  This thesis presents a theoretical investigation into the quantum field
theoretic aspects of quantum correlations and decoherence in the cosmological
spacetimes. We shall focus on the inflationary or dark energy dominated phase
of the universe, and we shall take the spacetime background to be de Sitter.
The primary objective of this thesis is to study the physics of the very early
universe and to gain insight into the interesting interplay among quantum
correlations, entanglement and decoherence which can affect the evolution of
our universe.
