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Given that our first direct detections confirming the existence of black holes only took place in this century, humanity can be forgiven for not knowing certain things about these mysterious cosmic objects.
We don’t even know everything we don’t know – a fact that has become evident in a new discovery. Running equations for quantum gravity corrections for the entropy of a black hole, two physicists discovered that black holes put pressure on the space around them.
Not a lot of pressure, of course – but it’s a finding that is fascinating with Stephen Hawking’s prediction that black holes emit radiation and therefore not only have a temperature, but slowly shrink over time, in the absence of accretion.
“Our discovery that Schwarzschild black holes have pressure as well as temperature is even more exciting given that it was a total surprise,” said physicist and astronomer Xavier Calmet of the University of Sussex in the UK. .
“If you consider black holes in general relativity alone, we can show that they have a singularity in their centers where the laws of physics as we know them have to break down.
“We hope that when quantum field theory becomes part of general relativity, we may be able to find a new description of black holes.”
When they made their discovery, Calmet and his colleague at the University of Sussex, physicist and astronomer Folkert Kuipers, were performing calculations using quantum field theory to try and probe the event horizon of a black hole. .
Specifically, they were trying to understand the fluctuations on a black hole’s event horizon that correct its entropy, a measure of the progression from order to disorder.
While performing these calculations, Calmet and Kuipers continued to encounter an additional number that appeared in their equations, but it took a while for them to recognize what they were looking at – the pressure.
“The moment we realized that the mysterious result of our equations was telling us that the black hole we were studying was under pressure – after months of struggling with it – was exhilarating,” Kuipers said.
It’s unclear what’s causing the pressure, and by the team’s calculations, it’s very low. Moreover, it is negative – expressed by -2E-46bars for a black hole the mass of the Sun, compared to the bar 1 of the Earth at sea level.
It means exactly what it seems to mean – the black hole would shrink, not grow. This is consistent with Hawking’s prediction, although at this point it is impossible to determine how negative pressure relates to Hawking radiation, or even if the two phenomena are related.
However, this discovery could have interesting implications for our attempts to square general relativity (at macro scales) with quantum mechanics (which operates at extremely small scales).
Black holes are seen as the key to this business. The singularity of the black hole is mathematically described as a one-dimensional point of extremely high density, at which point general relativity collapses – but the gravitational field around it can only be described relativistically.
Figuring out how the two regimes fit together could also help solve a really thorny black hole problem. According to general relativity, information that disappears beyond a black hole could disappear forever. In quantum mechanics, this is not possible. It’s the black hole information paradox, and the mathematical exploration of space-time around a black hole could help solve it.
“Our work is a step in that direction,” Calmet said, “and while the pressure from the black hole we are studying is minimal, the fact that it is present opens up multiple new possibilities, spanning the study of astrophysics, particle physics and quantum physics. “
The research was published in Physical examination D.
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