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arXiv 1007.5228math.GTmath.KT
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球形CR结构的组合不变量

A combinatorial invariant for Spherical CR structures

Elisha Falbel, Qingxue Wang

摘要:

研究了球面CR几何中$S^3$的四个泛点的交比。我们构造了一个由$S^3$中四个点的一般构型生成的群到pre-Bloch群$\mathcal {P}(\C)$的同态.如果$M$是一个具有CR三角剖分的$3$维球面CR流形,利用我们的同态,我们得到了$M$的一个$\mathcal {P}(\C)$值不变量.我们表明,当应用到它的布洛赫-维格纳函数,它是零。在一定条件下,证明了$M$的不变量位于Bloch群$\mathcal B(k)$中,其中$k$是交比产生的场.对于Whitehead链补的CR三角剖分,我们证明了它的不变量是$\mathcal B(k)$中的非平凡挠。

英文摘要:

We study a cross-ratio of four generic points of $S^3$ which comes from spherical CR geometry. We construct a homomorphism from a certain group generated by generic configurations of four points in $S^3$ to the pre-Bloch group $\mathcal {P}(\C)$. If $M$ is a $3$-dimensional spherical CR manifold with a CR triangulation, by our homomorphism, we get a $\mathcal {P}(\C)$-valued invariant for $M$. We show that when applying to it the Bloch-Wigner function, it is zero. Under some conditions on $M$, we show the invariant lies in the Bloch group $\mathcal B(k)$, where $k$ is the field generated by the cross-ratio. For a CR triangulation of Whitehead link complement, we show its invariant is a non-trivial torsion in $\mathcal B(k)$.

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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