Speaker
Description
We investigate the cosmological background evolution and perturbations in a
general class of spatially covariant theories of gravity, which propagates two tensor modes and
one scalar mode. We show that the structure of the theory is preserved under the disformal
transformation. We also evaluate the primordial spectra for both the gravitational waves and
the curvature perturbation, which are invariant under the disformal transformation. Due to
the existence of higher spatial derivatives, the quadratic Lagrangian for the tensor modes
itself cannot be transformed to the form in the Einstein frame. Nevertheless, there exists a
one-parameter family of frames in which the spectrum of the gravitational waves takes the
standard form in the Einstein frame.
