Open String and Morita Equivalence of the Dirac-Born-Infeld Action with Modulus \Phi

Based on the canonical quantization of open strings ending on D-branes with a background B field, we construct the open string propagator. We demonstrate the relation between the T duality of the underlying string theory and the Morita equivalence of the interpolating general Dirac-Born-Infeld theory on a noncommutative torus in the nonzero modulus \Phi sector. The general noncommutative Dirac-Born-Infeld action with the Wess-Zumino terms expressed by the background R-R fields is shown to be Morita invariant.