Hawking Radiation in the Spacetime of White Holes

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 and Rovelli, 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, Carballo, and Garay, 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.