Higher-derivative couplings in string theory: Dualities and the B field

The first quantum correction to the IIA string effective action arises at the eight-derivative level and takes the schematic form (t(8)t(8) - 1/8 epsilon(10)epsilon(10))R-4 + B-2 boolean AND X-8. This correction, however, cannot be complete by itself, as it is neither supersymmetric nor T-duality covariant. We reexamine these eight-derivative couplings and conjecture that the simple replacement R -> R(Omega(+)), where Omega(+) = 1/2H is the connection with torsion, nearly completely captures their dependence on the B field. The exception is in the odd odd spin structure sector, where additional terms are needed. We present here a complete result at the level of the five-point function and a partial one for the six-point function. Further evidence for this conjecture comes from considering T-duality as well as heterotic/IIA duality beyond leading order. Finally, we discuss the eleven-dimensional lift of the modified one-loop type IIA couplings. (C) 2013 Elsevier B.V. All rights reserved.