One of physicist Stephen Hawking’s most famous paradoxes may finally be solved: Black holes may actually be clinging to information about the massive stars that created them, according to new research.
The research suggests that this information may be lurking in the radiation around black holes – known colloquially as “quantum hair” – and could, in theory, be retrieved to recount the origins of those black holes.
These results were published March 6 in the journal Nature Physics letters b. (Opens in a new tab)may finally solve a thorny problem that Hawking has been working on in his later years.
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According to Hawking’s work, radiation slowly “leaks” out of black holes in the form of heat energy, which has become known as “Hawking radiation”. But due to its thermal nature, this radiation cannot transmit information. This means that as black holes evaporate, they systematically destroy all information about the stars that created them. This is against the laws of quantum mechanics, which state that information cannot be destroyed and that an object’s final state can reveal clues about its initial state. This problem has troubled cosmologists for decades and is known as the “Hawking information paradox”.
“[This research] is the final nail in the coffin of the paradox because we now understand the exact physical phenomenon by which information escapes from a decaying black hole,” said the study’s lead author. Xavier Calmette (Opens in a new tab), Professor of Physics at the University of Sussex, told Live Science via email. He proposes a modification of Hawking radiation to make it “non-thermal” and thus able to carry information with it away on the black hole’s eventual fate.
The black hole problem
black holes They are objects so massive that nothing can escape their gravity, not even light. They form when massive stars run out of fuel and collapse in on themselves.
In classical physics, black holes are “very simple things,” Calmette said. “So simple that it can be distinguished by three numbers: its mass, its angular momentum, and its electric charge.”
Famed physicist John Wheeler described this lack of characteristic by saying, “Black holes have no hair.” But, Calmette explained, while the final black hole is very simple, the parent star that spawned it is a complex astrophysical object, made up of a complex mix of protons, electrons, and neutrons that clump together to form the elements that build up the chemical composition. from that star.
While black holes do not hold any “memory” of the stars they once were, the rules of quantum physics state that information cannot simply be erased from the universe. In 1976, Hawking provided a fly for this cosmic ointment by showing that this information could not survive indefinitely inside closed black holes far from the outer universe either. Applying the rules of quantum mechanics to black holes, Hawking proposed that they emit a type of thermal radiation, which he later called Hawking radiation. Over long periods of time, the leakage of this radiation causes black holes to completely evaporate, leaving only a void behind. In this way, the information is irretrievably lost.
“However, this is not allowed by quantum physics, which assumes that the ‘life’ of this black hole can be rewound,” Calmette said. “Starting from the radiation, we should be able to reconstruct the original black hole and eventually the star.”
The search for the “hair” of the black hole
with his mate Steve Hsu (Opens in a new tab), a professor of theoretical physics at Michigan State University, has been working as a dead man since 2021 to crack Hawking’s paradox. In a previous study published in March 2022, the team argued that black holes You already have “quantum hair”, in the form of a unique quantum fingerprint in the gravitational fields that surround them
In their new paper, the team re-evaluated Hawking’s 1976 calculations, but this time they took into account the effects of “quantum gravity”—the description of gravity according to quantum mechanical principles—something Hawking did not.
“While these quantum gravitational corrections are very small, they are essential to the evaporation of a black hole,” Calmette said. “We have been able to show that these effects modify Hawking radiation so that this radiation becomes non-thermal. In other words, radiation is factored into quantum gravity.” Can contain information.”
While the quantum poetry proposed in Calmitand-Hsu’s previous work was an abstract mathematical concept, the team has now identified the exact physical phenomenon by which information escapes a black hole via Hawking radiation, and how it can be retrieved by an outside observer. This is not currently possible, as it would require a sufficiently sensitive instrument to measure Hawking radiation, which is currently theoretical.
Calmette acknowledged that there is currently no real way for astrophysicists to measure the effect the researchers suggest, because it is so small. Instead, he suggests, one way to develop this theory is to study simulations of black holes in labs on Earth. The team’s mathematical modeling of Hawking radiation and black holes could be invaluable in this simulation.
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