Consider the bipartite splitting [ 1 ] : [ 2.. N ] . The SD has the coefficients λ λ α α 1 [ 1 ] and eigenvectors | Φ Φ α α 1 [ 1 ] ⟩ | Φ Φ α α 1 [ 2.. N ] ⟩ . By expanding the | Φ Φ α α 1 [ 1 ] ⟩ 's in the local basis, one can write: