“This is a wonderful book about ‘mildly’ smooth actions of groups on the most important manifolds in mathematics: the circle and the line. Andrés Navas draws upon the classical contributions of Poincaré, Denjoy, Hölder, Plante, Thompson, Sacksteder, and Duminy, as well as the relatively recent achievements of Margulis and Witte Morris, to offer the first book-length exploration of this topic. The analytic techniques, the dynamical point of view, and the algebraic nature of objects considered here produce a blend of beautiful mathematics that will be used by researchers in several areas of science.”

“Groups of Circle Diffeomorphisms provides a great overview of the research on differentiable group actions on the circle. Navas’s book will appeal to those doing research on differential topology, transformation groups, dynamical systems, foliation theory, and representation theory, and will be a solid base for those who want to further attack problems of group actions on higher dimensional manifolds or of geometric group theory.”