Sector boundary drift
Uniform (isotropic) growth: Equations for growth expansion on a sloped surface:

Sector boundaries drift on a sloped surfaces, as
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Stochastic variations of height profile, cause random drift of the sector boundary:
The generic scaling of fluctuations of the above equation is super-diffusive:

Stochastic fluctuations of the rough surface thus lead to random drift of the sector boundary, such that
