Calmet and his graduate student Folkert Kuipers were examining quantum effects near the event horizons of black holes, something that is fiendishly hard to pin down. To tackle this, the researchers employed a technique to simplify their calculations. As they were working, a strange term appeared in the mathematics of their solution. After months of confusion, they realized what this newly discovered term meant: It was an expression of the pressure produced by a black hole. Nobody had known this was possible before, and it changes the way scientists think about black holes and their relationships with the rest of the universe.
Perhaps one of the @physicists can sort out my confusion on a key point. I don’t understand the presumption that Black Holes don’t produce pressure. I thought Hawking’s argument made clear that they did.
This is my naive understanding. Pairs of particles are popping into existence and the annihilating each other all the time. At the event horizon of a black hole, one particle can fall into the black hole, while the other speeds away. So they can’t annihilate each other. Ergo Hawking radiation.
But that’s also a clear argument for pressure too. The radiation exerts pressure. Of course it is tiny in comparison to gravity, but that’s the case here too.
So what is new here exactly? It can’t be the idea that black holes exert pressure, is it?
Perhaps they found more pressure than exerted by Hawking radiation alone? Or perhaps it is by a different mechanism?