The Proper Forcing Axiom: a tutorial
نویسندگان
چکیده
In these notes we will present an exposition of the Proper Forcing Axiom (PFA). We will first discuss examples of the consequences of PFA. We will then present two proper partial orders which are used to force two combinatorial principles which follow from PFA: The P-Ideal Dichotomy (PID) and Todorcevic’s formulation of the Open Coloring Axiom. On one hand, these posets and the proofs of their properness are quite typical of direct applications of PFA. On the other hand, these principles already capture a large number of the consequences of PFA and do not use any terminology or technical tools from the theory of forcing.
منابع مشابه
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