ABSTRACT
The chiral symmetry discussed earlier is visible only at the classical level and is not respected by regularizations. Loop integrals arising in the perturbative treatment of quantum field theory need to be regularized before sense can be made of them. There are several ways of carrying out regularizations. Simple procedures like large momentum cutoff are not gauge invariant, so that more elaborate procedures have to be followed. However, there is no regularization that respects both chiral invariance and the phase or global gauge invariance. At least a part of the symmetry shown by the classical theory is broken in the quantum theory. This phenomenon is called an anomaly. In the case of chiral symmetry, which is broken upon quantization of the field theory, one refers to a chiral anomaly. This anomaly may be calculated by using a regularization. We shall study three approaches to the anomaly.
