  The slow dynamics of topological solitons in the CP^1 sigma-model, known as
lumps, can be approximated by the geodesic flow of the L^2 metric on certain
moduli spaces of holomorphic maps. In the present work, we consider the
dynamics of lumps on an infinite flat cylinder, and we show that in this case
the approximation can be formulated naturally in terms of regular Kaehler
metrics. We prove that these metrics are incomplete exactly in the multilump
(interacting) case. The metric for two-lumps can be computed in closed form on
certain totally geodesic submanifolds using elliptic integrals; particular
geodesics are determined and discussed in terms of the dynamics of interacting
lumps.
