A Note on Open Strings in the Presence of Constant B-Field
  We consider the open string sigma-model in the presence of a constant Neveu-Schwarz B-field on the world-sheet that is topologically equivalent to a disk with n holes. First, we compute the sigma-model partition function. Second, we make a consistency check of ideas about the appearance of noncommutative geometry within open strings. 
Oleg Andreev