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arXiv 1002.1106math.GT
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2-桥纽结的满射与边界斜率

Epimorphisms and Boundary Slopes of 2-Bridge Knots

Jim Hoste, Patrick D. Shanahan

摘要:

本文研究了K_1大于或等于K_2的3-球面中纽结上的一个偏序,如果存在从K_1的纽结群到K_2的纽结群的满态映射,且该满态映射保持外围结构.如果K_1是二桥结,且K_1 > K_2,则K_2也必定是二桥结。此外,Ohtsuki、Riley和Sakuma给出了一种构造,对于给定的2桥结K_{p/q},该构造产生无限2桥结K_{p'/q'},其中K_{p'/q'} > K_{p/q}。在描述了所有具有4个或更少不同边界斜率的2桥结之后,我们用它来证明在任何这样的对中,K_{p'/q'}要么是环面结,要么具有5个或更多不同的边界斜率。我们还证明了具有恰好3个不同边界斜率的2-桥纽结相对于偏序是最小的。这一结果为所有K_{p'/q'} > K_{p/q}的2-桥纽结对都产生于Ohtsuki-Riley-Sakuma构造的猜想提供了一些证据。

英文摘要:

In this article we study a partial ordering on knots in the 3-sphere where K_1 is greater than or equal to K_2 if there is an epimorphism from the knot group of K_1 onto the knot group of K_2 which preserves peripheral structure. If K_1 is a 2-bridge knot and K_1 > K_2, then it is known that K_2 must also be 2-bridge. Furthermore, Ohtsuki, Riley, and Sakuma give a construction which, for a given 2-bridge knot K_{p/q}, produces infinitely 2-bridge knots K_{p'/q'} with K_{p'/q'}>K_{p/q}. After characterizing all 2-bridge knots with 4 or less distinct boundary slopes, we use this to prove that in any such pair, K_{p'/q'} is either a torus knot or has 5 or more distinct boundary slopes. We also prove that 2-bridge knots with exactly 3 distinct boundary slopes are minimal with respect to the partial ordering. This result provides some evidence for the conjecture that all pairs of 2-bridge knots with K_{p'/q'}>K_{p/q} arise from the Ohtsuki-Riley-Sakuma construction.

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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