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arXiv 1805.00366math.GR
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$\mathrm{Out}(F_n)$在$F_n$的第二有界上同调上的动力学

Dynamics of $\mathrm{Out}(F_n)$ on the second bounded cohomology of $F_n$

Antonius Hase

摘要:

研究了第二有界上同调$H^2_b(F_n, \mathbb{R})$上的$\mathrm{Out}(F_n)$ -作用,重点研究了由Brooks拟同构给出的可数维稠密不变子空间.我们表明,这个子空间没有有限维不变子空间,特别是没有不动点,部分回答了米克洛什Abért的问题。为此,我们引入一个元素的速度的概念$g\in \mathrm{Out}(F_n)$,它的措施下反复应用$g$的有界上同调类的渐近增长率。

英文摘要:

We study the $\mathrm{Out}(F_n)$-action on the second bounded cohomology $H^2_b(F_n, \mathbb{R})$, focusing on the countable-dimensional dense invariant subspace given by Brooks quasimorphisms. We show that this subspace has no finite-dimensional invariant subspaces, in particular no fixpoints, partially answering a question of Miklós Abért. To this end we introduce a notion of speed of an element $g\in \mathrm{Out}(F_n)$, which measures the asymptotic growth rate of bounded cohomology classes under repeated application of $g$.

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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