Monsky's Theorem

(mathmondays.com)

22 points | by hyperbrainer 4 hours ago

4 comments

  • prof-dr-ir 2 hours ago
    > no face of P, nor any face of one of the Ti, contains vertices of all three colors

    That should be 'edge', not 'face', no? Otherwise I do not understand what is happening at all with the examples.

    • dmurray 2 hours ago
      Yes, this would more normally be called "edge". It's not incorrect to call it a face, by analogy with higher-dimensional solids, but confusing.
    • erooke 2 hours ago
      Pretty sure they meant the word face, that would be the generic term for edge. (An edge being a 1 dimensional face)
  • ogogmad 2 hours ago
    Haven't read the article. But something about this reminds me of Arnold's topological proof of the unsolvability of the quintic (YouTube form: https://www.youtube.com/watch?v=BSHv9Elk1MU ; PDF: https://web.williams.edu/Mathematics/lg5/394/ArnoldQuintic.p...).

    It seems a lot of impossibility theorems - the type that the ancient Greeks would have understood - can be proven using algebraic topology. Perhaps Sperner's lemma can be seen as an algebraic topology theorem? I don't personally know.

    • PollardsRho 2 hours ago
      Thanks for sharing this proof! As someone who enjoys math but never got myself through enough Galois theory to finish the standard proof, it's fantastic to see a proof that's more elementary while still giving a sense of why the group structure is important.
  • bobmcnamara 1 hour ago
    Taaaake it to the limit: N=∞, area=0, job done