where J i j ( k , k ′ ) is the energetic cost of spin i being in state k while spin j is in state k ′ , and h i ( k ) is the energetic cost of spin i being in state k . Note: J i j ( k , k ′ ) = J j i ( k ′ , k ) . This model resembles the Sherrington-Kirkpatrick model in that couplings can be heterogeneous and non-local. There is no explicit lattice structure in this model.