario, our four dimensional Universe is confined onto the higher dimensional
object called the Brane in the ten dimensional space time. The
Dirac-Born-Infeld (DBI) inflation is based on this idea. DBI inflation predicts
a characteristic statistical feature in the Cosmic Microwave Background (CMB)
temperature anisotropies. In this thesis, we study the predictions of the DBI
inflation models on the CMB temperature anisotropies.
