paper

Cosmological Perturbations in the Projectable Version of Horava-Lifshitz Gravity

arXiv:1007.1006 · doi:10.1088/1475-7516/2011/08/015

Abstract

We consider linear perturbations about a homogeneous and isotropic cosmological background in the projectable version of Hořava-Lifshitz gravity. Starting from the action for cosmological perturbations, we identify the canonically normalized fluctuation variables. We find that - in contrast to what happens in the non-projectable version of the theory - the extra scalar cosmological perturbation mode is already dynamical at the level of linear perturbations. For values of the parameter in the range , the extra mode is ghost-like, for values and it is tachyonic. This indicates a problem for the projectable version of Hořava-Lifshitz gravity.

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