# Gauge-invariant perturbations around symmetry-reduced sectors of general relativity: applications to cosmology

@article{Dittrich2007GaugeinvariantPA, title={Gauge-invariant perturbations around symmetry-reduced sectors of general relativity: applications to cosmology}, author={Bianca Dittrich and Johannes Tambornino}, journal={Classical and Quantum Gravity}, year={2007}, volume={24}, pages={4543 - 4585} }

We develop a gauge-invariant canonical perturbation scheme for perturbations around symmetry-reduced sectors in generally covariant theories, such as general relativity. The central objects of investigation are gauge-invariant observables which encode the dynamics of the system. We apply this scheme to perturbations around a homogeneous and isotropic sector (cosmology) of general relativity. The background variables of this homogeneous and isotropic sector are treated fully dynamically which…

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