Hi! I have to understand how this integral is evaluated (it is taken from Fetter - Quantum theory of many particle systems)(14.24): http://dl.dropbox.com/u/158338/fis/fetter.pdf" [Broken] in particular, i don't know how the log brach cuts are defined.. as far as I know, log branch cuts can be define as the regions at fixed log argument.. (i.e. -inf to 0 for [-pi;pi[). Gnuplot says that the "natural" branch cut ([-pi;pi[) is the discontiunous line in this pic: http://dl.dropbox.com/u/158338/fis/arg-rminus.png" [Broken] ideas? thanks!