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arXiv 2006.14770math.GTmath.DG
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图流形及其有限覆盖的 Seifert 表示的体积

Volume of Seifert representations for graph manifolds and their finite covers

Pierre Derbez, Yi Liu, Shicheng Wang

AI总结:

本文研究图流形的 Seifert 表示体积,给出有效计算公式与表示限制,证明其体积为 π² 的有理倍数,并揭示有限覆盖中体积与覆盖次数之比的上确界可有限或无穷。

摘要:

对于任意闭可定向3维流形,在其基本群的所有 Seifert 表示构成的空间上定义了一个体积函数。该函数绝对值的最大值与 Brooks 和 Goldman 提出的流形 Seifert 体积一致。对于图流形的任意 Seifert 表示,作者建立了计算其体积的有效公式,并得到了类似于 Milnor–Wood 不等式(关于 Seifert 纤维空间上横截射影叶状结构的不等式)的表示限制。结果表明,任意图流形的 Seifert 体积都是 π² 的有理倍数。在给定非几何图流形的所有有限覆盖中,Seifert 体积与覆盖次数之比的上确界可以是正数,也可以是无穷大。文中发现并证实了这两种可能性的例子,并对有限情形确定了显式值。

英文摘要:

For any closed orientable 3-manifold, there is a volume function defined on the space of all Seifert representations of the fundamental group. The maximum absolute value of this function agrees with the Seifert volume of the manifold due to Brooks and Goldman. For any Seifert representation of a graph manifold, the authors establish an effective formula for computing its volume, and obtain restrictions to the representation as analogous to the Milnor--Wood inequality (about transversely projective foliations on Seifert fiber spaces). It is shown that the Seifert volume of any graph manifold is a rational multiple of $π^2$. Among all finite covers of a given non-geometric graph manifold, the supremum ratio of the Seifert volume over the covering degree can be a positive number, and can be infinite. Examples of both possibilities are discovered, and confirmed, with the explicit values determined for the finite ones.

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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