Finite Undecidability in Fields II: PAC, PRC and PpC Fields

Abstract

A field $K$ in a ring language $\mathcal{L}$ is finitely undecidable if $\mbox{Cons}(Σ)$ is undecidable for every nonempty finite $Σ\subseteq \mbox{Th}(K; \mathcal{L})$. We adapt arguments originating with Cherlin-van den Dries-Macintyre/Ershov (for PAC fields) and Haran (for PRC fields) to prove all PAC and PRC fields are finitely undecidable. We describe the difficulties that arise in adapting the proof to P$p$C fields, and show no bounded P$p$C field is finitely axiomatisable. This work is drawn from the author's PhD thesis and is a sequel to arXiv:2210.12729.

26 pages. Update expands on undecidability machinery, removes PpC finite undecidability, and fixes typos etc