Almost half a century has passed since Stephen Hawking discovered one of the most important paradoxes in physics. For half a century, researchers have been tearing their hair out trying to solve this riddle, which over the years has led some to question two of the most fundamental laws of physics: Einstein’s laws of general relativity and the laws of quantum theory. Mechanics.
Since the publication on Thursday, March 22, two studies in journals Physics letters B as well as Physical Review Letters, researchers around the world who have been busy solving the so-called “information paradox” until now will finally see that their scalps are spared. Astrophysicist Xavier Calmette of the University of Sussex, Roberto Casadio of the University of Bologna and Stephen Hsu of the University of Michigan claim to have solved a well-known problem by demonstrating that black holes have a property called “quantum hair”. The case is clearly capillary. If these results turn out to be correct, it will be a huge step forward in theoretical physics.
Black holes were originally thought to be “bald”
From the 1916 announcement of the theories about these extreme stars by Karl Schwarzschild and the first results demonstrating their existence by Robert Oppenheimer twenty years later, black blacks have been considered among the simplest in the universe. This is why, in the 1960s, several physicists, especially in the Soviet world, formulated the “hairless black hole theorem” or “baldness theorem.” This means that a black hole is described by only three parameters: mass, electric charge, and angular momentum (or spin). In short, he does not have “hair”, which is considered one of the signs that distinguish one person from another. Because whatever its method of formation and the nature of what was used to form it, it absorbs and “erases” all the characteristics of the matter that enters it.
Almost half a century has passed since Stephen Hawking discovered one of the most important paradoxes in physics. For half a century, researchers have been tearing their hair out trying to solve this riddle, which over the years has led some to question two of the most fundamental laws of physics: Einstein’s laws of general relativity and the laws of quantum theory. Mechanics.
Since the publication on Thursday, March 22, two studies in journals Physics letters B as well as Physical Review Letters, researchers around the world who have been busy solving the so-called “information paradox” until now will finally see that their scalps are spared. Astrophysicist Xavier Calmette of the University of Sussex, Roberto Casadio of the University of Bologna and Stephen Hsu of the University of Michigan claim to have solved a well-known problem by demonstrating that black holes have a property called “quantum hair”. The case is clearly capillary. If these results turn out to be correct, it will be a huge step forward in theoretical physics.
Black holes were originally thought to be “bald”
From the 1916 announcement of the theories about these extreme stars by Karl Schwarzschild and the first results demonstrating their existence by Robert Oppenheimer twenty years later, black blacks have been considered among the simplest in the universe. This is why, in the 1960s, several physicists, especially in the Soviet world, formulated the “hairless black hole theorem” or “baldness theorem.” This means that a black hole is described by only three parameters: mass, electric charge, and angular momentum (or spin). In short, he does not have “hair”, which is considered one of the signs that distinguish one person from another. Because whatever its method of formation and the nature of what was used to form it, it absorbs and “erases” all the characteristics of the matter that enters it.
So far everything has been fine. But in 1976, Stephen Hawking put his finger on a bone, a big one. A few years earlier, he had been able to demonstrate that black holes are not all that black after all: they do emit a small amount of radiation. Nicknamed “Hawking radiation” (or Bekenstein-Hawking, for those who prefer not to omit the name of the physicist who created the spark in Einstein) and coming from a region close to the event horizon, this radiation is needed as proof that the black hole is inexorably evaporating. to the point that in the very, very distant future, it will completely disappear. However, the fact that information can be forever carried away by the evaporation of a black hole is completely inconsistent with the laws, this time, of quantum mechanics!
Rewind, any movie
Why ? Because physicists believe that in quantum mechanics it is always possible to reverse the course of events, to trace their thread so as to always be able to determine the states that precede this state. And this, despite the violence and complexity of these very events. This is one of the postulates of quantum mechanics, which is based on the deterministic Schrödinger equation. In fact, when a star collapses on itself at the end of its life, quantum mechanics tells us that we should be able to find, inside the black hole itself, in the form of information, everything that was specific to the star during its lifetime. . However, as the author has shownBrief history of timeThe law of gravity, applied here to a black hole, tells us just the opposite.
“At the time Hawking formulated his paradox, it seemed that there were only two options: either Einstein’s law of relativity is wrong, or quantum mechanics, as we have defined it, does not work.”explains Science and the future Xavier Calmet, lead author of both articles. In any case, the prospect was terrifying, since the theories of gravity and those that govern the quantum world were the pillars upon which our understanding of the universe rests. Over the past decades, many ideas have been proposed to solve the information paradox without touching these two solid theoretical buildings. “Some are crazier than others”, comments Xavier Calmet. Among them are the hypothesis of the existence of a “wall of fire” through which information would be absorbed before falling into a black hole, various theories associated with exotic branches of string theory, or even the possibility that black holes simply do not exist. “We have just demonstrated that we do not need to speculate on new physics. Everything is explained by the laws of gravity and quantum mechanics.”the astrophysicist assures enthusiastically.
fossil footprint
For more than ten years, he and his team have been working on the development of complex equations based on methods specific to quantum field theory. They had to proceed from only one postulate: with the general theory of relativity, Einstein was right. According to their calculations, even if absorbed by a black hole, matter would leave a faint imprint in the star’s gravitational field. A fingerprint called “quantum hair” or “quantum hair” that will make black hole objects much more complex and specific than previously thought.
“We have identified a quantum mechanism that demonstrates that information is stored.”
To come to this conclusion, the team started with a problem: how to distinguish between two black holes formed by two stars of the same mass, the same diameter, but different composition? “We have mathematically demonstrated that the gravitational field of a black hole has a memory of the star’s composition.”explains Xavier Calmet. “That is, two black holes with the same mass and radius but different internal composition will exhibit very subtle differences in their gravitational field.” Therefore, matter, even crushed and swallowed by a black hole, would leave a kind of “quantum fossil signature” of its passage. Information stored in this way is no longer Hawking’s paradox.
“I think it will be difficult for many to accept such a conservative proposal”, says Xavier Calmet, at a time when many working groups are still working on the question of the paradox of information, relying either on much more radical theories or far from the standard model of physics. Moreover, if the work of Xavier Calmette and his team leads to consensus, they may be the first step towards unifying the theories of general relativity and quantum mechanics in the framework of the grand unified theory. Undoubtedly the greatest fantasy of physicists in over a century.