🌀 RG FLOW — 2D ISING

Initial coupling K=J/kT: 0.44 Initial field h: 0.0 RG steps: 10
Kc ≈ 0.4407 (exact 2D Ising)
K<Kc → disorder (K→0)
K>Kc → order (K→∞)
Real-space RG: majority rule block spin decimation. Fixed point at Kc = ln(1+√2)/2 ≈ 0.4407. Wilson (1971): RG fixed points classify universality classes.