Partition Function of the Reissner-Nordstr\"om Black Hole
  We consider a microscopic model of a stretched horizon of the Reissner-Nordstr\"om black hole. In our model the stretched horizon consists of discrete constituents. Using our model we obtain an explicit, analytic expression for the partition function of the hole. Our partition function implies, among other things, the Hawking effect, and provides it with a microscopic explanation as a phase transition taking place at the stretched horizon. The partition function also implies the Bekenstein-Hawking entropy law. The model and its consequences are similar to those obtained previously for the Schwarzschild black hole. 
Jarmo Makela
gr-qc