Equivalence of unravelability and universal unravelability
Determine whether unravelability implies universal unravelability: prove or refute that for every game tree T on a set A and every payoff set P ⊆ [T], if (T, P) is unravelable, then for every covering (π, ·): T′ → T the lifted game (T′, π−1(P)) is unravelable.
References
It is not clear to the author whether the unravelable sets also yield a σ-algebra or even whether every unravelable set is universally unravelable.
                — A formalization of Borel determinacy in Lean
                
                (2502.03432 - Manthe, 5 Feb 2025) in Subsection “Comparison to Martin’s proof,” within Section “Outline of the informal proof”