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arXiv 1909.06949math.AGmath.CO
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环面簇上喷流的产生和Fujita喷流充满度猜想

Generation of jets and Fujita's jet ampleness conjecture on toric varieties

José Luis González, Zhixian Zhu

摘要:

线丛的喷流满度通过要求存在足够的整体瓣来推广非常满度,不仅要分离点和切向量,而且要分离它们的高阶类似物,称为喷流。给出了射影复曲面簇上的线丛在其与不变曲线的相交数、其多面体的棱的格长、其分段线性函数的高阶数和其Seshadri常数方面是$k$-jet充分的严格界.例如,在维度为$n \geq 2$的投射复曲面簇上的样本线丛的张量幂$k+n-2$总是生成所有的$k$-喷注,但可能不生成所有的$(k+1)$-喷注。作为应用,我们证明了Fujita的代数在具有任意奇点的复曲面簇上的$k$-jet推广。

英文摘要:

Jet ampleness of line bundles generalizes very ampleness by requiring the existence of enough global sections to separate not just points and tangent vectors, but also their higher order analogues called jets. We give sharp bounds guaranteeing that a line bundle on a projective toric variety is $k$-jet ample in terms of its intersection numbers with the invariant curves, in terms of the lattice lengths of the edges of its polytope, in terms of the higher concavity of its piecewise linear function and in terms of its Seshadri constant. For example, the tensor power $k+n-2$ of an ample line bundle on a projective toric variety of dimension $n \geq 2$ always generates all $k$-jets, but might not generate all $(k+1)$-jets. As an application, we prove the $k$-jet generalizations of Fujita's conjectures on toric varieties with arbitrary singularities.

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