Low-energy expansion of the one-loop type-II superstring amplitude - art. no. 104011

The one-loop four-graviton amplitude in either of the type-ii superstring t heories is expanded in powers of the external momenta up to and including t erms of order s(4) In sR(4), where R-4 denotes a specific contraction of fo ur linearized Weyl tensors and s is a Mandelstam invariant. Terms in this s eries are obtained by integrating powers of the two-dimensional scalar fiel d theory propagator over the toroidal world sheet as well as the moduli of the toms. The values of these coefficients match expectations based on dual ity relations between string theory and eleven-dimensional supergravity.