B Black to white transition in LQC

[javisot]

TL;DR Summary

Trying to understand the black to white transition in LQC

In LQG and LQC there are solutions called "black to white transition". I'll add some references:

(Rovelli)https://arxiv.org/abs/1905.07251
(Rovelli)https://arxiv.org/abs/2302.03872
(Rovelli)https://arxiv.org/abs/1803.06330
(Rovelli)https://arxiv.org/pdf/1802.04264
(Rovelli)https://arxiv.org/abs/2108.12823
https://arxiv.org/abs/2304.02691
https://arxiv.org/abs/2110.07589
https://arxiv.org/abs/2009.01788
https://arxiv.org/abs/1911.12646
https://arxiv.org/abs/1801.03027
https://arxiv.org/abs/2304.10692
https://arxiv.org/abs/1804.02821

A black hole described by GR that evaporates when quantum effects are added (the conventional description of an evaporating black hole), when the black hole reaches the Planck scale during its evaporation we can no longer assure that the spacetime geometry describes a collapse or an expansion, the LQG people propose that the quantum effects described by LQG will be dominant when that happens. Producing a "white transition".


I would like to know if the following 2 criticisms to this work are appropriate:

1- We don't know if the quantum effects described by LQG(LQC) exist in nature.

2- Even assuming that such effects exist in nature, the transition starts from a Schwarzschild black hole that doesn't exist in nature.

 

[javisot]

Another alternative description of the white transition process has been published, this time by unimodular gravity https://arxiv.org/abs/2409.03006

Sabine's video
seems to support this mechanism called "black to white transition".

It seems that we can construct "black to white transition" using either LQG or unimodular gravity, why? Is there some correspondence between both theories that allows us to construct the same transition or is it just a coincidence?

 

[kodama]

seems similar to planck relics

 

[PeterDonis]

seems similar to planck relics

You'll need to give more information (and preferably a reference) about this.

 

[Demystifier]

It seems that we can construct "black to white transition" using either LQG or unimodular gravity, why? Is there some correspondence between both theories that allows us to construct the same transition or is it just a coincidence?

Both are based on a version of Wheeler-DeWitt equation, in a manageable approximation with only a few degrees of freedom, so it is probably not a coincidence. In a full theory, with infinite (or huge) number of degrees of freedom, white hole corresponds to a process in which entropy decreases, which is what makes it unphysical. I suspect that approximations based on a few degrees of freedom cannot see this statistical prohibition of white holes, which makes me suspicious about such approximations.

 

[kodama]

You'll need to give more information (and preferably a reference) about this.

arXiv:1906.09930 (hep-ph)
[Submitted on 24 Jun 2019 (v1), last revised 26 Nov 2019 (this version, v3)]
Dark matter as Planck relics without too exotic hypotheses

 

[javisot]

arXiv:1906.09930 (hep-ph)
[Submitted on 24 Jun 2019 (v1), last revised 26 Nov 2019 (this version, v3)]
Dark matter as Planck relics without too exotic hypotheses

I found the following, it is recent, one of the authors is the always controversial Abraham Loeb, "Could Planck Star Remnants be Dark Matter?"
https://arxiv.org/abs/2506.03334