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:
“Canadians look down on the United States and consider it Hell. They are right to do so. Canada is to the United States what, in Dante’s scheme, Limbo is to Hell.”
—Irving Layton (b. 1912)
“One of the most important things we adults can do for young children is to model the kind of person we would like them to be.”
—Carol B. Hillman (20th century)