Lack of thermalization in (1+1)-d QCD at large N_c

Motivated by recent works aimed at understanding the status ofequilibration and the eigenstate thermalization hypothesis in theorieswith confinement, we return to the 't Hooft model, the large-N_c limitof (1+1)-d quantum chromodynamics. This limit has been studiedextensively since its inception in the mid-1970s, with various exactresults being known, such as the quark and meson propagators, thequark-antiquark interaction vertex, and the meson decay amplitude. Wethen argue this model is an ideal laboratory to study non-equilibriumphenomena, since it is manifestly non-integrable, yet one retains a highlevel of analytic control through large-N_c diagrammatics. We firstelucidate what are the non-equilibrium manifestations of the phenomenonof large-N_c volume independence. We then find that within theconfined phase, there is a class of initial states that lead to aviolation of the eigenstate thermalization hypothesis, i.e. the systemnever thermalizes. This is due to the existence of heavy mesons with anextensive amount of energy, a phenomenon that has been numericallyobserved recently in the quantum Ising chain.