arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.13244math.GT
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4-球中2-球的解结数

Unknotting numbers of 2-spheres in the 4-sphere

Jason Joseph, Michael Klug, Benjamin Ruppik, Hannah Schwartz

摘要:

我们比较两个自然产生的概念unknotting数为2-领域的4-领域:即,最小数量的1-处理稳定需要获得一个unknotted表面,和最小数量的惠特尼移动所需的一个经常同伦unknotted 2-领域。我们将这些不变量分别称为球面的稳定数和卡森-惠特尼数。使用代数和几何技术,我们证明了稳定数是有界的一个以上的卡森-惠特尼数。我们还提供了明确的家庭领域,这些不变量是平等的,以及家庭,他们是不同的。此外,我们给出了额外的界限,这两个不变量,具体的例子,他们的非可加性,并应用到经典的unknotting数的1节。

英文摘要:

We compare two naturally arising notions of unknotting number for 2-spheres in the 4-sphere: namely, the minimal number of 1-handle stabilizations needed to obtain an unknotted surface, and the minimal number of Whitney moves required in a regular homotopy to the unknotted 2-sphere. We refer to these invariants as the stabilization number and the Casson-Whitney number of the sphere, respectively. Using both algebraic and geometric techniques, we show that the stabilization number is bounded above by one more than the Casson-Whitney number. We also provide explicit families of spheres for which these invariants are equal, as well as families for which they are distinct. Furthermore, we give additional bounds for both invariants, concrete examples of their non-additivity, and applications to classical unknotting number of 1-knots.

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