Explicit near-fully X-Ramanujan graphs

Ryan O'Donnell, Xinyu Wu

Let $p(Y_1,\dots ,Y_d,Z_1,\dots ,Z_e)$ be a self-adjoint noncommutative polynomial, with coefficients from ${\mathbb{C}}^{r\times r}$, in the indeterminates $Y_1,\dots ,Y_d$ (co…