Wigner's theorem


Also found in: Wikipedia.

Wigner's theorem

[′wig·nərz ‚thir·əm]
(quantum mechanics)
The theorem that, if ψ is an eigenfunction of the Hamiltonian operator and R is a symmetry element of the Hamiltonian, then R ψ is an eigenfunction of the Hamiltonian having the same eigenvalue as ψ.
Angular momentum of the electron spin is conserved in a collision of the second kind.