Extremal black holes are at zero temperature, hence they do not radiate.
my question is twofold:
1) is extremality of micro black holes a stable property? electric charge is quickly emitted from sub-atomic black holes due to Schwinger pair production, what about angular momentum? does a black hole loses its extremality quickly or slowly (compared to its evaporation time)?
2) can a black hole extremality state be changed by external sources? can we add matter and angular momentum appropiately to a schwarszchild black hole in order to become extremal or nearly-extremal? can we do the inverse process?