Active Gel: Cytoskeletal Contraction
Myosin-driven actomyosin cortex — contraction waves and active stress flow
Active Gel Theory: Actin density ρ, myosin motor field m, velocity v.
σ = η·∂v/∂x + ζ·m (active stress). ∂ρ/∂t = −∂(ρv)/∂x − τ⁻¹(ρ−ρ₀).
∂m/∂t = −∂(mv)/∂x + k_on·ρ·(1−m) − k_off·m + noise. Force balance: ∂σ/∂x = ξv.
Above threshold ζ_c, spontaneous flow and contraction waves emerge.