Citation: Pinhong Long, Huo Tang, Wenshuai Wang. Functional inequalities for several classes of q-starlike and q-convex type analytic and multivalent functions using a generalized Bernardi integral operator[J]. AIMS Mathematics, 2021, 6(2): 1191-1208. doi: 10.3934/math.2021073
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Let Ap denote the class of analytic and p-valent functions f(z) with the next form
f(z)=zp+∞∑n=1an+pzn+p,(p∈N={1,2,⋯}) | (1.1) |
in the open unit disk Δ={z∈C:∣z∣<1}.
For f∈Ap, its q-derivative or the q-difference Dqf(z) is given by
Dqf(z)=[p]qzp−1+∞∑n=1[n+p]qan+pzn+p−1,(0<q<1), |
where the q-derivative operator Dqf(z) (refer to [13] and [14]) of the function f is defined by
Dqf(z):={f(z)−f(qz)(1−q)z,(z≠0;0<q<1),f′(0),(z=0) |
provided that f′(0) exists, and the q-number [n]q is just [χ]q when χ=n∈N, here
[χ]q={1−qχ1−qforχ∈C,∑χ−1k=0qkforχ=n∈N. |
Note that Dqf(z)⟶f′(z) when q⟶1−, where f′ is the ordinary derivative of the function f.
Consider the generalized Bernardi integral operator Jηp,q:Ap⟶Ap with the next form
Jηp,qf(z)=[p+η]qzη∫z0tη−1f(t)dqt,(z∈Δ,ℜη>−1andf∈Ap). | (1.2) |
Then, for f∈Ap, we obtain that
Jηp,qf(z)=zp+∞∑n=1Lηp,q(n)an+pzn+p,(z∈Δ), | (1.3) |
where
Lηp,q(n)=[p+η]q[n+η]q:=Ln. | (1.4) |
Here we remark that if p=1, it is exactly q-Bernardi integral operator Jηq [21]. Further, if p=1 and q→1−, obviously it is the classical Bernardi integral operator Jη [5]. In fact, Alexander [1] and Libera [18] integral operators are special versions of Jη for η=0 and η=1, respectively.
For two analytic functions f and g, if there exists an analytic function h satisfying h(0)=0 and ∣h(z)∣<1 for z∈Δ so that f(z)=g(h(z)), then f is subordinate to g, i.e., f≺g.
Let Λ be the class of all analytic function ϕ via the form
ϕ(z)=1+∞∑n=1Anzn,(A1>0,z∈Δ). | (1.5) |
It is well known that the q-calculus [13,14], even the (p,q)-calculus [6], is a generalization of the ordinary calculus without the limit symbol, and its related theory has been applied into mathematical, physical and engineering fields (see [11,15,25]). Since Ismail et al.[12] firstly utilized the q-derivative operator to investigate the q-calculus of the class of starlike functions in disk, there had a great deal of work in this respect; for example, refer to Rehman et al. [24] for partial sums of generalized q-Mittag-Leffler functions, Srivastava et al. [31] for Fekete-Szegö inequality for classes of (p,q)-starlike and (p,q)-convex functions and [27] for close-to-convexity of a certain family of q-Mittag-Leffler functions, Seoudy and Aouf [26] for the coefficient estimates of q-starlike and q-convex functions and Uçar [33] for the coefficient inequality for q-starlike functions. Besides, by involving some special functions and operators or increasing the complexity of function classes, many new subclasses of analytic functions associated with q-calculus or (p,q)-calculus were considered. Here we may refer to [9,23], Ahmad et al. [2] for convolution properties for a family of analytic functions involving q-analogue of Ruscheweyh differential operator, Dweby and Darus [8] for subclass of harmonic univalent functions associated with q-analogue of Dziok-Srivastava operator, Mahmmod and Sokól [20] for new subclass of analytic functions in conical domain associated with Ruscheweyh q-differential operator, Srivastava et al. [28] for coefficient inequalities for q-starlike functions associated with the Janowski functions, [31] for Fekete-Szegö inequality for classes of (p,q)-starlike and (p,q)-convex functions using the q-Bernardi integral operator and [32] for some results on the q-analogues of the incomplete Fibonacci and Lucas polynomials. For the multivalent functions, Purohit [22] ever studied a new class of multivalently analytic functions associated with fractional q-calculus operators, while Shi et al. [29] investigated the multivalent q-starlike functions connected with circular domain. Moreover, Arif et al. [4] considered a q-analogue of the Ruscheweyh type operator, and Srivastava et al. [30] dealt with basic and fractional q-calculus and associated Fekete-Szegö problems for p-valently q-starlike functions and p-valently q-convex functions of complex order using certain integral operators, and Khan et al. [17] for a new integral operator in q-analog for multivalent functions. Stimulated by the previous results, in the paper we intend to introduce and investigate several new subclasses of q-starlike and q-convex type analytic and multivalent functions involving a generalized Bernardi integral operator, and establish the corresponding Fekete-Szegö type functional inequalities for these function classes. Besides, the corresponding bound estimates of the coefficients ap+1 and ap+2 are provided.
From now on we introduce some general subclasses of analytic and multivalent functions associated with the q-derivative operator and the generalized Bernardi integral operator.
Definition 1.1. Let f(z)∈Ap and μ,λ≥0. If the following subordination
(1−λ)(Jηp,qf(z)zp)μ+λDq(Jηp,qf)(z)[p]qzp−1(Jηp,qf(z)zp)μ−1≺ϕ(z) | (1.6) |
is satisfied for z∈Δ, then we call that f(z) belongs to the class LNηp,q(μ,λ;ϕ).
Definition 1.2. Let f(z)∈Ap and 0≤λ≤1. If the following subordination
(1−λ)zDq(Jηp,qf)(z)[p]qJηp,qf(z)+λ[p]q(1+qzDq[Dq(Jηp,qf)](z)Dq(Jηp,qf)(z))≺ϕ(z) | (1.7) |
is satisfied for z∈Δ, then we call that f(z) belongs to the class LMηp,q(λ;ϕ).
Definition 1.3. Let f(z)∈Ap and μ≥0. If the following subordination
(zDq(Jηp,qf)(z)[p]qJηp,qf(z))(Jηp,qf(z)zp)μ≺ϕ(z) | (1.8) |
is satisfied for z∈Δ, then we call that f(z) belongs to the class NSηp,q(μ;ϕ).
Remark 1.4. If we put
ϕ(z)=(1+z1−z)αfor0<α≤1 |
or
ϕ(z)=1+(1−2β)z1−zfor0≤β<1 |
in Definition (1.1–1.3), then the class LNηp,q(μ,λ;ϕ) (res. LMηp,q(λ;ϕ) and NSηp,q(μ;ϕ)) reduces to LNηp,q(μ,λ;α) (res. LMηp,q(λ;α) and NSηp,q(μ;α)) or LNηp,q(μ,λ;β) (res. LMηp,q(λ;β) and NSηp,q(μ;β)). Without the generalized Bernardi integral operator, the class LNηp,q(μ,λ;ϕ) (res. LMηp,q(λ;ϕ) and NSηp,q(μ;ϕ)) is the classical function class LN(μ,λ;ϕ) (res. LM(λ;ϕ) and NS(μ;ϕ)) when p=1 and q→1−.
Let Ω be the class of functions ω(z) denoted by
ω(z)=∞∑n=1Enzn,(z∈Δ) | (1.9) |
via the inequality |ω(z)|<1(z∈Δ). Now we recall some necessary Lemmas below.
Lemma 1.5 ([16]). Let the function ω∈Ω. Then
|E2−τE21|≤max{1,|τ|},(τ∈C). |
Specially, the sharp result holds for the next function
ω(z)=zorω(z)=z2,(z∈Δ). |
Lemma 1.6 ([7,10]). Let P be the class of all analytic functions h(z) of the following form
h(z)=1+∞∑n=1cnzn,(z∈Δ) |
satisfying ℜh(z)>0 and h(0)=1. Then there exist the sharp coefficient estimates ∣cn∣≤2(n∈N). In Particular, the equality holds for all n for the next function
h(z)=1+z1−z=1+∞∑n=12zn. |
Lemma 1.7 ([3,19]). Let the function ω∈Ω. Then
∣E2−κE21∣≤{−κifκ≤−1,1if−1≤κ≤1,κifκ≥1. |
For κ<−1 or κ>1, the inequality holds literally if and only if ω(z)=z or one of its rotations. If <κ<1, the inequality holds literally if and only if ω(z)=z2 or one of its rotations. In Particular, if κ=−1, then the sharp result holds for the next function
ω(z)=z(z+ξ)1+ξz,(0≤ξ≤1) |
or one of its rotations. If κ=1, then the sharp result holds for the next function
ω(z)=−z(z+ξ)1+ξz,(0≤ξ≤1) |
or one of its rotations. If −1<κ<1, then the upper bound is sharp as the followings
|E2−κE21|+(κ+1)|E1|2≤1,(−1<κ≤0) |
and
|E2−κE21|+(1−κ)|E1|2≤1,(0<κ<1). |
By (1.9) we give that
ϕ(ω(z))=1+A1E1z+(A1E2+A2E21)z2+(A1E3+2A2E1E2+A3E31)z3+…. | (2.1) |
In the section, with Lemma 1.5 we study Fekete-Szegö functional problem for the class LNηp,q(μ,λ;ϕ) and provide the following theorem.
Theorem 2.1. Let δ∈C. If f(z)∈Ap belongs to the class LNηp,q(μ,λ;ϕ), then
|ap+2−δa2p+1|≤A1[p]q|L2|[μ[p]q+λ([p+2]q−[p]q)]max{1;|A1[p]qΘ2L21[μ[p]q+λ([p+1]q−[p]q)]2−A2A1|}, |
where
Θ=2δL2[μ[p]q+λ([p+2]q−[p]q)]+L21[(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q]. |
Moreover, the sharp result holds for the next function
ω(z)=zorω(z)=z2,(z∈Δ). |
Proof. Assume that f(z)∈LNηp,q(μ,λ;ϕ). Then, from Definition 1.1, there exists an analytic function ω(z)∈Ω such that
(1−λ)(Jηp,qf(z)zp)μ+λDq(Jηp,qf)(z)[p]qzp−1(Jηp,qf(z)zp)μ−1=ϕ(ω(z)). | (2.2) |
Part case
(Jηp,qf(z)zp)μ−1=1+(μ−1)L1ap+1z+[(μ−1)L2ap+2+(μ−1)(μ−2)2L21a2p+1]z2+[(μ−1)L3ap+3+(μ−1)(μ−2)2L1L2ap+1ap+2+(μ−1)(μ−2)(μ−3)6L31a3p+1]z3+…, |
λDq(Jηp,qf)(z)[p]qzp−1=λ+λL1ap+1[p+1]q[p]qz+λL2ap+2[p+2]q[p]qz2+λL3ap+3[p+3]q[p]qz3+…, |
λDq(Jηp,qf)(z)[p]qzp−1(Jηp,qf(z)zp)μ−1=λ+λ[μ+([p+1]q[p]q−1)]L1ap+1z+λ{[μ+([p+2]q[p]q−1)]L2ap+2+(μ−1)[μ2+([p+1]q[p]q−1)]L21a2p+1}z2+…, |
(1−λ)(Jηp,qf(z)zp)μ=(1−λ)+(1−λ)μL1ap+1z+(1−λ)[μL2ap+2+μ(μ−1)2L21a2p+1]z2+(1−λ)[μL3ap+3+μ(μ−1)2L1L2ap+1ap+2+μ(μ−1)(μ−2)6L31a3p+1]z3+…. |
Since
(1−λ)(Jηp,qf(z)zp)μ+λDq(Jηp,qf)(z)[p]qzp−1(Jηp,qf(z)zp)μ−1=1+[μ+λ([p+1]q[p]q−1)]L1ap+1z+{[μ+λ([p+2]q[p]q−1)]L2ap+2+[(μ−1)2[μ−2λ(λμ−μ+1)]+λ(2μ−λμ−1)[p+1]q[p]q]L21a2p+1}z2+…, |
by (2.1) and (2.2) we see that
A1E1=[μ+λ([p+1]q[p]q−1)]L1ap+1, |
A1E2+A2E21=[μ+λ([p+2]q[p]q−1)]L2ap+2+[μ−12[μ−2λ(λμ−μ+1)]+λ(2μ−λμ−1)[p+1]q[p]q]L21a2p+1. |
Thereby
ap+1=A1E1[p]qL1[μ[p]q+λ([p+1]q−[p]q)] | (2.3) |
and
ap+2=(A1E2+A2E21)[p]qL2[μ[p]q+λ([p+2]q−[p]q)]−A21E21[p]2q{(μ−1)[μ−2λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q}2L2[μ[p]q+λ([p+1]q−[p]q)]2[μ[p]q+λ([p+2]q−[p]q)]. | (2.4) |
Further, with (2.3) and (2.4) we obtain that
ap+2−δa2p+1=A1[p]qL2[μ[p]q+λ([p+2]q−[p]q)][E2−ℏE21], |
where
ℏ={2δL2[μ[p]q+λ([p+2]q−[p]q)]+L21[(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q]}A1[p]q2L21[μ[p]q+λ([p+1]q−[p]q)]2−A2A1. |
Therefore, according to Lemma 1.5 we finish the proof of Theorem 2.1.
Corollary 2.2. If f(z)∈Ap belongs to the class LNηp,q(μ,λ;ϕ), then
|ap+2|≤A1[p]q|L2|[μ[p]q+λ([p+2]q−[p]q)]×max{1;|(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q2[μ[p]q+λ([p+1]q−[p]q)]2−A2A1|}. |
Moreover, the sharp result holds for the next function
ω(z)=zorω(z)=z2,(z∈Δ). |
When ϕ∈P, combining (2.3) and (2.4) with Lemma 1.6 we instantly establish the next corollary for the coefficient bounds of ap+1 and ap+2.
Corollary 2.3. If f(z)∈Ap belongs to the class LNηp,q(μ,λ;ϕ), then
|ap+1|≤2|E1|[p]q|L1|[μ[p]q+λ([p+1]q−[p]q)] |
and
|ap+2|≤2(|E2|+|E1|2)[p]q|L2|[μ[p]q+λ([p+2]q−[p]q)]+2E21[p]2q|(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q||L2|[μ[p]q+λ([p+1]q−[p]q)]2[μ[p]q+λ([p+2]q−[p]q)]. |
If we choose real δ and η, then by Lemma 1.7 we derive the next result for Fekete-Szegö problem.
Theorem 2.4. Let δ,η∈R and ϕ∈Λ satisfying
ϕ(z)=1+∞∑n=1Anzn,(A1,A2>0,z∈Δ). |
If f(z)∈Ap belongs to the class LNηp,q(μ,λ;ϕ), then
|ap+2−δa2p+1|≤{[p]qL2[μ[p]q+λ([p+2]q−[p]q)]{A2−A21[p]qΘ2L21|μ[p]q+λ([p+1]q−[p]q)]2},(δ≤Υ1);A1[p]qL2[μ[p]q+λ([p+2]q−[p]q)],(Υ1≤δ≤Υ2);[p]qL2[μ[p]q+λ([p+2]q−[p]q)]{−A2+A21[p]qΘ2L21|μ[p]q+λ([p+1]q−[p]q)]2},(δ≥Υ2), |
where
Υ1=(A2−A1)L21[μ[p]q+λ([p+1]q−[p]q)]2A21L2[p]q[μ[p]q+λ([p+2]q−[p]q)]−L21[(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q]2L2[μ[p]q+λ([p+2]q−[p]q)] |
and
Υ2=(A2+A1)L21[μ[p]q+λ([p+1]q−[p]q)]2A21L2[p]q[μ[p]q+λ([p+2]q−[p]q)]−L21[(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q]2L2[μ[p]q+λ([p+2]q−[p]q)]. |
Moreover, we take
Υ3=A2L21[μ[p]q+λ([p+1]q−[p]q)]2A21L2[p]q[μ[p]q+λ([p+2]q−[p]q)]−L21[(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q]2L2[μ[p]q+λ([p+2]q−[p]q)]. |
Then, each of the following results is true:
(A) For δ∈[Υ1,Υ3],
|ap+2−δa2p+1|+{2(A1−A2)L21[μ[p]q+λ([p+1]q−[p]q)]2+A21[p]qΘ}×|ap+1|22A21L2[p]q[μ[p]q+λ([p+2]q−[p]q)]≤A1[p]qL2[μ[p]q+λ([p+2]q−[p]q)]; |
(B) For δ∈[Υ3,Υ2],
|ap+2−δa2p+1|+{2(A1+A2)L21[μ[p]q+λ([p+1]q−[p]q)]2−A21[p]qΘ}×|ap+1|22A21L2[p]q[μ[p]q+λ([p+2]q−[p]q)]≤A1[p]qL2[μ[p]q+λ([p+2]q−[p]q)], |
where
Θ=2δL2[μ[p]q+λ([p+2]q−[p]q)]+L21[(μ−1)[μ−λ(λμ−μ+1)][p]q+2λ(2μ−λμ−1)[p+1]q]. |
Remark 2.5. Fixing the parameter p=1 in Theorems 2.1 and 2.4, we can state the new results for the univalent function classes LNη1,q(μ,λ;ϕ)=LNηq(μ,λ;ϕ). As Remark 1.4, we may consider LNηp,q(μ,λ;α) or LNηp,q(μ,λ;β) to establish latest results. On the other hand, for the different parameters μ and λ, we can deduce new results for LNηp,q(μ,λ;ϕ).
In the section we mainly consider Fekete-Szegö functional problem for the class LMηp,q(λ;ϕ) and establish the theorem as follows.
Theorem 3.1. Let δ∈C. If f(z)∈Ap belongs to the class LMηp,q(λ;ϕ), then
|ap+2−δa2p+1|≤A1[p]2q|L2|([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]×max{1;|A1[p]qΦL21([p+1]q−[p]q)2[λ([p+1]q−[p]q)+[p]q]2−A2A1|}, |
where
Φ=δL2[p]q([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]+L21([p+1]q−[p]q)[λ([p+1]2q−[p]2q)+[p]2q]. |
Moreover, the sharp result holds for the next function
ω(z)=zorω(z)=z2,(z∈Δ). |
Proof. If f∈LMηp,q(λ;ϕ), from Definition 1.2 there exists an analytic function ω(z)∈Ω such that
(1−λ)zDq(Jηp,qf)(z)[p]qJηp,qf(z)+λ[p]q(1+qzDq[Dq(Jηp,qf)](z)Dq(Jηp,qf)(z))=ϕ(ω(z)). | (3.1) |
Part case
zDq(Jηp,qf)(z)[p]qJηp,qf(z)=1+([p+1]q[p]q−1)L1ap+1z+[([p+2]q[p]q−1)L2ap+2−([p+1]q[p]q−1)L21a2p+1]z2+…, |
1[p]q(1+qzDq[Dq(Jηp,qf)](z)Dq(Jηp,qf)(z))=1+L1[p+1]q[p]q([p+1]q[p]q−1)ap+1z+[L2[p+2]q[p]q([p+2]q[p]q−1)ap+2−L21[p+1]2q[p]2q([p+1]q[p]q−1)a2p+1]z2+…. |
Since
(1−λ)zDq(Jηp,qf)(z)[p]qJηp,qf(z)+λ[p]q(1+qzDq[Dq(Jηp,qf)](z)Dq(Jηp,qf)(z))=1+([p+1]q[p]q−1)[λ([p+1]q[p]q−1)+1]L1ap+1z+{([p+2]q[p]q−1)[λ([p+2]q[p]q−1)+1]L2ap+2−([p+1]q[p]q−1)[λ([p+1]2q[p]2q−1)+1]L21a2p+1}z2+…, |
by (2.1) and (3.1) we note that
A1E1=([p+1]q[p]q−1)[λ([p+1]q[p]q−1)+1]L1ap+1 |
and
A1E2+A2E21=([p+2]q[p]q−1)[λ([p+2]q[p]q−1)+1]L2ap+2−([p+1]q[p]q−1)[λ([p+1]2q[p]2q−1)+1]L21a2p+1. |
Then, it leads to
ap+1=A1E1[p]2qL1([p+1]q−[p]q)[λ([p+1]q−[p]q)+[p]q] | (3.2) |
and
ap+2=[p]2qL2([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]×[(A1E2+A2E21)+A21E21[p]q{λ([p+1]2q−[p]2q)+[p]2q}([p+1]q−[p]q)[λ([p+1]q−[p]q)+[p]q]2]. | (3.3) |
Furthermore, in accordance with (3.2) and (3.3) we gain that
ap+2−δa2p+1=A1[p]2qL2([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q][E2−ϱE21], |
where
ϱ=A1[p]qΦL21([p+1]q−[p]q)2[λ([p+1]q−[p]q)+[p]q]2−A2A1. |
Thus, from Lemma 1.5 we give the Fekete-Szegö functional inequality in Theorem 3.1.
Corollary 3.2. If f(z)∈Ap belongs to the class LMηp,q(λ;ϕ), then
|ap+2|≤A1[p]2q|L2|([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]×max{1;|A1[p]q[λ([p+1]2q−[p]2q)+[p]2q]([p+1]q−[p]q)[λ([p+1]q−[p]q)+[p]q]2−A2A1|}. |
Moreover, the sharp result holds for the next function
ω(z)=zorω(z)=z2,(z∈Δ). |
If ϕ∈P, by (3.2) and (3.3) we take Lemma 1.6 to prove the next corollary for the coefficient bounds of ap+1 and ap+2.
Corollary 3.3. If f(z)∈Ap belongs to the class LMηp,q(λ;ϕ), then
|ap+1|≤2|E1|[p]2q|L1|([p+1]q−[p]q)[λ([p+1]q−[p]q)+[p]q] |
and
|ap+2|≤2[p]2q|L2|([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]×[(|E2|+|E1|2)+2|E1|2[p]q{λ([p+1]2q−[p]2q)+[p]2q}([p+1]q−[p]q)[λ([p+1]q−[p]q)+[p]q]2]. |
On the other hand, if we take real δ and η, then by Lemma 1.7 we give the next result for Fekete-Szegö problem.
Theorem 3.4. Let δ,η∈R and ϕ∈Λ satisfying
ϕ(z)=1+∞∑n=1Anzn,(A1,A2>0,z∈Δ). |
If f(z)∈Ap belongs to the class LMηp,q(λ;ϕ), then
|ap+2−δa2p+1|≤ |
{[p]2q|L2|([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]{A2−A21[p]qΦL21([p+1]q−[p]q)2[λ([p+1]q−[p]q)+[p]q]2},(δ≤Γ1);A1[p]2q|L2|([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q],(Γ1≤δ≤Γ2);[p]2q|L2|([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]{−A2+A21[p]qΦL21([p+1]q−[p]q)2[λ([p+1]q−[p]q)+[p]q]2},(δ≥Γ2), |
where
Γ1={(A2−A1)([p+1]q−[p]q){λ([p+1]q−[p]q)+[p]q}2−A21[p]q[λ([p+1]2q−[p]2q)+[p]2q)]}×L21([p+1]q−[p]q)L2A21[p]2q([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q] |
and
Γ2={(A2+A1)([p+1]q−[p]q){λ([p+1]q−[p]q)+[p]q}2−A21[p]q[λ([p+1]2q−[p]2q)+[p]2q)]}×L21([p+1]q−[p]q)L2A21[p]2q([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]. |
Moreover, we choose
Γ3={A2([p+1]q−[p]q){λ([p+1]q−[p]q)+[p]q}2−A21[p]q[λ([p+1]2q−[p]2q)+[p]2q)]}×L21([p+1]q−[p]q)L2A21[p]2q([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]. |
Then, each of the following results is true:
(A) For δ∈[Γ1,Γ3],
|ap+2−δa2p+1|+(A1−A2)L21([p+1]q−[p]q)2[λ([p+1]q−[p]q)+[p]q]2+A21[p]qΦA21L2[p]2q([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]|ap+1|2≤A1[p]2qL2([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]; |
(B) For δ∈[Γ3,Γ2],
|ap+2−δa2p+1|+(A1+A2)L21([p+1]q−[p]q)2[λ([p+1]q−[p]q)+[p]q]2−A21[p]qΦA21L2[p]2q([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]|ap+1|2≤A1[p]2qL2([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q], |
where
Φ=δL2[p]q([p+2]q−[p]q)[λ([p+2]q−[p]q)+[p]q]+L21[p+1]q([p+1]q−[p]q)[λ([p+1]q−[p]q)+[p]q]. |
Remark 3.5. Similarly, by taking the parameter p=1 in Theorems 3.1 and 3.4, we can obtain the new results for the univalent function classes LMη1,q(λ;ϕ)=LMηq(λ;ϕ). As Remark 1.4, we may consider LMηp,q(λ;α) or LMηp,q(λ;β) to establish latest results. Clearly, for special parameter λ, we can still imply new results for LMηp,q(λ;ϕ).
In the section we investigate Fekete-Szegö functional problem for the class NSηp,q(μ;ϕ) and obtain the corresponding theorem below.
Theorem 4.1. Let δ∈C. If f(z)∈Ap belongs to the class NSηp,q(μ;ϕ), then
|ap+2−δa2p+1|≤A1[p]q|L2|(μ[p]q+[p+2]q−[p]q)×max{1;|A1[p]qΨ2L21(μ[p]q+[p+1]q−[p]q)2−A2A1|}, |
where
Ψ=2δL2[p]q(μ[p]q+[p+2]q−[p]q)+(μ−1)[μ[p]q+2([p+1]q−[p]q)]L21. |
Moreover, the sharp result holds for the next function
ω(z)=zorω(z)=z2,(z∈Δ). |
Proof. Since f∈NSηp,q(μ;ϕ), from Definition 1.3 there exists an analytic function ω(z)∈Ω such that
(zDq(Jηp,qf)(z)[p]qJηp,qf(z))(Jηp,qf(z)zp)μ=ϕ(ω(z)). | (4.1) |
Part case
zDq(Jηp,qf)(z)[p]qJηp,qf(z)=1+([p+1]q[p]q−1)L1ap+1z+[([p+2]q[p]q−1)L2ap+2−([p+1]q[p]q−1)L21a2p+1]z2+…, |
(Jηp,qf(z)zp)μ=1+μL1ap+1z+[μL2ap+2+μ(μ−1)2L21a2p+1]z2+[μL3ap+3+μ(μ−1)2L1L2ap+1ap+2+μ(μ−1)(μ−2)6L31a3p+1]z3+…. |
Since
(zDq(Jηp,qf)(z)[p]qJηp,qf(z))(Jηp,qf(z)zp)μ=1+([p+1]q[p]q−1+μ)L1ap+1z |
+{([p+2]q[p]q−1+μ)L2ap+2+(μ−1)[([p+1]q[p]q−1)+μ2]L21a2p+1}z2+…, |
from (2.1) and (4.1) we know that
A1E1=([p+1]q[p]q−1+μ)L1ap+1 |
and
A1E2+A2E21=([p+2]q[p]q−1+μ)L2ap+2+(μ−1)[([p+1]q[p]q−1)+μ2]L21a2p+1. |
Thus it deduces that
ap+1=A1E1[p]qL1(μ[p]q+[p+1]q−[p]q) | (4.2) |
and
ap+2=(A1E2+A2E21)[p]qL2(μ[p]q+[p+2]q−[p]q)−(μ−1)A21E21[p]2q[μ[p]q+2([p+1]q−[p]q)]2L2(μ[p]q+[p+2]q−[p]q)(μ[p]q+[p+1]q−[p]q)2. | (4.3) |
Moreover, in the light of (4.2) and (4.3) we know that
ap+2−δa2p+1=A1[p]qL2(μ[p]q+[p+2]q−[p]q)[E2−ℵE21], |
where
ℵ=2δL2[p]q(μ[p]q+[p+2]q−[p]q)+(μ−1)[μ[p]q+2([p+1]q−[p]q)]L212L21(μ[p]q+[p+1]q−[p]q)2A1[p]q−A2A1. |
Hence, in view of Lemma 1.5 we get the Fekete-Szegö functional inequality in Theorem 4.1.
Corollary 4.2. If f(z)∈Ap belongs to the class NSηp,q(μ;ϕ), then
|ap+2|≤A1[p]q|L2|(μ[p]q+[p+2]q−[p]q)×max{1;|A1(μ−1)[p]q{μ[p]q+2([p+1]q−[p]q)}2(μ[p]q+[p+1]q−[p]q)2−A2A1|}. |
Moreover, the sharp result holds for the next function
ω(z)=zorω(z)=z2,(z∈Δ). |
Once ϕ∈P, together with (4.2) and (4.3) we apply Lemma 1.6 to prove the next corollary for the coefficient bounds of ap+1 and ap+2.
Corollary 4.3. If f(z)∈Ap belongs to the class NSηp,q(μ;ϕ), then
|ap+1|≤2E1[p]q|L1|(μ[p]q+[p+1]q−[p]q) |
and
|ap+2|≤2(|E2|+|E1|2)[p]q|L2|(μ[p]q+[p+2]q−[p]q)+2|μ−1||E1|2[p]2q[μ[p]q+2([p+1]q−[p]q)]|L2|(μ[p]q+[p+2]q−[p]q)(μ[p]q+[p+1]q−[p]q)2. |
Clearly, if we let δ and η be real, then from Lemma 1.7 we also show the following result for Fekete-Szegö problem.
Theorem 4.4. Let δ,η∈R and ϕ∈Λ satisfying
ϕ(z)=1+∞∑n=1Anzn,(A1,A2>0,z∈Δ). |
If f(z)∈Ap belongs to the class NSηp,q(μ;ϕ), then
|ap+2−δa2p+1|≤{[p]qL2(μ[p]q+[p+2]q−[p]q){A2−A21[p]qΨ2L21(μ[p]q+[p+1]q−[p]q)2},(δ≤Π1);A1[p]qL2(μ[p]q+[p+2]q−[p]q);[p]qL2(μ[p]q+[p+2]q−[p]q){−A2+A21[p]qΨ2L21(μ[p]q+[p+1]q−[p]q)2},(δ≥Π2), |
where
Π1=2(A2−A1)L21(μ[p]q+[p+1]q−[p]q)2−A21(μ−1)L21[p]q[μ[p]q+2([p+1]q−[p]q)]2L2A21[p]2q(μ[p]q+[p+2]q−[p]q) |
and
Π2=2(A2+A1)L21(μ[p]q+[p+1]q−[p]q)2−A21(μ−1)L21[p]q[μ[p]q+2([p+1]q−[p]q)]2L2A21[p]2q(μ[p]q+[p+2]q−[p]q). |
Moreover, we put
Π1=2A2L21(μ[p]q+[p+1]q−[p]q)2−A21(μ−1)L21[p]q[μ[p]q+2([p+1]q−[p]q)]2L2A21[p]2q(μ[p]q+[p+2]q−[p]q). |
Then, each of the following results is true:
(A) For δ∈[Π1,Π3],
|ap+2−δa2p+1|+2(A1−A2)L21(μ[p]q+[p+1]q−[p]q)2+A21[p]qΨ2L2A21[p]q[μ[p]q+([p+2]q−[p]q)]|ap+1|2≤A1[p]qL2(μ[p]q+[p+2]q−[p]q); |
(B) For δ∈[Π3,Π2],
|ap+2−δa2p+1|+2(A1+A2)L21(μ[p]q+[p+1]q−[p]q)2−A21[p]qΨ2L2A21[p]q[μ[p]q+([p+2]q−[p]q)]|ap+1|2≤A1[p]qL2(μ[p]q+[p+2]q−[p]q), |
where
Ψ=2δL2[p]q(μ[p]q+[p+2]q−[p]q)+(μ−1)[μ[p]q+2([p+1]q−[p]q)]L21. |
Remark 4.5. Similarly, by choose the parameter p=1 in Theorems 4.1 and 4.4, we can provide the new results for the univalent function classes NSη1,q(μ;ϕ)=NSηq(μ;ϕ). As Remark 1.4, we may consider NSηp,q(μ;α) or NSηp,q(μ;β) to establish latest results. Besides, for the fixed parameter μ, we can still infer new results for NSηp,q(μ;ϕ).
By involving a generalized Bernardi integral operator, several new subclasses of q-starlike and q-convex type analytic and multivalent functions are introduced to generalize the classical starlike and convex functions. Meanwhile, for these classes we may know integral operator and q-derivative as well as multivalency how to change the coefficients of functions. In our main results, we establish the Fekete-Szegö type functional inequalities for these function classes. Further, the corresponding bound estimates of the coefficients ap+1 and ap+2 are interpreted. In fact, if we use the other integral operators or take (p,q)-operator when certain function is univalent but not multivalent, we may get many similar results as in this article.
We thank the referees for their careful readings and using comments so that this manuscript is greatly improved. This work is supported by Institution of Higher Education Scientific Research Project in Ningxia of the People's Republic of China under Grant NGY2017011, Natural Science Foundation of Ningxia of the People's Republic of China under Grant 2020AAC03066, the Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region under Grant NJYT-18-A14, the Natural Science Foundation of Inner Mongolia of the People's Republic of China under Grant 2018MS01026, the Natural Science Foundation of the People's Republic of China under Grant 11561001, 42064004 and 11762016.
The authors declare no conflict of interest.
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