1.4 Experimental verification of SU(3) as the gauge group of QCD from four jet events measured at LEP. N$_{c}$ , C$_{F}$ , and T$_{F}$ are prop- erties of the group structure functions f and generators T de- fined by f $^{abc}$f ∗ abd = δ $^{cd}$N$_{c}$ , ( T $^{a}$T † $^{a}$)$_{ij}$ = δ$_{ij}$C$_{F}$ , and Tr ( T $^{a}$T † $^{b}$) = δ $^{ab}$T$_{F}$ , where repeated indices are summed over. Groups with N$_{c}$ = 3 are excluded by decay ratios while S0(3) and U(1)$_{3}$ do not have the correct ratios of group theoretic factors. Figure adapted from [44]. . . . . . . . . . . . . . . . . . . . . . . . . 9 1.5 (a) Phase transition from confined baryonic/mesonic matter to quark/gluon matter from the mean field quantum hadrodynam- ics (QHD) approach of Walecka [71]; figure adapted from [79]. (b) A sharp rise in energy reminiscent of a phase transition is seen at T ≈ 160 MeV in Hagedorn’s statistical model [69]; figure adapted from [70]. . . . . . . . . . . . . . . . . . . . . . . . . 11 1.6 (a) The q ¯ q potential from LQCD for heavy quarks shows evi- dence of plasma formation at high temperatures. For T > T$_{c}$ the potential becomes independent of distance for separations longer than a temperature-dependent characteristic length; fig- ure adapted from [80–83]. (b) Lattice calculations show a sharp rise in entropy density as a function of temperature, indicat- ing a significant change in the number of degrees of freedom at T$_{c}$ ∼ 180 MeV; figure adapted from [78]. . . . . . . . . . . . . 12 vii