UV-extending Ghost Inflation

Abstract

We present a setup that provides a partial UV-completion of the ghost inflation model up to a scale which can be almost as high as the Planck mass. This is achieved by coupling the inflaton to the Lorentz-violating sector described by the Einstein-aether theory or its khronometric version. Compared to previous works on ghost inflation our setup allows to go beyond the study of small perturbations and include the background dynamics in a unified framework. In the specific regime when the expansion of the Universe is dominated by the kinetic energy of the inflaton we find that the model predicts rather high tensor-to-scalar ratio r ~ 0.02 $\tilde{A}\cdot$ 0.2 and non-Gaussianity of equilateral type with f_NL in the range from -50 to -5.

30 pages, 1 figure; the predicted range of observables explicitly indicated in the abstract, footnote on the BICEP2 results added; version to be published in JCAP