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arXiv 1606.01765math.DS
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无支配分裂的$C^1$类同态的熵

Entropy of $C^1$ diffeomorphisms without a dominated splitting

Jerome Buzzi, Sylvain Crovisier, Todd Fisher

摘要:

一个经典的建设,由于纽豪斯创建马蹄铁从双曲周期轨道大周期和弱控制通过本地$C^1$ -扰动。我们的主要定理表明,当工作在$C^1$拓扑中时,可以使这样的马蹄铁的熵任意地接近由Ruelle不等式导出的上界,即,正的李雅普诺夫指数之和(或对于逆李雅普诺夫指数,取较小者)。适应经典的技术,我们使用的扰动是本地的,可以选择保持体积或辛形式或同宿连接。这种最佳熵的产生产生了一些后果$C^1$ -通用的同构,特别是在没有一个主导的分裂。例如,在保守的设置,我们发现的拓扑熵的公式,推导出的拓扑熵是连续的,但不是局部常数的一般的同构,我们证明了这些一般的同构没有措施的最大熵。在耗散的设置,我们显示了本地通用的存在无穷多个同宿类的熵有界远离零。

英文摘要:

A classical construction due to Newhouse creates horseshoes from hyperbolic periodic orbits with large period and weak domination through local $C^1$-perturbations. Our main theorem shows that, when one works in the $C^1$ topology, the entropy of such horseshoes can be made arbitrarily close to an upper bound deriving from Ruelle's inequality, i.e., the sum of the positive Lyapunov exponents (or the same for the inverse diffeomorphism, whichever is smaller). Adapting classical techniques, we use perturbations that are local and can be chosen to preserve volume or symplectic form or a homoclinic connection. This optimal entropy creation yields a number of consequences for $C^1$-generic diffeomorphisms, especially in the absence of a dominated splitting. For instance, in the conservative settings, we find formulas for the topological entropy, deduce that the topological entropy is continuous but not locally constant at the generic diffeomorphism and we prove that these generic diffeomorphisms have no measure of maximum entropy. In the dissipative setting, we show the locally generic existence of infinitely many homoclinic classes with entropy bounded away from zero.

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