This paper reviews some of the extensions of
SU
a symmetry which have been proposed in the last year. In many respects, it covers the same subject matter as Salam’s excellent report at the International Conference on High Energy Physics at Dubna in August 1964. The very recent and very important developments combining
SU
3
and ordinary spin in an
SU
6
symmetry scheme will not be discussed here. The main results obtained to date are listed in Matthews’s paper at this meeting, and the difficult problems related to the actual meaning and extent of
SU
6
symmetry are currently in a rapid process of discussion and analysis, the conclusions of which are quite unclear at the present time. As to references, complete lists are not attempted, and the papers quoted are usually meant as examples of many publications dealing with the same topics.
Higher symmetry schemes for strong interactions
