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arXiv 2502.04069math.GTmath.GRmath.QA
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纽结广群的第二有界上同调

Bounded cohomology of fundamental quandles of links

Indian Institute of Science Education and Research (IISER) Mohali(印度科学教育与研究学院)

Deepanshi Saraf, Mahender Singh

AI总结:

该研究给出广群第二有界上同调无限维的两个充分条件,证明非分裂不可解链环、分裂链环的广群及秩大于1的自由广群等的第二有界上同调无限维,且纽结广群的第二有界上同调可检测平凡纽结。

摘要:

本文研究了广群(quandle)的有界上同调及其在纽结理论中的应用。我们建立了两个关键结果,给出了广群第二有界上同调为无限维的充分条件。第一个条件涉及广群内自同构群上的齐次群拟同态子空间,第二个条件则与该内自同构群的一个子群上稳定交换子长度的消失有关。在拓扑应用方面,我们证明:任何链群不可解的非分裂链环的广群,以及任何分裂链环的广群,其二有界上同调都是无限维的。由这些结果我们得出结论:纽结广群的第二有界上同调可以检测平凡纽结。在代数层面,我们证明:若广群的自由积中至少一个自由因子的内自同构群是顺从的,则该自由积广群的第二有界上同调是无限维的。由此可推得,秩大于1的自由广群及其典范商的第二有界上同调都是无限维的。

英文摘要:

We study bounded cohomology of quandles, a recently introduced framework bringing geometric methods into quandle theory. We establish two general criteria guaranteeing the infinite dimensionality of the second bounded cohomology of a quandle. The first is formulated in terms of homogeneous quasimorphisms on the inner automorphism group, while the second is based on the vanishing of stable commutator length on a suitable subgroup. As topological applications, we prove that, for every link other than the unknot and the Hopf link, the second bounded cohomology of its fundamental quandle has dimension equal to the cardinality of the continuum. We further consider fundamental $n$-quandles of links, which are closely related to the $n$-fold cyclic branched covers of the 3-sphere. For every $n\geq 3$, we prove that the second bounded cohomology of the fundamental $n$-quandle of a hyperbolic knot other than the figure-eight knot has dimension equal to the cardinality of the continuum. As algebraic applications, we prove that the second bounded cohomology of a free product of quandles is infinite dimensional whenever the inner automorphism group of at least one free factor is amenable. In particular, this yields infinite-dimensionality of the second bounded cohomology for free quandles of rank greater than one and for their canonical quotients.

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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