Helson's zero-free conjecture for twisted Beurling Dirichlet series

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Let Nq\mathbb{N}_q be a Beurling system satisfying Bohr's condition, let f∈Hq2f\in\mathcal{H}_q^2 be outer, meaning that

{fg: g∈Hq∞}\{fg:\,g\in\mathcal{H}_q^\infty\}

is dense in Hq2\mathcal{H}_q^2, and let fχf_\chi denote the twisted Dirichlet series associated with ff and a completely multiplicative character χ\chi.

Helson's conjecture. The function fχf_\chi never has any zeros in its half-plane of convergence.

This is a special case of a conjecture made by Helson concerning twisted Dirichlet series. The claim relates outerness in the Hardy space of a Beurling system to zero-freeness of almost-everywhere twists, but the source gives no resolution status.

References

Primary source

Frederik Broucke, Athanasios Kouroupis and Karl-Mikael Perfekt, “A note on Bohr's theorem for Beurling integer systems”, arXiv:2301.11782 (2023).

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