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arXiv 2303.02789math.GT
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有理4-流形中固定最小亏格为0的迷向同调类的映射类

Mapping classes fixing an isotropic homology class of minimal genus $0$ in rational $4$-manifolds

Seraphina Eun Bi Lee

AI总结:

本文研究有理4-流形中本原迷向同调类的稳定化子,证明其任意元素可由几乎保持亏格0全纯Lefschetz纤维化的微分同胚表示,并解决了极大无挠阿贝尔子群的Nielsen实现问题。

摘要:

对任意 $N \geq 1$,令 $M_N$ 表示有理4-流形 $\mathbb{CP}^2 \\# N \overline{\mathbb{CP}^2}$。本文研究在拓扑映射类群 $\text{Mod}(M_N)$ 对 $H_2(M_N; \mathbb Z)$ 的自然作用下,一个本原迷向类 $w\in H_2(M_N; \mathbb Z)$(其最小亏格为0)的稳定化子 $\text{Stab}(w)$。虽然 $\text{Stab}(w)$ 的大多数元素不能由保持任何 Lefschetz 纤维化 $M_N \to Σ$ 的同胚表示,我们证明 $\text{Stab}(w)$ 的任意元素都可由一个微分同胚表示,该微分同胚几乎保持一个全纯、亏格为0的 Lefschetz 纤维化 $\text{pr}: M_N \to \mathbb{CP}^1$,其一般纤维代表同调类 $w$。我们还通过寻找 $Λ_w$ 在商映射 $q: \text{Homeo}^+(M_N)\to \text{Mod}(M_N)$ 下到 $\text{Diff}^+(M_N) \leq \text{Homeo}^+(M_N)$ 的一个提升,回答了 $\text{Mod}(M_N)$ 的某个极大无挠阿贝尔子群 $Λ_w$ 的 Nielsen 实现问题,该提升可以做到几乎保持 $\text{pr}: M_N \to \mathbb{CP}^1$。本文的所有结果对 $N \leq 8$ 时每个本原迷向类 $w \in H_2(M_N; \mathbb Z)$ 也成立,因为任何这样的类都具有最小亏格0。

英文摘要:

For any $N \geq 1$, let $M_N$ denote the rational $4$-manifold $\mathbb{CP}^2 \# N \overline{\mathbb{CP}^2}$. In this paper we study the stabilizer $\text{Stab}(w)$ of a primitive, isotropic class $w\in H_2(M_N; \mathbb Z)$ of minimal genus $0$ under the natural action of the topological mapping class group $\text{Mod}(M_N)$ on $H_2(M_N; \mathbb Z)$. Although most elements of $\text{Stab}(w)$ cannot be represented by homeomorphisms that preserve any Lefschetz fibration $M_N \to Σ$, we show that any element of $\text{Stab}(w)$ can be represented by a diffeomorphism that almost preserves a holomorphic, genus-$0$ Lefschetz fibration $\text{pr}: M_N \to \mathbb{CP}^1$ whose generic fibers represent the homology class $w$. We also answer the Nielsen realization problem for a certain maximal torsion-free, abelian subgroup $Λ_w$ of $\text{Mod}(M_N)$ by finding a lift of $Λ_w$ to $\text{Diff}^+(M_N) \leq \text{Homeo}^+(M_N)$ under the quotient map $q: \text{Homeo}^+(M_N)\to \text{Mod}(M_N)$ which can be made to almost preserve $\text{pr}: M_N \to \mathbb{CP}^1$. All results of this paper also hold for every primitive, isotropic class $w \in H_2(M_N; \mathbb Z)$ if $N \leq 8$ because any such class has minimal genus $0$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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