NIP preservation for the completion and original structure

Let (R,<,+)(R,<,+) be a dense archimedean ordered abelian group, let R{\mathscr{R}} be an expansion of it, and let R{\mathscr{R}}^{\square} be the completion structure used in the paper. Completion NIP conjecture. If R{\mathscr{R}} is NIP, then the pair (R,R)({\mathscr{R}}^{\square},{\mathscr{R}}) is NIP. This would reduce the study of NIP expansions of dense archimedean ordered groups to NIP expansions of (R,<,+)(\mathbb{R},<,+); the paper notes that the conjecture likely requires tools beyond those currently available.

Sources & referencesView supporting material

Primary source

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

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