Séminaires : Séminaire Général de Logique

Equipe(s) : lm,
Responsables :S. Anscombe, A. Khélif, A. Vignati
Email des responsables : sylvy.anscombe@imj-prg.fr, vignati@imj-prg.fr
Salle : 1013
Adresse :Sophie Germain
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Orateur(s) Rahman Mohammadpour - Wien,
Titre Specializing trees of height \omega_2 with finite approximation
Date10/02/2021
Horaire16:00 à 17:15
Diffusion https://u-paris.zoom.us/rec/share/D1xat237ZQVoKmpuIzvHv_vMNVizFHRJMC4ExYb3pWBJDtWTZAxWVU5KpkJaKjlM.2hcMddHxDVxnXYXs
RésumeIt is well-known that under CH one can attempt to specialize trees of height ω_2 without cofinal branches using a naive forcing with countable approximations. However, one has to require more (the nonexistence of ascending paths) than the lack of cofinal branches to make sure that the naive attempt does not fail. I will discuss these possible obstacles to specialize trees of height ω_2 , and then use models as side conditions to construct a forcing notion with finite conditions, which under PFA specializes a given tree of height ω_2 without cofinal branches. If time permits, I will mention generalizations of this result to taller trees.
Salle1013
AdresseSophie Germain
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