Accelerating Universe and Cosmological Perturbation in the Ghost Condensate

Abstract

In the simplest Higgs phase of gravity called ghost condensation, an accelerating universe with a phantom era (w<-1) can be realized without ghost or any other instabilities. In this paper we show how to reconstruct the potential in the Higgs sector Lagrangian from a given cosmological history (H(t), \rho(t)). This in principle allows us to constrain the potential by geometrical information of the universe such as supernova distance-redshift relation. We also derive the evolution equation for cosmological perturbations in the Higgs phase of gravity by employing a systematic low energy expansion. This formalism is expected to be useful to test the theory by dynamical information of large scale structure in the universe such as cosmic microwave background anisotropy, weak gravitational lensing and galaxy clustering.