Characterising one-player positionality for infinite duration games on graphs

Speaker: Pierre Ohlmann, IRIF
Tuesday 30 November 2021, 11:00, (Salle 1Z56, bât ENS)

Abstract: I will present a new result, asserting that a winning condition (or, more generally, a valuation) which admits a neutral letter is positional over arbitrary arenas if and only if for all cardinals there exists a universal graph which is monotone and well-founded. Here, "positional" refers only to the protagonist; this concept is sometimes also called "half-positionality".

This is the first known characterization in this setting. I will explain the result, quickly survey existing related work, show how it is proved and try to argue why it is interesting.