Unformatted text preview: n and x , F n ( x )-x is not an integer. Therefore we can write k n < F n ( x )-x < k n + 1 , (1) for some integer k n that may depend on n . Using this fact, show that the rotation number cannot be a rational number of the form (integer) /n . Since n can be any positive integer, this proves that the absence of periodic point leads to irrational rotation number. 4. Consider the map F : S 1 → S 1 given by F ( x ) = 2 x mod 1 (expansion map). Show that all the rational points are eventually periodic points (i.e. pre-images of periodic points). 1...
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- Spring '09
- Math, Blackboard bold, Periodic point, rotation number