With symmetry playing a central role in quantum mechanics, in this
chapter we commence with the simplest of symmetries of translation in space
and time. Here we consider the group structure of the symmetry operators.
This is followed by a rotational symmetry that plays a central role in atomic
and nuclear physics and is a major component of this chapter. Finally we
examine time and space reversion and isospin that are central to the study
of nuclear and particle physics.
