±½ disclinations annihilate via coarsening · order parameter φ(x,y) on grid
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Defects: — | Step: 0
Key physics: Nematic order parameter is headless: angle φ ≡ φ+π. This allows ±½ topological defects (disclinations) — impossible in XY model (only ±1 vortices).
Coarsening law: N(t) ~ t⁻¹ — defect number falls as pair-annihilation dominates.
+½ defect: comet-shaped. −½ defect: three-pronged. Opposites attract and annihilate.