The directed-family IP conjecture for expansions of infinite fields

Let F{\mathscr{F}} be an expansion of an infinite field FF. A family X{\mathcal X} of subsets of FF is directed when any two members have a common member containing their union. Directed-family IP conjecture. If F{\mathscr{F}} admits a definable directed family X{\mathcal X} of finite subsets of FF such that X=F\bigcup {\mathcal X}=F, then F{\mathscr{F}} has the independence property. This generalizes the natural-number conjecture and is intended to rule out NIP expansions of fields covered by such a definable exhaustion.

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Primary source

Erik Walsberg, “Externally definable quotients and NIP expansions of the real ordered additive group”, arXiv:1910.10572 (2020).

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