A-Z Index...
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The distinction between bosons and fermions is basic. There are two possible kinds of things in the universe. The two types are known as "bosons" and "fermions," and the dialectic between them describes all physical form. The whole scheme of quantum field theory, for example, is that fermions interact by exchanging bosons.
"The electons belong to the class of elementary particles called leptons. The leptons and quarks together constitute the class called fermions. According to the Standard Model all mass consists of fermions. Whether the fermions combine to form a table, a star, a human body, a flower or do not combine at all depend on the elementary forces - the electromagnetic, the gravitational, the weak and the strong forces. According to the Standard Model all force is mediated by exchange of (gauge) bosons. The electromagnetic force is mediated by exchange of photons, the strong force by exchange of gluons while the weak force is mediated by exchange of W and Z bosons."
- Steen Ingemann
Special quantum interactions
Identical particles have special quantum interactions, and the two ontological classes have fundamentally different natures: bosons are gregarious, and fermions are solitary.
- The solitary property of fermions leads to the Pauli exclusion principle, and to all chemistry and universal structure in general. For example the degeneracy pressure that stabilizes white dwarf and neutron stars is a result of fermions resisting further compression towards each other. Fermions are the skeletal scaffolding of the cosmos, bosons what bind it together.
- Bosons may overlap in the same quantum state, and in fact the more bosons that are in a state the more likely that still more will join. This is called "Bose condensation," and is related to "stimulated emission" and the laser. The state that is formed when many bosons occupy the same state is known as a Bose-Einstein condensate.
Spin statistics
All bosons have zero spin or an integer multiple of h-bar - all fermions have half integer spin. These "spin statistics" can be derived from relativistic quantum mechanics (and must be regarded as simply an empirical fact from the point of view of nonrelativistic quantum theory). There are no spinless fermions.
One could playfully ask whether the universe itself is a boson or a fermion? One of the craziest ideas i have entertained is that the universe in time might actually evolve from boson to fermion...
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Coherence
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