Effective action and Hawking radiation for dilaton coupled scalars in two dimensions

The effective one-loop action for general dilaton theories with an arbitrary dilaton-dependent measure and nonminimal coupling to scalar matter is computed. As an application we determine the Hawking flux to infinity from black holes in D dimensions. We resolve the recently resurrected problem of an apparent negative flux for nonminimally coupled scalars: For any $D>~4$ black hole the complete flux turns out to be precisely the one of minimal coupling. This result is obtained from a Christensen-Fulling type argument involving the (non)conservation of energy-momentum. It is compared with approaches using the effective action.