Metropolis simulation — sharper phase transition than Ising (first-order for q≥3 in 2D)
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The q=3 Potts model: each spin takes one of 3 states. Neighboring aligned spins lower energy by J.
Critical temperature T_c = 1/ln(1+√3) ≈ 0.995 (exact, 2D square lattice).
The transition is first-order — energy has a discontinuous jump at T_c, unlike Ising's continuous (second-order) transition.