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arXiv 2206.00575math.AG
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一般型曲面模空间的虚拟基本类

The virtual fundamental class for the moduli space of surfaces of general type

University of Kansas(堪萨斯大学)

Yunfeng Jiang

AI总结:

本文证明了一般型曲面的索引一覆盖的模堆与KSBA稳定一般型曲面模堆同构,并构造了虚拟基本类以证明Donaldson关于KSBA模空间虚拟基本类存在的猜想。

摘要:

我们证明了半log-canonical一般型曲面的索引一覆盖模堆与KSBA稳定一般型曲面模堆同构。通过定义$\lci$覆盖,我们构造了模堆,使其映射到一般型曲面模堆。接着构造了该堆上的完美障碍理论和虚拟基本类,并将其推前到KSBA模空间。从而证明了Donaldson关于KSBA模空间虚拟基本类存在的猜想。通过积分CM线丛的第一陈类的幂定义了tautological不变量,将其推广到稳定曲面的模空间。

英文摘要:

We prove that the moduli stack of index-one covers of semi-log-canonical surfaces of general type is isomorphic to the KSBA moduli stack of stable general type surfaces. Using the index-one covering Deligne-Mumford stack of a semi-log-canonical surface, we define the $\lci$ cover. The $\lci$ cover, as a Deligne-Mumford stack, has only locally complete intersection singularities. We then construct the moduli stack of $\lci$ covers so that it admits a proper map to the moduli stack of surfaces of general type. Next, we construct a perfect obstruction theory on this stack and a virtual fundamental class in its Chow group. We then pushforward the virtual fundamental class from the moduli stack of lci covers to the KSBA moduli space. Thus, our construction proves Donaldson's conjecture on the existence of a virtual fundamental class for KSBA moduli spaces. The smoothing of lci covering Deligne-Mumford stacks can not control all the non lci slc singularities. Thus, we construct the moduli stack of birational lci enhancement Deligne-Mumford stacks for all non lci slc singularities. The birational lci enhancement stack is in general nonseparated. We construct a separated good moduli space from this moduli stack and a perfect obstruction theory on it. A tautological invariant is defined by integrating a power of the first Chern class of the CM line bundle over the virtual fundamental class. This serves as a generalization of the tautological invariants defined by integrating tautological classes over the moduli space $\overline{M}_g$ of stable curves to the moduli space of stable surfaces.

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