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### Recent blog posts

- Prikry forcing may add a Souslin tree June 12, 2016
- The reflection principle $R_2$ May 20, 2016
- Prolific Souslin trees March 17, 2016
- Generalizations of Martin’s Axiom and the well-met condition January 11, 2015
- Many diamonds from just one January 6, 2015
- Happy new jewish year! September 24, 2014
- Square principles April 19, 2014
- Partitioning the club guessing January 22, 2014

### Keywords

very good scale L-space Hindman's Theorem Almost countably chromatic Stevo Todorcevic Minimal Walks 11P99 Small forcing Club Guessing middle diamond incompactness Almost-disjoint famiy Fast club Axiom R S-Space Fat stationary set Martin's Axiom Erdos-Hajnal graphs stationary reflection stationary hitting Kurepa Hypothesis tensor product graph Rock n' Roll Whitehead Problem Hedetniemi's conjecture Coherent tree Forcing Axioms Uniformization Mandelbrot set Weakly compact cardinal polarized partition relation Antichain Dushnik-Miller square square principles Distributive tree Forcing Almost Souslin Prikry-type forcing Knaster Generalized Clubs Non-saturation weak square Uniformly coherent Erdos Cardinal Poset Shelah's Strong Hypothesis Partition Relations approachability ideal Hereditarily Lindelöf space Rado's conjecture Reduced Power reflection principles Luzin set Cardinal function Constructible Universe xbox sap Diamond Jonsson cardinal HOD super-Souslin tree Cohen real Successor of Regular Cardinal Slim tree Universal Sequences 05A17 Successor of Singular Cardinal free Boolean algebra Selective Ultrafilter Fodor-type reflection Foundations P-Ideal Dichotomy Square-Brackets Partition Relations Aronszajn tree Large Cardinals OCA Ascent Path PFA(S)[S] Commutative cancellative semigroups Ostaszewski square Singular coﬁnality Parameterized proxy principle ccc projective Boolean algebra Chromatic number Prevalent singular cardinals Cardinal Invariants Rainbow sets coloring number Chang's conjecture Sakurai's Bell inequality diamond star weak diamond Singular cardinals combinatorics Souslin Tree 20M14 Absoluteness Postprocessing function PFA Microscopic Approach Nonspecial tree Singular Density b-scale

# Tag Archives: Whitehead Problem

## Jensen’s diamond principle and its relatives

This is chapter 6 in the book Set Theory and Its Applications (ISBN: 0821848127). Abstract: We survey some recent results on the validity of Jensen’s diamond principle at successor cardinals. We also discuss weakening of this principle such as club … Continue reading

## Shelah’s solution to Whitehead’s problem

Whitehead problem notes in hebrew : Table of contents Chapter 0 Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 References