Combinatorial Properties of the Raisonnier Filter
Spyridon Dialiatsis, Yurii Khomskii

Abstract:
The Raisonnier filter is a combinatorial object isolated by Jean Raisonnier in order to simplify Shelah's proof that if all Σ^1_3 sets are Lebesgue-measurable then there is an inner model with an inaccessible cardinal. In this paper, we study the combinatorics of a general version of the Raisonnier filter, with an eye to potential applications in descriptive set theory. We prove various results about the Raisonnier Filter generated by simple sets, and we study the ideals associated to the Raisonnier Filter being rapid and/or unbounded, connecting it to the null-additive and meagre-additive ideals studied by Pawlikowski and Shelah. Among the more interesting results is a converse to Raisonnier's theorem which indicates that Raisonnier's technique is unlikely to lead to similar results for other regularity properties. We also draw some conclusions regarding the Borel and dual Borel Conjectures.