φ⁴ Field Theory · Topological Charge · Kink-Antikink Collision
Topological charge Q=0
V(φ) = (1−φ²)²/4. Kink solution: φ_K(x,t) = tanh((x−vt)/√2 · γ_L) where γ_L=1/√(1−v²).
Topological charge Q = (φ(+∞)−φ(−∞))/2 ∈ {−1,0,+1} is conserved.
Kink-antikink annihilate into radiation; with damping they form bound state (bion).