No abstract

In this paper we give the boundary string field theory description of braneantibrane systems. From the world-sheet action of brane-antibrane systems we obtain the tachyon potential and discuss the tachyon condensation exactly. We also find the world-volume action including the gauge fields. Moreover we determine RR-couplings exactly for non-BPS branes and brane-antibranes. These couplings are written by superconnections and correspond to K 1 (M ) and K 0 (M ) for the non-BPS branes and brane-antibranes, respectively. We also show that Myers terms appear if we include the transverse scalars in the boundary sigma model action.

In this paper we explicitly show that the various noncompact abelian orbifolds are realized as special limits of parameters in type II (NSNS) Melvin background and its higher dimensional generalizations. As a result the supersymmetric ALE spaces (A-type C 2 /Z N ) and nonsupersymmetric orbifolds in type II and type 0 theory are all connected with each other by the exactly marginal deformation. Our results provide new examples of the duality between type II and type 0 string theory. We also discuss the decay of unstable backgrounds in this model which include closed string tachyons.