The Pauli principe, representation theory, and geometry of flag varieties

According to the Pauli exclusion principle, discovered in 1925, no two identical electrons may occupy the same quantum state. In terms of electron density matrix this amounts to an upper bound for its eigenvalues by 1. In 1926, it has been replaced by skew-symmetry of a multi-electron wave function. In this thesis we give two different solutions to a problem about the impact of this replacement on the electron density matrix, which goes far beyond the original Pauli principle.