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+ | ====== Minimal Coupling ====== | ||
+ | |||
+ | <tabbox Why is it interesting?> | ||
+ | |||
+ | <blockquote>Why minimal coupling? This requirement arises indirectly, as a consequence of the | ||
+ | general difficulty of constructing consistent interacting relativistic quantum field theories in | ||
+ | four space-time dimensions. | ||
+ | The perturbative construction of such theories involves regularization and renormaliza- | ||
+ | tion. If we want to have a closed theory, in which the limiting effect of the regulator can be | ||
+ | absorbed into a finite number of renormalization parameters, we must restrict ourselves to | ||
+ | renormalizable couplings, that is interaction vertices whose coefficients have non-negative | ||
+ | mass dimension (in units with ~ = c = 1, of course). Otherwise the insertion of these | ||
+ | vertices will, in general, be accompanied by positive powers of the cutoff mass, and taking | ||
+ | that mass to infinity will be counterproductive. This means that the vertices themselves | ||
+ | must be constructed from fields whose total mass dimension does not exceed four. This | ||
+ | criterion, when combined with gauge invariance, greatly restricts the possibilities, and in | ||
+ | particular enforces minimal coupling for the gauge fields.<cite> [[https://arxiv.org/pdf/hep-ph/0405147.pdf|Yang-Mills Theory In, Beyond, and Behind Observed Reality]] by Frank Wilczek</cite></blockquote> | ||
+ | |||
+ | <tabbox Layman> | ||
+ | |||
+ | <note tip> | ||
+ | Explanations in this section should contain no formulas, but instead colloquial things like you would hear them during a coffee break or at a cocktail party. | ||
+ | </note> | ||
+ | | ||
+ | <tabbox Student> | ||
+ | |||
+ | <note tip> | ||
+ | In this section things should be explained by analogy and with pictures and, if necessary, some formulas. | ||
+ | </note> | ||
+ | |||
+ | <tabbox Researcher> | ||
+ | |||
+ | <note tip> | ||
+ | The motto in this section is: //the higher the level of abstraction, the better//. | ||
+ | </note> | ||
+ | |||
+ | --> Common Question 1# | ||
+ | |||
+ | |||
+ | <-- | ||
+ | |||
+ | --> Common Question 2# | ||
+ | |||
+ | |||
+ | <-- | ||
+ | | ||
+ | <tabbox Examples> | ||
+ | |||
+ | --> Example1# | ||
+ | |||
+ | |||
+ | <-- | ||
+ | |||
+ | --> Example2:# | ||
+ | |||
+ | |||
+ | <-- | ||
+ | | ||
+ | <tabbox History> | ||
+ | |||
+ | </tabbox> | ||
+ | |||