$H^2(SL_3(\mathbb{Z}[t]); \mathbb{Q})$ is infinite dimensional

Abstract

We prove that $H^2(SL_3(\mathbb{Z}[t]); \mathbb{Q})$ is infinite dimensional. The proof follows an outline similar to recent results by Cobb, Kelly, and Wortman, using the Euclidean building for $SL_3(\mathbb{Q}((t^{-1})))$ and a Morse function from Bux-K\"ohl-Witzel.