Topological nature of the Hawking temperature of black holes

In this work, we determine that the Hawking temperature of two-dimensional black holes possesses a purely topological nature. We find a very simple but powerful formula, based on a topological invariant known as the Euler characteristic, which is able to provide the exact Hawking temperature of any two-dimensional black hole - and, in fact, of any metric that can be dimensionally reduced to two dimensions - in any given coordinate system, introducing a covariant way to determine the temperature only using virtually trivial computations. We apply the topological temperature formula to several known black hole systems as well as to the Hawking emission of solitons of integrable equations.