Abstract
In Hořava's theory of gravity, Lorentz symmetry is broken in exchange for renormalizability, but the original theory has been argued to be plagued with problems associated with a new scalar mode stemming from the very breaking of Lorentz symmetry. Recently, Blas, Pujolàs, and Sibiryakov have proposed a healthy extension of Hořava gravity, in which the behavior of the scalar mode is improved. In this paper, we study scalar modes of cosmological perturbations in extended Hořava gravity. The evolution of metric and density perturbations is addressed analytically and numerically. It is shown that for vanishing non-adiabatic pressure of matter the large scale evolution of cosmological perturbations converges to that described by a single constant, ζ, which is an analog of a curvature perturbation on the uniform-density slicing commonly used in usual gravitational theories. The subsequent evolution is thus determined completely by the value of ζ.