Scalar field perturbations in Horava-Lifshitz cosmology
  We study perturbations of a scalar field cosmology in Horava-Lifshitz
gravity, adopting the most general setup without detailed balance but with the
projectability condition. We derive the generalized Klein-Gordon equation,
which is sixth-order in spatial derivatives. Then we investigate scalar field
perturbations coupled to gravity in a flat Friedmann-Robertson-Walker
background. In the sub-horizon regime, the metric and scalar field modes have
independent oscillations with different frequencies and phases except in
particular cases. On super-horizon scales, the perturbations become adiabatic
during slow-roll inflation driven by a single field, and the comoving curvature
perturbation is constant.
