Hawking-Page phase transition, Page curve and islands in black holes

Abstract

We study the Page curve and the effect of the Hawking-Page phase transition in the Vaidya model of evaporating BTZ black holes, both with and without islands. The phase transition can occur before, at, or after the Page time. When it occurs before the Page time, the information release does not require an island yet still reproduces the Page curve. From the first law of entanglement, the entanglement temperature changes from negative to positive, diverging at the Page time. Thus, the information deposition phase corresponds to a negative temperature, and the release phase to a positive temperature. If the Hawking-Page phase transition takes place, all black hole information is released at once via a quantum jump. We speculate that first-order phase transitions universally affect black hole information, providing an alternative escape mechanism independent of Hawking radiation.