IAS Quantum Aspects of Black Holes Group Meeting

Abstract: We consider the algebra associated to a (neighborhood of a) cross-section of null infinity in semiclassical quantum gravity in asymptotically flat spacetimes. I will show that this algebra is equivalent to the algebra of observables in a subregion of the spacetime bounded by the cross-section. In the case of a black hole spacetime, the subregion is also bounded by the black hole horizon. In contrast to the AdS case, both algebras are Type III since the bulk reconstruction does not obtain operators to the past of the cut. If the spacetime contains a black hole then the algebra contains a Type II subalgebra whose entropy is the generalized entropy.