AI 中文总结
研究无选择公理集合论中拉姆齐理论的有限性类,回答关于高尔$\mathbf{FIN}_k$定理问题,证明其层次结构坍缩;还探讨彩虹拉姆齐和规范拉姆齐定理相关失败类,证明包含关系等,分析参数依赖性,部分严格性等问题未解决。
AI 中文摘要
我们研究了在没有选择公理的集合论中,由拉姆齐理论原则产生的有限性类。首先,我们回答了布罗特、曹和费尔南德斯 - 布雷顿关于高尔的$\mathbf{FIN}_k$定理的一个问题。$\mathbf{FIN}_k$运算为每个$k\geq1$产生一个有限性概念,但我们表明这个概念与$k$的值无关:所得层次结构坍缩,且每个层次都等同于$H$-有限性,即等同于$[X]^{<\omega}$的戴德金有限性。然后我们转向彩虹拉姆齐定理和规范拉姆齐定理。相应的失败类$\operatorname{\mathbf{RRT - Fin}_n^m}$和$\operatorname{\mathbf{CRT - Fin}}$是包含在$\operatorname{\mathbf{D - Fin}}$中的真正有限性类。我们证明了几个包含关系,将它们相对于布罗特 - 曹 - 费尔南德斯 - 布雷顿的标准拉姆齐理论有限性类进行定位,证明它们与坍缩的欣德曼 - 高尔类无关,并通过弗伦克尔 - 莫斯托夫斯基例子分析彩虹类的参数依赖性。严格性的更精细问题以及彩虹类的完整双参数结构在当前论证未解决的地方仍未解决。
英文摘要
We study finiteness classes arising from Ramsey-theoretic principles in set theory without the Axiom of Choice. First, we answer a question of Brot, Cao, and Fernández-Bretón concerning Gowers' $\mathbf{FIN}_k$ theorem. The $\mathbf{FIN}_k$ operation gives rise to a finiteness notion for each $k\geq 1$, but we show that this notion is independent of the value of $k$: the resulting hierarchy collapses, and every level is equivalent to $H$-finiteness, i.e., to Dedekind-finiteness of $[X]^{<ω}$. We then turn to the Rainbow Ramsey theorem and the Canonical Ramsey theorem. The corresponding failure classes $\operatorname{\mathbf{RRT-Fin}_n^m}$ and $\operatorname{\mathbf{CRT-Fin}}$ are genuine finiteness classes contained in $\operatorname{\mathbf{D-Fin}}$. We prove several inclusions placing them relative to standard Ramsey-theoretic finiteness classes of Brot--Cao--Fernández-Bretón, prove their independence from the collapsed Hindman--Gowers class, and analyze the parameter dependence of the rainbow classes through Fraenkel--Mostowski examples. The finer questions of strictness, and the full two-parameter structure of the rainbow classes, are left open where the present arguments do not settle them.
Comments15 pages