Quantum Pressure by Black Holes
Accepting that the first direct detections of black holes just occurred this century, humanity can be forgiven for not understanding much about these enigmatic cosmic objects.
We don’t even know everything we don’t know, according to a recent discovery. A pair of researchers discovered that black holes exert quantum pressure on the universe around them while calculating equations for quantum gravity corrections for the entropy of black holes.
To be fair, it’s not much pressure – but it’s a fascinating result that backs up Stephen Hawking’s prediction that black holes emit radiation and hence have a temperature, as well as the ability to shrink over time in the absence of accretion.
Black Hole – Laws Fail
“Our discovery that Schwarzschild black holes have both a pressure and a temperature is even more fascinating given how unexpected it was,” said physicist and astronomer Xavier Calmet of the University of Sussex in the United Kingdom.
“If you consider black holes solely in terms of general relativity, you can show that they have a singularity in their centres where the laws of physics as we know them must fail,” Xavier added.
“It is thought that by incorporating quantum field theory into general relativity, we will be able to come up with a new description of black holes.”
Calmet and his University of Sussex colleague, physicist and astronomer Folkert Kuipers, were using quantum field theory calculations to try to explore the event horizon of a black hole when they discovered their finding.
How Quantum Pressure Identified?
They were attempting to comprehend the oscillations at a black hole’s event horizon that correct its entropy, a measure of the movement from order to disorder.
Calmet and Kuipers kept coming across an additional figure in their equations while completing these calculations, but it took them a while to realise what they were looking at – pressure.
“After months of dealing with it, the pin-drop moment when we realised that the mysterious result in our equations was informing us that the black hole we were researching had a pressure was euphoric,” Kuipers said.
It’s unknown what’s creating the pressure, and it’s quite little, according to the team’s calculations. Furthermore, it’s negative – -2E-46bar for a black hole the mass of the Sun, vs 1bar at sea level for Earth.
Black Hole- Shrinking
This indicates that the black hole would be shrinking rather than growing, as the name implies. That matches Hawking’s prediction, though it’s impossible to say how negative pressure connects to Hawking radiation at this time, or even if the two phenomena are linked.
However, the discovery could have important ramifications for our efforts to reconcile general relativity and quantum physics (at macro scales) (which operates on extremely small scales).
This project is supposed to need the use of black holes. The black hole singularity is a one-dimensional location of extremely high density where general relativity fails, but the gravitational field around it can only be represented relativistically.
Understanding how the two regimes interact could potentially aid in the solution of a particularly difficult black hole problem. Information lost beyond a black hole, according to general relativity, could be lost forever. It isn’t possible according to quantum mechanics. This is the black hole information dilemma, which could be solved by mathematically probing the space-time around a black hole.
“Our discovery is a step in this direction,” Calmet said, “and while the pressure imposed by the black hole we studied is negligible, the fact that it exists opens up a slew of new possibilities in astrophysics, particle physics, and quantum physics.”
The findings were reported in the journal Physical Review D.