N-Representability Problem for Fermion Density Matrices. I. The Second-Order Density Matrix with N =3

Abstract

The N representability problem is the problem of how to recognize whether a given pth‐order reduced density matrix is derivable from an antisymmetaic N‐particle wavefunction ψ by integrating out all but coordinates from ψ^*ψ. The conditions under which a given second‐order density matrix is N representable by a three‐particle wavefunction are discussed.