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Nonperturbative low-energy effective action of the universal hypermultiplet

Sergei V. Ketov

hep-tharXiv:hep-th/0301074

Abstract

The non-perturbative (D-instanton corrected) low-energy effective action of the universal hypermultiplet in the type-IIA string theory compactified on a Calabi-Yau threefold is calculated in 4d, N=2 supergravity. The action is given by the quaternionic non-linear sigma-model whose metric is governed by the Eisenstein series E3/2. The U(1)xU(1) isometry and SL(2,Z) modular invariance play the key role in our construction.

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