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arXiv · hep-th/9610237

Fivebrane Instantons and $R^2$ couplings in $N=4$ String Theory

Jeffrey A. Harvey·Gregory Moore
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Abstract

We compute the gravitational coupling $F_1$ for IIA string theory on $K3 \times T^2$ and use string-string duality to deduce the corresponding term for heterotic string on $T^6$. The latter is an infinite sum of gravitational instanton effects which we associate with the effects of Euclidean fivebranes wrapped on $T^6$. These fivebranes are the neutral fivebranes or zero size instantons of heterotic string theory.

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Jeffrey A. Harvey, Gregory Moore. 1996-10-30. Fivebrane Instantons and $R^2$ couplings in $N=4$ String Theory. https://doi.org/10.1103/physrevd.57.2323

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