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A Note on Perturbations During a Regular Bounce

Ghazal Geshnizjani·Thorsten J. Battefeld
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Abstract

We point out an inconsistency in a method used in the literature for studying adiabatic scalar perturbations in a regular bouncing universe (in four dimensions). The method under scrutiny consists of splitting the Bardeen potential into two pieces with independent evolutions, in order to avoid a singular behavior at the boundaries of the region where the null energy condition (NEC) is violated. However, we argue that this method violates energy-momentum conservation. We then introduce a novel method which provides two independent solutions for the Bardeen potential around the boundaries, even in the case of adiabatic perturbations. The two solutions are well behaved and not divergent.

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Ghazal Geshnizjani, Thorsten J. Battefeld. 2005-06-16. A Note on Perturbations During a Regular Bounce. https://doi.org/10.1103/physrevd.73.048501

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