On Stability of Asymptotically Free Mimetic Hoava Gravity
Mar 23, 2021Citations per year
Abstract: (arXiv)
Asymptotically free mimetic gravity has been introduced as a proposal for a classical limiting curvature theory with the purpose of singularity resolution. It was found that in a spatially flat universe an initial stage of exponential expansion with graceful exit is a generic consequence, regardless of the matter content. In this work I will analyze linear stability of cosmological perturbations in such a model, considering only the degrees of freedom of pure mimetic gravity. I show that the addition of Hořava-gravity-like higher order spatial curvature terms can lift the gradient instability of scalar perturbations, even when the gradient term has the wrong sign throughout. Calculating the primordial spectra of tensor and scalar perturbations in the simplest single component model, I find that the initially scale invariant spectra turn out to be destroyed later by the rapidly varying speed of sound at horizon exit.Note:
- 29 pages, 0 figures; (version 3: adjustment of misleading use of terminology, correction of typos and small rewritings, added references)
- curvature: perturbation: scalar
- perturbation: scalar
- velocity: acoustic
- spectrum: tensor
- stability
- gravitation: model
- higher-order
- singularity
- resolution
- scaling
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