Why is Adjoint QCD₂ so Insensitive to N_c?

The spectrum of two-dimensional adjoint QCD is surprisingly insensitive to the number of colors N_c​. Many nominal finite-N_c​ contributions must vanish due to the singularity structure of the theory. A small set of surviving finite N_c terms modify the spectrum as seen in numerical studies. Several parton‑number–changing corrections vanish independently of finiteness requirements, and only one trace-diagonal finite-N_c correction remains. These cancellations hint at an additional symmetry of the theory. They also suggest that focusing on matrix elements, rather than contributions of individual single-momentum states, can simplify the computation of spectra in gauge theories with large symmetry.

In the talk I will review these findings, and suggest tests of the conjecture that some matrix elements only vanish between physical states. This should further clarify the nature of the suspected additional symmetry of adjoint QCD₂.