A study is made of Hawking radiation from four-dimensional black holes using effective field theory methods. The trace anomaly for the stress tensor in a general curved spacetime background is reproduced using Riegert's action. The semiclassical stress tensor is evaluated in a Schwarzschild background taking a time-independent limit for the quantum state. Imposing physical boundary conditions on an initial Cauchy surface leads to a unique state, analogous to the Unruh state with a vanishing ingoing flux and a finite outgoing flux. In particular, there is no sign of quantum hair arising from this nonlocal effective action.
Lowe et al. (Mon,) studied this question.