Black hole evaporation and the role of ultrashort distances

The role played by ultrahigh frequencies or ultrashort distances in the usual derivation of the Hawking effect is discussed. We demonstrate the robustness of Hawking's prediction of black-hole evaporation, by carrying out an explicit calculation, in which short-distance physics is explicitly regularized using the Pauli-Villars regularization scheme. We find that short-distance effects due to physics at small distance scales, 1/$ Lambda gg 1/T sb{H}$, where 1/$ Lambda$ is a covariantly chosen short-distance cutoff, can only contribute to the Hawking flux an amount that is exponentially suppressed by the large ratio $ Lambda$/$T sb{H}$. We argue further that this behavior is not specific to our choice of regularization, but is a generic feature of any covariant short-distance regularization. We do so by showing that no possible covariant and local counterterm exists which can contribute to the Hawking flux at late times far from the hole