We consider several properties of a set of anti-Dp-branes in the presence
of orientifold p-planes in type II theory. This system breaks all the
supersymmetries of the theory, but is free of tachyons. In particular, we
center on the case of a single anti-Dp-brane stuck at a negatively charged
orientifold p-plane, and study its strong coupling behaviour for p=2,3,4.
Interestingly enough, as the coupling increases the system undergoes a phase
transition where an additional antibrane is created. We conclude with some
remarks on the limit of large number of antibranes on top of orientifold
planes.Comment: 14 pages, Latex. Orientifold-antibrane short distance interaction
corrected, references adde