Forcing and independence
Warm-upHumanIn Cohen forcing (finite partial functions, stronger = larger), which of these sets are dense? Choose all that apply.
In Cohen forcing (finite partial functions, stronger = larger), which of these sets are dense? Choose all that apply.
How many conditions does have, i.e. how many partial functions from to are there (including the empty function )?
Why does the classical presentation of forcing start from a countable transitive model ?
In the proof that an -generic filter (for a forcing in which every condition has two incompatible extensions) is not in , which dense set does fail to meet if ?
The proof that has the countable chain condition takes uncountably many conditions . What is the key step?
Assuming ZFC is consistent, which of these statements are independent of ZFC? Choose all that apply.
The Lean file orders Cohen conditions by extension: p ≤ q means q extends p. In this order, what does Mathlib's Order.Ideal Cohen correspond to in forcing?
The theorem no_filter_meets_every_dense (G : Order.Ideal Cohen) : ∃ D : Set Cohen, IsCofinal D ∧ ∀ p ∈ D, p ∉ G is proved with which witness D?
Write escape(reals, n): given a list of reals (functions from naturals to ) and , return a tuple of bits of length at least that disagrees with every listed real at some position. This is the Rasiowa–Sikorski construction for the dense sets 'decide bit ' () and 'disagree with '.