  By the Pauli exclusion principle no quantum state can be occupied by more
than one electron. One can put it as a constraint on the electron density
matrix that bounds its eigenvalues by 1. Shortly after its discovery the Pauli
principle has been replaced by skew symmetry of a multi-electron wave function.
  In this paper we solve a longstanding problem about the impact of this
replacement on the electron density matrix, that goes far beyond the original
Pauli principle.
