Effective computation for nonlinear systems Abstract: Nonlinear dynamical and control systems are an important source of applications for theories of computation over the the real numbers, since these systems are usually to complicated to study analytically, but may be extremely sensitive to numerical error. Further, computer-assisted proofs and specification verification problems require a rigorous treatment of numerical errors. In this talk I will describe how to provide a semantics for effective computations on sets and maps, and discuss the computability of some important operators. I will show how these operations have been implemented in the tool Ariadne, and give examples of the use of Ariadne for the analysis, design and verification of nonlinear and hybrid systems.