On the "Causality argument" in bouncing cosmologies.
We exhibit a situation in which cosmological perturbations of astrophysical relevance propagating through a bounce are affected in a scale-dependent way. Involving only the evolution of a scalar field in a closed universe described by general relativity, the model is consistent with causality. Such a specific counterexample leads to the conclusion that imposing causality is not sufficient to determine the spectrum of perturbations after a bounce provided it is known before. We discuss consequences of this result for string motivated scenarios.
Martin
Jérôme
J
Institut d'Astrophysique de Paris, GReCO, FRE 2435-CNRS, 98bis Boulevard Arago, 75014 Paris, France. jmartin@iap.fr
Peter
Patrick
P