I'm looking at the claim in An algorithmic theory of learning: Robust concepts and random projection by R. I. Arriaga and S. Vempala (2006):
Further, it is NP-hard to learn a disjunction of k variables as a disjunction of few than k log n variable.
I believe this is meant in the PAC model, I believe without membership queries.The author states this without proof. This usually means the result is well-known or obvious but I haven't been able to track it down in an online resource (including a few papers surveying the basics) and it lacks citation.
(I asked a simpler question here but this wasn't strong enough to clear up my confusion on the claim in the paper.)