Ludwik Turko

Origin, development, and misunderstandings concerning internal symmetries

Internal symmetries, also called flavor symmetries, started in 30-ies of the last century, from Heisenberg's suggestion that if you could switch off the electric charge of the proton, there would be no way to distinguish between a proton and a neutron. This was the beginning of the SU(2) isospin symmetry, leading to the symmetry-based classification schemes of elementary particles – the eightfold way of SU(3) because of strangeness, through SU(4) because of charm, albeit without SU(6), leaving aside for some reason its truth and beauty. A proper understanding of the observable effects of internal symmetries is, however, not common knowledge. They are treated sometimes as a kind of nonabelian generalization of "regular" charges - Q, B, S, ... - which is not correct. Also, the very concept of internal symmetry-breaking is far from being obvious. Nevertheless, there is a simple way to catch the point. To follow this simple way, one seminar should be enough, to begin with ...