3 papers
math.GT2026
The Unsolvability of the Homeomorphism Problem
Stefan Friedl, Tobias Hirsch, Marc Kegel
In this short expository note, we give a detailed proof of Markov's theorem on the unsolvability of the homeomorphism problem and of the existence of unrecognizable manifolds in al…
math.GT2024
Algorithms in 4-manifold topology
Stefan Bastl, Rhuaidi Burke, Rima Chatterjee +28
We show that there exists an algorithm that takes as input two closed, simply connected, topological 4-manifolds and decides whether or not these 4-manifolds are homeomorphic. In p…
math.GT2024
Bounding the ribbon numbers of knots and links
Stefan Friedl, Filip Misev, Alexander Zupan
The ribbon number of a ribbon knot is the minimal number of ribbon intersections contained in any ribbon disk bounded by . We find new lower bounds for $r…