On the growth of torsion in the cohomology of some arithmetic groups of $\mathbb{Q}$-rank one

Werner Mueller, Frédéric Rochon

Given a number field $F$ with ring of integers ${\mathcal{O}}_F$, one can associate to any torsion free subgroup of $\mathrm{SL}(2,{\mathcal{O}}_F)$ of finite index a complet…