Complexity and the bulk volume, a new York time story
We study the boundary description of the volume of maximal Cauchy slices
using the recently derived equivalence between bulk and boundary symplectic
forms. The volume of constant mean curvature slices is known to be canonically
conjugate to "York time". We use this to construct the boundary deformation
that is conjugate to the volume in a handful of examples, such as empty AdS, a
backreacting scalar condensate, or the thermofield double at infinite time. We
propose a possible natural boundary interpretation for this deformation and use
it to motivate a concrete version of the complexity=volume conjecture, where
the boundary complexity is defined as the energy of geodesics in the K\"ahler
geometry of half sided sources. We check this conjecture for Ba\~nados
geometries and a mini-superspace version of the thermofield double state.
Finally, we show that the precise dual of the quantum information metric for
marginal scalars is given by a particularly simple symplectic flux, instead of
the volume as previously conjectured.