Integral Constraints On cosmological Perturbations and their Energy
  We show the relation between Traschen's integral equations and the energy, and ``position of the centre of mass'', of the matter perturbations in a Robertson-Walker spacetime. When the perturbations are ``localised'' we get a set of integral constraints that includes hers. We illustrate them on a simple example. 
Nathalie Deruelle (DARC, Observatoire de Paris and DAMTP, Cambridge),   Joseph Katz (Racah Institute of Physics, Jerusalem) ...