Gibbs Sampling — 2D Ising

M = 0.000 | E = 0.000
Gibbs sampler: for each spin, compute ΔE for flip, accept with probability min(1, e^{−ΔE/T}). Critical temperature T_c = 2/ln(1+√2) ≈ 2.269 for J=1. Watch spontaneous magnetization below T_c.