On the codimension-two cohomology of ${\mathrm{SL}}_n(\mathbb{Z})$

Benjamin Brück, Jeremy Miller, Peter Patzt +2

Borel-Serre proved that ${\mathrm{SL}}_n(\mathbb{Z})$ is a virtual duality group of dimension $\left(\genfrac{}{}{0ex}{}{n}{2}\right)$ and the Steinberg module ${\mathrm{St}}_n(\mathbb{Q})$ is its dualizing modu…