Mathematical Embarrassments

From Dick Lifton’s blog (thanks to Peter Haas for bringing it to our attention):

Terry Tao is one of the greatest mathematicians of our time…. Today I want to talk about a topic that he has discussed: mathematical embarrassments—the name is mine, but I hope he will agree with spirit of this term….

A mathematical embarrassment (ME) is a problem that should have been solved by now. An ME usually is easy to state, seems approachable, and yet resists all attempts at an attack. There may be many reasons that they are yet to be solved, but they “feel” like they should have been solved already.