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Projective Measure Without Projective Baire

About this Title

Sy David Friedman and David Schrittesser

Publication: Memoirs of the American Mathematical Society
Publication Year: 2020; Volume 267, Number 1298
ISBNs: 978-1-4704-4296-5 (print); 978-1-4704-6395-3 (online)
DOI: https://doi.org/10.1090/memo/1298
Published electronically: January 4, 2021
Keywords: Lebesgue measure, Baire property, projective sets, forcing, Mahlo cardinals

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Table of Contents

Chapters

  • 1. Introduction
  • 2. Notation and Preliminaries
  • 3. Overview of the Proof
  • 4. Stratified Forcing
  • 5. Easton Supported Jensen Coding
  • 6. Extension and Iteration
  • 7. Amalgamation
  • 8. Proof of the Main Theorem

Abstract

We prove that it is consistent (relative to a Mahlo cardinal) that all projective sets of reals are Lebesgue measurable, but there is a $\Delta ^1_3$ set without the Baire property. The complexity of the set which provides a counterexample to the Baire property is optimal.

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