Fortuity with a single matrix

We construct and study a supersymmetric quantum mechanical model with a single $U(N)$ adjoint fermionic matrix. The model is exactly solvable yet contains a large number of fortuitous states. We investigate these states exactly at finite $N$ and, in the large $N$ limit, via a unitary matrix model. In particular, we develop a way to “follow $N$” in the unitary matrix integral and study how the answer of the integral depends sensitively on the value of $N$.