Topological Kink — φ⁴ Field Theory

Kink and antikink solitons in the double-well potential, kink-antikink scattering

Parameters

φ⁴ Lagrangian:
L = ½(∂_μφ)² − V(φ)
V(φ) = λ/4 (φ²−m²/λ)²

Kink solution:
φ_K(x) = (m/√λ) tanh[m(x−vt)/√(2γ_L)]
Mass: M_K = 2√2 m³/(3λ)

Topological charge:
Q = (λ/2m)∫∂_xφ dx = ±1

After collision, kinks can reflect, form bound states (bions), or annihilate. The critical velocity separates these regimes.