Ising Model — Metropolis Sampling

2D Ising model with Metropolis-Hastings MCMC — watch the phase transition

T = 2.27 (T_c ≈ 2.269)
⟨M⟩ =
⟨E⟩/N =
Step: 0
H = -J Σ sᵢsⱼ — Metropolis: flip spin i with prob min(1, e^{-ΔE/kT}) — T_c = 2J/ln(1+√2) ≈ 2.269 (Onsager 1944)