10 Sommerfeld boundary algorithm

1D Gauge Wave, $\hat W$ system, $\ell_\infty$ error in $g_{xx}$ convergence plots.

The convergence rate for the error in $g_{xx}$, measured at t=50, for 10 Sommerfeld boundary algorithm, is:

$${\tilde c_r^{(50)}} = 2.000$$ (18)