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We present a method which forces the failure of Π 3 1 and Σ 3 1 -separation, while MA ( I ) holds, for I the family of indestructible ccc forcings. This shows that, in contrast to the assumption BPFA and ℵ 1 = ℵ 1 L which implies Π 3 1 -separation, that weaker forcing axioms do not decide separation on the third projective level.

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Publication Details

Journal
Annals of Pure and Applied Logic
Published
2025-10-20
DOI
https://doi.org/10.1016/j.apal.2025.103667
Primary Topic
Advanced Topology and Set Theory
Type
article
Field-Weighted Citation Impact
0.00
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article

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"> <mml:mrow> <mml:mi mathvariant="sans-serif">MA</mml:mi> </mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="script">I</mml:mi> </mml:math> ) and a failure of

Stefan Hoffelner
Annals of Pure and Applied Logic
Advanced Topology and Set Theory
article

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"> <mml:mrow> <mml:mi mathvariant="sans-serif">MA</mml:mi> </mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="script">I</mml:mi> </mml:math> ) and a failure of

Stefan Hoffelner
article en

Abstract

We present a method which forces the failure of Π 3 1 and Σ 3 1 -separation, while MA ( I ) holds, for I the family of indestructible ccc forcings. This shows that, in contrast to the assumption BPFA and ℵ 1 = ℵ 1 L which implies Π 3 1 -separation, that weaker forcing axioms do not decide separation on the third projective level.

Annals of Pure and Applied LogicVol. 177(3)
TU Wien (AT)
Openalex Percentile: Top 64%
Advanced Topology and Set Theory
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