Quantum Cosmological Perturbations of Multiple Fluids

Understand

The formalism to treat quantization and evolution of cosmological perturbations of multiple fluids is described.

• We first construct the Lagrangian for both the gravitational and matter parts, providing the necessary relevant variables and momenta leading to the quadratic Hamiltonian describing linear perturbations.
• The final Hamiltonian is obtained without assuming any equations of motions for the background variables.
• This general formalism is applied to the special case of two fluids, having in mind the usual radiation and matter mix which made most of our current Universe history.