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Exact log-Sobolev constant on odd cycles

Determine the exact value of the log-Sobolev constant β for simple random walk on the n-cycle when n is odd.

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Background

For the simple random walk on the n-cycle with even n, the log-Sobolev, modified log-Sobolev, and spectral constants coincide (up to the stated equalities). However, for odd n, despite comparable bounds, the exact value of the log-Sobolev constant β remains unknown, leaving a basic gap even in this classical model.

References

When n is odd, however, the precise value of β is embarrassingly still unknown.

Modern aspects of Markov chains: entropy, curvature and the cutoff phenomenon (2508.21055 - Salez, 28 Aug 2025) in Section 3.3, Hyper-contractivity – Example: Random walk on the n-cycle