Research Article | Open Access

Kh. Zennir, H. Dridi, S. Alodhaibi, S. Alkhalaf, "Nonexistence of Global Solutions for Coupled System of Pseudoparabolic Equations with Variable Exponents and Weak Memories", *Journal of Function Spaces*, vol. 2021, Article ID 5573959, 11 pages, 2021. https://doi.org/10.1155/2021/5573959

# Nonexistence of Global Solutions for Coupled System of Pseudoparabolic Equations with Variable Exponents and Weak Memories

**Academic Editor:**Shuangping Tao

#### Abstract

The most important behavior for evolution system is the blow-up phenomena because of its wide applications in modern science. The article discusses the finite time blowup that arise under an appropriate conditions. The nonsolvability of boundary value problem for damped pseudoparabolic differential equations with variable exponents is investigated. Such problem has been previously studied in the case if and are constants. New here is the case of variables of nonlinearity and which make the problem has a scientific interest.

#### 1. Introduction and Overview

Boundary value problems for evolutionary equations of parabolic in degenerate sense are well studied (see, for example, [1â€“4]). In this article, we study boundary value problems for coupled system of pseudoparabolic equations with -Laplacian in the presence of weak viscoelasticities. Such problems have not been studied in depth. To begin with, let is an open bounded domain in for with smooth boundary ; we then consider in for with initial condition and boundary condition

The lack of stability of solutions of partial differential equations is a huge restriction for qualitative studies. The terms responsible for the blow-up phenomenon in our system (1) is that of more complicated nonlinearities when they dominate the damped terms, especially when it comes with the existence of a large class of Laplacian operator

The functions are given by the nonlinearities respectively. The weak-viscoelastic term is .

There exists a function such that where and . There exist two positive constants and such that

For more details, see [5â€“8] and references therein.

With -Laplacian, which is nonlinear differential operator, in [9], a problem of elliptic equation is considered as

The variable exponents and are two continuous functions on such that with

We assume that satisfies the Zhikov-Fan condition, i.e., for all , with and

We state assumptions on and as follows:

satisfies

Define positive constants , and by for some constants which will be specified later.

Fan et al. discussed the existence and multiplicity of solutions of (9) for , where is a function defined on .

Regarding nonlinear parabolic equation, we mention the work by [1]. The author proposed the problem. where is a bounded domain of with smooth boundary and . Time existence of solutions of system (16) was proved.

Whereas, in [10], nonlinear pseudoparabolic was considered

Global in time nonexistence of (17) was shown under an appropriate conditions on and .

System (1), where the exponents and , the existence/nonexistence results have been extensively studied (please see [11â€“15]).

The paper is organized as follows. In Section 2, we state the properties of the -growth conditions and present assumptions of the kernel functions. In Section 3, we state our main results and prove some auxiliary lemmas. In Section 4, we prove the global nonexistence of solutions given in Theorem 9. The paper is concluded by explanatory commentaries.

#### 2. Preliminary

We try to list here some useful mathematical tools.

First, let be an open bounded domain in for with smooth boundary and be a measurable function. Denoting by

We define the modular of a measurable function as where

The special Orlicz Musielak space is a Lebesgue space with variable-exponent, and it consists of all the measurable function defined on for which

Let be the Luxembourg norm on this space (see [16]).

The Sobolev space consists of functions whose distributional gradient exists and satisfies . This space is a Banach with respect to the norm

Lemma 1 (Corollary 8.2.5 in [17]). (1)*If (12) holds with , then**where is a bounded domain and is a positive constant. The norm of the space is given by
*(2)*If**is a measurable function and
with
**Then
with a continuous and compact embedding and
where is an embedding constant.*

Proposition 2 (Section 1 and Lemma 3.2.20 in [17]). *Let . The spaces and are separable, uniformly convex, and reflexive Banach spaces. The conjugate space of is , where
**For and , we have
*

Lemma 3 (Lemma 3.2.4 in [17]). *If is a measurable function on and , then and are equivalent. For , we have
*(1)* implies *(2)* implies *

Lemma 4 (Section 2 in [18] and Lemma 3.2.5 in [17]). *If is a measurable function on , then
for all .*

Lemma 5 (Lemma 3.2.20 in [17]). *If a.e. in , there is a continuous inclusion and for all ,
where
*

*The following notation will be used throughout this paper for and . We have the following technical lemma.*

Lemma 6. *Let . For any with , , we have
*

*Proof. *Since
holds for any , we have
Using the notation (36), we obtain the desired result.

#### 3. Main Results

Before stating our main theorems, we define the weak solution for the problem (1)â€“(4).

*Definition 7. *The pair is said to be weak solution to (1)â€“(4) on if it satisfies,
for all test functions .

Here, we present without proof, the first known result concerning the local existence (in time) for the problem (1)â€“(4).

Theorem 8. *Assume that (10), (12), and (14) hold. Then, the problem (1)â€“(4) has a unique local solution satisfying
for depending on .*

To prove the previous theorem, we can adopt the Faedo-Galerkin method which is the same procedure used in [4].

We introduce the main result concerned with the finite time blowup of solutions of the problem (1)â€“(4).

We define and find by (10) and (14).

Theorem 9. *Assume that (10)â€“(14) hold. Given satisfying
**Then, any solution of (1) with (3) and (4) blows up in finite time where
and and are given in (66).**In order to prove Theorem 9, we need to exploit some lemmas. First, we define the modified energy functional associated to the problem (1)â€“(4) by
*

Lemma 10. *Let be the solution of (1)â€“(4) with (10)â€“(14). Then, the energy functional satisfies
*

*Proof. *Multiplying (1) by and (1) by , integrating by parts over , summing and using (14) and Lemma 6. Then, it is clear that and are bounded, so the potential exists and is given by (85) as follows
Differentiating (49) with respect to time, it follows that
Hence, the proof is finished .

Lemma 11. *Let be a strong solution of (1)â€“(4) with (10)â€“(14). Then, we have
*

*Proof. *Using Youngâ€™s inequality, we obtain
which proves the lemma.

Lemma 12. *Let be a strong solution of (1)â€“(4) with (10)â€“(14). Then, we have
*

*Proof. *By using both equivalences (8) and (10), we deduce
The proof is completed by direct use of (54).

In condition (10), holds, which yields

We derive a shaper estimate than that in Lemma 13.

Lemma 13. *Let be a strong solution of (1)â€“(4) with (10)â€“(14). Then, we have
where is an embedding constant defined in Lemma 1.*

*Proof. *First of all, note that, for ,
Then, owing to Lemmas 1 and 4, we have
Similarly, for , we have
Hence, by Lemmas 3 and 4, (58) is estimated as
The substitution of (60) in the estimate (53) ends the proof.

Now, we can see that (56) takes the following form where

Let be a function defined by

Then, is increasing in decreasing for , such that as , and we have for

Since, by the fact (43), i.e., holds. Then, by (63), we can find for all

Lemma 14. *Under the assumptions of Lemma 13. Then, the pair defined in (66) is negative.*

*Proof. *Direct use of (63) and (66). Thus, we obtain
By considering (68), (69). Then, we use Youngâ€™s inequality to get
To provide this, we take sufficiently large and small enough.

Lemma 15. *Let be a strong solution of (1)â€“(4) with (10)â€“(14) and initial condition satisfying (44) and (45). Then, there exists a constants and such that
*

*Proof. *Since
holds by (61). Then, there exists and such that . Thus, we have
which implies that
Now, to establish (72), we suppose by contradiction that
for some and by continuity of we can choose such that
Again, the use of (61) leads to