  We explore the holographic principle in the context of asymptotically flat
space-times by means of the asymptotic symmetry group of this class of
space-times, the so called Bondi-Metzner-Sachs (BMS) group. In particular we
construct a (free) field theory living at future (or past) null infinity
invariant under the action of the BMS group. Eventually we analyse the quantum
aspects of this theory and we explore how to relate the correlation functions
in the boundary and in the bulk.
