Lattice of classical ±1 spins with H = −J Σ s_i s_j − h Σ s_i. Exactly solved in d = 1 (no transition) and d = 2 (Onsager 1944). Paradigm of critical phenomena.
Lattice of classical ±1 spins with H = −J Σ s_i s_j − h Σ s_i. Exactly solved in d = 1 (no transition) and d = 2 (Onsager 1944). Paradigm of critical phenomena.