Therefore, the eigenvalues of ρel (R, t) are 0 and 1. Furthermore, since the trace of ρel (R, t) is 1 and ρ el (R, t) is hermitian, one eigenvalue is λ1 (R, t) = 1 with algebraic/geometric multiplicity 1 and one eigenvalue is λ2 (R, t) = 0 with algebraic/geometric multiplicity N -1, ∀R, t. It follows that the eigenvalues of ρ el (R, t)