Migdal-Kadanoff (1976): Bond-moving approximation — move bonds before decimating. For 2D Ising with b=2:
K' = ½ ln[cosh(2K²)] (1D chain decimation after bond moving)
Fixed points: K*=0 (high-T, disordered), K*=∞ (low-T, ordered), K*_c (critical — unstable). MK gives K*_c ≈ 0.305 for d=2, b=2 (exact: 0.4407).
RG flow: K<K*_c flows to 0 (disordered); K>K*_c flows to ∞ (ordered). The eigenvalue at K*_c gives ν = 1/log_b(λ).