Cosmological Perturbations in the "Healthy Extension'' of Horava-Lifshitz gravity

Understand

We study linear cosmological perturbations in the ``healthy extension'' of Horava-Lifshitz gravity which has recently been analyzed \cite{BPS2}.

• We find that there are two degrees of freedom for scalar metric fluctuations, but that one of them decouples in the infrared limit.
• Also, for appropriate choices of the parameters defining the Lagrangian, the extra mode can be made well-behaved even in the ultraviolet.