Branes, orientifolds and the creation of elementary strings

The potential of a configuration of two Dirichlet branes for which the number of ND-directions is eight is determined, Depending on whether one of the branes is an anti-brane or a brane, the potential vanishes or is twice as large as the dilaton-gravitational potential, This is shown to be related to the fact that a fundamental string is created when two such branes cross. Special emphasis is given to the D0-D8 system, for which an interpretation of these results in terms of the massive IIA supergravity is presented. It is also shown that the branes cannot move non-adiabatically in the transverse direction, The configuration of a zero-brane and an orientifold 8-plane is analyzed in a similar way, and the implications for the type IA-heterotic duality and the heterotic matrix theory are discussed. (C) 1998 Elsevier Science B.V.