Speaker: Djanira dos Santos Gomes (Universität Bern)
Date and Time: Thursday, March 12th 2026, 16:30-18:00
Venue: ILLC Seminar Room F1.15, Science Park 107 and online.
Title: Virtual Group Knowledge and Group Belief in Topological Evidence Models.
Abstract. We study notions of (virtual) group knowledge and group belief within multi-agent evidence models, obtained by extending the topological semantics of evidence-based belief and fallible knowledge from individuals to groups. We completely axiomatize and show the decidability of the logic of (“hard” and “soft”) group evidence, and do the same for an especially interesting fragment of it: the logic of group knowledge and group belief. We also extend these languages with dynamic evidence-sharing operators, and completely axiomatize the corresponding logics, showing that they are co-expressive with their static bases.