New formulations of D = 10 supersymmetry and D8–O8 domain walls

We discuss a generalized form of IIA/IIB supergravity depending on all R–R potentials C(p) (p = 0, 1, . . . , 9) as the effective field theory of type IIA/IIB superstring theory. For the IIA case we explicitly break this R–R democracy to either p ≤ 3 or p ≥ 5, which allows us to write a new bulk action that can be coupled to N = 1 supersymmetric brane actions. The case of eight-branes is studied in detail using the new bulk & brane action. The supersymmetric negative-tension branes without matter excitations can be viewed as orientifolds in the effective action. These D8-branes and O8-planes are fundamental in type I' string theory. A BPS eight-brane solution is given which satisfies the jump conditions on the wall. It implies a quantization of the mass parameter in string units. Also, we find a maximal distance between the two walls, depending on the string coupling and the mass parameter. We derive the same results via supersymmetric flow equations