Eq. 4 states that 𝑃 ̂|ψ E (x)⟩ is an eigenfunction with the same eigenvalue (E), which implies that E would be a 'degenerate' eigenvalue; however, that is not true in virtue of linear dependency of the eigenvectors |ψ⟩ and 𝑃 ̂|ψ⟩. On the other hand, for the 'particle in an n-dimensional box' i.e. 'Hilbert space' 21 its centrosymmetric potential V(r) is only dependent on the distance the centre, and its eigenvector angular momentum 𝐿 ̂2 is as follows: |l, m⟩