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arXiv 1701.04488math.AG
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关于三次超曲面的$\mathrm{CH}_2$的注记

Remarks on the $\mathrm{CH}_2$ of cubic hypersurfaces

René Mboro

摘要:

本文给出了将特征$\neq 2$的代数闭域上光滑三次超曲面$X$上的$2$ -圈问题,转化为$1$ -圈在其线簇$F(X)$上的问题的两种方法.第一种方法依赖于$X$的双切线和Tsen-Lang定理。它允许证明$\mathrm{CH}_2(X)$是由$\mathrm{CH}_1(F(X))$通过通用$\mathbb P^1$ -bundle对$F(X)$的作用生成的。当基场的特征是$0$时,我们使用该结果来证明,如果$dim(X)\geq 7$,则$\mathrm{CH}_2(X)$由包含在$X$中的平面类生成,如果$dim(X)\geq 9$,则$\mathrm{CH}_2(X)\simeq \mathbb Z$。类似的结果,稍微弱的界限,已经获得了潘。第二种方法包括一个扩展的$X$的高维的反演公式沈开发的$X$曲线的情况下,$X$的子类。该反演公式允许将$\mathrm{CH}_2(X)$中的扭转循环提升到$\mathrm{CH}_1(F(X))$中的扭转循环。对于复杂的立方$5$ -折叠,它允许证明,双有理不变提供的同调平凡,扭转余维$3$周期消灭阿贝尔-雅可比态射的组$\mathrm{CH}^3(X)_{tors,AJ}$是由控制组$\mathrm{CH}_1(F(X))_{tors,AJ}$这是一个双有理不变的$F(X)$,可能总是平凡的法诺品种。

英文摘要:

This paper presents two approaches to reducing problems on $2$-cycles on a smooth cubic hypersurface $X$ over an algebraically closed field of characteristic $\neq 2$, to problems on $1$-cycles on its variety of lines $F(X)$. The first one relies on bitangent lines of $X$ and Tsen-Lang theorem. It allows to prove that $\mathrm{CH}_2(X)$ is generated, via the action of the universal $\mathbb P^1$-bundle over $F(X)$, by $\mathrm{CH}_1(F(X))$. When the characteristic of the base field is $0$, we use that result to prove that if $dim(X)\geq 7$, then $\mathrm{CH}_2(X)$ is generated by classes of planes contained in $X$ and if $dim(X)\geq 9$, then $\mathrm{CH}_2(X)\simeq \mathbb Z$. Similar results, with slightly weaker bounds, had already been obtained by Pan. The second approach consists of an extension to subvarieties of $X$ of higher dimension of an inversion formula developped by Shen in the case of curves of $X$. This inversion formula allows to lift torsion cycles in $\mathrm{CH}_2(X)$ to torsion cycles in $\mathrm{CH}_1(F(X))$. For complex cubic $5$-folds, it allows to prove that the birational invariant provided by the group $\mathrm{CH}^3(X)_{tors,AJ}$ of homologically trivial, torsion codimension $3$ cycles annihilated by the Abel-Jacobi morphism is controlled by the group $\mathrm{CH}_1(F(X))_{tors,AJ}$ which is a birational invariant of $F(X)$, possibly always trivial for Fano varieties.

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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