User:Johnjbarton/sandbox/standard model

Gauge theories Penrose pg 451-455.
 * Weyl's theory generalizes the concept of length in classical field.
 * Weyl's gauge transformation failed for EM because mass would be history dependent.
 * QM uses scaling by $$e^{i\theta}$$, avoiding the mass-history issue.
 * $$\psi \rightarrow e^{i\theta}\psi $$ symmetry in EM
 * Yang-mills is generalization of EM; the basis of QCD (pg 649)
 * gauge bosons of QCD are gluons, analogs of photons.