Inflation in general covariant Ho\v{r}ava-Lifshitz gravity without projectability

Understand

In this paper, we study inflation in the general covariant Ho\v{r}ava-Lifshitz gravity without the projectability condition.

• We write down explicitly the equations of the linear scalar perturbations of the FRW universe for a single scalar field without specifying to any gauge.
• Applying these equations to a particular gauge, we are able to obtain a master equation of the perturbations, in contrast to all the other versions of the theory without the projectability condition.
• This is because in the current version of the theory it has the same degree of freedom of general relativity.