Portal de Periódicos da CAPES

Perturbations in bouncing cosmologies: Dynamical attractor versus scale invariance

2005; American Physical Society; Volume: 71; Issue: 6 Linguagem: Inglês

10.1103/physrevd.71.063505

1550-7998

Paolo Creminelli, Alberto Nicolis, Matías Zaldarriaga,

Galaxies: Formation, Evolution, Phenomena

For bouncing cosmologies such as the ekpyrotic/cyclic scenarios we show that it is possible to make predictions for density perturbations which are independent of the details of the bouncing phase. This can be achieved, as in inflationary cosmology, thanks to the existence of a dynamical attractor, which makes local observables equal to the unperturbed solution up to exponentially small terms. Assuming that the physics of the bounce is not extremely sensitive to these corrections, perturbations can be evolved even at the nonlinear level. The resulting spectrum is not scale invariant and thus incompatible with experimental data. This can be explicitly shown in synchronous gauge where, contrary to what happens in the commonly used Newtonian gauge, all perturbations remain small going towards the bounce and the existence of the attractor is manifest.