Lecture 14: Holography of information in flat space
In this lecture, we first reviewed aspects of the Hilbert space of massless excitations in four-dimensional flat space.
We then discussed how the principle of holography of information manifests itself in flat space. The result is that, in a theory of quantum gravity, under weak assumptions, a state of massless excitations can be completely identified using observations in a small neighbourhood of the past boundary of future null infinity. This is contrast to local quantum field theories, where observations on all of future null infinity would be required to identify the state.
This result applies to the UV-completion of the low-energy theory provided the full theory shares the low-energy properties of low-energy quantum gravity
