Wedge holography in flat space and celestial holography

Abstract

In this paper, we study codimension two holography in flat spacetimes, based on the idea of the wedge holography. We propose that a region in a d+1 dimensional flat spacetime surrounded by two end of the world branes, which are given by d dimensional hyperbolic spaces, is dual to a conformal field theory (CFT) on a d-1 dimensional sphere. Similarly, we also propose that a d+1 dimensional region in the flat spacetime bounded by two d dimensional de Sitter spaces is holographically dual to a CFT on a d-1 dimensional sphere. Our calculations of the partition function, holographic entanglement entropy and two point functions, support these duality relations and imply that such CFTs are nonunitary. Finally, we glue these two dualities along null surfaces to realize a codimension two holography for a full Minkowski spacetime and discuss a possible connection to the celestial holography.