OpenAI reports a smooth diffeomorphism with simple Lebesgue spectrum

A C∞ diffeomorphism of the three-torus preserves standard volume and has simple Lebesgue Koopman spectrum on its entire mean-zero L² space.

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Understanding the problem

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A C∞ diffeomorphism of the three-torus preserves standard volume and has simple Lebesgue Koopman spectrum on its entire mean-zero L² space.

Why it matters

If correct, solves the probability-preserving form of Banach’s simple Lebesgue-spectrum problem in smooth dynamics.

What counts as progress

Can a smooth volume-preserving diffeomorphism have simple Lebesgue spectrum on its entire mean-zero space?

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