The $\hat{G}^{4}\lambda^{16}$ Term in IIB Supergravity

Abstract

The supersymmetry constraints on the $\hat{G}^{4}\lamda^{16}$ term in the effective action of type IIB superstring theory are studied in order to determine the dependence of its coefficient on the complex scalar field, $\tau$. The resulting expression is consistent with the $SL(2,{\Bbb Z})$ invariant conjectures in the literature.