Speaker
Prof.
Seong Chan Park
(Yonsei University Seoul, South Korea)
Description
No global symmetry is exact in the presence of gravity. The global U(1) PQ symmetry for the QCD axion is explicitly broken by non-perturbative effects of gravity such as axionic wormholes. The gravitational violation of the PQ symmetry due to wormholes is large enough to invalidate the PQ mechanism, which is entitled as the axion quality problem. We suggest a novel solution to this quality problem based on non-minimal coupling in metric and Palatini formulation of gravity.
