What is the biggest unsolved problem in topology
The Poincaré conjecture for differentiable 4-manifolds? (As opposed to the Poincaré conjecture for 3-manifolds, which Perelman solved.)
Could you explain the Poincaré for 4-manifolds? Is it harder to prove than 3-manifolds?
wasnt that proved by freedman in around 1980?
Friedman showed it for topological 4-manifolds in 1982, but the case of differentiable 4-manifolds is still open as far as I know.
And I really don't know much about topology, I was just throwing out an answer.
Separate names with a comma.