We use the formalism of two-mode squeezed states and the theory of gau
ge invariant cosmological perturbations to calculate two-point correla
tion functions and the entropy of density perturbations. In particular
we discuss modulation in the power spectrum of density perturbations.
We also present a simple picture for entropy in terms of the quantum
noise in the state. The relevance of the entropy of density perturbati
ons for large-scale structures in the universe is examined.