The density matrix in the two-particle function method

The first- and second-order density matrices D ^(N) and D for the function g⁽ⁿ⁾ = A_N[g(1, 2) …? g(N ? 1, N)] are expressed by the g function itself and its density matrix D . In a singlet state the generating functions for spatial parts of these matrices are simply connected with there solvent of the Fredholm equation in which the spatial part of D is a kernel. Some special cases of g(1, 2) are considered. It isestablished that the number of large eigenvalues of D does not exceed that of different eigenvalues of D . Thus the degeneracy in the spectrum of D causes the appearance of such large eigenvalues.