Reducing the Heterotic Supergravity on nearly-Kahler coset spaces

Abstract

We study the dimensional reduction of the ${\cal N}=1$, ten-dimensional Heterotic Supergravity to four dimensions, at leading order in $\alpha'$, when the internal space is a nearly-K\"{a}hler manifold. Nearly-K\"{a}hler manifolds in six dimensions are all the non-symmetric coset spaces and a group manifold. Here we reduce the theory using as internal manifolds the three six-dimensional non-symmetric coset spaces, omitting the case of the group manifold in the prospect of obtaining chiral fermions when the gauge fields will be included. We determine the effective actions for these cases, which turn out to describe ${\cal N}=1$ four-dimensional supergravities of the no-scale type and we study the various possibilities concerning their vacuum.Comment: 18 pages, references added, comments added, a shorter version will appear in the proceedings of the 4th workshop of the RTN project 'Constituents, Fundamental Forces and Symmetries of the Universe', Varn