The φ⁴ model (∂²φ/∂t² = ∂²φ/∂x² − φ(φ²−1)) supports stable topological solitons: kinks (φ: −1→+1) and antikinks (φ: +1→−1). Watch them collide, scatter, and annihilate.
V(φ) = ¼(φ²−1)² · Exact kink: φ(x,t) = tanh((x−vt)/√2·γ_L) · Topological charge Q = ½∫∂φ/∂x dx = ±1