Earlier quoted context omitted.
I imagine this holds only for black holes that are massive enough to be stable? All those itsy bitsy ones created by the LHC, they've evaporated, yes?
Correct. It's not so much that the small ones are unstable, but just that there's a continuous curve of lifetimes that's a function of mass. For the LHC, the lifetime of a black hole it could conceivably create would be 10^-86 seconds. It didn't even do that, but if it had, it would have evaporated before it moved the diameter of an electron. There's no functional difference between that black hole and a vastly bigge…
> Black holes [above a certain mass] can't evaporate now because the cosmic background radiation is too hot
And that mass--the Stable-Black-Hole-In-A-Vacuum mass--it's decreasing. And whatever it is at a given time, more massive holes grow, and less massive holes shrink. Do I have that right?
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I'm trying to extrapolate backwards to a time when the universe was hotter and the SBHIAV mass was smaller. It seems like there ought to have been a point when the universe was so hot that holes expanded greedily, perhaps to the point where the expanding universe couldn't escape. Golly I wish they taught cosmology at my local university...