There is no "positive" or "negative" mass. They are both virtual. Their sum-total energy is zero.
Virtual pairs appear and disappear all the time. They are like water boiling in a pot making foam; there are virtual "bubbles" everywhere around you. As long as they disappear back into nothingness, everything about them is virtual.
It's only that the event horizon throws a snag into the mechanism, and swallows up one of the particles, thereby preventing recombination. The only way for that to happen is that if the other particle gets promoted from virtual to real. The only way that could happen is if the black hole itself provides the required energy to make that particle real.
Again, the BH does not pick "positive" vs "negative" mass. It just swallows up one random member of a virtual pair. The other member, left alone, cannot recombine; it sucks up some energy from the BH's gravitational field and becomes a real particle, with positive energy and mass.
To sum it up, it's the virtual pair "foam" that slowly sucks up energy from the BH.
Virtual pairs appear and disappear all the time. They are like water boiling in a pot making foam; there are virtual "bubbles" everywhere around you. As long as they disappear back into nothingness, everything about them is virtual.
It's only that the event horizon throws a snag into the mechanism, and swallows up one of the particles, thereby preventing recombination. The only way for that to happen is that if the other particle gets promoted from virtual to real. The only way that could happen is if the black hole itself provides the required energy to make that particle real.
Again, the BH does not pick "positive" vs "negative" mass. It just swallows up one random member of a virtual pair. The other member, left alone, cannot recombine; it sucks up some energy from the BH's gravitational field and becomes a real particle, with positive energy and mass.
To sum it up, it's the virtual pair "foam" that slowly sucks up energy from the BH.