At the University of Sussex, physicists have found, in a scientific first, that black holes exert pressure on their environment.
Professor Xavier Calmet. Image Credit: University of Sussex.
In 1974, Stephen Hawking achieved the seminal breakthrough that black holes discharge thermal radiation. Before this discovery, black holes were considered to be inert, the final stages of a dying hefty star.
Researchers from the University of Sussex have now shown that they are indeed highly complicated thermodynamic systems, with not only temperature but also pressure.
The unexpected breakthrough was made by Professor Xavier Calmet and Folkert Kuipers in the Department of Physics and Astronomy at the University of Sussex. The study has been recently reported in the journal Physical Review D.
Calmet and Kuipers were puzzled by an additional figure that was presented in equations that they were running on quantum gravitational corrections to the black hole’s entropy.
When a discussion was held on this curious result on Christmas Day 2020, the realization that what they were seeing was behaving as a pressure dawned. After additional calculations, they verified their interesting discovery that quantum gravity can result in pressure in black holes.
Our finding that Schwarzschild black holes have a pressure as well as a temperature is even more exciting given that it was a total surprise. I’m delighted that the research that we are undertaking at the University of Sussex into quantum gravity has furthered the scientific communities’ wider understanding of the nature of black holes.
Xavier Calmet, Professor of Physics, University of Sussex
Calmet continued, “Hawking’s landmark intuition that black holes are not black but have a radiation spectrum that is very similar to that of a black body makes black holes an ideal laboratory to investigate the interplay between quantum mechanics, gravity and thermodynamics.”
“If you consider black holes within only general relativity, one can show that they have a singularity in their centers where the laws of physics as we know them must breakdown. It is hoped that when quantum field theory is incorporated into general relativity, we might be able to find a new description of black holes,” added Calmet.
“Our work is a step in this direction, and although the pressure exerted by the black hole that we were studying is tiny, the fact that it is present opens up multiple new possibilities, spanning the study of astrophysics, particle physics and quantum physics,” concluded Calmet.
According to Folkert Kuipers, a doctoral researcher in the School of Mathematical and Physical Science at the University of Sussex, “It is exciting to work on a discovery that furthers our understanding of black holes– especially as a research student.”
“The pin-drop moment when we realized that the mystery result in our equations was telling us that the black hole we were studying had a pressure after months of grappling with it–was exhilarating,” added Kuipers.
“Our result is a consequence of the cutting-edge research that we are undertaking into quantum physics at the University of Sussex and it shines a new light on the quantum nature of black holes,” concluded Kuipers.