Spectral Functions for BTZ Black Hole Geometry
  Using an orbifold description of the Euclidean BTZ black hole, we show that there is a special relation between the spectrum and the truncated heat kernel of this black hole with the Patterson-Selberg zeta function. 
A. A. Bytsenko (DF/UEL), M. E. X. Guimaraes (MAT/UnB) and F. L.   Williams (Univ. Massachusetts, Amherst, USA)