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Abstract

Present knowledge of higher-derivative terms in string e ective actions is, with a few exceptions, restricted to the NS-NS sector, a situation which prevents the development of a variety of interesting applications for which the RR terms are relevant. We here provide the formalism as well as e cient techniques to determine the latter directly from string-amplitude calculations. As an illustration of these methods, we compute the dependence of the type-IIB action on the three- and five-form RR field strengths at four-point, genus-one, order-( 0)3 level. We explicitly verify that our results are in accord with the SL(2,Z) S-duality invariance of type-IIB string theory. Extensions of our method to other bosonic terms in the type-II e ective actions are discussed as well.