The density matrix in the two‐particle function method

The first‐ and second‐order density matrices D ( N ) and D   2 ( N )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   2 ( N )does not exceed that of different eigenvalues of D . Thus the degeneracy in the spectrum of D causes the appearance of such large eigenvalues.