LargeScale Evolution of a Perturbed Universe
Abstract
We present a straightforward derivation of the largescale evolution of a perturbed RobertsonWalker space. The origin of the Friedmannlike behavior of the perturbed model is clarified in a comoving gauge, and thus in a corresponding gaugeinvariant formalism, using the covariant equations. Thus, when the imperfect fluid contributions are negligible, the largescale perturbations in a nearly flat background evolve like separate Friedmann models. However, there exists a preferable gauge invariant quantity (ζ) which is conserved in the large scale even considering the background spatial curvature (for a nearly flat background model), the cosmological constant, and the anisotropic pressure. Its independence from the anisotropic pressure allows us to generalize ζ, to a class of generalized gravity theories. Our notation is that commonly used in cosmological models (even those for perturbed universes), while keeping most general expressions including the background spatial curvature and the cosmological constant. This allows simple derivations of both the integral form solution in the large scale and also Bardeen's secondorder evolution equation in the general case.
 Publication:

The Astrophysical Journal
 Pub Date:
 October 1991
 DOI:
 10.1086/170588
 Bibcode:
 1991ApJ...380..307H
 Keywords:

 Computational Astrophysics;
 Galactic Evolution;
 Perturbation Theory;
 Gravitation Theory;
 Universe;
 Astrophysics;
 COSMOLOGY;
 GALAXIES: FORMATION