# Applicability of quantum statistics and the essence of bosons and fermions

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There is a known tale for undergraduate students:

• Each species of “particle” has spin, a.k.a. intrinsic angular momentum, a  quantitative property that is measured in .
• Particles with an integer spin are called bosons, and with half-integer – half-integer – fermions. It’s all that exists in 3D.
• Particles of the same species are indistinguishable (both bosons and fermions, but in a different fashion).
• Bosons obey Bose–Einstein statistics, fermions obey Fermi–Dirac statistics, and both are instances of quantum particle statistics.

I, Incnis Mrsi, am a self-educated theoretical physicist. I read few textbooks and possibly there are some books that explain all these things correctly, not for children. When I took part in arranging all this stuff in English Wikipedia, I had to clarify some nuances.

First of all, has any “particle” certain intrinsic angular momentum? One can read my reasoning about it at https://en.wikipedia.org/wiki/Talk:Spin%E2%80%93statistics_theorem#The_spin_can_be_uncertain.2C_but_bosons_never_mix_with_fermions In short, it depend on exact definition of a “species” that often relies on a traditional nomenclature, not objective criteria. There is no essential difference, IMHO, between π/ρ, p++, and singlet/triplet O2 situations, but for subatomic particles physicists traditionally speak about different particles, whereas for atoms and molecules scientists traditionally speak about different states of the same object.

A related question is: to which extent is quantum statistics applicable to composite particles? I tried to answer with the https://en.wikipedia.org/w/index.php?title=Particle_statistics&diff=599715275&oldid=581345617 sequence of edits (a cumulative diff is shown).

The third subtopic is now split to a separate posting http://physicsoverflow.org//22129/crowding-of-bosons-and-the-density-of-bose-condensate

As it was suggested at http://physicsoverflow.org//21978/review-of-wiki-edits-or-articles%C2%A0-would-it-be-appropriate , I put the topic into the Q&A category. Note that I am now indifferent about the fate of Wikipedia articles, but I am willing to hear your criticism. Thoughts?

Closed as per community consensus as the post is not graduate-level upward physics