English

Bohr phenomenon for certain close-to-convex analytic functions

Complex Variables 2026-04-15 v2

Abstract

We say that a class B\mathcal{B} of analytic functions ff of the form f(z)=n=0anznf(z)=\sum_{n=0}^{\infty} a_{n}z^{n} in the unit disk D:={zC:z<1}\mathbb{D}:=\{z\in \mathbb{C}: |z|<1\} satisfies a Bohr phenomenon if for the largest radius Rf<1R_{f}<1, the following inequality n=1anznd(f(0),f(D)) \sum\limits_{n=1}^{\infty} |a_{n}z^{n}| \leq d(f(0),\partial f(\mathbb{D}) ) holds for z=rRf|z|=r\leq R_{f} and for all functions fBf \in \mathcal{B}. The largest radius RfR_{f} is called Bohr radius for the class B\mathcal{B}. In this article, we obtain Bohr radius for certain subclasses of close-to-convex analytic functions. We establish the Bohr phenomenon for certain analytic classes Sc(ϕ),Cc(ϕ),Cs(ϕ),Ks(ϕ)\mathcal{S}_{c}^{*}(\phi),\,\mathcal{C}_{c}(\phi),\, \mathcal{C}_{s}^{*}(\phi),\, \mathcal{K}_{s}(\phi). Using Bohr phenomenon for subordination classes \cite[Lemma 1]{bhowmik-2018}, we obtain some radius RfR_{f} such that Bohr phenomenon for these classes holds for z=rRf|z|=r\leq R_{f}. Generally, in this case RfR_{f} need not be sharp, but we show that under some additional conditions on ϕ\phi, the radius RfR_{f} becomes sharp bound. As a consequence of these results, we obtain several interesting corollaries on Bohr phenomenon for the aforesaid classes.

Keywords

Cite

@article{arxiv.2008.00187,
  title  = {Bohr phenomenon for certain close-to-convex analytic functions},
  author = {Vasudevarao Allu and Himadri Halder},
  journal= {arXiv preprint arXiv:2008.00187},
  year   = {2026}
}

Comments

18 pages

R2 v1 2026-06-23T17:34:15.647Z