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Martin's Axiom and Delta^2_1 well-ordering of the reals

Uri Abraham·Saharon Shelah
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Abstract

Assuming an inaccessible cardinal kappa, there is a generic extension in which MA + 2^{aleph_0} = kappa holds and the reals have a Delta^2_1 well-ordering.

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Uri Abraham, Saharon Shelah. 1994-08-15. Martin's Axiom and Delta^2_1 well-ordering of the reals. https://arxiv.org/abs/math/9408214

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