In this paper, applying the theory of fixed points in complete gauge spaces, we establish some conditions for the existence and uniqueness of monotonic and positive solutions for nonlinear systems of ordinary differential equations. Moreover, the paper contains an application of the theoretical results to the study of a class of systems of nonlinear ordinary differential equations.
Citation: Adrian Nicolae Branga. Some conditions for the existence and uniqueness of monotonic and positive solutions for nonlinear systems of ordinary differential equations[J]. Electronic Research Archive, 2022, 30(6): 1999-2017. doi: 10.3934/era.2022101
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In this paper, applying the theory of fixed points in complete gauge spaces, we establish some conditions for the existence and uniqueness of monotonic and positive solutions for nonlinear systems of ordinary differential equations. Moreover, the paper contains an application of the theoretical results to the study of a class of systems of nonlinear ordinary differential equations.
In last years, it was noted that several real-world phenomena cannot be modeled by partial or ordinary differential equations or classical difference equations defined using the standard integrals and derivatives. These problems required the concept of fractional calculus (fractional integrals and derivatives), where the classical calculus was insufficient. Differential equations of fractional order are considered to be interesting tools in the modeling of several problems in different fields of engineering and science, as electrochemistry, control, electromagnetic, porous media, viscoelasticity. See for example [1,2,3,4,5,6,7]. On the other hand, in the recent years impulsive differential equations have become essential as mathematical models of problems in social and physical sciences. There was a great development in impulsive theory in particular in the field of impulsive differential equations with fixed moments. For instance, see the works of Samoilenko and Perestyuk [8], Benchohra et al. [9], Lakshmikantham et al. [10], etc. Further works for differential equations at variable moments of impulse have been appeared. For example, we cite the papers of Frigon and O'Regan [11,12], Graef and Ouahab [13], Bajo and Liz [14], etc.
It is also observed that fixed point theory is an important mathematical tool to ensure the existence and uniqueness of many problems intervening nonlinear relations. As a consequence, existence and uniqueness problems of fractional differential equations have been resolved using fixed point techniques. This theory has been developed in many directions and has several applications. Moreover, we could apply it in different types of spaces, like metric spaces, abstract spaces, and Sobolev spaces. This use of fixed point theory makes very easier the resolution of many problems modeled by fractional ordinary, partial differential and difference equations. For instance, see [15,16,17,18,19,20].
The theory for impulsive fractional differential equations in Banach spaces have been sufficiently developed by Feckan et al. [21] by using fixed point techniques. In the real world, many phenomena are subject to transient external effects as they develop. In comparison to the entire duration of the phenomenon being observed, the durations of these external effects are incredibly brief. The logical conclusion is that these external forces are real impulses. Impulsive differential equations are now a major component of the modeling of physical real-world issues in order to study these abrupt shifts. Biological systems including heartbeat, blood flow, and impulse rate have been discussed in relation to many applications of this kind of impulsive differential equations. For more details, see, [22,23,24,25,26,27].
On the other hand, in last years the study of Hyers-Ulam (HU) stability analysis for nonlinear fractional differential equations has attracted the attention of several researchers. Note that HU stability is considered as an exact solution near the approximate solution for these equations with minimal error. The following works [28,29,30,31,32] deal with such a stability analysis. For Hyers-Ulam (HU) stabilities, there are generalized Hyers-Ulam (GHU), Hyers-Ulam-Rassias (HUR), and generalized Hyers-Ulam-Rassias (GHUR) stabilities.
Much of the work on the topic of fractional differential equations deals with the governing equations involving Riemann-Liouville and Caputo-type fractional derivatives. Another kind of fractional derivative is the Hadamard type [33], which was introduced in 1892. This derivative differs significantly from both the Riemann-Liouville type and the Caputo type in the sense that the kernel of the integral in the definition of the Hadamard derivative contains a logarithmic function of arbitrary exponent. It seems that the abstract fractional differential equations involving Hadamard fractional derivatives and Hilfer-Hadamard fractional derivatives have not been fully explored so far. Several applications of where the Hadamard derivative and the Hadamard integral arise can be found in the papers by Butzer, Kilbas and Trujillo [34,35,36]. Other important results dealing with Hadamard fractional calculus and Hadamard differential equations can be found in [37,38]. The presence of the δ-differential operator (δ=xddx) in the definition of Hadamard fractional derivatives could make their study uninteresting and less applicable than Riemann-Liouville and Caputo fractional derivatives. Moreover, this operator appears outside the integral in the definition of the Hadamard derivatives just like the usual derivative D=ddx is located outside the integral in the case of Riemann-Liouville, which makes the fractional derivative of a constant of these two types not equal to zero in general. Hadamard [33] proposed a fractional power of the form (xddx)α. This fractional derivative is invariant with respect to dilation on the whole axis.
The existence and HU stability of the following implicit FDEs involving Hadamard derivatives were investigated in [39] as follows:
{HDϖz(υ)=ϕ(υ,z(υ),HDϖz(υ)), ϖ∈(0,1), z(1)=z1, z1∈R, |
where υ∈[1,G], G>1, HDϖ refers to the Hadamard fractional (HF) derivative of order ϖ.
The following coupled system containing the Caputo derivative was examined in [40] for its existence, uniqueness, and several types of Hyers-Ulam stability:
{CDϖz(υ)=ϕ(υ,s(υ),CDϖz(υ)), υ∈U,CDθs(υ)=ψ(υ,z(υ),CDθs(υ)), υ∈U,z′(G)=z′′(0)=0, z(1)=ϱz(η) ϱ,η∈(0,1),s′(G)=s′′(0)=0, s(1)=ϱs(η) ϱ,η∈(0,1), |
where υ∈U=[0,1], ϖ,θ∈(2,3] and ϕ,ψ:U×R2→R are continuous functions.
For the following coupled system containing the Riemann-Liouville derivative, the authors of [41] demonstrated the existence, uniqueness, and several types of Hyers-Ulam stability:
{Dϖz(υ)=ϕ(υ,s(υ),Dϖz(υ)), υ∈U, Dθs(υ)=ψ(υ,z(υ),Dθs(υ)), υ∈U, Dϖ−2z(0+)=π1Dϖ−2z(G−), Dϖ−2z(0+)=ℓ1Dϖ−1z(G−),Dϖ−2s(0+)=π2Dϖ−2s(G−), Dϖ−2s(0+)=ℓ2Dϖ−1s(G−), |
where υ∈U=[0,G], G>0, ϖ,θ∈(1,2] and π1,π2,ℓ1,ℓ2≠1, Dϖ,Dθ are Riemann-Liouville derivatives of fractional orders ϖ, θ respectively and ϕ,ψ:U×R2→R are continuous functions.
Inspired by the previous work, we investigate the coupled impulsive implicit FDEs (CII-FDEs) incorporating Hadamard derivatives as follows:
{HDϖz(υ)=ϕ(υ,HDϖz(υ),HDθs(υ)), υ∈U, υ≠υi, i=1,2,...k,HDθs(υ)=ψ(υ,HDθs(υ),HDϖz(υ)), υ∈U, υ≠υj, j=1,2,...m,Δz(υi)=Iiz(υi), Δz′(υi)=˜Iiz(υi), i=1,2,...k, Δs(υj)=Ijs(υj), Δs′(υj)=˜Ijs(υj), j=1,2,...m, z(G)=1Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη, z′(G)=B∗(z), s(G)=1Γ(θ)∫G1ln(Gη)θ−1B(η,s(η))dηη, s′(G)=B∗(s), | (1.1) |
where ϖ,θ∈(1,2], ϕ,ψ:U×R2→R, B:U×C(U,R)→R and B∗:U→R are continuous functions and
Δz(υi)=z(υ+i)−z(υ−i), Δz′(υi)=z′(υ+i)−z′(υ−i),Δs(υi)=s(υ+i)−s(υ−i), Δs′(υi)=s′(υ+i)−s′(υ−i). |
The derivatives HDϖ,HDθ are the Hadamard derivative operators of order ϖ and θ, respectively; z(υ+i),s(υ+i) are right limits and z(υ−i),s(υ−i) are left limits; Ii,Ij,˜Ii,˜Ij:R→R are continuous functions. The system (1.1) is used to describe certain features of applied mathematics and physics such as blood flow problems, chemical engineering, thermoelasticity, underground water flow, and population dynamics. For more details, we refer the readers to see the monograph [42].
Using the Banach contraction and Kransnoselskii FP theorems, we establish necessary and sufficient criteria for the existence and uniqueness of a positive solution for the problem (1.1). Additionally, we analyze other Hyers-Ulam (HU) stabilities such as generalized Hyers-Ulam (GHU), Hyers-Ulam-Rassias (HUR), and generalized Hyers-Ulam-Rassias (GHUR) stabilities.
In this part, we present certain key terms and lemmas that are utilized throughout the rest of this paper, for more information, see [42,43].
Assume that PC(U,R+) equipped with the norms ‖z‖=max{|z(υ)|:υ∈U}, ‖s‖=max{|s(υ)|:υ∈U} is a Banach space (shortly, BS), then the products of these norms are also a BS under the norm ‖(z+s)‖=‖z‖+‖s‖. Assume that ℑ1 and ℑ2 represent the piecewise continuous function spaces described as
ℑ1=PC2−ϖ,ln(U,R+)={z:U→R+ so that z(υ+i),z′(υ+i) and z(υ−i),z′(υ−i) exist ,i=1,2,...k},ℑ2=PC2−θ,ln(U,R+)={s:U→R+ so that s(υ+j),s′(υ+j) and s(υ−j),s′(υ−j) exist ,j=1,2,...m}, |
with norms
‖z‖ℑ1=sup{|z(υ)ln(υ)2−ϖ|, υ∈U} and ‖s‖ℑ2=sup{|s(υ)ln(υ)2−θ|, υ∈U}, |
respectively. Clearly, the product ℑ=ℑ1×ℑ2 is a BS endowed with ‖(z+s)‖ℑ=‖z‖ℑ1+‖s‖ℑ2.
The following definitions are recalled from [44].
Definition 2.1. For the function z(υ), the Hadamard fractional (HF) integral of order ϖ is described as
HIϖz(υ)=1Γ(ϖ)∫υ1ln(υη)ϖ−1z(η)dηη, υ∈(1,G] |
where Γ(.) is the Gamma function.
Definition 2.2. For the function z(υ), the HF derivative of order ϖ∈[a−1,a), a∈Z+ is described as
HDϖz(υ)=1Γ(a−ϖ)(υddυ)a∫υxln(υη)a−ϖ+1z(η)dηη, υ∈(x,G]. |
Lemma 2.3. [45] Assume that ϖ>0 and z is any function, then the derivative equation HDϖz(υ)=0 has solutions below:
z(υ)=r1(lnυ)ϖ−1+r2(lnυ)ϖ−2+r3(lnυ)ϖ−3+...+ra(lnυ)ϖ−a, |
and the formula
HIϖHDϖz(υ)=z(υ)+r1(lnυ)ϖ−1+r2(lnυ)ϖ−2+r3(lnυ)ϖ−3+...+ra(lnυ)ϖ−a, |
is satisfied, where ri∈R, i=1,2,...,a and ϖ∈(a−1,a).
Theorem 2.4. [46] Assume that Ξ is a non-empty, convex and closed subset of a BS ℑ. Let E and ˜E be operators so that
(1) for z,s∈Ξ, E(z,s)+˜E(z,s)∈Ξ;
(2) the operator ˜E is completely continuous;
(3) the operator Ξ is contractive.
Then there is a solution (z,s)∈Ξ for the operator equation E(z,s)+˜E(z,s)=(z,s).
The definitions and observations below are taken from [47,48].
Definition 3.1. The coupled problem (1.1) is called HU stable if there are Λϖ,θ=max{Λϖ,Λθ}>0 so that, for φ=max{φϖ,φθ} and for each solution (z,s)∈ℑ to inequalities
{|HDϖz(υ)−ϕ(υ,HDϖz(υ),HDθs(υ))|≤φϖ, υ∈U, |Δz(υi)−Iiz(υi)|≤φϖ, |Δz′(υi)−˜Iiz(υi)|≤φϖ, i=1,2,...k,|HDθs(υ)−ϕ(υ,HDθs(υ),HDϖz(υ))|≤φθ, υ∈U, |Δs(υj)−Ijs(υj)|≤φθ, |Δs′(υj)−˜Ijs(υj)|≤φθ, j=1,2,...m, | (3.1) |
there is a unique solution (˜z,˜s)∈ℑ with
‖(z,s)−(˜z,˜s)‖ℑ≤Λϖ,θφ, υ∈U. |
Definition 3.2. The coupled problem (1.1) is called GHU stable if there is Φ∈C(R+,R+) with ξ(0)=0, so that, for any solution (z,s)∈ℑ of (3.1), there is a unique solution (˜z,˜s)∈ℑ of with of (1.1) fulfilling
‖(z,s)−(˜z,˜s)‖ℑ≤Φ(φ), υ∈U. |
Set ℧ϖ,θ=max{℧ϖ,℧θ}∈C(U,R) and Λ℧ϖ,℧θ=max{Λ℧ϖ,Λ℧θ}>0.
Definition 3.3. The coupled problem (1.1) is called HUR stable with respect to ℧ϖ,θ if there is a constant Λ℧ϖ,℧θ so that, for any solution (z,s)∈ℑ for the inequalities below
{|HDϖz(υ)−ϕ(υ,HDϖz(υ),HDθs(υ))|≤℧ϖ(υ)φϖ, υ∈U,|HDθs(υ)−ϕ(υ,HDθs(υ),HDϖz(υ))|≤℧θ(υ)φθ, υ∈U, | (3.2) |
there is a unique solution (˜z,˜s)∈ℑ with
‖(z,s)−(˜z,˜s)‖ℑ≤Λ℧ϖ,℧θ℧ϖ,θφ, υ∈U. | (3.3) |
Definition 3.4. The coupled problem (1.1) is called GHUR stable with respect to ℧ϖ,θ if there is a constant Λ℧ϖ,℧θ so that, for any a proximate solution (z,s)∈ℑ of (3.2), there is a unique solution (˜z,˜s)∈ℑ of with of (1.1) fulfilling
‖(z,s)−(˜z,˜s)‖ℑ≤Λ℧ϖ,℧θ℧ϖ,θ(υ), υ∈U. |
Remark 3.5. If there are functions ℜϕ,ℜψ∈C(U,R) depending upon z, s, respectively, so that
(R1) |ℜϕ(υ)|≤φϖ, |ℜψ(υ)|≤φθ, υ∈U;
(R2)
{HDϖz(υ)=ϕ(υ,HDϖz(υ),HDθs(υ))+ℜϕ(υ), Δz(υi)=Ii(z(υi))+ℜϕi, Δz′(υi)=˜Ii(z(υi))+ℜϕi,HDθs(υ)=ϕ(υ,HDθs(υ),HDϖz(υ))+ℜψ(υ), Δs(υj)=Ij(s(υj))+ℜψj, Δs′(υj)=˜Ij(s(υj))+ℜψj. |
Then, (z,s)∈ℑ is a solution of the system of inequalities (3.1).
In the following part, we establish requirements for the existence and uniqueness of solutions to the suggested system (1.1)
Theorem 4.1. For the function w, the solutions of the following subsequent linear impulsive BVP
{HDϖz(υ)=w(υ), υ∈U, υ≠υi, i=1,2,...k,Δz(υi)=Ii(z(υi)), Δz′(υi)=˜Ii(z(υi)), υ≠υi, i=1,2,...k,z(G)=1Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη, z′(G)=B∗(z), |
takes the form
z(υ)=GD0(ϖ)B∗(z)(lnυ)ϖ−2+u∑i=1D1i(ϖ)(lnυ)ϖ−2Iiz(υi)+u∑i=1D2i(ϖ)(lnυ)ϖ−2˜Iiz(υi)+D3(ϖ)(lnυ)ϖ−2Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη+D0(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫Gυuln(Gη)ϖ−2w(η)dηη+D4(ϖ)(lnυ)ϖ−2Γ(ϖ)∫Gυuln(Gη)ϖ−1w(η)dηη+u∑i=1D5i(ϖ)(lnυ)ϖ−2Γ(ϖ)∫υiυi−1ln(υiη)ϖ−1w(η)dηη+u∑i=1lnυ3−ϖ(logυiυ)ϖ−2D5i(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫υiυi−1ln(υiη)ϖ−2w(η)dηη+1Γ(ϖ)∫υυuln(υη)ϖ−1w(η)dηη, | (4.1) |
where u=1,2,...,k and
D0(ϖ)=ln(υG)ln(G)2−ϖ,D1i(ϖ)=(ϖ−1)(lnυ−ϖ+2)(lnυi)3−ϖ−(ϖ−2)(lnυ2−ϖ+1)(lnυi)2−ϖlnυi,D2i(ϖ)=lnυυi(3−ϖ)(lnυi)2−ϖ,D3(ϖ)=(ϖ−1−logGυϖ−2)(lnυ)2−ϖ,D4(ϖ)=logGυGϖ−1(lnG)2−ϖ,D5i(ϖ)=(lnυϖ−1Gϖ−2+logυi(Gυiυ2)ϖ−2)(lnυi)2−ϖ. |
Proof. Assume that
HDϖz(υ)=w(υ), ϖ∈(1,2], υ∈U. | (4.2) |
Using Lemma 2.3, for υ∈(1,υ1], we have
z(υ)=r1(lnυ)ϖ−1+r2(lnυ)ϖ−2+1Γ(ϖ)∫υ1ln(υη)ϖ−1w(η)dηη,z′(υ)=r1(ϖ−1)υ(lnυ)ϖ−2+r2(ϖ−2)υ(lnυ)ϖ−3+1Γ(ϖ−1)∫υ11υln(υη)ϖ−2w(η)dηη. | (4.3) |
Again, applying Lemma 2.3, for υ∈(υ1,υ2], we get
z(υ)=l1(lnυ)ϖ−1+l2(lnυ)ϖ−2+1Γ(ϖ)∫υυ1ln(υη)ϖ−1w(η)dηη,z′(υ)=l1(ϖ−1)υ(lnυ)ϖ−2+l2(ϖ−2)υ(lnυ)ϖ−3+1Γ(ϖ−1)∫υυ11υln(υη)ϖ−2w(η)dηη. | (4.4) |
Using initial impulses
l1=r1−(ϖ−2)(lnυ1)1−ϖI1(z(υ1))+υ1(lnυ1)2−ϖ˜I1(z(υ1))+(lnυ1)2−ϖΓ(ϖ−1)∫υ11ln(υ1η)ϖ−2w(η)dηη−(ϖ−2)(lnυ1)1−ϖΓ(ϖ)∫υ11ln(υ1η)ϖ−1w(η)dηη,l2=r2+(ϖ−1)(lnυ1)2−ϖI1(z(υ1))−υ1(lnυ1)3−ϖ˜I1(z(υ1))−(lnυ1)3−ϖΓ(ϖ−1)∫υ11ln(υ1η)ϖ−2w(η)dηη+(ϖ−1)(lnυ1)2−ϖΓ(ϖ)∫υ11ln(υ1η)ϖ−1w(η)dηη. |
From l1 and l2 on (4.4), one has
z(υ)=r1(lnυ)ϖ−1−r2(lnυ)ϖ−2+((ϖ−1)−(ϖ−2)(logυ1υ))(logυ1υ)ϖ−2I1(z(υ1))+υ1(lnυ−lnυ1)(logυ1υ)ϖ−2˜I1(z(υ1))+(lnυ−lnυ1)(logυ1υ)ϖ−2Γ(ϖ−1)∫υ11ln(υ1η)ϖ−2w(η)dηη+((ϖ−1)−(ϖ−2)(logυ1υ))(logυ1υ)ϖ−2Γ(ϖ)∫υ11ln(υ1η)ϖ−2w(η)dηη+1Γ(ϖ)∫υυ1ln(υη)ϖ−1w(η)dηη. |
Analogously for υ∈(υu,G), we have
z(υ)=r1(lnυ)ϖ−1+r2(lnυ)ϖ−2+u∑i=1((ϖ−1)−(ϖ−2)(logυiυ))(logυiυ)ϖ−2Ii(z(υi))+u∑i=1υi(lnυ−lnυi)(logυiυ)ϖ−2˜Ii(z(υi))+u∑i=1(lnυ−lnυi)(logυiυ)ϖ−2Γ(ϖ−1)∫υiυi−1ln(υiη)ϖ−2w(η)dηη+u∑i=1((ϖ−1)−(ϖ−2)(logυiυ))(logυiυ)ϖ−2Γ(ϖ)∫υiυi−1ln(υiη)ϖ−2w(η)dηη+1Γ(ϖ)∫υυuln(υη)ϖ−1w(η)dηη, | (4.5) |
and
z′(υ)=(ϖ−1)r1υ(lnυ)ϖ−2+(ϖ−1)r2υ(lnυ)ϖ−3+u∑i=1(ϖ−1)(ϖ−2)υ(logυe−logeυi)(logυiυ)ϖ−2Ii(z(υi))+u∑i=1υiυ[(ϖ−1)−(ϖ−2)logυυi](logυiυ)ϖ−2˜Ii(z(υi))+1υΓ(ϖ−1)∫υυuln(υη)ϖ−2w(η)dηη,+u∑i=1((ϖ−1)−(ϖ−2)logυυi)(logυiυ)ϖ−2υΓ(ϖ−1)∫υiυi−1ln(υiη)ϖ−2w(η)dηη+u∑i=1(ϖ−1)(ϖ−2)(logυe−logeυi)(logυiυ)ϖ−2υΓ(ϖ)∫υiυi−1ln(υiη)ϖ−2w(η)dηη. | (4.6) |
Applying the boundary stipulations z(G)=1Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη and z′(G)=B∗(z), we obtain that
r1=GB∗(z)ln(G)2−ϖ−(lnG)1−ϖ(ϖ−2)Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη+(lnG)1−ϖΓ(ϖ)∫Gυuln(Gη)ϖ−1w(η)dηη+u∑i=1(lnυϖ−1i−ϖ−2lnυi)(lnυi)2−ϖIi(z(υi))−(ϖ−2)u∑i=1υi(lnυi)ϖ−1˜Ii(z(υi))−(ϖ−2)Γ(ϖ−1)u∑i=1(lnυi)2−ϖ∫υiυi−1ln(υiη)ϖ−2w(η)dηη−(lnG)2−ϖΓ(ϖ−1)∫Gυuln(Gη)ϖ−2w(η)dηη+1Γ(ϖ)u∑i=1(lnυϖ−1i−ϖ−2lnυi)(lnυi)2−ϖ∫υiυi−1ln(υiη)ϖ−1w(η)dηη, |
and
r2=(lnG)2−ϖΓ(ϖ−1)∫G1ln(Gη)ϖ−1B(η,z(η))dηη−GB∗(z)ln(G)3−ϖ+u∑i=1υi(lnυi)3−ϖ˜Ii(z(υi))+(ϖ−1)u∑i=1(lnG(ϖ−2)(logυie−logeυi)−1)(lnυi)2−ϖIi(z(υi))+(lnG)3−ϖΓ(ϖ−1)∫υυuln(Gη)ϖ−2w(η)dηη+1Γ(ϖ−1)u∑i=1(lnG(ϖ−2)(logυie−logeυi)−1)(lnυi)2−ϖ∫υiυi−1ln(υiη)ϖ−1w(η)dηη+1Γ(ϖ−1)u∑i=1(lnυi)3−ϖ∫υiυi−1ln(υiη)ϖ−2w(η)dηη−(lnG)2−ϖΓ(ϖ−1)∫Gυiln(Gη)ϖ−1w(η)dηη, |
for u=1,2,...,k. Substituting r1 and r2 in (4.5), we have (4.1).
Corollary 4.2. Theorem 2.4 provides the following solution for our coupled problem (1.1):
z(υ)=GD0(ϖ)B∗(z)(lnυ)ϖ−2+u∑i=1D1i(ϖ)(lnυ)ϖ−2Ii(zi)+u∑i=1D2i(ϖ)(lnυ)ϖ−2˜Ii(zi)+D3(ϖ)(lnυ)ϖ−2Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη+D0(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫Gυuln(Gη)ϖ−2ϕ(η,HDϖz(η),HDθs(η))dηη+D4(ϖ)(lnυ)ϖ−2Γ(ϖ)∫Gυuln(Gη)ϖ−1ϕ(η,HDϖz(η),HDθs(η))dηη+u∑i=1D5i(ϖ)(lnυ)ϖ−2Γ(ϖ)∫υiυi−1ln(υiη)ϖ−1ϕ(η,HDϖz(η),HDθs(η))dηη+u∑i=1lnυ3−ϖ(logυiυ)ϖ−2D5i(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫υiυi−1ln(υiη)ϖ−2ϕ(η,HDϖz(η),HDθs(η))dηη+1Γ(ϖ)∫υυuln(υη)ϖ−1ϕ(η,HDϖz(η),HDθs(η))dηη, | (4.7) |
where u=1,2,...,k and
s(υ)=GD0(θ)B∗(s)(lnυ)θ−2+u∑j=1D1j(θ)(lnυ)θ−2Ij(sj)+u∑j=1D2j(θ)(lnυ)θ−2˜Ij(sj)+D3(θ)(lnυ)θ−2Γ(θ)∫G1ln(Gη)θ−1B(η,s(η))dηη+D0(θ)(lnυ)θ−2Γ(θ−1)∫Gυuln(Gη)θ−2ψ(η,HDθs(η),HDϖz(η))dηη+D4(θ)(lnυ)θ−2Γ(θ)∫Gυuln(Gη)θ−1ψ(η,HDθs(η),HDϖz(η))dηη+u∑j=1D5i(θ)(lnυ)θ−2Γ(θ)∫υjυj−1ln(υjη)θ−1ψ(η,HDθs(η),HDϖz(η))dηη+u∑j=1lnυ3−θ(logυjυ)θ−2D5j(θ)(lnυ)θ−2Γ(θ−1)∫υjυj−1ln(υiη)θ−2ψ(η,HDθs(η),HDϖz(η))dηη,+1Γ(θ)∫υυuln(υη)θ−1ψ(η,HDθs(η),HDϖz(η))dηη, | (4.8) |
where u=1,2,...,m.
For convenience, we use the notations below:
p(υ)=ϕ(υ,a1(υ),a2(υ))≤ϕ(υ,z(υ),a(υ)) and a(υ)=ψ(υ,p1(υ),p2(υ))≤ψ(υ,s(υ),p(υ)). |
Hence, for υ∈U, Eqs (4.7) and (4.8) can be written as
z(υ)=GD0(ϖ)B∗(z)(lnυ)ϖ−2+u∑i=1D1i(ϖ)(lnυ)ϖ−2Ii(zi)+u∑i=1D2i(ϖ)(lnυ)ϖ−2˜Ii(zi)+D3(ϖ)(lnυ)ϖ−2Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη+D0(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫Gυuln(Gη)ϖ−2p(η)dηη+D4(ϖ)(lnυ)ϖ−2Γ(ϖ)∫Gυuln(Gη)ϖ−1p(η)dηη+u∑i=1D5i(ϖ)(lnυ)ϖ−2Γ(ϖ)∫υiυi−1ln(υiη)ϖ−1p(η)dηη+u∑i=1lnυ3−ϖ(logυiυ)ϖ−2D5i(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫υiυi−1ln(υiη)ϖ−2p(η)dηη+1Γ(ϖ)∫υυuln(υη)ϖ−1p(η)dηη, |
for u=1,2,...,k and
s(υ)=GD0(θ)B∗(s)(lnυ)θ−2+u∑j=1D1j(θ)(lnυ)θ−2Ij(sj)+u∑j=1D2j(θ)(lnυ)θ−2˜Ij(sj)+D3(θ)(lnυ)θ−2Γ(θ)∫G1ln(Gη)θ−1B(η,s(η))dηη+D0(θ)(lnυ)θ−2Γ(θ−1)∫Gυuln(Gη)θ−2a(η)dηη+D4(θ)(lnυ)θ−2Γ(θ)∫Gυuln(Gη)θ−1a(η)dηη+u∑j=1D5i(θ)(lnυ)θ−2Γ(θ)∫υjυj−1ln(υjη)θ−1a(η)dηη+u∑j=1lnυ3−θ(logυjυ)θ−2D5j(θ)(lnυ)θ−2Γ(θ−1) intυjυj−1ln(υiη)θ−2a(η)dηη+1Γ(θ)∫υυuln(υη)θ−1a(η)dηη, |
for u=1,2,...,m.
If z and s are solutions to the CII-FDEs (1.1), then for υ∈U, we can write
z(υ)=GD0(ϖ)B∗(z)(lnυ)ϖ−2+u∑i=1D1i(ϖ)(lnυ)ϖ−2Ii(zi)+u∑i=1D2i(ϖ)(lnυ)ϖ−2˜Ii(zi)+D3(ϖ)(lnυ)ϖ−2Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη+D0(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫Gυuln(Gη)ϖ−2ϕ(η,a1(η),a2(η))dηη+D4(ϖ)(lnυ)ϖ−2Γ(ϖ)∫Gυuln(Gη)ϖ−1ϕ(η,a1(η),a2(η))dηη+u∑i=1D5i(ϖ)(lnυ)ϖ−2Γ(ϖ)∫υiυi−1ln(υiη)ϖ−1ϕ(η,a1(η),a2(η))dηη+u∑i=1lnυ3−ϖ(logυiυ)ϖ−2D5i(ϖ)(lnυ)ϖ−2Γ(ϖ−1)∫υiυi−1ln(υiη)ϖ−2ϕ(η,a1(η),a2(η))dηη+1Γ(ϖ)∫υυuln(υη)ϖ−1ϕ(η,a1(η),a2(η))dηη, |
for u=1,2,...,k and
s(υ)=GD0(θ)B∗(s)(lnυ)θ−2+u∑j=1D1j(θ)(lnυ)θ−2Ij(sj)+u∑j=1D2j(θ)(lnυ)θ−2˜Ij(sj)+D3(θ)(lnυ)θ−2Γ(θ)∫G1ln(Gη)θ−1B(η,s(η))dηη+D0(θ)(lnυ)θ−2Γ(θ−1)∫Gυuln(Gη)θ−2ψ(η,p1(η),p2(η))dηη+D4(θ)(lnυ)θ−2Γ(θ)∫Gυuln(Gη)θ−1ψ(η,p1(η),p2(η))dηη+u∑j=1D5i(θ)(lnυ)θ−2Γ(θ)∫υjυj−1ln(υjη)θ−1ψ(η,p1(η),p2(η))dηη+u∑j=1lnυ3−θ(logυjυ)θ−2D5j(θ)(lnυ)θ−2Γ(θ−1)∫υjυj−1ln(υiη)θ−2ψ(η,p1(η),p2(η))dηη+1Γ(θ)∫υυuln(υη)θ−1ψ(η,p1(η),p2(η))dηη, |
for u=1,2,...,m.
Our next step is to convert the considered system (1.1) into a FP problem. Give the definition of the operators E,˜E:ℑ→ℑ as
E(z,s)(υ)=(E1z(υ),E2z(υ)) and ˜E(z,s)(υ)=(E1(z,s)(υ),E2(s,z)(υ)), |
where
{E1(z(υ))=GD0(ϖ)B∗(z)(lnυ)ϖ−2+∑ui=1D1i(ϖ)(lnυ)ϖ−2Ii(zi)+∑ui=1D2i(ϖ)(lnυ)ϖ−2˜Ii(zi)+D3(ϖ)(lnυ)ϖ−2Γ(ϖ)∫G1ln(Gη)ϖ−1B(η,z(η))dηη, u=1,2,...,k,E2(s(υ))=GD0(θ)B∗(s)(lnυ)θ−2+∑uj=1D1j(θ)(lnυ)θ−2Ij(sj)+∑uj=1D2j(θ)(lnυ)θ−2˜Ij(sj)+D3(θ)(lnυ)θ−2Γ(θ)∫G1ln(Gη)θ−1B(η,s(η))dηη, u=1,2,...,m, | (4.9) |
and
(4.10) |
The preceding assertions must be true in order to conduct further analysis:
For and there exist so that
with and
For the continuous functions there are positive constants
so that for any
where
For all and there are so that
with
For each and for all there are constants and so that
For the continuous functions there are positive constants so for any
For each and for all there are , so that
Here, we demonstrate that the operator has at least one FP using Kransnoselskii's FP theorem. For this, we choose a closed ball
where
Theorem 4.3. There exists at least one solution to the CII-FDEs (1.1) provided that the assertions and are true.
Proof. For any we get
(4.11) |
From (4.9), we have
for This leads to
(4.12) |
Analogously, one can write
(4.13) |
where
Further, we obtain for that
(4.14) |
From assertion we can write
which implies that
(4.15) |
Taking on (4.14) and using (4.15), one has
(4.16) |
In the same scenario, we get
(4.17) |
where
Applying (4.12), (4.13), (4.16) and (4.17) in (4.11), we have
which implies that After that, for any and one writes
Applying and one has
where
and
Hence, is a contraction mapping. Now, we claim that is continuous and compact. For this, we build a sequence in so that Hence, we obtain
(4.18) |
Since
(4.19) |
and
(4.20) |
Applying (4.19) and (4.20) in (4.18), we conclude that
which yields as this proves the continuity of Next, using (4.16) and (4.17), we get
Therefore, is uniformly bounded on Finally, we show that is equicontinuous. To get this result, take with and for any (clearly is bounded), we obtain
which yields that
Similarly, we get
Hence
Therefore is a relatively compact on Thanks to the theorem of Arzelà-Ascoli, is compact. Thus, it is completely continuous. So, the CII-FDEs (1.1) admits at least one solution. This finishes the proof.
Theorem 4.4. Assume that – are fulfilled with
(4.21) |
then the CII-FDEs (1.1) possesses a unique solution.
Proof. Let be an operator defined by where
for and
for In light of Theorem 4.3, one can obtain
for Passing we have
where
Analogously,
where
Hence
This suggests that is a contraction. Consequently, the CII-FDEs (1.1) has a unique solution.
In this section, we examine various stability types for the suggested system, including the HU, GHU, HUR, and GHUR stability.
Theorem 5.1. If the assertions – and the condition (4.21) are true and
then the unique solution of CII-FDEs (1.1) is HU stable and as a result, GHU stable.
Proof. Take into account that is an approximate solution of (3.1) and consider is a solution of the coupled problem shown below
(5.1) |
From Remark 3.5, we get
(5.2) |
It follows from Corollary 4.2 that the solution of system (5.2) is
(5.3) |
for and
(5.4) |
for Consider
As in Theorem 4.4, one has
(5.5) |
for and
(5.6) |
Arranging (5.5) and (5.6), we get
(5.7) |
and
(5.8) |
respectively. Assume that and Then (5.7) and (5.8) can be written as
Hence
(5.9) |
where
From system (5.9), we observe that
which yields that
Let us consider and
Then, we can write
which leads to the supposed coupled problem (1.1) is HU stable. Further, if
Then the suggested coupled problem (1.1) is GHU stable.
For the final result, we suppose the following assertion:
There are nondecreasing functions so that
Theorem 5.2. If the assertions – and and the condition (4.21) are fulfilled and
then the unique solution of CII-FDEs (1.1) is HUR stable and consequently GHUR stable.
Proof. According to Definitions 3.3 and 3.4, we can get our conclusion by following the same procedures as in Theorem 5.1.
Example 6.1. Consider
(6.1) |
where for In view of problem (6.1), we observe that and Further, it's simple to locate and Based on Theorem 4.4, we find that
Therefore problem (6.1) has a unique solution. Further
Therefore, according to Theorem 5.1, the coupled system (6.1) is HU stable and consequently GHU stable. Similarly, we can confirm that Theorems 4.3 and 5.2 are true.
In this manuscript, we used fixed point results of Banach and Kransnoselskii to give necessary and sufficient conditions for the existence of a unique positive solution for a system of impulsive fractional differential equations intervening a fractional derivative of the Hadamard type. We also studied some Hyers-Ulam (HU) stabilities such as generalized Hyers-Ulam (GHU), Hyers-Ulam-Rassias (HUR), and generalized Hyers-Ulam-Rassias (GHUR) stabilities. At the end, we provided a concrete example making effective the obtained results.
The authors thank the Basque Government for Grant IT1555-22. This work was supported in part by the Basque Government under Grant IT1555-22.
The authors declare that they have no competing interests.
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