We study cosmological applications of extended vector–tensor theories, whose Lagrangians contain up to two derivatives with respect to metric and vector field. We derive background equations under the assumption of homogeneous and isotropic universe and study the nature of cosmological perturbations on top of the background. We found an example of healthy cosmological solutions in non-trivial degenerate theory of gravity for the first time, where those perturbations do not suffer from any instabilities, that is, ghost and gradient instabilities.
|ジャーナル||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|出版ステータス||Published - 2018 8 10|
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