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arXiv 2202.09104math.CO
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关于超平面排列的形式性与组合形式性

On Formality and Combinatorial Formality for hyperplane arrangements

Tilman Möller, Paul Mücksch, Gerhard Roehrle

AI总结:

本文证明超平面排列的 niceness 组合性质蕴含形式性,并证明形式性具有遗传性,同时指出 k-形式性不具遗传性。

摘要:

一个超平面排列被称为形式性的,如果超平面定义形式之间的所有线性依赖关系都由对应于余维数为二的交集的依赖关系生成。这一概念的重要性源于具有非球面补集的复排列是形式性的这一事实。本文的目的有两个方面。虽然 Yuzvinsky 的工作表明形式性不是组合性质,但在我们的第一个主要定理中,我们证明了排列的 niceness 这一组合性质确实蕴含形式性。我们的第二个主要定理表明形式性是遗传的,即它会传递给限制。这是相当反直觉的,因为相比之下,已知的形式性充分条件,即非球面性、自由性和 niceness(得益于我们的第一个定理),本身并不是遗传的。我们还证明了由 Brandt 和 Terao 提出的更强的 k-形式性性质不是遗传的。

英文摘要:

A hyperplane arrangement is called formal provided all linear dependencies among the defining forms of the hyperplanes are generated by ones corresponding to intersections of codimension two. The significance of this notion stems from the fact that complex arrangements with aspherical complements are formal. The aim of this note is twofold. While work of Yuzvinsky shows that formality is not combinatorial, in our first main theorem we prove that the combinatorial property of niceness of arrangements does entail formality. Our second main theorem shows that formality is hereditary, i.e. is passed to restrictions. This is rather counter-intuitive, as in contrast the known sufficient conditions for formality, i.e. asphericity, freeness and niceness (owed to our first theorem), are not hereditary themselves. We also demonstrate that the stronger property of $k$-formality, due to Brandt and Terao, is not hereditary.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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