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Crystallographic groups and flat manifolds from surface braid groups
Topology and its Applications ( IF 0.6 ) Pub Date : 2020-12-23 , DOI: 10.1016/j.topol.2020.107560
Daciberg Lima Gonçalves , John Guaschi , Oscar Ocampo , Carolina de Miranda e Pereiro

Let M be a compact surface without boundary, and n2. We analyse the quotient group Bn(M)/Γ2(Pn(M)) of the surface braid group Bn(M) by the commutator subgroup Γ2(Pn(M)) of the pure braid group Pn(M). If M is different from the 2-sphere S2, we prove that Bn(M)/Γ2(Pn(M))Pn(M)/Γ2(Pn(M))φSn, and that Bn(M)/Γ2(Pn(M)) is a crystallographic group if and only if M is orientable.

If M is orientable, we prove a number of results regarding the structure of Bn(M)/Γ2(Pn(M)). We characterise the finite-order elements of this group, and we determine the conjugacy classes of these elements. We also show that there is a single conjugacy class of finite subgroups of Bn(M)/Γ2(Pn(M)) isomorphic either to Sn or to certain Frobenius groups. We prove that crystallographic groups whose image by the projection Bn(M)/Γ2(Pn(M))Sn is a Frobenius group are not Bieberbach groups. Finally, we construct a family of Bieberbach subgroups G˜n,g of Bn(M)/Γ2(Pn(M)) of dimension 2ng and whose holonomy group is the finite cyclic group of order n, and if Xn,g is a flat manifold whose fundamental group is G˜n,g, we prove that it is an orientable Kähler manifold that admits Anosov diffeomorphisms.



中文翻译:

表面编织群的晶体学群和平面流形

M为无边界的紧致曲面,并且ñ2。我们分析商群ñ中号/Γ2Pñ中号 编织层组 ñ中号 按换向器子组 Γ2Pñ中号 纯编织族 Pñ中号。如果M与2球面不同小号2,我们证明 ñ中号/Γ2Pñ中号Pñ中号/Γ2Pñ中号φ小号ñ, 然后 ñ中号/Γ2Pñ中号当且仅当M是可取向的时,是晶体组。

如果M是可定向的,我们证明关于M的结构的许多结果ñ中号/Γ2Pñ中号。我们表征该组的有限阶元素,并确定这些元素的共轭类。我们还表明,存在一个有限子群的单个共轭类ñ中号/Γ2Pñ中号 同构 小号ñ或某些Frobenius团体。我们证明了那些晶体群的图像由投影ñ中号/Γ2Pñ中号小号ñ是Frobenius团体而不是Bieberbach团体。最后,我们构建了一个Bieberbach子族GñGñ中号/Γ2Pñ中号 尺寸 2ñG并且其整齐性群是阶n的有限循环群,并且如果XñG 是一个平面流形,其基本群是 GñG,我们证明它是可定向的Kähler流形,它接受Anosov微分同构。

更新日期:2020-12-23
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