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A Model in Which Well-Orderings of the Reals Appear at a Given Projective Level

Authors: Vladimir Kanovei; Vassily A. Lyubetsky;

A Model in Which Well-Orderings of the Reals Appear at a Given Projective Level

Abstract

The problem of the existence of analytically definable well-orderings at a given level of the projective hierarchy is considered. This problem is important as a part of the general problem of the study of the projective hierarchy in the ongoing development of descriptive set theory. We make use of a finite support product of the Jensen-type forcing notions to define a model of set theory ZFC in which, for a given n>2, there exists a good Δn1 well-ordering of the reals but there are no such well-orderings in the class Δn−11. Therefore the existence of a well-ordering of the reals at a certain level n>2 of the projective hierarchy does not imply the existence of such a well-ordering at the previous level n−1. This is a new result in such a generality (with n>2 arbitrary), and it may lead to further progress in studies of the projective hierarchy.

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Keywords

generic models, definability, forcing, QA1-939, well-orderings; projective hierarchy; forcing; finite support product; generic models; definability, finite support product, well-orderings, projective hierarchy, Mathematics

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
3
Top 10%
Average
Average
gold