Séminaire / Seminar GReCO |
| « Gravitational Waves in Isotropic Universes » |
|
Emer O''Shea |
| The waves are modelled as small perturbations of the background Robertson-Walker geometry using the gauge-invariant and covariant approach of Ellis-Bruni. We work in linear approximation in terms of the Ellis-Bruni variables and show that all perturbation variables must vanish except the perturbed shear of the matter world-lines and the anisotropic stress perturbation of the matter distribution. We then specialise to the pure gravity waves, for which the Weyl tensor is radiative (i.e. type N in the Petrov classification). For such waves we demonstrate that the histories of their wave fronts in the background RW space-time can be shear-free null hypersurfaces and we construct explicit examples for which the presence of the anisotropic stress is essential. |
|
jeudi 6 mars 2003 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |