2.11 Chew-Frautschi plot of the Regge trajectories α ( M $^{2}$) for the Λ and Σ hadrons. Poles at half-integer values of α correspond to the masses of the narrow resonances. Figure adapted from [314]. 47 2.12 (a) Open strings ending on a D brane. (b) D branes as the source of closed strings. Figure adapted from [322]. . . . . . . 57 2.13 (a) Open string with i and j Chan-Paton degrees of freedom. (b) Open string scattering amplitude; the Chan-Paton index for the right end of each string becomes that of the left end of the next. In the hadronic string theory this corresponds to 3 meson to 2 meson scattering. Figures adapted from [323, 324]. . . . . 59 2.14 (a) Heavy q ¯ q potential for N$_{c}$ = 3 and λ = 10 (blue, dotted), 10 2 (green, short dash), 10 3 (red, long dash), and 10 4 (black, solid). As λ → ∞ the potential develops a kink at | x | = . 24 /T ; for larger distances the potential continues to rise, but very slowly. Figure adapted from [337]. (b) The AdS/CFT scaled energy density of the SYM plasma with Mach cone for a heavy quark with v = 3 / 4. Figure adapted from [341]. . . . . . . . . . . . . 70 x