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2026-05-16 13:17:55 UTC
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John Carlos Baez on Nostr: - True! But you can do more with covers if you allow branch points. I believe the ...

- True! But you can do more with covers if you allow branch points. I believe the great icosahedron is a branched cover of the Riemann sphere.

I don't actually know this! What I know is that the small stellated dodecahedron is a branched cover of the Riemann sphere by a Riemann surface of genus 4:

https://blogs.ams.org/visualinsight/2016/06/15/small-stellated-dodecahedron/

The theory of this stuff makes me think the great icosahedron is a branched cover of the Riemann sphere by itself. For example, Wikipedia lists the Euler characteristic of the great icosahedron as being 2, like the sphere's:

https://en.wikipedia.org/wiki/Kepler%E2%80%93Poinsot_polyhedron

Perhaps this leads in a different direction than the one I wanted to explore today... or perhaps it's related.