Description
Recent progress in semiclassical gravity is suggesting that, in spherical black holes with outer and inner horizons, the Hawking process drives the complete evaporation of the trapped region in timescales shorter than the Hawking time. However, this does not mark the end of the story, as this process is accompanied by the formation of an anti-trapped region, or white hole. In this work, we present a novel analytic treatment of black hole evaporation. Within simplified two-dimensional models describing the formation of charged and regular black holes, we show that the emergence of the anti-trapped region is unavoidable and is caused by the amplification of negative energy fluxes created along the \textit{outgoing} direction inside the black hole. This picture suggests that the energy fluxes originated by the white hole along the \textit{ingoing} direction can trigger the subsequent formation of a black hole, producing a cascade of black-to-white hole transitions which might terminate in a spacetime free of horizons. The analytic techniques developed in this work set the grounds to investigate this scenario in an exhaustive way.