论文标题
曲线图的模型理论
The model theory of the curve graph
论文作者
论文摘要
在本文中,我们在模型理论,几何拓扑结构和几何群体理论之间发展了一个桥梁。特别是,我们从模型理论的角度研究了伊万诺夫·梅孔肯(Ivanov Metaconj),更广泛地试图回答一个总体问题:为什么表面的曲线图在表面和映射班级群体的研究中起着如此重要的作用? 更具体地说,我们考虑了有限类型的表面$σ$及其曲线图$ \ Mathcal C(σ)$,并在图理论的语言中研究了其一阶理论。至关重要的是,$ \ MATHCAL C(σ)$与表面映射类组的一个称为增强的Cayley图的特定对象可进行双解析。我们使用这种双重解释来证明曲线图的理论为$ω$ - 稳定,以计算其莫利等级,并表明它在$ \ forall \ forall \ forall \ event \ formist $的类别中具有量词消除。我们还表明,与表面自然相关的许多复合物在$ \ MATHCAL C(σ)$中都可以解释。这表明这些复合物都是$ω$ - 稳定,并承认其莫利等级的先验界限。我们能够使用Morley等级来证明各种复合物不是BI - 与曲线图有关。由于消除了量词,我们表明代数相交数在曲线图的一阶理论中无法定义。最后,我们证明了表面的曲线图具有一种新型现象,我们称之为解释刚度。也就是说,如果表面$σ_1$和$σ_2$允许相互解释的曲线图,则$σ_1$和$σ_2$彼此同构。一路上,获得了许多技术结果。
In this paper we develop a bridge between model theory, geometric topology, and geometric group theory. In particular, we investigate the Ivanov Metaconjecture from the point of view of model theory, and more broadly we seek to answer the general question: why does the curve graph of a surface play such a central role in the study of surfaces and mapping class groups? More specifically, we consider a surface $Σ$ of finite type and its curve graph $\mathcal C(Σ)$, and we investigate its first-order theory in the language of graph theory. Crucially, $\mathcal C(Σ)$ is bi-interpretable with a certain object called the augmented Cayley graph of the mapping class group of the surface. We use this bi-interpretation to prove that the theory of the curve graph is $ω$--stable, to compute its Morley rank, and to show that it has quantifier elimination with respect to the class of $\forall\exists$--formulae. We also show that many of the complexes which are naturally associated to a surface are interpretable in $\mathcal C(Σ)$. This shows that these complexes are all $ω$--stable and admit certain a priori bounds on their Morley ranks. We are able to use Morley ranks to prove that various complexes are not bi--interpretable with the curve graph. As a consequence of quantifier elimination, we show that algebraic intersection number is not definable in the first order theory of the curve graph. Finally, we prove that the curve graph of a surface enjoys a novel phenomenon that we call interpretation rigidity. That is, if surfaces $Σ_1$ and $Σ_2$ admits curve graphs that are mutually interpretable, then $Σ_1$ and $Σ_2$ are homeomorphic to each other. Along the way, numerous technical results are obtained.