Conservation Laws for Cosmological Perurbations
  We briefly recall the problem of defining conserved quantities such as energy in general relativity, and the solution by introducing a symmetric background. We apply the general formalism to perturbed Robertson-Walker spacetimes with de Sitter geometry as background. We relate the obtained conserved quantities to Traschen's integral constraints and mention a few applications in cosmology. 
Nathalie Deruelle (DARC, Observatoire de Paris) and Jean-Philippe Uzan   (DARC, Observatoire de Paris)