States Outside The Quark Model
While the quark model is derivable from the theory of quantum chromodynamics, the structure of hadrons is more complicated than this model reveals. The full quantum mechanical wave function of any hadron must include virtual quark pairs as well as virtual gluons. Also, there may be hadrons which lie outside the quark model. Among these are the glueballs (which contain only valence gluons), hybrids (which contain valence quarks as well as gluons) and "exotic hadrons" (such as tetraquarks or pentaquarks).
Read more about this topic: Quark Model
Famous quotes containing the words states and/or model:
“The Constitution of the United States is not a mere lawyers’ document. It is a vehicle of life, and its spirit is always the spirit of the age. Its prescriptions are clear and we know what they are ... but life is always your last and most authoritative critic.”
—Woodrow Wilson (1856–1924)
“The striking point about our model family is not simply the compete-compete, consume-consume style of life it urges us to follow.... The striking point, in the face of all the propaganda, is how few Americans actually live this way.”
—Louise Kapp Howe (b. 1934)