Neutral Letter Conjecture (Ohlmann’s conjecture)

Determine whether, for every positional objective W ⊆ Σ^ω, the objective obtained by adding a neutral letter ε (which can be removed from any word without changing membership) to W, denoted W^ε, is also positional over all games.

Background

Ohlmann gave a universal-graph characterisation of positional objectives under a neutral-letter assumption and conjectured that adding a neutral letter preserves positionality, which would remove the assumption. The authors later resolve this for ω-regular objectives but the conjecture remains interesting in broader settings.