Apparent ghosts and spurious degrees of freedom in non-local theories

Abstract

Recent work has shown that non-local modifications of the Einstein equations can have interesting cosmological consequences and can provide a dynamical origin for dark energy, consistent with existing data. At first sight these theories are plagued by ghosts. We show that these apparent ghost-like instabilities do not describe actual propagating degrees of freedom, and there is no issue of ghost-induced quantum vacuum decay.

18 pages, 3 figures. v2: cross-reference to 1311.3435 added

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• An Improved Cosmological Model
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