In the article, our aim focuses on the certain quasi-subordination subclasses of analytic and bi-univalent functions associated with the Dziok-Srivastava operator. To state our results, at first we will recall some notations and basic properties for analytic and bi-univalent functions and Dziok-Srivastava operator.
Let $ \mathcal{A} $ be the class of normalized analytic function $ f(z) $ by
in the open unit disk $ \Delta = \{z\in\mathbb{C}: \mid z\mid<1\} $.
Let the subclass $ \mathcal{S} $ of $ \mathcal{A} $ be the set of all univalent functions in $ \Delta $. According to the Koebe one quarter theorem [1], the inverse $ f^{-1} $ of every $ f\in\mathcal{S} $ satisfies
where $ \rho\geq \frac{1}{4} $ denotes the radius of the image $ f(\Delta) $ and $ \Delta_{\rho} = \{z\in\mathbb{C}: \mid z\mid<\rho\} $. It is recalled that
If both the function $ f\in\mathcal{A} $ and its inverse $ f^{-1} $ are univalent in $ \Delta $, then it is bi-univalent. Denote by $ \Sigma $ the class of all bi-univalent functions $ f\in\mathcal{A} $ in $ \Delta $.
For given $ f, g\in\mathcal{A} $, define the Hadamard product or convolution $ f\ast g $ by
where $ f(z) $ is given by (1.1) and $ g(z) = z+\sum\limits^{\infty}_{k = 2} b_{k}z^{k} $. Assume that the Gaussian hypergeometric function $ {}_{q}F_{s}(\alpha_{1},\cdots,\alpha_{q};\beta_{1},\cdots,\beta_{s};z) $ is defined by
for the complex parameters $ \alpha_{k} $ and $ \beta_{j} $ with $ \beta_{j}\neq0, -1, -2, -3,\ldots $ $ (k = 1,\cdots, q;j = 1, \cdots, s) $, where $ (\ell)_{n} $ denotes the Pochhammer symbol or shifted factorial by
Dziok and Srivastava [2, 3] ever introduced the convolution operator $ {}_{q}\mathcal{I}_{s}(\alpha_{1},\cdots,\alpha_{q};\beta_{1},\cdots,\beta_{s}) $$ = {}_{q}\mathcal{I}_{s} $ later named by themselves as follows
where
Note that
Here we remind some reduced versions of Dziok-Srivastava operator $ {}_{q}\mathcal{I}_{s}(\alpha_{1},\cdots,\alpha_{q};\beta_{1},\cdots,\beta_{s}) $ for suitable parameters $ \alpha_{k}(k = 1,\cdots,q) $ and $ \beta_{j}(j = 1,\cdots,s) $; refer to the generalized Bernardi operator $ \mathcal{J}_{\eta} = {}_{2}\mathcal{I}_{1}(1,1+\eta;2+\eta)(\Re (\eta)>-1) $ [4]; Carlson-Shaffer operator $ \mathcal{L}(a,c) = {}_{2}\mathcal{I}_{1}(a,1;c) $ [5]; Choi-Saigo-Srivastava operator $ \mathcal{I}_{\lambda,\mu} = {}_{2}\mathcal{I}_{1}(\mu,1;\lambda+1)(\lambda>-1, \mu\geq0) $ [6]; Hohlov operator $ \mathcal{I}^{a,b}_{c} = {}_{2}\mathcal{I}_{1}(a,b;c) $ [7, 8]; Noor integral operator $ \mathcal{I}^{n} = {}_{2}\mathcal{I}_{1}(2,1;n+1) $ [9]; Owa-Srivastava fractional differential operator $ \Omega^{\lambda}_{z} = {}_{2}\mathcal{I}_{1}(2,1;2-\lambda)(0\leq\lambda<1) $ [10, 11]; Ruscheweyh derivative operator $ \mathcal{D}^{\delta} = {}_{2}\mathcal{I}_{1}(1+\delta,1;1) $ [12].
In 1967, Lewin [13] introduced the analytic and bi-univalent function and proved that $ \mid a_{2}\mid<1.51 $. Moreover, Brannan and Clunie [14] conjectured that $ \mid a_{2}\mid\leq\sqrt{2} $, and Netanyahu [15] obtained that $ \max\limits_{f\in\sum}\mid a_{2}\mid = \frac{4}{3} $. Later, Styer and Wright [17] showed that there exists function $ f(z) $ so that $ \mid a_{2}\mid>\frac{4}{3} $. However, so far the upper bound estimate $ \mid a_{2}\mid<1.485 $ of coefficient for functions in $ \sum $ by Tan [18] is best. Unfortunately, as for the coefficient estimate problem for every Taylor-Maclaurin coefficient $ \mid a_{n}\mid(n\in\mathbb{N}\setminus \{1,2\}) $ it is probably still an open problem. Based on the works of Brannan and Taha [19] and Srivastava et al. [20], many subclasses of analytic and bi-univalent functions class $ \sum $ were introduced and investigated, and the non-sharp estimates of first two Taylor-Maclaurin coefficients $ \mid a_{2}\mid $ and $ \mid a_{3}\mid $ were given; refer to Deniz [21], Frasin and Aouf [22], Hayami and Owa [23], Patil and Naik [24, 25], Srivastava et al. [26, 27], Tang et al. [28] and Xu et al. [29, 30] for more detailed information. Recently, Srivastava et al. [31, 32] gave some new subclasses of the function class $ \sum $ of analytic and bi-univalent functions to unify the works of Deniz [21], Frasin [33], Keerthi and Raja [34], Srivastava et al. [35], Murugusundaramoorthy et al.[36] and Xu et al. [29], etc. Besides, we also refer to Goyal et al. [37] for the subclasses of analytic and bi-univalent associated with quasi-subordination. Since Fekete-Szegö [38] studied the determination of the sharp upper bounds for the subclass of $ \mathcal{S} $, Fekete-Szegö functional problem was considered in many classes of functions; refer to Abdel-Gawad [39] for class of quasi-convex functions, Koepf [40] for class of close-to-convex functions, Orhan and Rǎducanu [16] for class of starlike functions, Magesh and Balaji [41] for class of convex and starlike functions, Orhan et al. [42] for the classes of bi-convex and bi-starlike type functions, Panigrahi and Raina [43] for class of quasi-subordination functions, Tang et al. [28] for classes of m-mold symmetric bi-univalent functions. In addition, Murugusundaramoorthy et al. [36, 44, 45] and Patil and Naik [46] ever introduced and investigated several new subclasses of the function class $ \sum $ of analytic and bi-univalent functions involving the hohlov operator. Moreover, Al-Hawary et al. [47] studied the Fekete-Szegö functional problem for the classes of analytic functions of complex order defined by the Dziok-Srivastava operator. Motivated by the statements above, in the article we are ready to introduce and investigate two new subclasses of the function class $ \sum $ of analytic and bi-univalent functions associated with the Dziok-Srivastava operator and quasi-subordination, and consider the corresponding bound estimates of the coefficient $ a_2 $ and $ a_3 $ as well as the corresponding Fekete-Szegö functional inequalities. Furthermore, the consequences and connections to some earlier known results would be pointed out.
For two analytic functions $ f $ and $ g $, if there exist two analytic functions $ \varphi $ and $ h $ with $ \mid\varphi(z)\mid\leq1 $, $ h(0) = 0 $ and $ \mid h(z)\mid<1 $ for $ z\in\Delta $ so that $ f(z) = \varphi(z)g(h(z)) $, then $ f $ is quasi-subordinate to $ g $, i.e., $ f\prec_{\text{quasi}}g $. Note that if $ \varphi\equiv1 $, then $ f $ is subordinate to $ g $ in $ \Delta $, i.e., $ f\prec g $. Further, if $ h(z) = z $, then $ f $ is majorized by $ g $ in $ \Delta $, i.e. $ f\leq g $. For the related work on quasi-subordination, refer to Robertson [48], and Frasin and Aouf [22]. Write
First we will introduce the following general subclasses of analytic and bi-univalent functions associated with the Dziok-Srivastava operator.
Definition 1.1 A function $ f(z)\in\sum $ given by (1.1), belongs to the class $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $ if the following quasi-subordinations are satisfied
and
for $ z, w\in\Delta $, where $ \eta\geq0 $ and the function $ g $ is the inverse of $ f $ given by (1.2).
Definition 1.2 A function $ f(z)\in\sum $ given by (1.1), belongs to the class $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}} $ $ (\tau,\mu,\lambda,\gamma;\phi) $ if the following quasi-subordinations are satisfied:
for $ z, w\in\Delta $, where $ \tau\in \mathbb{C}\setminus\{0\} $, $ 0\leq\mu\leq1 $, $ 0\leq\lambda\leq1 $, $ 0\leq\gamma\leq1 $ and the function $ g $ is the inverse of $ f $ given by (1.2).
Lemma 1.3(see [1, 49]) Let $ \mathcal{P} $ be the class of all analytic functions $ q(z) $ of the following form
satisfying $ \Re q(z)>0 $ and $ q(0) = 1 $. Then the sharp estimates $ \mid c_{n}\mid\leq2(n\in\mathbb{N}) $ are true. In particular, the equality holds for all $ n $ for the next function
Denote the functions $ s $ and $ t $ in $ \mathcal{P} $ by
Equivalently, from (2.1) we know that
Given $ \phi\in\mathcal{P} $ with $ \phi'(0)>0 $, let $ \phi(\Delta) $ be symmetric with respect to the real axis. When the series expansion form of $ \phi $ is denoted by
by (2.2)–(2.3) and (2.4) it follows that
In the section we study the estimates for the class $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $. Now, we establish the next theorem.
Theorem 2.1 If $ f(z) $ given by (1.1) belongs to the class $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $, then
Proof If $ f(z)\in\mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $, then by Definition 1.1 and Lemma 1.3, there exist two analytic functions $ u(z) $ and $ v(w)\in\mathcal{P} $ so that
Expanding the left half parts of (2.11) and (2.12), we obtain that
In addition, we know that
Therefore, from (2.10)–(2.15) we have that
From (2.16) and (2.18), it infers that
Then, we show that
By (2.17) and (2.19), we have that
Therefore, by (2.22)–(2.23) we obtain that
We follow from Lemma 1.3 and (2.22)–(2.24) that
then (2.7) holds. Similarly, from (2.17), (2.19) and (2.21), it also implies that
Hence, from (2.22) and (2.25), we obtain that
Therefore, from Lemma 1.3 it shows that
On the other hand, by (2.23) and (2.25), we infer that
Thus, from Lemma 1.3, we see that
Next, we consider Fekete-Szegö problems for the class $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $.
Theorem 2.2 If $ f(z) $ given by (1.1) belongs to the class $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $ and $ \delta\in\mathbb{R} $, then
where $ \Xi = \Xi(\eta,B_{0},E_{1},E_{2}) $ is the same as in Theorem 2.1.
Proof From (2.25), it follows that
By (2.24) we easily obtain that
Hence, from Lemma 1.3, we imply that
Corollary 2.3 If $ f(z) $ given by (1.1) belongs to the class $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $ and $ \delta\in\mathbb{R} $, then
Remark 2.4 Without quasi-subordination (i.e., $ \varphi(z)\equiv1 $), if we choose some suitable parameters $ \alpha_{k} $ $ (k = 1,\cdots,q) $, $ \beta_{j} $ $ (j = 1,\cdots,s) $ and $ \eta $, we obtain the following reduced versions for $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $ in Theorem 2.1.
(Ⅰ) $ \mathcal{QH_{\sum}}^{a,b}_{c}(\alpha;\phi) = \mathcal{J}^{a,b;c}_{\sum}(\alpha,\phi) $, refer to Patil and Naik [46].
Remark 2.5 Without Dziok-Srivastava operator, we can collect the following reduced versions for $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) $ in Theorem 2.1.
(Ⅰ) $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\eta;\phi) = \mathcal{J}^{q}_{\eta}(\phi) $ $ (\eta\geq0) $, refer to Goyal et al. [37].
(Ⅱ) $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(1;\phi) = \mathcal{H}_{\sum}(\phi) $ for $ \varphi(z)\equiv1 $, refer to Ali et al. [50] and Tang et al. [51] for Corollary 2.2; $ \mathcal{QH_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(0;\phi) = \mathcal{S}^{*}_{\sum}(\phi) $ for $ \varphi(z)\equiv1 $, refer to Brannan and Taha. [19] and Tang et al. [51] for Corollary 2.4.
Now, we study the coefficients for the class $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $ and establish the next theorem.
Theorem 3.1 If $ f(z) $ given by (1.1) belongs to the class $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $, then
for
Proof Here, we follow the method of Theorem 2.1. If $ f(z)\in\mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $, then by Definition 1.2 there exist two analytic functions $ u(z),v(z): \Delta\rightarrow\Delta $ with $ u(0) = 0 $ and $ v(0) = 0 $ such that
Expanding the left half parts of (3.5) and (3.6), we have that
Therefore, From (2.14)–(2.15) and (3.5)–(3.8), we get that
From (3.9) and (3.11), we know that
Then, it infers that
By (3.10) and (3.12), we have that
Therefore, by (3.15)–(3.16) we know that
Therefore, from (3.15)–(3.17) and Lemma 1.3, we obtain that
Similarly, from (3.10) and (3.12), it implies that
Hence, by (3.15) and (3.18), it follows that
So, we obtain from Lemma 1.3 that
On the other hand, by (3.16) and (3.18), we infer that
Thus, from Lemma 1.3 we see that
Next, we consider Fekete-Szegö problems for the class $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $.
Theorem 3.2 Let $ f(z) $ given by (1.1) belong to the class $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $ and $ \delta\in\mathbb{R} $. Then
if
or
where $ \Phi = \Phi(\mu,\lambda,\gamma,p_{2}(q,s),p_{3}(q,s)) $, $ \Theta = \Theta(\mu,\lambda,\gamma) $ and $ \Psi = \Psi(\mu,\lambda,\gamma) $ are the same as in Theorem 3.1.
Proof From (3.18), it follows that
By (3.17) we easily obtain that
$ a_{3}-\delta a^{2}_{2} = \frac{B_{1}E_{1}\tau(c_{1}-d_{1})(1+\gamma-\gamma\lambda)^{2}}{4p_{3}(q,s)\Theta(\mu,\lambda,\gamma)} $
when
Remark 3.3 In fact, from Theorems 3.1 and 3.2, we may consider the coefficient bound estimates and Fekete-Szegö problem for the classes $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\gamma,1,\gamma;\phi) $, $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}} $ $ (\tau,1,0,1;\phi) $, $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(1,\mu,0,0;\phi) $, $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(1,0,1,\gamma;\phi) $ and $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(1,0,\lambda,0;\phi) $, etc. Similarly, if we choose some suitable parameters $ \alpha_{k}(k = 1,\cdots,q) $, $ \beta_{j}(j = 1,\cdots,s) $, $ \tau, \mu, \lambda $ and $ \gamma $ without quasi-subordination (i.e., $ \varphi(z)\equiv1 $), we provide the following reduced versions for $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $ in Theorem 3.1.
(Ⅰ) $ \mathcal{QS_{\sum}}^{a,1}_{ a}(1,0,1,0;\phi) = \mathcal{S}_{\sum}(\phi) $, refer to Ma and Minda [52];
(Ⅱ) $ \mathcal{QS_{\sum}}^{a,1}_{ a}(1,0,\lambda,0;\phi) = \mathcal{G}^{\phi,\phi}_{\sum}(\gamma) $, refer to Magesh and Yamini [53];
(Ⅲ) $ \mathcal{QS_{\sum}}^{a,1}_{ a}(\tau,\mu,0,0;\phi) = \sum(\tau,\mu,\phi) $, refer to Srivastava and Bansal [35];
(Ⅳ) $ \mathcal{QS_{\sum}}^{a,1}_{ a}(\tau,\gamma,1,\gamma;\phi) = \mathcal{S}_{\sum}(\gamma,\tau;\phi) $, refer to Deniz [21];
(Ⅴ) $ \mathcal{QS_{\sum}}^{a,b}_{c}(\tau,\gamma,1,\gamma;\phi) \equiv\mathcal{S}^{a,b,c}_{\sum}(\tau,\gamma;\phi) $, $ \mathcal{QS_{\sum}}^{a,b}_{c}(\tau,\mu,0,0;\phi) \equiv\mathcal{K}^{a,b,c}_{\sum}(\tau,\mu;\phi) $ and $ \mathcal{QS_{\sum}}^{a,b}_{ c}(1,0,1,0;\phi) = \mathcal{J}_{\sum}(0,\phi) $, refer to refer to Patil and Naik [46];
(Ⅵ) $ \mathcal{QS_{\sum}}^{a,1}_{ a}(\tau,1,0,1;\phi) = \mathcal{S}_{\sum}(\tau,1,0,1;\phi) $ and $ \mathcal{QS_{\sum}}^{a,1}_{ a}(\tau,\gamma,\lambda,\gamma;\phi) = \mathcal{S}_{\sum}(\tau,\gamma,\lambda,\gamma;A,B) $, refer to srivastava et al. for Corollary 1 and Example 10 in [32], respectively. Here, the function $ \phi $ in the second equality is defined by
Remark 3.4 Let $ \varphi(z)\equiv1 $ and $ \phi(z) = \frac{1+(1-2\beta)z}{1-z} $ for $ 0\leq\beta<1 $. If we take some suitable parameters $ \tau, \mu, \lambda $ and $ \gamma $, we also have the following reduced versions for $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $ in Theorems 3.1 and 3.2. For example, $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,0,1,0;\beta) = {}_{q}\mathcal{S}_{s}(\tau,\beta) $, $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,1,1,1;\beta) = {}_{q}\mathcal{C}_{s}(\tau,\beta) $, refer to Al-Hawary et al. [47] for the classes of analytic and univalent (but not bi-univalent) functions.
Remark 3.5 In addition, if we only choose some suitable parameters $ \tau, \mu, \lambda $ and $ \gamma $, we give some reduced versions for $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\mu,\lambda,\gamma;\phi) $ without Dziok-Srivastava operator in Theorem 3.1. For example, $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(\tau,\gamma,0,0;\phi) = \mathcal{K}^{q}_{\gamma,\tau}(\phi) $$ (1\geq\gamma\geq0) $, $ \mathcal{QS_{\sum}}^{\alpha_{1},\cdots,\alpha_{q}}_{ \beta_{1},\cdots,\beta_{s}}(1,\alpha,1,0;\phi) = \mathcal{H}^{q}_{\alpha}(\phi) $$ (\alpha\geq0) $, refer to Goyal et al. [37].