No CrossRef data available.
Published online by Cambridge University Press: 28 September 2006
We show that the Bianchi group $\mathrm{PSL}_2(\mathcal{O}_d)$, where $\mathcal{O}_d$ is the ring of integers in $\mathbb{Q}(\sqrt{d})$, $d\,{<}\,0$, has a free quotient of rank$\,{\geq}\, |d|^{\frac {1}{4}-\epsilon}$, as $|d|\,{\to}\,\infty$. To do so, we give an estimate for a sifted character sum.