  We provide a mathematical account of the recent Physical Reviews Letter by
Tarnopolsky--Kruchkov--Vishwanath. The new contributions are a spectral
characterization of magic angles, its accurate numerical implementation and an
exponential estimate on the squeezing of all bands as the angle decreases.
Pseudospectral phenomena due to the non-hermitian nature of operators appearing
in the model play a crucial role in our analysis.
