The generic pair conjecture for dependent theories

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Assume that TT is a first-order theory and that

λ=λ<λ>∣T∣,\lambda=\lambda^{<\lambda}>|T|,

with 2λ=λ+2^\lambda=\lambda^+. Let ⟨Mα:α<λ+⟩\langle M_\alpha:\alpha<\lambda^+\rangle be a ≺\prec-increasing continuous sequence with Mα∈EC⁡λ(T)M_\alpha\in\operatorname{EC}_\lambda(T), and suppose that

⋃α<λ+Mα∈EC⁡λ+(T)\bigcup_{\alpha<\lambda^+}M_\alpha\in\operatorname{EC}_{\lambda^+}(T)

is saturated. Generic pair conjecture. The theory TT is dependent if and only if there is a club E⊆λ+E\subseteq\lambda^+ such that for all α<β\alpha<\beta in EE of cofinality λ+\lambda^+, the pairs (Mβ,Mα)(M_\beta,M_\alpha) have the same isomorphism type. The conjecture is presented as the structure-side counterpart to non-structure results for independent theories. The source states that the structure side is proved when λ=κ\lambda=\kappa is measurable, while the general conjecture remains open.

References

Primary source

Saharon Shelah, “Dependent theories and the generic pair conjecture”, arXiv:math/0702292 (2013).

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