English

Cyclicity and iterated logarithms in the Dirichlet space

Functional Analysis 2025-10-23 v2

Abstract

Let D(μ)D(\mu) denote a harmonically weighted Dirichlet space on the unit disc D\mathbb D. We show that outer functions fD(μ)f\in D(\mu) are cyclic in D(μ)D(\mu), whenever logf\log f belongs to the Pick-Smirnov class N+(D(μ))N^+(D(\mu)). If ff has HH^\infty-norm less than or equal to 1, then cyclicity can also be checked via iterated logarithms. For example, we show that such outer functions ff are cyclic, whenever log(1+log(1/f))N+(D(μ))\log(1+ \log(1/f))\in N^+(D(\mu)). This condition can be checked by verifying that log(1+log(1/f))D(μ)\log(1+ \log(1/f))\in D(\mu). If ff satisfies a mild extra condition, then the conditions also become necessary for cyclicity.

Keywords

Cite

@article{arxiv.2409.20298,
  title  = {Cyclicity and iterated logarithms in the Dirichlet space},
  author = {Alexandru Aleman and Stefan Richter},
  journal= {arXiv preprint arXiv:2409.20298},
  year   = {2025}
}

Comments

9 pages, 1 figure

R2 v1 2026-06-28T19:02:19.799Z