Kink Soliton — φ⁴ Field Theory

Topological kinks interpolate between vacua at φ=±1; kink-antikink collisions form bions

φ_kink = tanh((x-x₀)/√2 · m/√(1-v²))
V(φ) = λ/4·(φ²-1)² double-well
Mass M = 2√2·m³/3λ
Topological charge Q=∮∂_xφ dx
Kink+antikink → radiation / bion