On open string sigma-model and noncommutative gauge fields

We consider the ordinary and noncommutative Dirac-Born-Infeld theories with in the open string sigma-model. First, we propose a renormalization scheme, hybrid point splitting regularization, that leads directly to the Seiberg- Witten description including the two-form Phi. We also show how such a form appears within the standard renormalization scheme just by some freedom in changing variables. Second, we propose a Wilson factor which has the nonco mmutative gauge invariance on the classical level and then compute the sigm a-model partition function within one of the known renormalization scheme t hat preserves the noncommutative gauge invariance. As a result, we find the noncommutative Yang-Mills action, (C) 2000 Published by Elsevier Science B .V. Ail rights reserved.