Ive taken a general relativity course and in it we learned about how black holes are characterized by the parameters of mass, angular momentum, and charge. I have some questions about other parameters though. 1) Can a black hole have a vibrational parameter? This would really only be applicable in a rotating black hole, where the singularity is a ring rather than a point. It seems to me that some massive object could cause vibrations in this ring by exerting a greater force on the close end than on the far end. Even if this scenario isn't the explanation, can black holes vibrate? And if so, what are the modified equations using this vibration? 2) In a frame of reference that is moving relative to a black hole, does the black hole appear differently? i.e. are the equations describing the black hole modified at all? Since the relativistic mass gained by the black hole is not uniform in all directions (I recall seeing a picture of an ellipsoid to describe it), it seems like the black hole might appear differently in a moving frame and Id be interested to see the limit of this difference as the speed approaches c. 3) Are there any other parameters of black holes besides mass, angular momentum, charge (and possibly vibration and speed)?