ABSTRACT
We begin this chapter by introducing the notion of chaos in dynamical systems. We state LI and Yorke theorem (period 3 implies chaos) and present part of its proof following the original one. We then introduce the notion of topological entropy and show some results that deal with the question of how the topological entropy of a map depends on the map itself. We finish this chapter by studying the Schwarzian derivative of a map and Singer's theorem.
