What’s hot at mathoverflow 21/2017

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

Is there a “universal” connected compact metric space?

A short proof for simple connectedness of the projective line

Trace of non-commutable matrices

When is it easier to work projectively?

Is \Omega J_{p^n-1}S^2$ commutative up to homotopy?

Why aren’t proceedings from ICM 2014 on mathscinet?