Theory Group Seminar, 14 November 2017
Prateek Agrawal, Harvard University
The strong CP problem and UV instantons
The absence of sizeable CP violation in the strong sector is a long standing puzzle. A class of solutions rely on a global U(1) symmetry that is anomalous with the QCD. These lead to robust low energy predictions, for example a massless up quark or a light axion. I will present simple extensions to these solutions which can dramatically change these predictions. In our models, contributions from small instantons play a significant role in affecting the low energy physics while preserving the solution to the strong CP problem.