Minkowski Initial

Currently only Cartesian coordinates are supported, and the metric and extrinsic curvature are set as:

$$\begin{eqnarray*} g_{xx} = g_{yy} = g_{zz} &=& 1 \\ g_{xy} = g_{xz} = g_{yz} &=& 0 \\ K_{ij} &=& 0 \end{eqnarray*}$$

Depending on the metric_type and conformal_storage the conformal factor is set to

$$\begin{eqnarray*} \psi &=& 1 \\ \psi_{,i} &=& 0 \\ \psi_{,ij} &=& 0 \end{eqnarray*}$$