Purpose

Maximal computes the lapse function in order to maintain the maximal slicing condition

$$\text{Tr}K_{ij} = 0 \;.$$

The lapse condition is

$$\nabla^2\alpha = \alpha [ K_{ij}K^{ij} + 4\pi(\rho + S) ] \;.$$ (part371)

One may choose among 3 different elliptic solvers (SOR, PETSc, and BAM), and different boundary conditions. It is also possible to use `mixed slicing' (using a cheap method often and the expensive maximal only once in a while). A combination often used for mixed slicing is 4 times 1+log and every fifth time maximal.