Nematic Defect Annihilation

In a nematic liquid crystal, the director field n̂ (a headless vector) allows topological defects with half-integer winding numbers. A +½ defect (comet shape) and a −½ defect (trefoil shape) attract each other. When they meet, they annihilate — the elastic energy E ∝ K·ln(d) drives them together. The director field is shown as short rods; defect cores glow red (+½) and blue (−½). The simulation uses overdamped relaxational dynamics (Q-tensor).