Shigeyoshi Owa

Current Organizations / Institutes

The organizations/institutes from the scholar's latest article

1 Decembrie 1918 University

Research Subjects

Functional Analysis

Research Interests

Shigeyoshi Owa has a total of 114 co-authors. Here are the top co-authors by number of shared publications:

Hari Mohan Srivastava
Department of Mathematics and Statistics, University of Victoria, Victoria, BC V8W 3R4, Canada
18 shared publications
Mamoru Nunokawa
18 shared publications
Hatun Ozlem Guney
Department of Mathematics, Faculty of Science, Dicle University, Diyarbakır, Türkiye
14 shared publications
Tadayuki Sekine
10 shared publications
Milutin Obradović
Department of Mathematics, Faculty of Technology and Metallurgy, University of Belgrade, 4 Karnegijeva Street, Belgrade 11000, Serbia
9 shared publications
H. M. Srivastava
8 shared publications

Latest Publications

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Open Access
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- 6 August 2026
- Published by MDPI AG in Mathematics
Applications of Fractional Derivatives for p-Valently α-Convex Functions of Order β
by Muhammet Kamali, Shigeyoshi Owa
Let $A_{p}$ denote the class of p-valently functions $f (z)$ in the open unit disc U with $f^{(j)} (0) = 0 (j = 0, 1, 2, \dots, p - 1)$ . In general, we write $f (z) \in A_{p}$ by $f (z) = z^{p} + \sum_{k = 1}^{\infty} a_{p + k} z^{p + k} (p \in N) .$ For $f (z) \in A_{p}, p$ -valently $α$ -convex functions of order $β$ in U are introduced. Some interesting properties for such functions can be seen. In this paper, we introduce fractional derivatives $D_{z}^{j + λ} f (z)$ for $f (z) \in A_{p}$ with $j = 0, 1, 2, \dots, p - 1$ and $0 \leq λ < 1$ . Applying the fractional derivatives $D_{z}^{j + λ} f (z)$ , we would like to generalize p-valently $α$ -convex functions of order $β$ in U. Some results for such functions $f (z) \in A_{p}$ are discussed with example functions. Further, a conjecture for our research in this paper is given with an example function.
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- 6 August 2026
- Published by MDPI AG in Mathematics
Open Access
Applications of Fractional Derivatives for p-Valently α-Convex Functions of Order β
by Muhammet Kamali, Shigeyoshi Owa
Let $A_{p}$ denote the class of p-valently functions $f (z)$ in the open unit disc U with $f^{(j)} (0) = 0 (j = 0, 1, 2, \dots, p - 1)$ . In general, we write $f (z) \in A_{p}$ by $f (z) = z^{p} + \sum_{k = 1}^{\infty} a_{p + k} z^{p + k} (p \in N) .$ For $f (z) \in A_{p}, p$ -valently $α$ -convex functions of order $β$ in U are introduced. Some interesting properties for such functions can be seen. In this paper, we introduce fractional derivatives $D_{z}^{j + λ} f (z)$ for $f (z) \in A_{p}$ with $j = 0, 1, 2, \dots, p - 1$ and $0 \leq λ < 1$ . Applying the fractional derivatives $D_{z}^{j + λ} f (z)$ , we would like to generalize p-valently $α$ -convex functions of order $β$ in U. Some results for such functions $f (z) \in A_{p}$ are discussed with example functions. Further, a conjecture for our research in this paper is given with an example function.
Open Access
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- 30 March 2026
- Published by RGN Publications in Communications in Mathematics and Applications
New Application of Libera Integral Operator
by Muhammet Kamali, Hatun Özlem Guney, Shigeyoshi Owa
In this paper, we introduce the new subclass $A_{j}(n, \alpha, \beta)$ of $A(n)$ using $Lf(z)$. Some interesting properties of functions $f(z) \in A(n)$ are studied with illustrative examples.
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- 30 March 2026
- Published by RGN Publications in Communications in Mathematics and Applications
Open Access
New Application of Libera Integral Operator
by Muhammet Kamali, Hatun Özlem Guney, Shigeyoshi Owa
In this paper, we introduce the new subclass $A_{j}(n, \alpha, \beta)$ of $A(n)$ using $Lf(z)$. Some interesting properties of functions $f(z) \in A(n)$ are studied with illustrative examples.
Open Access
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- 23 September 2025
- Published by Communications Faculty of Sciences University of Ankara Series A1 Mathematics and Statistics in Communications Faculty of Sciences University of Ankara Series A1 Mathematics and Statistics
Generalization properties of Bernardi integral operator
by Muhammet Kamali, Hatun Özlem Guney, Shigeyoshi Owa
Let $A\left( n\right)$ be the class of analytic functions $f\left(z\right)$ of the form \begin{equation*} f\left( z\right) =z+\sum_{k=n}^{\infty }a_{k}z^{k},\;\;\left( n=2,3,4,...\right) \end{equation*} in the open unit disk $U.$ We introduce the integral operator $B_{j}f\left( z\right) $$=B\left( B_{j-1}f\left( z\right) \right) $, $B_{1}f\left( z\right) =Bf\left( z\right)$ and $B_{0}f\left( z\right) =f\left( z\right) $. In the present paper, we define the subclass $M_{j}\left( n,\gamma ,\alpha \right) $ and discuss some interesting properties of $f\left( z\right) \in A\left( n\right)$ concerning with the class $M_{j}\left( n,\gamma ,\alpha \right) .$
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- 23 September 2025
- Published by Communications Faculty of Sciences University of Ankara Series A1 Mathematics and Statistics in Communications Faculty of Sciences University of Ankara Series A1 Mathematics and Statistics
Open Access
Generalization properties of Bernardi integral operator
by Muhammet Kamali, Hatun Özlem Guney, Shigeyoshi Owa
Let $A\left( n\right)$ be the class of analytic functions $f\left(z\right)$ of the form \begin{equation*} f\left( z\right) =z+\sum_{k=n}^{\infty }a_{k}z^{k},\;\;\left( n=2,3,4,...\right) \end{equation*} in the open unit disk $U.$ We introduce the integral operator $B_{j}f\left( z\right) $$=B\left( B_{j-1}f\left( z\right) \right) $, $B_{1}f\left( z\right) =Bf\left( z\right)$ and $B_{0}f\left( z\right) =f\left( z\right) $. In the present paper, we define the subclass $M_{j}\left( n,\gamma ,\alpha \right) $ and discuss some interesting properties of $f\left( z\right) \in A\left( n\right)$ concerning with the class $M_{j}\left( n,\gamma ,\alpha \right) .$
Open Access
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- 5 August 2025
- Published by MDPI AG in Axioms
New Class of Specific Functions with Fractional Derivatives
by Hatun Özlem Güney, Shigeyoshi Owa
Let $A_{n}$ be the class of specific analytic functions $f (z) = z + \sum_{k = 1}^{\infty} a_{1 + \frac{k}{n}} z^{1 + \frac{k}{n}} (n \in N = {1, 2, 3, \dots})$ in the open unit disk $U .$ For $f (z) \in A_{n},$ fractional derivatives $D_{z}^{λ} f (z)$ and $D_{z}^{j + λ} f (z)$ $(0 \leq λ < 1, j \in N)$ are defined by using Gamma functions. Applying such fractional derivatives, we introduce a new subclass $A_{n} (j, λ, α, β)$ of $A_{n} .$ In this paper, we establish sufficient conditions for $f (z)$ for $A_{n} (j, λ, α, β),$ coefficient inequalities for $| a_{1 + \frac{1}{n}} |$ and $| a_{1 + \frac{k}{n}} |$ $(k = 2, 3, 4, \dots)$ of $f (z) \in A_{n} (j, λ, α, β),$ and some interesting argument properties of fractional derivatives for $f (z) \in A_{n}$ through an example.
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- 5 August 2025
- Published by MDPI AG in Axioms
Open Access
New Class of Specific Functions with Fractional Derivatives
by Hatun Özlem Güney, Shigeyoshi Owa
Let $A_{n}$ be the class of specific analytic functions $f (z) = z + \sum_{k = 1}^{\infty} a_{1 + \frac{k}{n}} z^{1 + \frac{k}{n}} (n \in N = {1, 2, 3, \dots})$ in the open unit disk $U .$ For $f (z) \in A_{n},$ fractional derivatives $D_{z}^{λ} f (z)$ and $D_{z}^{j + λ} f (z)$ $(0 \leq λ < 1, j \in N)$ are defined by using Gamma functions. Applying such fractional derivatives, we introduce a new subclass $A_{n} (j, λ, α, β)$ of $A_{n} .$ In this paper, we establish sufficient conditions for $f (z)$ for $A_{n} (j, λ, α, β),$ coefficient inequalities for $| a_{1 + \frac{1}{n}} |$ and $| a_{1 + \frac{k}{n}} |$ $(k = 2, 3, 4, \dots)$ of $f (z) \in A_{n} (j, λ, α, β),$ and some interesting argument properties of fractional derivatives for $f (z) \in A_{n}$ through an example.
Open Access
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Cited by 2
- 17 February 2025
- Published by Springer Nature in Afrika Matematika
New sufficient conditions for p-valent functions
by Hatun Özlem Güney, Sevtap Sümer, Shigeyoshi Owa
Let $$\mathcal {A}_{p}$$ $A_{p}$ be the class of functions f(z) of the form $$ f(z)=z^{p}+a_{p+1}z^{p+1}+a_{p+2}z^{p+2}+\cdots , (p\in \mathbb {N}=\{1,2,3,\ldots \}) $$ $f (z) = z^{p} + a_{p + 1} z^{p + 1} + a_{p + 2} z^{p + 2} + \dots, (p \in N = {1, 2, 3, \dots})$ that are analytic in the open unit disc $$\mathbb {U}=\big \{ z\in \mathbb {C}: |z| <1\big \}$$ $U = {z \in C : | z | < 1}$ . For $$f(z)\in \mathcal {A}_{p}$$ $f (z) \in A_{p}$ , Nunokawa considered some conditions such that f(z) is $$p-$$ $p -$ valent in $$\mathbb {U}$$ $U$ . Applying the results by Nunokawa, we discuss some interesting properties for functions $$f(z)\in \mathcal {A}_{p}$$ $f (z) \in A_{p}$ . Also, we give some examples for our results.
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- 17 February 2025
- Published by Springer Nature in Afrika Matematika
Open Access
New sufficient conditions for p-valent functions
by Hatun Özlem Güney, Sevtap Sümer, Shigeyoshi Owa
Let $$\mathcal {A}_{p}$$ $A_{p}$ be the class of functions f(z) of the form $$ f(z)=z^{p}+a_{p+1}z^{p+1}+a_{p+2}z^{p+2}+\cdots , (p\in \mathbb {N}=\{1,2,3,\ldots \}) $$ $f (z) = z^{p} + a_{p + 1} z^{p + 1} + a_{p + 2} z^{p + 2} + \dots, (p \in N = {1, 2, 3, \dots})$ that are analytic in the open unit disc $$\mathbb {U}=\big \{ z\in \mathbb {C}: |z| <1\big \}$$ $U = {z \in C : | z | < 1}$ . For $$f(z)\in \mathcal {A}_{p}$$ $f (z) \in A_{p}$ , Nunokawa considered some conditions such that f(z) is $$p-$$ $p -$ valent in $$\mathbb {U}$$ $U$ . Applying the results by Nunokawa, we discuss some interesting properties for functions $$f(z)\in \mathcal {A}_{p}$$ $f (z) \in A_{p}$ . Also, we give some examples for our results.
Cited by 2
Open Access
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- 9 May 2024
- Published by MDPI AG in Mathematics
New Properties of Analytic Functions
by Hatun Özlem Güney, Shigeyoshi Owa
In the present paper, we consider the class $\bar{A}$ of functions $f (z)$ of the form $f (z) = z + \sum_{k = 1}^{\infty} a_{1 + \frac{k}{3}} z^{1 + \frac{k}{3}}$ that are analytic in the open unit disc $U .$ If $a_{1 + \frac{k}{3}} = 0$ for $k \neq 3 n$ $(n = 1, 2, 3, \dots),$ then $f (z)$ is given by $f (z) = z + \sum_{k = 2}^{\infty} a_{k} z^{k} .$ For such functions $f (z) \in \bar{A},$ some interesting properties for subordinations and strongly starlike functions are given. Also, some interesting examples for the results are shown.
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- 9 May 2024
- Published by MDPI AG in Mathematics
Open Access
New Properties of Analytic Functions
by Hatun Özlem Güney, Shigeyoshi Owa
In the present paper, we consider the class $\bar{A}$ of functions $f (z)$ of the form $f (z) = z + \sum_{k = 1}^{\infty} a_{1 + \frac{k}{3}} z^{1 + \frac{k}{3}}$ that are analytic in the open unit disc $U .$ If $a_{1 + \frac{k}{3}} = 0$ for $k \neq 3 n$ $(n = 1, 2, 3, \dots),$ then $f (z)$ is given by $f (z) = z + \sum_{k = 2}^{\infty} a_{k} z^{k} .$ For such functions $f (z) \in \bar{A},$ some interesting properties for subordinations and strongly starlike functions are given. Also, some interesting examples for the results are shown.
Open Access
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- 7 February 2024
- Published by MDPI AG in Mathematics
On Some Interesting Classes of Analytic Functions Related to Univalent Functions
by Hatun Özlem Güney, Daniel Breaz, Shigeyoshi Owa
Let $\bar{A}$ be the new general class of functions $f (z)$ of the form $f (z) = z + \sum_{k = 1}^{\infty} a_{1 + \frac{k}{2}} z^{1 + \frac{k}{2}}$ that are analytic in the open unit disc $U .$ In the present paper, for $f (z) \in \bar{A},$ we consider classes $\bar{S^{*}} (α),$ $\bar{C} (α)$ and $\bar{R} (α)$ and obtain some interesting properties of $f (z) \in \bar{A}$ concerning $\bar{S^{*}} (α),$ $\bar{C} (α)$ and $\bar{R} (α)$ , applying subordinations of $f (z) .$
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- 7 February 2024
- Published by MDPI AG in Mathematics
Open Access
On Some Interesting Classes of Analytic Functions Related to Univalent Functions
by Hatun Özlem Güney, Daniel Breaz, Shigeyoshi Owa
Let $\bar{A}$ be the new general class of functions $f (z)$ of the form $f (z) = z + \sum_{k = 1}^{\infty} a_{1 + \frac{k}{2}} z^{1 + \frac{k}{2}}$ that are analytic in the open unit disc $U .$ In the present paper, for $f (z) \in \bar{A},$ we consider classes $\bar{S^{*}} (α),$ $\bar{C} (α)$ and $\bar{R} (α)$ and obtain some interesting properties of $f (z) \in \bar{A}$ concerning $\bar{S^{*}} (α),$ $\bar{C} (α)$ and $\bar{R} (α)$ , applying subordinations of $f (z) .$
Open Access
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Cited by 1
- 12 January 2024
- Published by Wiley in Journal of Function Spaces
New Integral Operator for Analytic Functions
by H. Özlem Güney, Shigeyoshi Owa, Adel A. Attiya
Let A p n be the class of functions f z given by f z = z p + a p + n z p + n + a p + n + 1 z p + n + 1 + ⋯ which are analytic in the open unit disk U . For f z ∈ A p n , new integral operators O − j f z and O j f z j = 0 , 1 , 2 , ⋯ . are considered. The operators O − j f z and O j f z satisfy O j O − j f z = O − j O j f z = f z and O − j ∗ O j f z = O j ∗ O − j f z = f ∗ f z for the convolution ∗ of O − j f z and O j f z . In the present paper, the dominants for both operators O − j f z and O j f z and subordinations for O − j f z and O j f z are discussed. Also, new subclass T p γ m , δ , ρ ; m , j concerning with m different boundary points is defined and discussed. Moreover, some interesting problems of T p γ m , δ , ρ ; m , j associated with O j f z are obtained. Furthermore, some interesting examples for our results are considered.
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- 12 January 2024
- Published by Wiley in Journal of Function Spaces
Open Access
New Integral Operator for Analytic Functions
by H. Özlem Güney, Shigeyoshi Owa, Adel A. Attiya
Let A p n be the class of functions f z given by f z = z p + a p + n z p + n + a p + n + 1 z p + n + 1 + ⋯ which are analytic in the open unit disk U . For f z ∈ A p n , new integral operators O − j f z and O j f z j = 0 , 1 , 2 , ⋯ . are considered. The operators O − j f z and O j f z satisfy O j O − j f z = O − j O j f z = f z and O − j ∗ O j f z = O j ∗ O − j f z = f ∗ f z for the convolution ∗ of O − j f z and O j f z . In the present paper, the dominants for both operators O − j f z and O j f z and subordinations for O − j f z and O j f z are discussed. Also, new subclass T p γ m , δ , ρ ; m , j concerning with m different boundary points is defined and discussed. Moreover, some interesting problems of T p γ m , δ , ρ ; m , j associated with O j f z are obtained. Furthermore, some interesting examples for our results are considered.
Cited by 1
Open Access
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- 1 January 2024
- Published by National Library of Serbia in Filomat
Some general properties of analytic and p-valent functions
by Sevtap Sümer Eker, Hatun Özlem Güney, Shigeyoshi Owa
Let Ap be the class of functions f (z) of the form f (z) = zp + ap+1zp+1 + ap+2zp+2 + ..., (p ? N = {1, 2, 3,...}) which are analytic in the open unit disc U. In this article, we consider some generalization properties of the functions in Ap and generalize results by applying fractional derivatives.
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- 1 January 2024
- Published by National Library of Serbia in Filomat
Open Access
Some general properties of analytic and p-valent functions
by Sevtap Sümer Eker, Hatun Özlem Güney, Shigeyoshi Owa
Let Ap be the class of functions f (z) of the form f (z) = zp + ap+1zp+1 + ap+2zp+2 + ..., (p ? N = {1, 2, 3,...}) which are analytic in the open unit disc U. In this article, we consider some generalization properties of the functions in Ap and generalize results by applying fractional derivatives.
Open Access
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- 28 January 2023
- Published by MDPI AG in Axioms
Some Properties for Subordinations of Analytic Functions
by Hatun Özlem Güney, Daniel Breaz, Shigeyoshi Owa
Let the class of functions of $f (z)$ of the form $f (z) = z + \sum_{k = 2}^{\infty} a_{k} z^{k}$ , which are denoted by $A$ and called analytic functions in the open-unit disk. There are many interesting properties of the functions $f (z)$ in the class $A$ concerning the subordinations. Applying the three lemmas for $f (z) \in A$ provided by Miller and Mocanu and by Nunokawa, we consider many interesting properties of $f (z) \in A$ with subordinations. Furthermore, we provide simple examples for our results. We think it is very important to consider examples of the results.
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- 28 January 2023
- Published by MDPI AG in Axioms
Open Access
Some Properties for Subordinations of Analytic Functions
by Hatun Özlem Güney, Daniel Breaz, Shigeyoshi Owa
Let the class of functions of $f (z)$ of the form $f (z) = z + \sum_{k = 2}^{\infty} a_{k} z^{k}$ , which are denoted by $A$ and called analytic functions in the open-unit disk. There are many interesting properties of the functions $f (z)$ in the class $A$ concerning the subordinations. Applying the three lemmas for $f (z) \in A$ provided by Miller and Mocanu and by Nunokawa, we consider many interesting properties of $f (z) \in A$ with subordinations. Furthermore, we provide simple examples for our results. We think it is very important to consider examples of the results.

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