arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 0709.3218math.AG
收藏

P^N上自反层的Chern类的正性

Positivity of Chern Classes for Reflexive Sheaves on P^N

Cristina Bertone, Margherita Roggero

摘要:

众所周知,由全局截面生成的秩$n$向量丛在$\PP^N$上的陈类$c_i$,如果是$i\leq n$则是非负的,否则为零。本文讨论以下问题:上述结果是否对更广泛的自反层类成立?我们证明了对于任意秩的自反层,具有$i\geq 4$的陈数$c_i$可以是任意负的;相反,对于$i\leq 3$,我们证明了具有较弱假设的$c_i$的正性.对于由$H^0\FF$在某个非空开子集上生成的每一个自反层$\FF$,我们得到了$c_1$,$c_2$和$c_3$的下界,并对其中任何一个达到最小允许值或接近最小允许值的层进行了完全分类.

英文摘要:

It is well known that the Chern classes $c_i$ of a rank $n$ vector bundle on $\PP^N$, generated by global sections, are non-negative if $i\leq n$ and vanish otherwise. This paper deals with the following question: does the above result hold for the wider class of reflexive sheaves? We show that the Chern numbers $c_i$ with $i\geq 4$ can be arbitrarily negative for reflexive sheaves of any rank; on the contrary for $i\leq 3$ we show positivity of the $c_i$ with weaker hypothesis. We obtain lower bounds for $c_1$, $c_2$ and $c_3$ for every reflexive sheaf $\FF$ which is generated by $H^0\FF$ on some non-empty open subset and completely classify sheaves for which either of them reach the minimum allowed, or some value close to it.

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。

↑