A finiteness condition for complex continued fraction algorithms

Abstract

It is desirable that a given continued fraction algorithm is simple in the sense that the possible representations can be characterized in an easy way. In this context the so-called finite range condition plays a prominent role. We show that this condition holds for complex $\hat{\mathbf{I}}\pm$-Hurwitz algorithms with parameters $\hat{\mathbf{I}}\pm \in {\mathbb{Q}}^2$. This is equivalent to the existence of certain finite partitions related to these algorithms and lies at the root of explorations into their Diophantine properties. Our result provides a partial answer to a recent question formulated by Lukyanenko and Vandehey.

12 pages, 6 figures