Is there, theoretically, a lower bound on the mass of a black hole? Or could you have a black hole that weights the same as an electron for example?
1 Answer
We don’t know.
Dimensional analysis suggests a black hole should finish its Hawking evaporation somewhere around the Planck mass. But without a theory of quantum gravity, we don’t know whether there is some prefactor like $\frac12$ or $\frac{2^{10}}{5^4}$ out front. It could also be that the gravitational constant $G$ is different at short distances, so that our prediction of the Planck mass is wrong.