14 Answers votes newest views recent 0Awfully sophisticated proof for simple facts 0Theorems that are ‘obvious’ but hard to prove 2Proofs without words 1Interesting Calculus Questions/Exercises 13What are some proofs of Godel’s Theorem which are *essentially different* from the original proof? 3Questions regarding “second and higher-order-undecidability” 2Continuous Measurement in Quantum Mechanics 10What are some mathematical concepts that were (pretty much) created from scratch and do not owe a debt to previous work? 4Most ‘unintuitive’ application of the Axiom of Choice? (2) 6Does the fact that this vector space is not isomorphic to its double-dual require choice? 3Intersection Probabilities for Random Walk in d>2 6Colloquial catchy statements encoding serious mathematics 1Improved versions of discontinuous functions 8How is the Ising model an example of a lattice model as per Kontsevich?