Heterotic moduli, the double extension and the alpha'^2 metric

Abstract

We compute the heterotic moduli-space metric through ${\alpha }^{\prime 2}$ for backgrounds admitting a smooth ${\alpha }^{\prime }\to 0$ limit. The Kaehler potential is unchanged when written in an appropriate field basis suggested by the ten-dimensional supersymmetry equations, while the metric receives ${\alpha }^{\prime 2}$ corrections. We discuss this and clarify the roles of the extension bundle, F-terms, the D-terms and the string-derived moduli space metric.

v3, improvements, simplifications to appendix A and the final result. 29 pages