Figure 5.

(a) Close-up of the harmonic hedgehog located between the first two red points in Fig. 4a. The numerical error spikes when the polar angle of W is close to an element of the set $\left\{\frac{360^{\circ }}{15},\frac{360^{\circ }}{14},\frac{360^{\circ }}{13},\cdots ,\frac{360^{\circ }}{8}\right\}$. The eight red points indicate the numerical error for these Farey angles. (b) The plot from (a) with the numerical error estimate superimposed in red.