String theory origin of constrained multiplets

We study the non-linearly realized spontaneously broken supersymmetry of the (anti-) D3-brane action in type IIB string theory. The worldvolume fields are one vector A(mu), three complex scalars phi(i) and four 4d fermions lambda(0), lambda(i). These transform, in addition to the more familiar N = 4 linear supersymmetry, also under 16 spontaneously broken, non-linearly realized supersymmetries. We argue that the worldvolume fields can be packaged into the following constrained 4d non-linear N = 1 multiplets: four chiral multiplets S, Y-i that satisfy S-2 = SYi = 0 and contain the worldvolume fermions lambda(0) and lambda(i); and four chiral multiplets W-alpha, H-i that satisfy SW alpha = S (D) over bar ((alpha) over dot) (H) over bar ((i) over bar) = 0 and contain the vector A(mu) and the scalars phi(i). We also discuss how placing an anti-D3-brane on top of intersecting O7-planes can lead to an orthogonal multiplet Phi that satisfies S(Phi - Phi) = 0, which is particularly interesting for inflationary cosmology.