A Jacobian counterexample turned into a folded 3D surface visualization

repligate · x · 2026-07-21

A visual explainer turns the “Jacobian counterexample” into a folded 3D surface, showing how three different inputs can map to the same target in the pleat region while only one input reaches it outside the fold. The post is more of a technical curiosity / meme than a full exposition, but the image itself carries the core idea.

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