Experimantal HEP Seminar
Joint Seminar with the School of Computer Science

Entanglement entropy, black holes and holography

Stephen Hsu

University of Oregon

After an introduction to black hole entropy and holography, we describe results related to the entanglement entropy of black holes. We observe that the entanglement entropy resulting from tracing over a subregion of an initially pure state can grow faster than the surface area of the subregion (indeed, proportional to the volume), in contrast to examples studied previously. The pure states with this property have long-range correlations between interior and exterior modes and are constructed by purification of the desired density matrix. We show that imposing a no-gravitational collapse condition on the pure state is sufficient to exclude faster than area law entropy scaling. This observation leads to an interpretation of holography as an upper bound on the realizable entropy (entanglement or von Neumann) of a region, rather than on the dimension of its Hilbert space.