NIP preservation for the completion and original structure

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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.

References

Primary source

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

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