Symmetries in Physical Theories

Abstract

We review the application of Noether's theorem to global internal and external symmetries. Applying the gauge procedure of Yang-Mills, we exhibit the emergence of physical interactions as a consequence of gauge symmetries. This procedure is carried out for U(1), SU(2) and Poincaré transformations. We connect Poincaré gauge theory with the corresponding theory of gravity, Einstein-Cartan-Sciama-Kibble theory, and examine the physical consequences of a torsionful affine connection.