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arXiv math/0010009math.GT
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Vassiliev不变量和立方纽结复形

Vassiliev invariants and the cubical knot complex

Ilya Kofman, Xiao-Song Lin

摘要:

我们构造了一个三次CW-复形CK(M^3),它的有理上同调代数包含了3-流形M^3中纽结的Vassiliev不变量。对于每个退化的1-奇异和2-奇异纽结,我们通过将细胞附着到CK(R^3)来构造\bar{CK}(R^3),并且我们证明了π_1(\bar{CK}(R^3))=1和π_2(\bar{CK}(R^3))=Z。给出了瓦西里耶夫不变量在上同调中非平凡的条件。特别地,对于R^3,我们证明了v_2唯一生成H^2(CK,D),其中D是退化奇异纽结的子复形。更一般地说,我们表明,任何Vassiliev不变量来自康威多项式是非平凡的上同调。H^*(CK)中的上积提供了一个新的Vassiliev不变量在有序奇异结点上赋值的分次交换代数.我们展示了如何上积自然产生的一个余交换微分分次霍普夫代数有序弦图。

英文摘要:

We construct a cubical CW-complex CK(M^3) whose rational cohomology algebra contains Vassiliev invariants of knots in the 3-manifold M^3. We construct \bar{CK}(R^3) by attaching cells to CK(R^3) for every degenerate 1-singular and 2-singular knot, and we show that π_1(\bar{CK}(R^3))=1 and π_2(\bar{CK}(R^3))=Z. We give conditions for Vassiliev invariants to be nontrivial in cohomology. In particular, for R^3 we show that v_2 uniquely generates H^2(CK,D), where D is the subcomplex of degenerate singular knots. More generally, we show that any Vassiliev invariant coming from the Conway polynomial is nontrivial in cohomology. The cup product in H^*(CK) provides a new graded commutative algebra of Vassiliev invariants evaluated on ordered singular knots. We show how the cup product arises naturally from a cocommutative differential graded Hopf algebra of ordered chord diagrams.

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