Abstract :
By intersecting the RR charged Dp–Dp pair (p=6,4,2,0) with the RR F7-brane and by intersecting the NSNS charged F1–F1 and NS5–NS5 pairs with the NSNS F6-branes, the possibility of stabilizing the brane–antibrane systems is considered. The behavior of the corresponding supergravity solutions indicates that the RR F7-brane content of the solution plays the role of keeping the brane and the antibrane from annihilating each other completely since the two-brane configuration structure still persists in the vanishing inter-brane distance limit of the supergravity solution. In terms of the stringy description, we interpret this as representing that the RR F7-brane “delays” the brane–antibrane annihilation process but only until this non-supersymmetric and hence unstable F7-brane itself decays. Then next, the behavior of the supergravity solutions representing F1–F1 and NS5–NS5 again for vanishing inter-brane separation reveals that as they approach, these “NS”-charged brane and antibrane always collide and annihilate irrespective of the presence or the absence of the NSNS F6-brane. And we have essentially attributed this to the absence of (open) stringy description of the instability in the “NS”-charged case. This interpretation may provide a resolution to the contrasting features between the instability of “R”-charged brane–antibrane systems and that of “NS”-charged ones. Certainly, however, it poses another puzzle that in the “NS”-charged case, the quantum entity, that should take over the semi-classical instability as the inter-brane distance gets smaller, is missing. This is rather an embarrassing state of affair that needs to be treated with great care.
