pytc.xtc._contract_tucker_x_residual¶

pytc.xtc._contract_tucker_x_residual(phi_p, phi_q, u_r, u_s, z)[source]¶

Contract an orbital-leg Tucker X core without reconstructing X.

z represents X[r,s,c] = U[r,a] Z[a,b,c] U[s,b]. The returned quantity is the X contribution to the unsymmetrized Delta-U tile, -sum_c phi_p[p,c] phi_q[q,c] X[r,s,c].