The twisted Euclidean algorithm: Applications to number theory and geometry

We introduce a generalization of the Euclidean algorithm for rings equipped with an involution, and completely enumerate all isomorphism classes orders over definite, rational quaternion algebras orthogonal involution that admit such algorithm. give two applications: first, any order admits has class number 1; second, we show how existence relates to problem constructing explicit Dirichlet domains Kleinian subgroups isometry group hyperbolic 4-space.