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arXiv 1111.5561math.DS
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Dehn扭同伦环面同胚的动力学

Dynamics of homeomorphisms of the torus homotopic to Dehn twists

Braulio Garcia, Fabio Armando Tal, Salvador Addas-Zanata

摘要:

本文考虑与Dehn扭同伦的环面同胚$f$.我们证明了如果$f$的垂直旋转集降为零,则存在紧连通本质“水平”集K,它在$f$下不变.换句话说,如果我们考虑$f$对垂直旋转数为零的圆柱的升力$\hat{f}$,则所有点在$\hat{f}$的迭代下都有一致有界运动。此外,我们给出了一个简单的明确的条件,当满足时,意味着垂直旋转集包含一个区间,从而也意味着积极的拓扑熵。作为上述结果的推论,我们证明了一个版本的Boyland的猜想,这个设置:如果$f$是面积保持和有一个升降机$\hat{f}$的圆柱与零勒贝格测度垂直旋转数,然后要么是所有点的轨道下一致有界$\hat{f}$,或有点在圆柱上的正垂直速度和其他负垂直速度。

英文摘要:

In this paper we consider torus homeomorphisms $f$ homotopic to Dehn twists. We prove that if the vertical rotation set of $f$ is reduced to zero, then there exists a compact connected essential "horizontal" set K, invariant under $f$. In other words, if we consider the lift $\hat{f}$ of $f$ to the cylinder, which has zero vertical rotation number, then all points have uniformly bounded motion under iterates of $\hat{f}$. Also, we give a simple explicit condition which, when satisfied, implies that the vertical rotation set contains an interval and thus also implies positive topological entropy. As a corollary of the above results, we prove a version of Boyland's conjecture to this setting: If $f$ is area preserving and has a lift $\hat{f}$ to the cylinder with zero Lebesgue measure vertical rotation number, then either the orbits of all points are uniformly bounded under $\hat{f}$, or there are points in the cylinder with positive vertical velocity and others with negative vertical velocity.

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