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arXiv · 2407.12674

Sharp isoperimetric inequalities on the Hamming cube near the critical exponent

Polona Durcik·Paata Ivanisvili·Joris Roos
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Abstract

An isoperimetric inequality on the Hamming cube for exponents $\beta\ge 0.50057$ is proved, achieving equality on any subcube. This was previously known for $\beta\ge \log_2(3/2)\approx 0.585$. Improved bounds are also obtained at the critical exponent $\beta=0.5$, including a bound that is asymptotically sharp for small subsets. A key ingredient is a new Bellman-type function involving the Gaussian isoperimetric profile which appears to be a good approximation of the true envelope function. Verification uses computer-assisted proofs and interval arithmetic. Applications include progress towards a conjecture of Kahn and Park as well as sharp Poincar\'e inequalities for Boolean-valued functions near $L^1$.

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Polona Durcik, Paata Ivanisvili, Joris Roos. 2024-07-17. Sharp isoperimetric inequalities on the Hamming cube near the critical exponent. https://arxiv.org/abs/2407.12674

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