Frustrated magnetic systems with exponentially many metastable states
Spin glasses (Edwards-Anderson model, 1975) have random ferromagnetic and antiferromagnetic bonds J_ij = ±1. Frustration prevents any single ground state — the system wanders among O(2^N) metastable states. The left panel shows Ising spins on a 2D grid; the right panel plots energy vs. Monte Carlo time. Below the glass temperature T_g, relaxation becomes logarithmically slow.