Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- Part I Let’s Be Independent
- Part II What is New in Set Theory
- 10 Introduction to Part Two
- 11 Classical Extensions
- 12 Iterated Forcing and Martin’s Axiom
- 13 Some More Large Cardinals
- 14 Limitations of Martin’s Axiom and Countable Supports
- 15 Proper Forcing and PFA
- 16 N2 and other Successors of Regulars
- 17 Singular Cardinal Hypothesis and Some PCF
- 18 Forcing at Singular Cardinals and Their Successors
- References
- Index
15 - Proper Forcing and PFA
from Part II - What is New in Set Theory
Published online by Cambridge University Press: 28 September 2020
- Frontmatter
- Dedication
- Contents
- Preface
- Part I Let’s Be Independent
- Part II What is New in Set Theory
- 10 Introduction to Part Two
- 11 Classical Extensions
- 12 Iterated Forcing and Martin’s Axiom
- 13 Some More Large Cardinals
- 14 Limitations of Martin’s Axiom and Countable Supports
- 15 Proper Forcing and PFA
- 16 N2 and other Successors of Regulars
- 17 Singular Cardinal Hypothesis and Some PCF
- 18 Forcing at Singular Cardinals and Their Successors
- References
- Index
Summary
A new chapter in the theory of forcing was opened by Shelah’s discovery of proper forcing in [100]. The novelty of Shelah’s approach is a move from infinite combinatorics to the technique of elementary submodels, which has since integrated set theory to the extent that it is hard to imagine a forcing argument that does not use it. A major reference on the technique and results about proper forcing is Shelah’s book [105]. Throughout this chapter, we fix an uncountable regular cardinal χ which is so large that all arguments relative to the forcing notions we discuss are contained in the set H(χ) of all sets x with |TC(x)| < χ.
- Type
- Chapter
- Information
- Fast Track to Forcing , pp. 90 - 103Publisher: Cambridge University PressPrint publication year: 2020