Category: What’s hot at MathOverflow

The two ways Feynman diagrams appear in mathematics

Concepts in topology successfully transferred to graph theory and combinatorics with non-trivial applications?

Concepts in topology successfully transferred to graph theory and combinatorics with non-trivial applications?

Why is the definition of higher homotopy groups the “right one”? Why is there no symplectic version of spectral geometry? Pullback and homology Is this generalization of Borsuk-Ulam true? Roots of unity Vandermonde matrix is totally positive Why are free objects “free”? Does there exist any non-contractible manifold with fixed point property?  

Is there a geometric interpretation for Reidemeister torsion?

Open subsets of Euclidean space in dimension 5 and higher admitting exotic smooth structures

3D Billiards problem inside a torus