Black holes galore in D>4

Abstract

The black hole solutions to Einstein’s vacuum equations in four dimensions contain just one example: the Kerr black hole. Over the past two decades, we have understood that higher-dimensional black holes are far more plentiful. I give a straightforward account of the reasons for this abundance based on three key ideas: (i) Horizons in can be long. (ii) Long horizons are flexible. (iii) Long horizons are unstable. I conclude with some comments and conjectures about the classification problem.