We characterize the geometric moduli of non-Kaehler manifolds with torsion.
Heterotic supersymmetric flux compactifications require that the
six-dimensional internal manifold be balanced, the gauge bundle be hermitian
Yang-Mills, and also the anomaly cancellation be satisfied. We perform the
linearized variation of these constraints to derive the defining equations for
the local moduli. We explicitly determine the metric deformations of the smooth
flux solution corresponding to a torus bundle over K3.Comment: 23 pages, harvmac; v2: typos corrected, minor clarifications,
reference adde
