In this paper a completely integrable Hamiltonian system on $T^*M$ is constructed for every Riemannian symmetric space $M$. We show that the solutions of this system correspond to the solutions of Nahm's equations for suitably chosen maps. Nahm's equations were introduced by Nahm as a rewriting of Bogomolny equations for magnetic monopoles.

We represent our system as a degeneration of a certain case of Hitchin's algebraically integrable system. We prove the complete integrability of our system by means of this representation.

Some concrete examples of our Hamiltonian system on $T^*M$ are described. When $M= S^n$, we obtain the classical system of C. Neumann. If the configuration space $M$ of our system is the $n$-dimensional hyperbolic space, we get the Minkowskian analogue of the C. Neumann system. Other examples that we describe are a many-body C. Neumann system, a spherical pendulum, and a spherical pendulum with an additional magnetic force.

This article addresses the question of which non-empty, compact, proper subsets $E$ of the extended complex plane $\widehat{\mathbb C}$ have the feature that, for some $K$ in $[1,\infty)$, the family of$K$-quasiconformal self-mappings of $\widehat{\mathbb C}$ which leave $E$ invariant acts transitively on the set $E\times E^c$, where $E^c$ is the complement of $E$ in $\widehat{\mathbb C}$. The main result in the paper asserts that the class of sets with this property comprises all one- and two-point subsets of $\widehat{\mathbb C}$, all quasicircles in $\widehat{\mathbb C}$ and all images of the Cantor ternary set under quasiconformal self-mappings of $\widehat{\mathbb C}$. It is shown that the third category includes the limit set of any non-cyclic, finitely generated Schottky group.