Topics on string cosmology, and supergravity

The first part of this thesis is based on the evolution of oscillon inspired by the axion-monodromy models in the reheating area of cosmology, with the simulations that is done numerically using open source GRChombo. We study the effect of gravity on the dynamics of oscillon and find out the region of parameter space where oscillon feels in- stability and collapses to black holes. The second part is a short review of GRChombo open source code and its key features along with the applications. The last part is devoted to the analytical construction of 3d off-shell N=(1,1) general massive super- gravity (GMG) solutions using Killing spinor analysis and implementing the algebraic computation with xAct package. We compare the result with other known solutions such as topological massive supergravity (TMG) as well as new massive supergravity (NMG).