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arxiv: 1007.4468 · v2 · pith:BDF6A4CXnew · submitted 2010-07-26 · 🧮 math.LO

Externally definable sets and dependent pairs

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keywords definabledependentexternallypairsprovesetstheoremanswers
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We prove that externally definable sets in first order NIP theories have honest definitions, giving a new proof of Shelah's expansion theorem. Also we discuss a weak notion of stable embeddedness true in this context. Those results are then used to prove a general theorem on dependent pairs, which in particular answers a question of Baldwin and Benedikt on naming an indiscernible sequence.

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