Weak-type level-set conjecture for normalized Hardy functions

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Let D\mathbb{D} be the unit disc, let μ\mu be the measure used in the paper on D\mathbb{D}, and let f∈H2f\in H^2. For λ\lambda in the relevant range 0<λ<10<\lambda<1, consider the level set

{z∈D:∣f(z)∣2(1−∣z∣2)>λ∥f∥H22}.\left\{z\in\mathbb{D}:|f(z)|^2(1-|z|^2)>\lambda\|f\|_{H^2}^2\right\}.

Weak-type level-set conjecture.

μ({z∈D:∣f(z)∣2(1−∣z∣2)>λ∥f∥H22})≤1λ−1.\mu\left(\left\{z\in\mathbb{D}:|f(z)|^2(1-|z|^2)>\lambda\|f\|_{H^2}^2\right\}\right)\leq\frac{1}{\lambda}-1.

The conjecture would imply the preceding Burbea conjecture through the distributional estimate discussed in the source. The supplied passage does not establish this sharp bound, so its resolution is left open here.

References

Primary source

Ole Fredrik Brevig, Joaquim Ortega-Cerdà, Kristian Seip and Jing Zhao, “Contractive inequalities for Hardy spaces”, arXiv:1706.00738 (2018).

Additional references

2 papers in this index state this conjecture (2010–2017). The statement above is taken from the most recent of them; the others are arXiv:1008.0381.

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