Fermion regularization, fermion measure and axion fields

Abstract

Axion fields were originally introduced to control CP violation due to the theta term in QCD. Pauli-Villars regularization, or the use of a parity symmetric fermion measure, however, preserves CP in the fermion sector. A CP violation arising from the theta term can then be neutralized in a natural way by setting theta equal to zero.

4 pages; regularization argument expanded and measure argument simplified; invited talk at "New trends in Field Theories", Varanasi, November 2016