Main Question or Discussion Point
In the book General Relativity by Norbert Straumann, He derives the Kerr's solution in the chapter about black holes and then modifies it to get the Kerr-Newman solution. Then he calculates the g-factor of a rotating charged black hole using the Kerr-Newman solution(and gets the amazing result 2). But all along the way, he calls the gravitating body a black hole. But these solutions aren't only for black holes right? So he only calls the object black hole because he's doing all of these things in the black holes' chapter? If this is correct, so any rotating charged object has g-factor 2 in GR? In contrast to classical physics where there is no g?