On the structure of fundamental groups of conic-line arrangements having a cycle in their graph

Michael Friedman; David Garber

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arXiv · 1304.7561

On the structure of fundamental groups of conic-line arrangements having a cycle in their graph

Michael Friedman·David Garber

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Abstract

The fundamental group of the complement of a plane curve is a very important topological invariant. In particular, it is interesting to find out whether this group is determined by the combinatorics of the curve or not, and whether it is a direct sum of free groups and a free abelian group, or it has a conjugation-free geometric presentation. In this paper, we investigate the structure of this fundamental group when the graph of the conic-line arrangement is a unique cycle of length $n$ and the conic passes through all the multiple points of the cycle. We show that if n is odd, then the affine fundamental group is abelian but not conjugation-free. For the even case, if n>4, then using quotients of the lower central series, we show that the fundamental group is not even a direct sum of a free abelian group and free groups.

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Michael Friedman, David Garber. 2013-04-29. On the structure of fundamental groups of conic-line arrangements having a cycle in their graph. https://arxiv.org/abs/1304.7561

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