Comment on the Damour-Ruffini treatment of black-hole evaporation

The approach of Damour and Ruffini to the problem of black-hole evaporation is examined, and it is shown that the hypothesis of analytic continuation of the wave function inside the horizon cannot be considered as an extension of the same hypothesis in the flat-space case, but is an independent requirement. This requirement enters in the second-quantization treatment given by Hawking as the definition of the Fock vacuum state. An alternative definition of vacuum yields no pair production