Novel approach to the study of quantum effects in the early Universe

We develop a theoretical frame for the study of quantum gravitational waves. All the significant physical quantities can be formulated using Bogolubov transformations and the quadratic Hamiltonian operator corresponding to the classical version of a damped parametrically excited oscillator where the varying mass is replaced by the square cosmological scale factor. The destruction of quantum coherence due to the gravitational evolution in de Sitter scenarios is discussed