Tubular Solutions in NS5-brane, Dp-brane and Macroscopic Strings Background

We present our searches for the tubular bound states of a D2-brane with m D0-brane and n fundamental strings in the NS5-brane, Dp-brane or macroscopic strings backgrounds by solving the Dirac-Born-Infeld equation. The geometry of tubular configurations we considered are taken to be parallel to the background branes or macroscopic strings. The n fundamental strings therein may be the circular strings Fc or the straight strings Fs, which are along the cross section or the axis of the tube respectively. We show that the stable tubular bound states of (nFs, mD0, D2) which are prevented form collapse by the angular momentum, as original found in flat space, could be formed in the NS5-brane, D6-brane and macroscopic strings background. However, they becomes unstable in the D2-brane and D4-brane background. We also show that the classically stable tubular bound states of (nFc, mD0, D2) could be prevented form collapse by the forces in the backgrounds of D6-brane or macroscopic strings. There are also the stable tubular bound states of (mD0, D2) which could be found, however, only in the D6-brane background. Among these tubular solutions only that in the macroscopic strings background is a supersymmetric BPS configuration. E-mail: [email protected]