A Hamiltonian matrix $Y$ with $Y^3=9Y$ is joined, avoiding eigenvalue $1$, to $0$ or to $\mathrm{diag}(3,0,\dots,0,-3,0,\dots,0)$

Initializing...

A Hamiltonian matrix $Y$ with $Y^3=9Y$ is joined, avoiding eigenvalue $1$, to $0$ or to $\mathrm{diag}(3,0,\dots,0,-3,0,\dots,0)$ · Prove2Me