Edwards-Anderson model · Frustration · P(q) order parameter · Simulated annealing
E = — m = — q_EA = —
H = -Σ J_ij σ_i σ_j - h Σ σ_i
Edwards-Anderson (1975): random ±J couplings create frustration — no configuration satisfies all bonds simultaneously.
Replica symmetry breaking (Parisi 1979): order parameter P(q) has non-trivial structure below T_g — infinitely many pure states organized in ultrametric hierarchy.
Red edges: ferromagnetic (J>0). Blue: antiferromagnetic. Green bonds: satisfied. Purple: frustrated.