On Reflection of Stationary Sets in P

@inproceedings{Jech1998OnRO,
  title={On Reflection of Stationary Sets in P},
  author={Thomas Jech and Saharon Shelah},
  year={1998}
}
Let κ be an inaccessible cardinal, and let E0 = {x ∈ Pκκ : cf λx = cf κx} and E1 = {x ∈ Pκκ : κx is regular and λx = κx }. It is consistent that the set E1 is stationary and that every stationary subset of E0 reflects at almost every a ∈ E1.