Archive For Mathematical Logic ( IF 0.4 ) Pub Date : 2021-04-05 , DOI: 10.1007/s00153-021-00765-8 Danul K. Gunatilleka
We show that the quantifier elimination result for the Shelah-Spencer almost sure theories of sparse random graphs \(G(n,n^{-\alpha })\) given by Laskowski (Isr J Math 161:157–186, 2007) extends to their various analogues. The analogues will be obtained as theories of generic structures of certain classes of finite structures with a notion of strong substructure induced by rank functions and we will call the generics Baldwin–Shi hypergraphs. In the process we give a method of constructing extensions whose ‘relative rank’ is negative but arbitrarily small in context. We give a necessary and sufficient condition for the theory of a Baldwin–Shi hypergraph to have atomic models. We further show that for certain well behaved classes of theories of Baldwin–Shi hypergraphs, the existentially closed models and the atomic models correspond.
中文翻译:
鲍德温-史超图理论及其原子模型
我们证明了Shelah-Spencer的量化消除结果几乎确定了稀疏随机图\(G(n,n ^ {-\ alpha})\)的理论Laskowski(Isr J Math 161:157–186,2007)给出的结果扩展到了它们的各种类似物。将获得类似物作为某些类的有限结构的泛型结构的理论,并具有由秩函数引起的强子结构的概念,我们将其称为泛型Baldwin–Shi超图。在此过程中,我们提供了一种构造扩展名的方法,该扩展名的“相对等级”为负,但在上下文中任意较小。我们为Baldwin-Shi超图理论具有原子模型提供了充要条件。我们进一步证明,对于鲍德温-史超图的某些行为良好的理论类别,存在闭式模型和原子模型是相对应的。