Editing Bound state (section)

==Examples==
[[Image:Particle overview.svg|thumb|400px|An overview of the various families of elementary and composite particles, and the theories describing their interactions]]
*A [[proton]] and an [[electron]] can move separately; when they do, the total center-of-mass energy is positive, and such a pair of particles can be described as an ionized atom. Once the electron starts to "orbit" the proton, the energy becomes negative, and a bound state&nbsp;– namely the [[hydrogen atom]]&nbsp;– is formed. Only the lowest-energy bound state, the [[ground state]], is stable. Other [[excited state]]s are unstable and will decay into stable (but not other unstable) bound states with less energy by emitting a [[photon]].
*A [[positronium]] "atom" is an [[resonance|unstable bound state]] of an [[electron]] and a [[positron]]. It decays into [[photon]]s.
*Any state in the [[quantum harmonic oscillator]] is bound, but has positive energy.  Note that <math>\lim_{x\to\pm\infty}{V_{\text{QHO}}(x)} = \infty</math> , so the [[#Normalization|below]] <!-- Dead link --> does not apply.
*A [[atomic nucleus|nucleus]] is a bound state of [[proton]]s and [[neutron]]s ([[nucleon]]s).
*The [[proton]] itself is a bound state of three [[quark]]s (two [[up quark|up]] and one [[down quark|down]]; one [[color charge|red]], one [[color charge|green]] and one [[color charge|blue]]). However, unlike the case of the hydrogen atom, the individual quarks can never be isolated. See [[color confinement|confinement]].
*The [[Hubbard model|Hubbard]] and [[Jaynes-Cummings-Hubbard model|Jaynes–Cummings–Hubbard (JCH)]] models support similar bound states.  In the Hubbard model, two repulsive [[bosonic]] [[atoms]] can form a bound pair in an [[optical lattice]].<ref>
{{cite journal
|author1=K. Winkler |author2=G. Thalhammer |author3=F. Lang |author4=R. Grimm |author5=J. H. Denschlag |author6=A. J. Daley |author7=A. Kantian |author8=H. P. Buchler |author9=P. Zoller | title = Repulsively bound atom pairs in an optical lattice
|journal = [[Nature (journal)|Nature]]
| year = 2006
| volume = 441
|issue=7095 | pages = 853–856
|arxiv = cond-mat/0605196 |bibcode = 2006Natur.441..853W |doi = 10.1038/nature04918 | pmid=16778884|s2cid=2214243 }}
</ref><ref>
{{cite journal
| title = Dimer of two bosons in a one-dimensional optical lattice
|author1=Javanainen, Juha |author2=Odong Otim |author3=Sanders, Jerome C. | journal = [[Phys. Rev. A]]
| volume = 81
| issue = 4
| pages = 043609
|date=Apr 2010
| doi = 10.1103/PhysRevA.81.043609
|arxiv = 1004.5118 |bibcode = 2010PhRvA..81d3609J |s2cid=55445588 }}
</ref><ref>
{{cite journal
|author1=M. Valiente  |author2=D. Petrosyan
 |name-list-style=amp | title = Two-particle states in the Hubbard model
| journal = J. Phys. B: At. Mol. Opt. Phys.
| year = 2008
| volume = 41
|issue=16
 | pages = 161002
| doi=10.1088/0953-4075/41/16/161002
|bibcode = 2008JPhB...41p1002V |arxiv=0805.1812|s2cid=115168045
 }}
</ref> The JCH Hamiltonian also supports two-[[polariton]] bound states when the photon-atom interaction is sufficiently strong.<ref>
{{cite journal
| title = Two-polariton bound states in the Jaynes-Cummings-Hubbard model
|author1=Max T. C. Wong  |author2=C. K. Law
 |name-list-style=amp | journal = [[Phys. Rev. A]]
| volume = 83
| issue = 5
| pages = 055802
|date=May 2011
| doi = 10.1103/PhysRevA.83.055802
| publisher = [[American Physical Society]]
|arxiv = 1101.1366 |bibcode = 2011PhRvA..83e5802W |s2cid=119200554 }}
</ref>