Dynamical Solution of the Strong CP Problem

by Prof. Gerrit Schierholz (DESY)

Thursday 13 Jan 2022, 17:00 → 18:30 Asia/Seoul

Online (zoom) (KIAS)

Title: Dynamical Solution of the Strong CP Problem

Speaker: Prof. Gerrit Schierholz (DESY)

Abstract: The vacuum of quantum chromodynamics has an incredibly rich structure at the nonperturbative level, which is intimately connected with the topology of gauge fields, and put to a test by the strong CP problem. I investigate the long-distance properties of the theory in the presence of a topological $\theta$ term. This is done on the lattice, using the gradient flow to isolate the long-distance modes in the functional integral measure and tracing it over successive length scales.  The gradient flow serves as a particular, infinitesimal realization of the coarse-graining step of momentum space RG transformations. I find that the color fields produced by quarks and gluons are screened for vacuum angles $|\theta |\gtrsim 0$, not unexpectedly, thus providing a natural solution of the strong CP problem.

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