Dynamical solution of the strong CP problem within QCD ?

Abstract

The strong CP problem is inseparably connected with the topology of gauge fields and the mechanism of color confinement, which requires nonperturbative tools to solve it. In this talk I present results of a recent lattice investigation of QCD with the $\theta$ term in collaboration with Yoshifumi Nakamura. The tool we are using to address the nonperturbative properties of the theory is the gradient flow, which is a particular realization of momentum space RG transformations. The novel result is that within QCD the vacuum angle $\theta$ is renormalized, together with the strong coupling constant, and flows to $\theta =0$ in the infrared limit. This means that CP is conserved by the strong interactions.

arXiv comment12 pages, 10 figures, invited talk given at `XVth Quark Confinement and the Hadron Spectrum Conference', Stavanger, August 2022

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Cited by in corpus (3)

• $\Lambda$ parameter of the SU(3) Yang-Mills theory from the continuous $\beta$ function
• Absence of strong CP violation
• QCD knows new quarks