增长间隙与生成集
Growth gaps and generating sets
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中文总结 AI 辅助
该研究证明有限生成群的无限指数子群的增长间隙存在与否可依赖于有限生成集,具体对高阶半单李群中不可约格Λ的Λ×Λ群,存在带与不带增长间隙的有限对称生成集,且增长间隙可任意小,而非初等双曲群的增长间隙存在与否与生成集无关。
中文摘要 AI 辅助
我们证明,给定有限生成群的无限指数子群的增长间隙是否存在,可能取决于有限生成集。更准确地说,对于具有Kazhdan性质(T)的高阶半单李群G中的任何不可约格Λ,群Λ×Λ存在一个具有增长间隙的有限对称生成集,以及另一个不具有增长间隙的有限对称生成集。我们还证明,增长间隙可以被做得任意小。相比之下,对于非初等双曲群,增长间隙的存在与否与有限生成集无关。
英文摘要
We show that the existence of a growth gap for infinite-index subgroups of a given finitely genrated group can depend on the finite generating set. More precisely, for any irreducible lattice $Λ$ in a higher rank semisimple Lie group $G$ with Kazhdan's property (T), the group $Λ\times Λ$ admits one finite symmetric generating set with a growth gap and another without a growth gap. We also prove that the growth gap can be made arbitrarily small. In contrast, for a non-elementary hyperbolic group the existence of a growth gap is independent of the finite generating set.