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arXiv · 2007.15754

Bounding non-rationality of divisors on 3-fold Fano fibrations

Caucher Birkar·Konstantin Loginov
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Abstract

In this paper we investigate non-rationality of divisors on 3-fold log Fano fibrations $(X,B)\to Z$ under mild conditions. We show that if $D$ is a component of $B$ with coefficient $\ge t>0$ which is contracted to a point on $Z$, then $D$ is birational to $\mathbb{P}^1\times C$ where $C$ is a smooth projective curve with gonality bounded depending only on $t$. Moreover, if $t>\frac{1}{2}$, then genus of $C$ is bounded depending only on $t$.

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Caucher Birkar, Konstantin Loginov. 2020-07-30. Bounding non-rationality of divisors on 3-fold Fano fibrations. https://arxiv.org/abs/2007.15754

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