Newton Fractal — Basin Boundaries

Newton's method for z^n = 1: fractal boundaries between convergence basins
z ↦ z − f(z)/f'(z)  ·  color = which root + speed of convergence
Click to zoom in (3×) · Right-click to zoom out

Polynomial

30
1e-3

View

Center0 + 0i
Zoom

Roots

Newton's method applied to z^n − 1 produces a stunning fractal. Each point in the complex plane is colored by which root the iteration converges to, and shaded by how quickly. The boundaries between basins are fractal — they are nowhere smooth, and every boundary point is simultaneously on the boundary of all n basins (Julia-set style). The Hausdorff dimension of the boundary is strictly greater than 1. Zoom in to explore infinite self-similar complexity.