Supersymmetry, spectrum and fate of D0-Dp systems with B-field

It has been shown that DO-Dp (p = 2, 4, 6, 8) systems can be BPS in the pre sence of B-field even if they are not otherwise. We review the number of re maining supersymmetries, the open string ground state spectrum and the cons truction of the DO-Dp systems as solitonic solutions in the noncommutative super-Yang-Mills theory. We derive the complete mass spectrum of the fluctu ations to discuss the stability of the systems. The results are found to ag ree with the analysis in the string picture. In particular, we show that su persymmetry is enhanced in D0-D8 depending on the B-fields and it is consis tent with the degeneracy of mass spectrum. We also derive potentials and di scuss their implications for these systems. (C) 2001 Elsevier Science B.V. All rights reserved.