EntityQ7624462· pop 6· linked from 73 articlesstrong CP problemSign in to savethe observation that the θ angle in quantum chromodynamics that would violate CP symmetry seems fine-tuned to 0ConnectionsInternational Standard Book NumberEntityquarkEntitydigital object identifierEntitystrong interactionEntityForbesEntityweak interactionEntitydark matterEntityparticle physicsEntityStandard ModelEntitystring theoryEntityQ180686EntitybibcodeEntityQ118398Entityquantum chromodynamicsEntityQ22908627EntityparityEntityground stateEntityaxionEntityspontaneous symmetry breakingEntitygauge theoryEntityCategoriesParticle physicsUnsolved problems in physics