2019-12-20 11:00  P7F

Strong CP violation: from fact to fancy and back

Goran Senjanovic

I demonstrate explicitly that there is no strong CP problem in the Standard Model—and thus there can be no solution to a non-existing problem. I go then through the most popular ‘solutions’ and show how they fare no better than the SM, but simply trade the small strong CP parameter for other ad-hoc assumed small terms. In particular, I focus on the PQ mechanism with the axion and discuss its pros and cons.