Quasi-classical Hawking Temperatures and Black Hole Thermodynamics

The semi-classical derivation of Hawking radiation for axially symmetric, stationary spacetimes with a Killing horizon is examined following the recent quasi-classical tunneling analysis and a simple formula is found for the inverse Hawking temperature $\beta =1\mathrm{/}{T}_H$. The formula is invariant under canonical transformations and is shown to be equivalent to the integral of a closed differential 1-form around the horizon enclosing a pole. The Hawking temperature is then given in terms of the winding number in the first homotopy group of the torus formed from the compactified imaginary parts of the analytically continued radial and time variables.