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arXiv · 1110.2618

The Self-Accelerating Universe with Vectors in Massive Gravity

Kazuya Koyama·Gustavo Niz·Gianmassimo Tasinato
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Abstract

We explore the possibility of realising self-accelerated expansion of the Universe taking into account the vector components of a massive graviton. The effective action in the decoupling limit contains an infinite number of terms, once the vector degrees of freedom are included. These can be re-summed in physically interesting situations, which result in non-polynomial couplings between the scalar and vector modes. We show there are self-accelerating background solutions for this effective action, with the possibility of having a non-trivial profile for the vector fields. We then study fluctuations around these solutions and show that there is always a ghost, if a background vector field is present. When the background vector field is switched off, the ghost can be avoided, at the price of entering into a strong coupling regime, in which the vector fluctuations have vanishing kinetic terms. Finally we show that the inclusion of a bare cosmological constant does not change the previous conclusions and it does not lead to a ghost mode in the absence of a background vector field.

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Kazuya Koyama, Gustavo Niz, Gianmassimo Tasinato. 2011-10-12. The Self-Accelerating Universe with Vectors in Massive Gravity. https://doi.org/10.1007/jhep12(2011)065

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