On some mathematical topics I found interesting.
Geometric group theory
Not all finitely-presented groups are fundamental groups of closed 3-manifolds
Positive curvature versus negative curvature
On subgroups of surface groups
Graphs and Free Groups
Fiber product of graphs and Howson’s theorem for free groups
Surfaces and commutators in free groups
How Stallings proved finitely generated groups are subgroup separable
« Older posts
Exploring the works of Gilbert Baumslag
Gödel Lost Lettre and P=NP
Geometric Group Theory
Geometry and the Imagination
Here there be dragons
Image des Mathématiques
Low Dimensional Topology
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