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 . We analyse the quotient group of the surface braid group by the commutator subgroup of the pure braid group . If M is different from the 2-sphere , we prove that , and that 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 . 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 isomorphic either to or to certain Frobenius groups. We prove that crystallographic groups whose image by the projection is a Frobenius group are not Bieberbach groups. Finally, we construct a family of Bieberbach subgroups of of dimension and whose holonomy group is the finite cyclic group of order n, and if is a flat manifold whose fundamental group is , 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
令M为无边界的紧致曲面,并且。我们分析商群 编织层组 按换向器子组 纯编织族 。如果M与2球面不同,我们证明 , 然后 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。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 同构 或某些Frobenius团体。我们证明了那些晶体群的图像由投影是Frobenius团体而不是Bieberbach团体。最后,我们构建了一个Bieberbach子族 的 尺寸 并且其整齐性群是阶n的有限循环群,并且如果 是一个平面流形,其基本群是 ,我们证明它是可定向的Kähler流形,它接受Anosov微分同构。