arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1902.00871math.GR
收藏

RAAG的自同构群的立方复形和交换子群

Cube complexes and abelian subgroups of automorphism groups of RAAGs

Benjamin Millard, Karen Vogtmann

摘要:

我们构造了直角Artin群的无扭外自同构群$U(A_Γ)$的自由阿贝尔子群,从而给出了虚上同调维度的下界。群$U(A_Γ)$以前曾被Charney、Stambaugh和第二作者研究过,他们构造了一个可收缩的立方体复形,它在这个复形上适当地作用,并且是余紧的,给出了虚上同调维数的上界。我们的自由交换子群的秩等于这个复形中主立方体的维数。这些通常是最大维数,因此上界和下界一致。在许多情况下,当主立方体不是最大维数,我们证明了有一个不变的严格低维的可收缩子复形。

英文摘要:

We construct free abelian subgroups of the group $U(A_Γ)$ of untwisted outer automorphisms of a right-angled Artin group, thus giving lower bounds on the virtual cohomological dimension. The group $U(A_Γ)$ was previously studied by Charney, Stambaugh and the second author, who constructed a contractible cube complex on which it acts properly and cocompactly, giving an upper bound for the virtual cohomological dimension. The ranks of our free abelian subgroups are equal to the dimensions of the principal cubes in this complex. These are often of maximal dimension, so that the upper and lower bounds agree. In many cases when the principal cubes are not of maximal dimension we show there is an invariant contractible subcomplex of strictly lower dimension.

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。

↑