The lattice of sets of natural numbers is rich (2021)

(jdh.hamkins.org)

80 points | by benmandrew 3 days ago

5 comments

  • scythmic_waves 45 minutes ago
    > The power set lattice (P(N)) of all sets of natural numbers, not to scale, some sets omitted...
  • munchler 3 hours ago
    What a beautiful illustration. It makes intuitive the very abstract concepts discussed in the text. It’s fun to zoom in and browse around the structure.
    • michael0church 3 hours ago
      It’s also genuinely surprising. We’re used to thinking of the countable as the small infinity, which it is, and yet a structure we feel like we can visualize contains so much complexity.

      There is also, weirdly, a way in which massive finite numbers like TREE(3) “feel” larger than N, and large countable infinities “feel” larger than w_1, even though the opposite is clearly true.

      • aeneasmackenzie 8 minutes ago
        All describable or recognizable complexity is part of the subcountable set of computable subsets of N. Higher infinities thus mostly contain fake elements about which nothing can be said, so they don’t feel any bigger.
      • voidmain 3 hours ago
        The visualization is of the power set, which is uncountable.
        • michael0church 3 hours ago
          Right. But because it’s the smallest structure of its type (speaking loosely) it feels like something we should have a grasp on, even though it contains more complexity than we could ever describe or compute with (since both of those are countable.)
      • zaebal 3 hours ago
        TREE(3) is unimaginably small, compared to ω
  • flobosg 4 hours ago
    (2021)
    • genxy 1 hour ago
      math is timeless
      • flobosg 2 minutes ago
        Blog entries, alas, are not.
  • gregw2 3 hours ago
    What a great visualization!

    Now can your favorite LLM make me a similar one for the Real #s?