3.2 Repeated Games 71 differential games; this type of game is considered to bridge the gap between stochas- tic games and differential games. They allow the reader to become familiar with one of the most general definitions of dynamic games having complete information which is in use, and for which there are some theoretical results. To conclude on differential games, note that they can also be considered as a lim- iting case of difference games. Continuous-time dynamics have been much used to design a discrete-time strategy for power control (e.g., see Foschini and Milijanic (1993)). Finally, evolutionary games will be studied in Sec. 3.5. This type of game involves a large number of players, and studies the evolution of the population of players as they interact with each other (e.g., in a pairwise manner). The (potentially strong) rationality assumption is not necessary in evolutionary games, and the solu- tion concepts (e.g., the evolutionarily stable state) which are used ensure stability with respect to a fraction of the population of players. Usually, time is assumed to be continuous in evolutionary games but this assumption is not necessary. 3.2 REPEATED GAMES