2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/57565New elements of the dual cone of the set of fermion N-representable 2-density operators are proposed. So far, the explicit form of the corresponding necessary conditions for N-representability is obtained for N=3. In this case the new condition is stronger than the known B- and C-conditions for 3-representability. The results provide evidence that in the spectral decomposition of the N-representable 2-density operator there exists an intrinsic relation between the eigenvalue and the corresponding eigenfunction. keywords: fermion N-representability problem, conditions for N-representability10 pagesMathematical PhysicsSpectral Theory47xxtext