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arXiv 0901.2974math.GT
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穿孔环面上曲线的自相交数

Self-intersection numbers of curves on the punctured torus

Moira Chas, Anthony Phillips

摘要:

在穿孔环面上的自由同伦曲线类的成员的最小自交点的数目,是根据用基本群及其逆的生成元对该类进行最小描述所需的字母数目L而定的:如果L是偶数,则它小于或等于(L-2)^2/4;如果L是奇数,则它小于或等于(L-1)(L-3)/4。达到这个界限的类用生成元来明确描述;如果L是偶数,则有(L-2)^2 + 4个生成元,如果L是奇数,则有2(L-1)(L-3)+ 8个生成元;对于自相交数等于比最大值小小于的类,也给出了类似的描述和总数。证明使用组合计算和拓扑操作的代表曲线。计算机生成的数据被制成表格,对于每个非负整数,对于每个长度L小于或等于12,计算有多少长度L类具有该自相交数。实验数据也提出了对裤子表面。

英文摘要:

The minimum number of self-intersection points for members of a free homotopy class of curves on the punctured torus is bounded above in terms of the number L of letters required for a minimal description of the class in terms of the generators of the fundamental group and their inverses: it is less than or equal to (L-2)^2/4 if L is even, and (L-1)(L-3)/4 if L is odd. The classes attaining this bound are explicitly described in terms of the generators; there are (L-2)^2 + 4 of them if L is even, and 2(L-1)(L-3) + 8 if L is odd; similar descriptions and totals are given for classes with self-intersection number equal to one less than the maximum. Proofs use both combinatorial calculations and topological operations on representative curves. Computer-generated data are tabulated counting, for each non-negative integer, how many length-L classes have that self-intersection number, for each length L less than or equal to 12. Experimental data are also presented for the pair-of-pants surface.

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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