Hawking radiation in the spacetime of white holes

Abstract

A white hole (WH) is a time-reversed black hole (BH) solution in general relativity with a spacetime region to which cannot be entered from the outside. Recently they have been proposed as a possible solution to the information loss problem (Haggard et al. in Phys Rev D 92:104020, 2015). In particular it has been argued that the quantization of the gravitational field may prevent a BH from collapsing entirely with an exponential decay law associated to the black-hole-to-white-hole (BHWH) tunneling scenario (Barcelo et al. in Class Quantum Gravit 34:105007, 2017). During this period of BHWH transition the Hawking radiation should take place. Taking this possibility into account, we utilize the Hamilton–Jacobi and Parkih–Wilczek methods to study the Hawking radiation viewed as a quantum tunneling effect to calculate the tunneling rate of vector particles tunneling inside (outside) the horizon of a WH (BH), respectively. We show that there is a Hawking radiation associated to a WH spacetime equal to the BH Hawking temperature when viewed from the outside region of the WH geometry. In the framework of Parkih–Wilczek method, surprisingly, we show that Hawking temperature is affected by the initial radial distance at which the gravitational collapse starts.