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%%% This file is part of PlanetPhysics snapshot of 2011-09-01 %%% Primary Title: quantum chromodynamics (QCD) %%% Primary Category Code: 03. %%% Filename: QuantumChromodynamicsQCD.tex %%% Version: 2 %%% Owner: bci1 %%% Author(s): bci1 %%% PlanetPhysics is released under the GNU Free Documentation License. %%% You should have received a file called fdl.txt along with this file. %%% If not, please write to gnu@gnu.org. \documentclass[12pt]{article} \pagestyle{empty} \setlength{\paperwidth}{8.5in} \setlength{\paperheight}{11in}

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\textbf{QCD} or \emph{Quantum chromodynamics} is the advanced, standard mathematical and quantum physics treatment, or theory, of strong \htmladdnormallink{force}{http://planetphysics.us/encyclopedia/Thrust.html} or \htmladdnormallink{nuclear interactions}{http://planetphysics.us/encyclopedia/HotFusion.html} such as those among quarks and gluons, \htmladdnormallink{partons}{http://planetphysics.us/encyclopedia/QuarkAntiquarkPair.html}, `Yukawa' mesons, and so on, with an intrinsic threefold symmetry for RGB quarks (or `eightfold-way' \htmladdnormallink{diagrams}{http://planetphysics.us/encyclopedia/TrivialGroupoid.html} resulting from \htmladdnormallink{representations}{http://planetphysics.us/encyclopedia/CategoricalGroupRepresentation.html} of the \htmladdnormallink{quantum group}{http://planetphysics.us/encyclopedia/ComultiplicationInAQuantumGroup.html} $SU(3)$ first reported by the US Nobel Laureate Gell-Mann and others. This is not only a rather `colorful' theory (as its name suggests) but also a very highly formalized, mathematical one that affords major simplifications by postulating intrinsic symmetries of magnetic--like `color', `flavor', `strangeness' and top/down {\em quark} (and \htmladdnormallink{anti-quark}{http://planetphysics.us/encyclopedia/NeutrinoRestMass.html}) intrinsic properties, each time involving three color charges. {\em Single quarks}, such as the $u$ or $d$ ones have however never been observed, with the proton and \htmladdnormallink{neutron}{http://planetphysics.us/encyclopedia/Pions.html} `consisting of' three such quarks with a resulting `white' color, or \htmladdnormallink{charge}{http://planetphysics.us/encyclopedia/Charge.html} colorless proton and neutron, as well as stable `white' nuclei `consisting of' the latter two \htmladdnormallink{quantum particles}{http://planetphysics.us/encyclopedia/QuantumParticle.html}, dynamically confined by the very short range, nuclear \htmladdnormallink{strong interactions}{http://planetphysics.us/encyclopedia/QuarkAntiquarkPair.html}. The quark interactions are mediated by {\em gluons}--as well as their exchange-- and the latter also carry charge color--but unlike the photons that mediate the electromagnetic interactions in QED-- gluons have multiple interactions with each other leading to major computational difficulties in QCD, that are not encountered in \htmladdnormallink{QED}{http://planetphysics.us/encyclopedia/LQG2.html}. Major obstacles in QCD \htmladdnormallink{computations}{http://planetphysics.us/encyclopedia/LQG2.html} of \htmladdnormallink{observable}{http://planetphysics.us/encyclopedia/QuantumSpinNetworkFunctor2.html} nuclear (quantum) eigenvalues are therefore encountered in attempting approximate, perturbative approaches that \htmladdnormallink{work}{http://planetphysics.us/encyclopedia/Work.html} extremely well for electromagentic interactions (governed by the charge $U(1)$ \htmladdnormallink{symmetry group}{http://planetphysics.us/encyclopedia/TopologicalOrder2.html}), for example with Richard Feynman's approach in QED.

Electro-weak (QEW) interactions were successfully approached in QED--like fashion but with \htmladdnormallink{quantum field}{http://planetphysics.us/encyclopedia/CosmologicalConstant.html} carriers that are--unlike the photon--massive, and therefore the electro-weak interactions have limited range, unlike the photons of zero \htmladdnormallink{mass}{http://planetphysics.us/encyclopedia/CosmologicalConstant.html} at rest. Thus, QCD and QED are more than just `one pole apart', as $U(1)$ and $SU(3)$ are very different \htmladdnormallink{group}{http://planetphysics.us/encyclopedia/TrivialGroupoid.html} symmetries. This makes obvious the need for more fundamental, or extended quantum symmetries, such as those afforded by either several larger groups such as $U(1) \times SU(2) \times SU(3)$, or by spontaneously broken, multiple (or localized) symmetries of a less restrictive kind present in \htmladdnormallink{quantum groupoids}{http://planetphysics.us/encyclopedia/WeakHopfAlgebra.html}, such as for example in \htmladdnormallink{weak Hopf algebra}{http://planetphysics.us/encyclopedia/WeakHopfAlgebra.html} representations, \htmladdnormallink{locally compact groupoid}{http://planetphysics.us/encyclopedia/LocallyCompactGroupoid.html} {\em $G_{lc}$}, unitary representations, and so on, to the higher dimensional (quantum) symmetries of \htmladdnormallink{quantum double groupoids}{http://planetphysics.us/encyclopedia/LongRangeCoupling.html}, quantum \htmladdnormallink{double algebroids}{http://planetphysics.us/encyclopedia/GeneralizedSuperalgebras.html}, \htmladdnormallink{quantum categories/}{http://planetphysics.us/encyclopedia/QuantumCategories.html} \htmladdnormallink{supercategories}{http://planetphysics.us/encyclopedia/SuperCategory6.html} and/or quantum \htmladdnormallink{supersymmetry superalgebras}{http://planetphysics.us/encyclopedia/HamiltonianAlgebroid3.html} (or graded `\htmladdnormallink{Lie' algebras}{http://planetphysics.us/encyclopedia/BilinearMap.html}, see- for example- the \htmladdnormallink{QFT}{http://planetphysics.us/encyclopedia/HotFusion.html} books by Weinberg (1995, 2003) \htmladdnormallink{superalgebroids}{http://planetphysics.us/encyclopedia/GeneralizedSuperalgebras.html} in \htmladdnormallink{quantum gravity}{http://planetphysics.us/encyclopedia/LQG2.html}, or in QCD of the extremely hot, very early, \htmladdnormallink{physical Universe}{http://planetphysics.us/encyclopedia/MultiVerses.html}, extremely close to the time of the `Big Bang'.

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