# Unitarity and Holography in Gravitational Physics

### APA

Marolf, D. (2009). Unitarity and Holography in Gravitational Physics. Perimeter Institute. https://pirsa.org/09010030

### MLA

Marolf, Donald. Unitarity and Holography in Gravitational Physics. Perimeter Institute, Jan. 23, 2009, https://pirsa.org/09010030

### BibTex

@misc{ pirsa_PIRSA:09010030, doi = {10.48660/09010030}, url = {https://pirsa.org/09010030}, author = {Marolf, Donald}, keywords = {Quantum Gravity, Quantum Fields and Strings}, language = {en}, title = {Unitarity and Holography in Gravitational Physics}, publisher = {Perimeter Institute}, year = {2009}, month = {jan}, note = {PIRSA:09010030 see, \url{https://pirsa.org}} }

University of California, Santa Barbara

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Talk Type

Abstract

Because the gravitational Hamiltonian is a pure boundary term on-shell, asymptotic gravitational fields store information in a manner not possible in local field theories. Two properties follow from this purely gravitational behavior. The first, 'Boundary Unitarity,' holds under AdS-like boundary conditions. This is the statement that the algebra of boundary observables is independent of time; i.e., that the algebra of boundary observables at any one time t_1 in fact coincides with the algebra of boundary observables at any other time t_2. As a result, any information available at the boundary at time t_1 remains available at any other time t_2. The second, 'Perturbative Holography,' holds under either AdS-like or asymptotically flat boundary conditions. In the AdS context, it is the statement that the algebra of boundary observables at any time t includes all perturbative observables anywhere in the spacetime. In the asymptotically flat context, Perturbative Holography is that statement that the algebra of observables on I^+ within any neighborhood of i^0 contains all perturbative observables. Perturbative Holography holds about any classical solution with a regular past infinity; i.e., spacetimes which collapse to form classical black holes are explicitly allowed. We derive the above properties and discuss their implications for information in black hole evaporation.