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تسجيل مستخدم جديدDevils Staircase -- Rotation Number of Outer Billiard with Polygonal Invariant Curves
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Zijian Yao
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In this paper, we discuss rotation number on the invariant curve of a one parameter family of outer billiard tables. Given a convex polygon $eta$, we can construct an outer billiard table $T$ by cutting out a fixed area from the interior of $eta$. $T$ is piece-wise hyperbolic and the polygon $eta$ is an invariant curve of $T$ under the billiard map $phi$. We will show that, if $beta $ is a periodic point under the outer billiard map with rational rotation number $tau = p / q$, then the $n$th iteration of the billiard map is not the local identity at $beta$. This proves that the rotation number $tau$ as a function of the area parameter is a devils staircase function.
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