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arXiv 1005.1902math.DS
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一类无穷区间交换映射的不变测度

The Invariant Measures of some Infinite Interval Exchange Maps

W. Patrick Hooper

摘要:

对一类无穷区间交换变换的局部有限遍历不变测度进行了分类.这些变换自然地产生于某些平移曲面上直线流的返回映射,并且对这些变换的不变测度的研究等价于对这些平移曲面上沿某一方向的直线流的不变测度的研究。对于我们的方法适用的表面和方向,我们可以在一组方向的豪斯多夫维数大于1/2的直线流的局部有限遍历不变测度的特征。在某些情况下,我们将这种特性提升为一种分类。例如,当表面承认一个由幂零群的余紧作用,我们证明了每个遍历不变测度的直线流是一个Maharam措施,我们精确地描述了Maharam措施的出现。当所考虑的曲面是有限区域时,沿我们所知方向的直线流是唯一遍历的。我们的方法适用于翻译表面承认在非平行方向上的一对圆柱体分解的多个扭曲。

英文摘要:

We classify the locally finite ergodic invariant measures of certain infinite interval exchange transformations (IETs). These transformations naturally arise from return maps of the straight-line flow on certain translation surfaces, and the study of the invariant measures for these IETs is equivalent to the study of invariant measures for the straight-line flow in some direction on these translation surfaces. For the surfaces and directions for which our methods apply, we can characterize the locally finite ergodic invariant measures of the straight-line flow in a set of directions of Hausdorff dimension larger than 1/2. We promote this characterization to a classification in some cases. For instance, when the surfaces admit a cocompact action by a nilpotent group, we prove each ergodic invariant measure for the straight-line flow is a Maharam measure, and we describe precisely which Maharam measures arise. When the surfaces under consideration are finite area, the straight-line flows in the directions we understand are uniquely ergodic. Our methods apply to translation surfaces admitting multi-twists in a pair of cylinder decompositions in non-parallel directions.

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