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A uniqueness theorem for iterations. (English) Zbl 1042.03036

It is a result of Woodin that two different generic ultrapowers of the same model of \(\text{ZFC}+ \text{MA}_{\aleph_1}\) have no new reals in common. The author strengthens this to iterations of arbitrary countable length, in the process providing a shorter proof of Woodin’s original result. The author proves that for \(M\) a countable model of \(\text{ZFC}+ \text{MA}_{\aleph_1}\), for every real \(x\) there is a unique shortest iteration \(j: M\rightarrow N\) with \(x\in N\), or none at all.

MSC:

03E40 Other aspects of forcing and Boolean-valued models
03E50 Continuum hypothesis and Martin’s axiom
Full Text: DOI

References:

[1] The axiom of determinacy, forcing axioms, and the nonstationary ideal 1 (1999) · Zbl 0954.03046
[2] Mathematical logic and foundations of set theory (Proceedings of the international colloquium, Jerusalem, 1968) pp 84– (1970)
[3] DOI: 10.4064/fm168-1-3 · Zbl 0969.03059 · doi:10.4064/fm168-1-3
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