[QUAST Seminar] The Mechanism behind the Information Encoding for Islands

I will explain a recent work which uncovers the mechanism behind the information encoding of entanglement islands. Entanglement islands are closed subregions in a gravitational universe whose information was conjectured to be fully encoded in a nongravitational system away from it. In the context of black hole information paradox, one can think of the entanglement island as the interior of the black hole after the Page time and the nongravitational system as the early-time Hawking radiation. Hence entanglement island resolves the information paradox if the above conjecture is true. This conjecture is recently proved in a controllable setup of islands in general dimensions. It turns out that the previously established result that entanglement islands can only exist in massive gravities plays an essential role in the proof. We will see that this question is in fact tightly related to the issue of local observables in a gravitational universe and the setup we considered in fact provides an explicit example of the ``gravitational observer" postulated by Witten et al.