"Quantum hair" may solve Hawking's black hole paradox

Stephen Hawking's black hole information paradox has puzzled scientists for half a century and led some to question the fundamental laws of physics. Now, physicists at the University of Sussex in the UK say they may have solved the famous problem, demonstrating that black holes possess a property known as 'quantum hair'.

If correct, this would mark a major advance in theoretical physics.

Professor Xavier Calmet from the University of Sussex, who led the research, said that after 10 years of researching the mathematics behind the problem, the rapid progress his team made last year gave them the confidence to finally solve the problem.

"There is a general consensus in the scientific community that solving this paradox will require a huge paradigm shift in physics, forcing a potential reconfiguration of quantum mechanics or general relativity," Calmet said. "What we found -- and I think it's particularly exciting -- is that there is no necessary."

Hawking's black hole paradox boils down to the following: The laws of quantum physics state that information is conserved. Black holes challenge this law because once an object enters a black hole, it's basically gone forever -- and any information encoded in it. Hawking discovered this paradox, and it has puzzled scientists for decades.

The 2019 Event Horizon telescope captured an image of the light surrounding the black hole at the center of the galaxy M87

Countless solutions have been proposed, including the "firewall theory," which assumes that information burns up before entering the black hole, where black holes are thought to have fuzzy boundaries, and the various aspects of string theory. strange branch.

But most of these proposals require rewriting the laws of quantum mechanics, or Einstein's theory of gravity, two pillars of modern physics.

In contrast, the quantum hair theorem claims to resolve the paradox by bridging the gap between general relativity and quantum mechanics using a new mathematical formula.

The name is a nod to the classical physics-based view that black holes can be viewed as surprisingly simple objects, defined only by their mass and rotational speed. Predictions of bare, featureless black holes have been dubbed the "No-hair theorem" since the 1970s.

Calmet and his collaborators think black holes are more complex—or grosser. They believe that when matter collapses into a black hole, it leaves a faint imprint in the gravitational field.

The imprint is called "quantum hair," and the authors say it will provide a mechanism by which information is preserved during the black hole's collapse. According to this theory, two black holes with the same mass and radius, but with different internal compositions, will have very subtle differences in their gravitational fields.

"Our solution does not require any speculative thinking; instead, our study shows that the two theories can be used to make consistent calculations about black holes and explain how information is stored, without radical New physics theories."

There is currently no obvious way to test this theory through astronomical observations, because the gravitational fluctuations are too small to measure. But the theory is likely to come under intense scrutiny from the theoretical community.

Professor Toby Wiseman, a theoretical physicist at Imperial, called the paper "a good piece of work" but was still not convinced it solved a decades-old paradox.

Crucially, he said, the paper showed that it might be possible to gain some additional information about the inside of a black hole, but did not show that the phenomenon could explain all the information that was apparently lost. "They don't show it, and that's the crux of the paradox," he said.

"My feeling is that to really solve this paradox, you have to fully understand how quantum mechanics and gravity fit together," he said. "They're looking for small corrections, but not a full combination of the two."

"When you have a big claim, you have to support it," Calmet said. "It takes a while for people to fully embrace it. This paradox has been around for a long time, and very famous people around the world have been studying it for years. this problem."

The research was published in the journal Physical Review Letters [1].

Link:

[1] https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.128.111301

[2]https://www.theguardian.com/science/2022/mar/17/quantum-hair-could-resolve-stephen-hawking-black-hole-paradox-say-scientists