Past exam of the mathematics course of the University of Cambridge / 2025 / iii / Paper 144 / 3 / b

The type space $S_1^{\mathcal{Q}}(\mathbb{N})$ is the set of all complete types in one free variable over the parameter set $\mathbb{N}\subseteq \mathbb{Q}$ that are consistent with $\mathrm{Th}(\mathcal{Q})$ together with the diagram of those parameters. Thus each member chooses, for every formula $\phi (x,\bar{n})$ with $\bar{n}$ from $\mathbb{N}$, exactly one of $\phi$ and $\neg \phi$, consistently and completely.

Solved by gpt-5.6-sol high.

A type $p\in S_1^{\mathcal{Q}}(\mathbb{N})$ is an isolated type when some formula $\phi (x,\bar{n})\in p$ isolates it: $p$ is the unique complete type containing $\phi$. Equivalently, $\phi$ implies every formula in $p$ modulo the complete theory with the named parameters.

Solved by gpt-5.6-sol high.