∂A/∂t = r·A + D(1+i·c₁)∇²A − s(k₀²+∇²)²A − (1+i·c₂)|A|²A.
Colour shows phase (hue) and amplitude (brightness). Cross the
Benjamin–Feir line 1 + c₁·c₂ = 0 to go from frozen spirals
to defect turbulence. Add the Swift–Hohenberg term (s) for
stripes, or a pacemaker (Ω) for target waves.
Drag on the field to stir in new defects.
−s(k₀²+∇²)²A (Swift–Hohenberg) selects a stripe wavelength; a central
pacemaker Ω emits target waves. s=0, Ω=0 ⇒ pure CGLE.
Stripes need low D (~0.3).
A = u + i·v on a periodic grid.
Drop ∇² and it is the Stuart–Landau oscillator; keep it and this same
equation describes BZ near onset and liquid-crystal light-valve patterns.
The −s(k₀²+∇²)²A term is Swift–Hohenberg: it selects a finite
wavelength (λ≈2π/k₀) so the field forms stationary stripes / labyrinths —
the Turing side of a light valve, which the pure CGLE (s=0) cannot make. It
only wins over the diffusion when D is small (~0.3). The
pacemaker Ω is a local frequency offset in a central disk that
radiates target waves. Integrated with forward Euler and a 9-point
isotropic Laplacian (applied twice for ∇⁴); |A| capped at 3 for stability.