This has two connected components where Z 2 acts as an automorphism, which is the composition of an involutive outer automorphism of SU(3) C with the interchange of the left and right copies of SU(2) with the reversal of U(1) B−L. It was shown by Mohapatra & Senjanovic (1975) that left-right symmetry can be spontaneously broken to give a chiral low energy theory, which is the Standard Model of Glashow, Weinberg, and Salam, and also connects the small observed neutrino masses to the breaking of left-right symmetry via the seesaw mechanism.