KEK Theory Seminar (Dr. Hajime Fukuda)
The strong CP problem is one of the long-standing problems in the Standard Model. I will first review the strong CP problem and the solutions proposed so far. Then, among these solutions, I will focus on the Peccei-Quinn mechanism. However, the quality, why it is a good "symmetry", is highly mysterious. Based on our recent works, I will discuss models realizing a good symmetry.