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| | quantum chromodynamics -- Britannica Concise Encyclopedia - The online encyclopedia you can trust! (Site not responding. Last check: 2007-11-07) |
 | | The strong force is observed to behave in a similar way, acting only upon certain particles, principally quarks that are bound together in the protons and neutrons of the atomic nucleus, as well as in less stable, more exotic forms of matter. |
 | | So by analogy with QED, quantum chromodynamics has been built upon the concept that quarks interact via the strong force because they carry a form of strong charge,; which has been given the name of colour; other particles, such as the electron, which do not carry the colour charge, do not interact in this way. |
 | | Like QED, quantum chromodynamics is a gauge-invariant theory, which means that its basic equations give the same results at different points in space and time. |
| www.britannica.com /ebc/article-9062162 (1260 words) |
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