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The hierarchy of bound states in quantum chromodynamics:
if quarks themselves were bound states (which they are not according to the standard model of particle physics) then one would call them bound states of preons
hadrons are bound states of quarks
(and of gluons, while glueballs are bound states purely of gluons)
(at temperatures that these bound states decay one speaks of a quark gluon plasma)
mesons are bound states specifically of two quarks
pions, rho-mesons and omega-mesons are bound states of an up quark with a down quark
kaons are bound states of a strange quark with either an up quark or a down quark
B-mesons are bound states of a bottom quark with either an up quark or a down quark or a strange quark or a charm quark
baryons are bound states specifically of three quarks, or rather of one quark and a diquark
nuclei are bound states of three among the up quarks and the down quarks
protons are bound states of 2 up quarks and 1 down quark
neutrons are bound states of 1 up quarks and 2 down quark
atomic nuclei are bound states of of nuclei (protons and neutrons)
atoms are bound states of atomic nuclei and electrons
(at temperature high enough that these bound states decay, one speaks of a plasma)
Here the last two steps go beyond QCD as they also involve electrons from quantum electrodynamics.
There are also bound states purely in QED:
Hypothetically:
brane intersections/bound states/wrapped branes/polarized branes
D-branes and anti D-branes form bound states by tachyon condensation, thought to imply the classification of D-brane charge by K-theory
intersecting D-branes/fuzzy funnels:
Dp-D(p+6) brane bound state
intersecting$\,$M-branes:
On bound states in QED and QCD:
Paul Hoyer, Bound states – from QED to QCD, Lectures at “Mini-school on theoretical methods in particle physics” at the Higgs Centre for Theoretical Physics, University of Edinburgh on 30 September to 4 October 2013 (arXiv:1402.5005)
Changyong Liu, On bound states in Quantum Field Theory (arXiv:1811.06457)
Paul Hoyer, Journey to the Bound States (arXiv:2101.06721)
See also
Last revised on January 18, 2021 at 23:59:03. See the history of this page for a list of all contributions to it.