Determinant of 3-Metric

The determinant of the 3-metric at each point on the grid is placed in the grid function detg. This is always the determinant of the conformal metric, that is it does not include any conformal factor.

$${\tt detg} \equiv det g = -g_{13}^2*g_{22}+2*g_{12}*g_{13}*g_{23}-g_{11}*g_{23}^2- g_{12}^2*g_{33}+g_{11}*g_{22}*g_{33}$$ (part222)