Holographic RG from ERG: Locality and General Coordinate Invariance in the Bulk

Abstract

In earlier papers it was shown that the correct kinetic term for scalar, vector gauge field and the spin two field in $AdS_{D+1}$ space is obtained starting from the ERG equation for a $CFT_D$ perturbed by scalar composite, conserved vector current and conserved traceless energy momentum tensor respectively. In this paper interactions are studied and it is shown that a flipped version of Polchinski ERG equation that evolves towards the UV can be written down and is useful for making contact with the usual AdS/CFT prescriptions for correlation function calculations. The scalar-scalar-spin-2 interaction in the bulk is derived from the ERG equation in the large $N$ semiclasical approximation. It is also shown that after mapping to AdS the interaction is local on a scale of the bare cutoff rather than the moving cutoff (which would have corresponded to the AdS scale). The map to $AdS_{D+1}$ plays a crucial role in this locality. The local nature of the coupling ensures that this interaction term in the bulk action is obtained by gauge fixing a general coordinate invariant scalar kinetic term in the bulk action. A wave function renormalization of the scalar field is found to be required for a mutually consistent map of the two fields to $AdS_{D+1}$.