Trace formulas for TBG

Becker et al. produced a striking trace formula for the sum of fourth powers of generalized magic angles, $\theta$, for the chiral model of twisted bilayer graphene (TBG) with the exact Bistritzer–MacDonald potential: $\sum {\theta }^4=8\pi \mathrm{/}\sqrt{3}$. The purpose of this note is to generalize this formula to a larger class of potentials satisfying the symmetries of the model.