Shelah's diamond principle conjecture for stationary subsets
Let λ\lambdaλ and κ\kappaκ be cardinals, with λ=λ<λ>κ+\lambda=\lambda^{<\lambda}>\kappa^+λ=λ<λ>κ+, κ=cf(κ)\kappa=\operatorname{cf}(\kappa)κ=cf(κ), and λ≠ℵ1\lambda\ne\aleph_1λ=ℵ1. The weaker alternative allows…