PFA and complemented subspaces of ℓ_∞/c₀ #
by Alan Dow Journal of Logic and Analysis, 2016
Section 2 of the paper starts:
Let A_n, n ∈ ℕ be a partition of ℕ into infinite sets.
Here we prove formally that there exists a partition of ℕ into infinitely many infinite sets.
The idea is to use the 2-adic valuation.
(We first prove it for just two sets as a warmup.)
We also introduce the ideals A⊥ and I (introduced on page 2 of the paper) and prove A⊥ ⊆ I.