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Daniel Asimov
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What's the lowest-dimensional Euclidean space in which a hexagonal 2-torus smoothly embeds isometrically?

Here a hexagonal 2-torus TH means any Riemannian flat torus obtained by identifying opposite edges of a regular hexagon in the plane.

It's easy to see that TH can be smoothly (C) isometrically embedded in ℝ6, and for that matter (if suitably scaled) in the unit sphere S5, and also in ℂℙ2.

But is it known whether TH can be smoothly isometrically embedded in ℝ5 or ℝ4 ?

(Also of interest is whether TH can be smoothly isometrically immersed in ℝ5 or ℝ4.)

Daniel Asimov
  • 2.9k
  • 24
  • 26