Speaker: Idse Heemskerk (UCSB)
Over the last years, we have taken three different approaches to the problem of bulk locality in gauge/gravity duality. In retrospect, these approaches correspond to the different ways of thinking about quantum field theory in the bulk. In this talk we review and compare these, evaluating what we have learned.
In the S-matrix approach, we studied crossing constraints on two-to-two scattering amplitudes, and provided evidence for the conjecture that a large $N$ expansion and a hierarchy in the spectrum of operator dimension are sufficient conditions for a conformal theory to have a local bulk dual.
In the path integral approach we attempted to connect the holographic and Wilsonian renormalization groups. An important role for multi-trace operators was discovered. Although locality remains unexplained, several parallels between holographic and Wilsonian renormalization were made and a physical picture of how the bulk dynamics might emerge from the perspective of the renormalization group was sketched.
Most recently, we considered the construction of the bulk field operators in terms of smeared boundary operators. Aside from extending the previous work on this construction in several directions, we formulated conditions for obtaining the field operators without already knowing the bulk dynamics and addressed some paradoxes related to a cat inside a black hole.