23 Answers votes newest views recent 4When Animals Attack 9“Sums-compact” objects = f.g. objects in categories of modules? 4Can a vector space over an infinite field be a finite union of proper subspaces? 5Errata for Atiyah-Macdonald 5Closedness of finite-dimensional subspaces 3Are there locally compact groups which have no compact open subgroups and no discrete infinite cyclic subgroups? 1Discrete cyclic subgroup. 6Applications of the Chinese remainder theorem 4Expressing adj(A) as a polynomial in A? 0Unbounded operator bounded in a dense subset 2How would one even begin to try to prove that a simple number-theoretic statement is undecidable? 7Cardinality of the permutations of an infinite set 0Knuth’s intuition that Goldbach might be unprovable 4Galois theory timeline 1Shortest/Most elegant proof for $L(1,\chi)\neq 0$ 0What are examples of mathematical concepts named after the wrong people? (Stigler’s law) -3Solutions to the Continuum Hypothesis 17Examples of common false beliefs in mathematics. (3) 23Quick proofs of hard theorems 3Math paper authors' order 5Suggestions for good books on class field theory 1Subset of the plane that intersects every line exactly twice 2What does it mean for a mathematical statement to be true?