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arXiv 2201.10730math.NT
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数域上的不定 $k$-泛二次整形式

On indefinite $k$-universal integral quadratic forms over number fields

Zilong He, Yong Hu, Fei Xu

AI总结:

本文研究数域上整二次格的不定 $k$-泛性质,证明 $k\geq3$ 时满足局部—整体原则,并刻画 $k=1,2$ 时局部泛而非整体泛的格的存在条件与类数。

摘要:

一个整二次格若对给定正整数 $k$ 表示所有秩为 $k$ 的整二次格,则称为不定 $k$-泛的。对于 $k\geq 3$,我们证明不定 $k$-泛性质在数域上满足局部—整体原则。对于 $k=2$,我们表明数域 $F$ 存在局部 $2$-泛但非不定 $2$-泛的整二次格,当且仅当 $F$ 的类数为偶数;此外,$F$ 上此类格仅有有限多个类。对于 $k=1$,我们证明 $F$ 存在局部经典 $1$-泛但非经典不定 $1$-泛的经典整格,当且仅当 $F$ 拥有一个二次非分歧扩张,且 $F$ 的所有二进素数在其中完全分裂;此时 $F$ 上此类格有无穷多个类。所有具有此性质的二次域均被确定。

英文摘要:

An integral quadratic lattice is called indefinite $k$-universal if it represents all integral quadratic lattices of rank $k$ for a given positive integer $k$. For $k\geq 3$, we prove that the indefinite $k$-universal property satisfies the local-global principle over number fields. For $k=2$, we show that a number field $F$ admits an integral quadratic lattice which is locally $2$-universal but not indefinite 2-universal if and only if the class number of $F$ is even. Moreover, there are only finitely many classes of such lattices over $F$. For $k=1$, we prove that $F$ admits a classic integral lattice which is locally classic $1$-universal but not classic indefinite $1$-universal if and only if $F$ has a quadratic unramified extension where all dyadic primes of $F$ split completely. In this case, there are infinitely many classes of such lattices over $F$. All quadratic fields with this property are determined.

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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