Bréchet, SylvainHobson, MichaelLasenby, Anthony2013-02-222013-02-222013-02-222009https://infoscience.epfl.ch/handle/20.500.14299/891090909.5384An analysis of adiabatic perturbations of a perfect fluid is performed to first-order about a general FLRW background using the 1+3 covariant and gauge-invariant formalism. The analog of the Mukhanov-Sasaki variable and the canonical variables needed to quantise respectively the scalar and tensor perturbations in a general FLRW background space-time are identified. The dynamics of the vector perturbations is also discussed.text::preprint