We perform a careful investigation of which p-form fields can be introduced consistently with the supersymmetry algebra of IIA and/or IIB ten-dimensional supergravity. In particular the ten-forms, also known as top-forms, require a careful analysis s
ince in this case, as we will show, closure of the supersymmetry algebra at the linear level does not imply closure at the non-linear level. Consequently, some of the (IIA and IIB) ten-form potentials introduced in earlier work of some of us are discarded. At the same time we show that new ten-form potentials, consistent with the full non-linear supersymmetry algebra can be introduced. We give a superspace explanation of our work. All of our results are precisely in line with the predictions of the E(11) algebra.
We construct the half-supersymmetric instanton solutions that are electric-magnetically dual to the recently discussed half-supersymmetric Q7-branes. We call these instantons `Q-instantons. Whereas the D-instanton is most conveniently described using
the RR axion chi and the dilaton phi, the Q-instanton is most conveniently described using a different set of fields chi and T, where chi is an axionic scalar. The real part of the Q-instanton on-shell action is a function of T and the imaginary part is linear in chi. Discrete shifts of the axion chi correspond to PSL(2,Z) transformations that are of finite order. These are e.g. pure S-duality transformations relating weak and strongly coupled regimes. We argue that near each orbifold point of the quantum axion-dilaton moduli space PSL(2,Z)PSL(2,R)/SO(2) the higher order R^4 terms in the string effective action contain contributions from an infinite sum of single multiply-charged instantons with the Q-instantons corresponding to the orbifold points tau=i,rho where tau is the complex axion-dilaton field.
We discuss how all variant 10d and 11d maximal supergravities, including star supergravities and supergravities in different signatures, can be obtained as different real slices of three complex actions. As an application we study the recently introd
uced domain-wall/cosmology correspondence in this approach. We give an example in 9d and 10d where the domain-wall and corresponding cosmology can be viewed as different real slices of the same complex solution. We argue how in this case the pseudo-supersymmetry of the cosmological solutions can be understood as the invariance under supersymmetry of a variant supergravity.
