Hawking temperature in the tunneling picture

We examine Hawking radiation from a Schwarzschild black hole in several reference frames using the quasi-classical tunneling picture. It is shown that when one uses, Gamma proportional to exp(Im[closed integral p dr]), rather than, Gamma proportional to exp(2Im[integral p dr]), for the tunneling probability/decay rate one obtains twice the original Hawking temperature. The former expression for Gamma is argued to be correct since integral p dr is invariant under canonical transformations, while integral p dr is not. Thus, either the tunneling methods of calculating Hawking radiation are suspect or the Hawking temperature is twice that originally calculated. (c) 2006 Elsevier B.V. All rights reserved.