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A smooth surface metric with no local immersion in $\mathbb R^3$
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Category:Differential geometry Lean version:YES! ✔
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A smooth surface metric with no local isometric immersion in ℝ3. Constructs a smooth positive-definite metric on $(-1,1)^2$ for which no neighborhood of the origin admits a smooth isometric immersion into ℝ3. This answers the unrestricted smooth local isometric realization problem for surfaces negatively, even after shrinking the neighborhood.

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released 2026-09-24  |  7 lemmas · 10 proofs · 8,579 words  |  PLAY LEVEL 1 »  (pdf)
We construct a smooth positive-definite Riemannian metric on $(-1,1)^2$ that agrees with the Euclidean metric to every order at the origin, yet no neighborhood of the origin admits a smooth isometric immersion into Euclidean three-space. This gives a negative answer to the unrestricted smooth local isometric realization problem for surfaces.

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