Algebraic Graph Theory Seminar- Serhii Bardyla (10.4.2026)
Friday 10.4.2026 at 13:15, Lecture room M IX (online too)
Serhii Bardyla (University of Vienna):
Actions of finite groups on orientable surfacesUltrafilters in Combinatorics, Topological Algebra and Set Theory
Abstract:
In this talk, we discuss ultrafilters and their role in combinatorics, topological algebra and set theory. In particular, we present some classical combinatorial results that can be proven using idempotent ultrafilters. We introduce Schur ultrafilters and describe their relationship to P-points and Ramsey ultrafilters. Using Schur ultrafilters we give a new representation of Bohr compactifications of topological groups, and characterize automatic continuity of group operations in certain compact right topological groups. Finally, we present a topological counterpart of Hindman's theorem which addresses colorings of topological groups.
The talk is intended to be self-contained and accessible to a broad mathematical audience.