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arXiv 2602.21032math.NTmath.AT
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全球域上Γ覆盖的无分支扩张分布

Distributions of unramified extensions of global fields

Princeton University(普林斯顿大学);Harvard University(哈佛大学)

Will Sawin, Melanie Matchett Wood

AI总结:

研究全球域上Γ覆盖的无分支扩张分布,通过分析伽罗华群的分布,提出新的猜想,并引入第三同调群中的不变量来细化结果。

摘要:

给定有限群Γ,我们证明了在有限域F_q上的项目线P^1_{F_q}上Γ覆盖的基本群中素数到q|Γ|部分的分布结果。等价地,这相当于研究Γ扩展的极大无分支扩张的伽罗华群的分布,从而提出新的猜想。特别地,这使我们能够观察并预测基域中根的次数对分布的影响。我们引入了研究这些群以及其第三同调群中由Artin-Verdier对偶性产生的类的概念。这一不变量细化了在函数域情况下对应于Hurwitz空间稳定分量的提升不变量。函数域结果的主要输入是应用我们最近开发的方法来确定从矩出发的群(或更一般的代数结构)的分布。我们在数域情况下证明了某些组不存在,支持我们在预测某些组以零概率出现时的猜想。

英文摘要:

Given a finite group $Γ$, we prove results on the distribution of the prime-to-$q|Γ|$ part of fundamental groups of $Γ$-covers of the projective line $\mathbb P^1_{\mathbb F_q}$ over a finite field $\mathbb F_q$ as $q\to\infty$. Equivalently, this is a result on the distribution of the Galois groups of maximal unramified extensions of $Γ$-extensions of $\mathbb F_q(t)$, and thereby motivates a new conjecture on the distribution of Galois groups of maximal unramified extensions of $Γ$-extensions of a number field. In particular, this allows us to see and predict the effect of roots of unity in the base field on such distributions. We introduce the idea to study these groups along with the class in their 3rd homology group that arises from Artin-Verdier Duality. This invariant refines the lifting invariant that, in the function field setting, corresponds to stable components of Hurwitz space. One major input into our function field results is an application of our recently developed methods to determine a distribution of groups (or more general algebraic structures) from its moments. We prove non-existence results in the number field case that support our conjectures in the case where our conjectures predict certain kinds of groups occur with probability zero.

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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