Speaker
Description
Classical gravity coupled to a holographic CFT_4 (matter) is considered. The effect of the quantum dynamics of matter on gravity is studied around de Sitter space. The structure of the graviton propagator is modified and non-trivial poles appear due to matter quantum effects.
The position and residues of such poles are mapped as a function of the relevant parameters, the number of colors $N$ of the CFT$_4$, the two $R^2$ couplings of gravity as well as the curvature of de Sitter The instabilities induced are determined. Such instabilities can be important in cosmology as they trigger the departure from de Sitter space and in some regions of parameters are more important than the well-known scalar instabilities. It is also determined when the presence of such instabilities is unreliable, if the associate scales are larger than the ``species" cutoff of the gravitational theory.
