arXiv subjects

J. Sokół

Publications and source records attributed to J. Sokół.

4 recordsLinked to original sources

arXiv2026

Hadamard product of convex functions and Jackson operator

In this paper we consider some properties of Jackson's difference operator for convex univalent functions in $|z|<1$ with complex parameter $q$ as a Hadamard product of two power series. Jackson in 1908 introduced for a real $q$, $q\in[0,1)$, the difference operator \mbox{${\rm d}_qf(z)$} for an analytic function $f$ in the unit disc $|z|<1$ in the complex plane. Thanks to this operator, many mathematicians have extended the theory of functions in $q$-theory. The $q$-theory has found many applications in theory of hypergeometric series, special functions, combinatorics, number theory, fluid mechanics, quantum mechanics and physics.

math.CV↗

arXiv2026

On a certain subclass of strongly starlike functions

Let $\mathcal{S}^*(α_1,α_2)$, where $ α_1, α_2 \in (0,1]$, represent the class of functions $f$ that are analytic in the open unit disk $\mathbb{D}$, normalized by $f(0) = f'(0) - 1=0$, and satisfying the following double-sided inequality: \begin{equation*} -\frac{πα_1}{2}< \arg\left\{\frac{zf'(z)}{f(z)}\right\} <\frac{πα_2}{2}, \quad (z\in\mathbb{D}). \end{equation*} In this manuscript, we estimate the coefficients and logarithmic coefficients associated with functions that belong to the class $\mathcal{S}^*(α_1,α_2)$. As a result, we provide a general bound for the coefficients of a strongly starlike function, which has been an open question until now. Finally, we derive upper and lower bounds for the expression ${\rm Re}\{zf'(z)/f(z)\}$, where $f\in \mathcal{S}^*(α_1,α_2)$.

math.CV↗

arXiv2018

On starlike functions related with the convex conic domain

In the present paper, we study a new subclass $\mathcal{M}_p(α,β)$ of $p$--valent functions and obtain some inequalities concerning the coefficients for the desired class. Also, by use of the Hadamard product, we define a general operator and find a condition such that it belongs to the class $\mathcal{M}_p(α,β)$.

math.CV↗

arXiv2017

On Booth lemniscate of starlike functions

Assume that $Δ$ is the open unit disk in the complex plane and $\mathcal{A}$ is the class of normalized analytic functions in $Δ$. In this paper we introduce and study the class \begin{equation*} \mathcal{BS}(α):=\left\{f\in \mathcal{A}: \left(\frac{zf'(z)}{f(z)}-1\right)\prec \frac{z}{1-αz^2}, \, z\inΔ\right\}, \end{equation*} where $0\leqα\leq1$ and $\prec$ is the subordination relation. Some properties of this class like differential subordination, coefficients estimates and Fekete-Szegö inequality associated with the $k$-th root transform are considered.

math.CV↗