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arXiv 2104.15072math.AG
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关于具有典型奇点的锥丛的Shokurov猜想

Shokurov's conjecture on conic bundles with canonical singularities

Jingjun Han, Chen Jiang, Yujie Luo

摘要:

圆锥丛是相对维数$1$的正规簇之间的收缩$X\to Z$,使得$-K_X$相对充足。我们证明了一个猜想Shokurov预测,如果$X\to Z$是一个圆锥丛,使$X$具有典型的奇异性和$Z$是$\mathbb{Q}$ -Gorenstein,那么$Z$总是$\frac{1}{2}$ -LC,和多重性的纤维余维$1$点有界从上面由$2$。值$\frac{1}{2}$和$2$均为锐值。这是通过解决一个更一般的猜想Shokurov的奇异性的基础lc-平凡纤维化的相对尺寸$1$与规范的奇异性。

英文摘要:

A conic bundle is a contraction $X\to Z$ between normal varieties of relative dimension $1$ such that $-K_X$ is relatively ample. We prove a conjecture of Shokurov which predicts that, if $X\to Z$ is a conic bundle such that $X$ has canonical singularities and $Z$ is $\mathbb{Q}$-Gorenstein, then $Z$ is always $\frac{1}{2}$-lc, and the multiplicities of the fibers over codimension $1$ points are bounded from above by $2$. Both values $\frac{1}{2}$ and $2$ are sharp. This is achieved by solving a more general conjecture of Shokurov on singularities of bases of lc-trivial fibrations of relative dimension $1$ with canonical singularities.

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