On NS-NS couplings at order
Mohammad R. Garousi (Department of Physics, Faculty of Science, Ferdowsi University of Mashhad, P.O. Box 1436, Mashhad, Iran)
Recently, imposing the gauge-symmetry and the T-duality constraints on the string frame effective actions of type II superstring theories at order , the NS-NS couplings have been found in a particular scheme which has 445 couplings in 15 different structures. In this paper, using a field redefinition, we write them in terms of 251 couplings which appear in 9 different structures. The 9 structures involve only Riemann curvature, and . The number of couplings in the structures , , , , are 2, 2, 1, 7, 22, respectively, and the number of couplings in the structures , , , are 12, 22, 77, 106, respectively. The new couplings are also fully consistent with the sphere-level S-matrix element of four NS-NS vertex operators.