Field Theoretic Approach to Flat Space Holography

Abstract

Flat space holography proposes a duality between quantum gravity in asymptotically flat spacetimes and field theories defined at null infinity, offering a non-AdS realisation of the holographic principle. A central feature of this framework is that the dual theory is defined on a null surface, in contrast to the timelike boundary of AdS/CFT. This requires any candidate dual field theory to be compatible with the Carroll limit in which the speed of light is sent to zero. Exploiting the fact that the asymptotic symmetry group of flat space --- the BMS group --- is the conformal extension of the Carroll group acting on null infinity, we construct explicit BMS-invariant field theories on the boundary. These models reproduce known results for two- and three-point correlation functions in the literature and provide a first step towards a field-theoretic formulation of flat space holography in the Carrollian framework. Furthermore, we clarify several conceptual and structural aspects of the field-theoretic approach to flat space holography, advancing the development of a more coherent boundary perspective.