Non-rigidity
摘要
Circle diffeomorphims with well behaved rotation number are rigid, i.e. the conjugacies to the corresponding rotations are differentiable, Theorem 8.1.4 . The exponential convergence of fast renormalization to rotations is the main reason for this rigidity phenomenon, Theorem 7.1.1 . This chapter presents two examples of maps which show that the convergence of renormalizations to rotations is a delicate matter.