Intuition for symplectic groups

A refinement of Serre’s finiteness theorem on unstable homotopy groups of spheres

Exotic 4-spheres and the Tate-Shafarevich Group

Does every compact metric space have a canonical probability measure?

Why doesn’t this construction of the tangent space work for non-Riemannian metric manifolds?

What can be the applications of a theory of schemes à la Grothendieck to the category of groups?