2011

Ph.D

HBNI

The Early Universe in the frame work of M theory is studied in this thesis. Early Universe is assumed to be homogeneous, anisotropic, and is dominated by mutually BPS intersecting branes of M theory. Due to the lack of knowledge of the exact brane dynamics, the U duality symmetry of the M theory, is used to get an equation of states. Verified the equations of states obtained by duality, also hold for known cases like black holes. Then Einstein's equations are solved to get evolution of early universe. Thge evolution of the homogeneous early universe is studied using analytical and numerical methods. It is found that aymptotically three spatial directions expand to infinity, and the remaining spatial directions reach stabilised values. From string theory perspective, the dilation is hence stabilised also. A physical description of the stabilisation mechanism is given. It is found, only 22'55' and its U dual configuration can be achieved stabilisation of 7 spacelike dimensions. Also from the perspective of four dimensional space time, the effective four dimensional newton's constant G4 is now time varying. Its time dependence will follow from explicit solutions. It is found in the present case that, asymptotically, G4, exhibits, characteristic log periodic oscillations.