The Universe as a Hologram

Ofer Aharony

Our current theories of particle physics are based on quantum field theory, which is a local theory - it includes only interactions
between particles at the same point in space-time. When we try to include also gravitational interactions (for example through string
theory) we find that this breaks down, and one can no longer describe the theory using local degrees of freedom. We will illustrate this by
discussing black holes. It seems that to describe a theory of quantum gravity in three spatial dimensions one actually needs only a
two-dimensional description - this is the idea of "holography", first formulated ten years ago by 't Hooft and Susskind. We will describe
this idea in general, and describe in particular how it works for the example that is best understood, of quantum gravity in anti-de Sitter
space.