arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1607.07214math.NT
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极大序模上逆的平方根差的Galois模结构

Galois module structure of the square root of the inverse different over maximal orders

Cindy Tsang

摘要:

设$K$是一个具有整数环$\mathcal{O}_K$的数域,$G$是一个\mbox{finite group of}奇数阶.给定一个$G$ -Galois $K$ -代数$K_h$,令$A_h$是$K_h/K$的逆差的平方根,它由Hilbert公式存在.若$K_h/K$是弱分歧的,则通过B的一个结果,$A_h$在$\mathcal{O}_{K}G$上是局部自由的. Erez,在这种情况下,它确定$\mathcal{O}_KG$的局部自由类组$\mbox{Cl}(\mathcal{O}_KG)$中的类。在$\mbox{Cl}(\mathcal{O}_KG)$中这样一个类被称为$A$ -可实现的,如果$K_h/K$是驯服的,则驯服的$A$ -可实现的。令$\mathcal{A}(\mathcal{O}_KG)$和$\mathcal{A}^t(\mathcal{O}_KG)$分别表示所有$A$可实现类和驯服$A$可实现类的集合.对于$G$阿贝尔,我们将证明两个集合$\mathcal{A}(\mathcal{O}_KG)$和$\mathcal{A}^t(\mathcal{O}_KG)$是相等的,当扩展标量的最大阶$KG$。

英文摘要:

Let $K$ be a number field with ring of integers $\mathcal{O}_K$ and let $G$ be a \mbox{finite group of} odd order. Given a $G$-Galois $K$-algebra $K_h$, let $A_h$ be the square root of the inverse different of $K_h/K$, which exists by Hilbert's formula. If $K_h/K$ is weakly ramified, then $A_h$ is locally free over $\mathcal{O}_{K}G$ by a result of B. Erez, in which case it determines a class in the locally free class group $\mbox{Cl}(\mathcal{O}_KG)$ of $\mathcal{O}_KG$. Such a class in $\mbox{Cl}(\mathcal{O}_KG)$ is said to be $A$-realizable, and tame $A$-realizable if $K_h/K$ is tame. Let $\mathcal{A}(\mathcal{O}_KG)$ and $\mathcal{A}^t(\mathcal{O}_KG)$ denote the sets of all $A$-realizable classes and tame $A$-realizable classes, respectively. For $G$ abelian, we will show that the two sets $\mathcal{A}(\mathcal{O}_KG)$ and $\mathcal{A}^t(\mathcal{O}_KG)$ are equal when extended scalars to the maximal order in $KG$.

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