Singularity, complexity, and quasi-integrability of rational mappings

We investigate global properties of the mappings entering the description of symmetries of integrable spin and vertex models, by exploiting their nature of birational transformations of projective spaces. We give an algorithmic analysis of the structure of invariants of such mappings. We discuss some characteristic conditions for their (quasi)-integrability, and in particular its links with their singularities (in the 2-plane). Finally, we describe some of their properties qua dynamical systems, making contact with Arnol'd's notion of complexity, and exemplify remarkable behaviours. © 1993 Springer-Verlag.