5,892 research outputs found
T-duality invariant effective actions at orders
We use compatibility of the -dimensional effective actions for diagonal
metric and for dilaton with the T-duality when theory is compactified on a
circle, to find the the -dimensional couplings of curvatures and dilaton as
well as the higher derivative corrections to the -dimensional Buscher
rules at orders and . We observe that the T-duality
constraint on the effective actions fixes the covariant effective actions at
each order of up to field redefinitions and up to an overall factor.
Inspired by these results, we speculate that the -dimensional effective
actions at any order of must be consistent with the standard Buscher
rules provided that one uses covariant field redefinitions in the corresponding
reduced -dimensional effective actions. This constraint may be used to
find effective actions at all higher orders of .Comment: 24 pages, latex file, no figure; v2: major modifications; v3: the
version appears in JHE
Sphere-level Ramond-Ramond couplings in Ramond-Neveu-Schwarz formalism
We calculate in details the sphere-level scattering amplitude of two
Ramond-Ramond (RR) and two Neveu-Schwarz-Neveu-Schwarz (NSNS) vertex operators
in type II superstring theories in Ramond-Neveu-Schwarz (RNS) formalism. We
then compare the expansion of this amplitude at order with the
eight-derivative couplings of the gravity and B-field that have been recently
found based on S-dual and T-dual Ward identities. We find exact agreement.
Moreover, using the above S-matrix element, we have found various couplings
involving the dilaton field, and shown that they are also fully consistent with
these Ward identities.Comment: 34 pages, Latex file, no figure; v3: the version appears in np
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