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arXiv math/0111064math.AGmath.COmath.SG
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一个复曲面变体的特征

The signature of a toric variety

Naichung Conan Leung, Victor Reiner

摘要:

我们确定一个组合量(交替和的h-向量)定义为任何简单的多面体作为一个环面品种的签名。这个量是由Charney和Davis在他们的工作中引入的,特别表明它的非负性与Hopf关于非正弯曲流形的欧拉示性数的猜想密切相关。我们证明了积极的(或非负的)下界,这个数量的几何假设下的多面体。这些假设导致了复曲面因子上某些线丛的丰富性(或较弱的条件),然后使用Hirzebruch签名公式计算得出下界。此外,我们还证明了在这些关于多面体的假设下,对应的复曲面簇的第i个L-类是对任意i的有效类的(-1)^i倍。

英文摘要:

We identify a combinatorial quantity (the alternating sum of the h-vector) defined for any simple polytope as the signature of a toric variety. This quantity was introduced by Charney and Davis in their work, which in particular showed that its non-negativity is closely related to a conjecture of Hopf on the Euler characteristic of a non-positively curved manifold. We prove positive (or non-negative) lower bounds for this quantity under geometric hypotheses on the polytope. These hypotheses lead to ampleness (or weaker conditions) for certain line bundles on toric divisors, and then the lower bounds follow from calculations using the Hirzebruch Signature Formula. Moreoever, we show that under these hypotheses on the polytope, the i-th L-class of the corresponding toric variety is (-1)^i times an effective class for any i.

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