Question

It is well known that in the canonical quantization program for quantum gravity, like LQG/Wheeler-De Witt/Polymer QM, almost every prescription when applied to cosmology/gravitational collapse leads to the avoidance of the singularity via a bounce. In the context of gravitational collapse, this give rise to white holes formation: after falling inside the black hole the star bounces producing a white hole.

Since for external stationary observers, like us, the star never even fall inside the horizon due to time dilation, how could evidence of such phenomena be obtained? Are there ways to see, for a stationary observer, if the star bounce off to form a white hole for stationary observers? What evidence should we find to state that an astronomical object is a white hole?

Answer 1

Models of quantum gravity predict collapsing stars may bounce at a singularity, forming a white hole, but direct observation is not possible due to time dilation. Evidence for white holes would be indirect and unusual compared to typical black hole observations.

Step-by-step explanation:

When considering the fate of a collapsing star that leads to a black hole formation, advanced models like Loop Quantum Gravity (LQG) and the Wheeler-DeWitt equation suggest that the expected singularity may be replaced by a bounce, potentially leading to the creation of a white hole. However, for stationary observers at a safe distance, such as humans on Earth, the star's infall appears to freeze at the event horizon due to extreme time dilation, making direct observation of any bounce or white hole formation impossible. Instead, evidence for a white hole would have to be indirect, perhaps manifesting as unexpected radiation or particles emanating from a region where a black hole was anticipated but without the characteristic accretion disk emissions or gravitational wave signatures expected of black hole mergers.