Two-dimensional SU(N) gauge theory, strings and wings: comparative analysis of meson spectra and covariance

't Hooft's two-dimensional SU(N) gauge theory model for mesons is studied in two different axial gauges. Using numerical techniques employed in aerodynamical wing theory, the bound state spectra in the A+=0 and A1=0 gauges are compared. Agreement is found in the weak coupling limit. Furthermore, Lorentz covariance of the weak coupling A1=0 theory is numerically confirmed. The massive-end string model, which is equivalent to 't Hooft's A+=0 model when the x+=tau gauge is chosen, is also investigated. It is found that the numerical spectrum of the string model in the x0=tau gauge differs from the x+=tau gauge string spectrum as well as from the A1=0 gauge theory spectrum. A Bethe-Salpeter equation approach to the spectrum of the gauge theory in the A1=0 gauge is developed for any coupling. While the strong coupling theory in this gauge presents severe difficulties, the weak coupling limit is shown to be completely consistent. (Auth.)