Holographic cosmology

Abstract

The standard AdS/CFT correspondence ``holographically'' relates a well-defined gravitational theory in a background of $AdS_{d+1}$ type with a conformal field theory on the flat $d$ dimensional boundary of the space. But the duality has been generalized to apply to many strong coupling problems, and different gravitational spaces. The example we study here is of cosmology, which was started by the relation $\Psi(\Phi)=Z(\Phi)$ proposed by Maldacena. A phenomenological approach to holography gives results as consistent with CMBR and traditional tests of cosmology as the standard $\Lambda $ CDM plus inflation ansatz, and fixes the parameters of the (large $N$) field theory. A top-down approach has less flexibility, but can predict many interesting features.