Black Holes, Cavities and Blinking Islands

We consider the evolution of the entanglement entropy and entanglement islands in the two-sided generalization of the Schwarzschild black hole in a cavity. Introducing a reflecting boundary in the eternal black exteriors we regulate infrared modes of Hawking radiation and find that entanglement entropy saturates at some constant value. This value could be lower than black hole thermodynamic entropy, thus not leading to Page formulation of information paradox. We find a universal effect induced by the presence of a boundary, which we call “blinking island” — for some time the entanglement island inevitably disappears, thus leading to a non-unitary evolution. The talk is based on the paper arXiv:2311.16244.