beecee Posted January 5, 2022 Posted January 5, 2022 https://phys.org/news/2022-01-black-hole-fuzzball-wormhole-debate.html Resolving the black hole 'fuzzball or wormhole' debate: The study attempts to put to rest the debate over Stephen Hawking's famous information paradox, the problem created by Hawking's conclusion that any data that enters a black hole can never leave. This conclusion accorded with the laws of thermodynamics, but opposed the fundamental laws of quantum mechanics. "What we found from string theory is that all the mass of a black hole is not getting sucked in to the center," said Samir Mathur, lead author of the study and professor of physics at The Ohio State University. "The black hole tries to squeeze things to a point, but then the particles get stretched into these strings, and the strings start to stretch and expand and it becomes this fuzzball that expands to fill up the entirety of the black hole." The study, published Dec. 28 in the Turkish Journal of Physics, found that string theory almost certainly holds the answer to Hawking's paradox, as the paper's authors had originally believed. The physicists proved theorems to show that the fuzzball theory remains the most likely solution for Hawking's information paradox. The researchers have also published an essay showing how this work may resolve longstanding puzzles in cosmology; the essay appeared in December in the International Journal of Modern Physics. more at link..... the paper: https://journals.tubitak.gov.tr/physics/abstract.htm;jsessionid=1060E4C8647824F1697AE550C414D174?id=30416 Contrasting the fuzzball and wormhole paradigms for black holes Authors: BIN GUO, MARCEL HUGHES, SAMIR MATHUR, MADHUR MEHTA Abstract: We examine an interesting set of recent proposals describing a `wormhole paradigm' for black holes. These proposals require that in some effective variables, semiclassical low-energy dynamics emerges at the horizon. We prove the `effective small corrections theorem' to show that such an effective horizon behavior is not compatible with the requirement that the black hole radiate like a piece of coal as seen from outside. This theorem thus concretizes the fact that the proposals within the wormhole paradigm require some nonlocality linking the hole and its distant radiation. We try to illustrate various proposals for nonlocality by making simple bit models to encode the nonlocal effects. In each case, we find either nonunitarity of evolution in the black hole interior or a nonlocal Hamiltonian interaction between the hole and infinity; such an interaction is not present for burning coal. We examine recent arguments about the Page curve and observe that the quantity that is argued to follow the Page curve of a normal body is not the entanglement entropy but a different quantity. It has been suggested that this replacement of the quantity to be computed arises from the possibility of topology change in gravity which can generate replica wormholes. We examine the role of topology change in quantum gravity but do not find any source of connections between different replica copies in the path integral for the Rényi entropy. We also contrast the wormhole paradigm with the fuzzball paradigm, where the fuzzball does radiate like a piece of coal. Just as in the case of a piece of coal, the fuzzball does not have low-energy semiclassical dynamics at its surface at energies E∼TE∼T (effective dynamics at energies E≫TE≫T is possible under the conjecture of fuzzball complementarity, but these E≫TE≫T modes have no relevance to the Page curve or the information paradox).
MigL Posted January 6, 2022 Posted January 6, 2022 I'm fairly certain that C Rovelli, a proponent of LQG also shows that BHs can only collapse to a certain point, and then must 'bounce, to something similar to a White Hole, but in the past, also preserving information. This is similar to the 'bounce' that LQG predicts as the initiator of the Big Bang, but I cannot recall where I read this. The problem is that both String theory and LQG are 'theories in search of a universe to describe'. They are both getting more and more elaborate, but there is no experimental verification of even their most basic presumptions.
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