Calabi-Yau black holes and (0,4) sigma models

When an M-theory fivebrane wraps a holomorphic surface $\mathcal{P}$ in a Calabi-Yau 3-fold $X$ the low energy dynamics is that of a black string in 5 dimensional $\mathcal{N}=1$ supergravity. The infrared dynamics on the string worldsheet is an $\mathcal{N}=(0,4)$ 2D conformal field theory. Assuming the 2D CFT can be described as a nonlinear sigma model, we describe the target space geometry of this model in terms of the data of $X$ and $\mathcal{P}$. Variations of weight two Hodge structures enter the construction of the model in an interesting way.