Mathematical proof of confinement in QCD
Prove confinement in four-dimensional pure SU(3) Yang–Mills gauge theory in the sense that only color-singlet states appear in the physical spectrum, thereby establishing the weak form of confinement referenced by the Clay Mathematics Institute’s prize problem.
References
The Clay foundation offers a big prize for mathematical proof of (a weak form) of confinement , and as yet no one has claimed it successfully.
— QCD at 50: Golden Anniversary, Golden Insights, Golden Opportunities
(2403.06038 - Wilczek, 9 Mar 2024) in Section Confinement and Freedom