ABSTRACT

This chapter shows that all the particle interactions fit very neatly into the simple Lie algebra. It discusses other embeddings, based on larger algebras. These theories are called Grand Unified theories, where the term “grand” is added for obscure historical reasons. One of the salient features of the weak interactions is that they violate parity. Parity is the symmetry in which the signs of all space coordinates are changed. Helicity or handedness is not invariant under a parity transformation because a mirror interchanges left and right. Electrons and their heavier cousins, muons and taus, and all the quarks have both left-and right-handed parts. The weak interactions have very short range and their force particles are massive.