Coefficient-growth conjecture for the Cauchy transform

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Let ν\nu be a measure for which the Cauchy transform has Taylor expansion

Cν(z)=∑n≥0νnzn.\mathcal{C}_\nu(z)=\sum_{n\geq 0}\nu_nz^n.

Let {Mn}n≥0\{M_n\}_{n\geq 0} be a logarithmically convex sequence satisfying

∑n≥0(log⁡(1/Mn))21+n2=∞.\sum_{n\geq 0}\frac{\bigl(\log(1/M_n)\bigr)^2}{1+n^2}=\infty.

Coefficient-growth conjecture. The conclusion of the uncertainty theorem referred to as \thref{UncertThmRSD} can be reached if merely

sup⁡n≥0∣νn∣Mn<∞.\sup_{n\geq 0}\frac{|\nu_n|}{M_n}<\infty.

This proposes that the theorem's conclusion remains valid under the displayed coefficient bound and divergence condition, rather than the stronger hypothesis used in the theorem; the source does not state whether it is resolved.

References

Primary source

Bartosz Malman, “Shift operators, Cauchy integrals and approximations”, arXiv:2308.06495 (2023).

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