Abstract
In this paper, we deal with an initial boundary value problem for a pLaplacian evolution equation with nonlinear memory term and inner absorption term subject to a weighted linear nonlocal boundary condition. We find the effects of a weighted function as regards determining blowup of nonnegative solutions or not and establish the precise blowup estimate for the linear diffusion case under some suitable conditions.
Keywords:
pLaplacian evolution equation; nonlinear memory; global existence; blowup; weight function1 Introduction
In the past decades, there have been many works dealing with global existence and blowup properties of solutions for nonlinear parabolic equations, especially the initial boundary value problems with nonlocal terms in equations or boundary conditions, we refer to [110] and references therein. For the study of an initial boundary value problem for local parabolic equations with nonlocal boundary condition, we refer to [14]. For example, Friedman [1] studied the linear parabolic equation
subject to the weighted linear nonlocal Dirichlet boundary condition
where A is an elliptic operator,
and the nonnegative continuous function satisfies suitable conditions. He proved that when , the solution approaches to 0 monotonously and exponentially as . As regards more general discussions on an initial boundary value problem for a linear parabolic equation with a weighted linear nonlocal Neumann boundary condition, one can refer to [2] by Pao, where the following problem:
where
was considered. He studied the asymptotic behavior of solutions and found the influence of the weight function on the existence of global and blowup solutions. Later, Akila [3] adopted the method of an upperlower solution to consider the semilinear parabolic equation
under a similar weighted linear nonlocal boundary condition. Wang et al.[4] studied a porous medium equation with power form source term,
under the weighted linear nonlocal Dirichlet boundary condition (1.1). By virtue of the method of an upperlower solution, they obtained global existence, blowup properties, and blowup rate of solutions.
For the study of initial boundary value problem with nonlocal parabolic equation, especially the nonlocal problem with timeintegral, we refer to [510]. Under a homogeneous Dirichlet boundary condition, Li and Xie [5] studied the nonlinear diffusion equation
where , . They obtained the sufficient conditions of global existence and blowup of solutions under appropriate critical conditions. Furthermore, under the following assumptions:
and
they derived the following blowup rate:
for the special case and . It is necessary to point out that assumption (1.2) seems to be reasonable, but unfortunately, the authors of [5] did not give a relationship between and equation (1.2). The characterization of the monotonicity condition (1.2) was given by Souplet in [6], who proved the existence of monotone in time solutions for the above problem and obtained the blowup rate (1.4) without the assumption of condition (1.3).
Zhou et al.[7] considered the following singular diffusion equation with memory term:
where , , . They got similar results by the method of upperlower solution. We should notice that this kind of equation can be turned into a degenerate porous medium equation by suitable transformation. In addition, for the system of porous medium equations with nonlinear memory terms and a homogeneous Dirichlet boundary condition, one can refer for example to [8,9].
Recently, Liu and Mu [10] considered the following semilinear parabolic equation with memory term:
subject to a weighted nonlinear nonlocal boundary,
where . They gave the conditions of global existence and blowup of solutions and the blowup rate of solutions for , by establishing an auxiliary function.
In view of the works mentioned above, a nonlocal parabolic equation with timeintegral term does not seem to be so much investigated as nonlocal equations with spaceintegral terms. Already at first glance, the problem with a memory term has some difficulties in proving the existence of nonglobal solutions. First if t is sufficiently small, the nonlinear memory term vanishes, and then it is not clear whether the comparison principle holds in proving the existence of global small solutions. As far as we know, there are a few papers about the blowup phenomenon for the pLaplacian evolution equation with nonlinear memory term. Motivated by it, we consider the global existence and blowup properties of the following pLaplacian evolution equation with nonlinear memory term and inner absorption term:
subject to weighted linear nonlocal boundary and initial conditions
where , , , , , and () is a bounded domain with smooth boundary. The weight function in the boundary condition is continuous, nonnegative on , and on ∂Ω, while the nonnegative and nontrivial initial data satisfies the compatibility conditions for and for , which is the closed relationship for local solvability of our problem (1.5)(1.7) (see Section 2).
The nonlocal diffusion model like equation (1.5) arises in many natural phenomena. In some sense, this kind of nonlocal problem is closer to the actual model than the local problem, such as the model of nonNewton flux through a porous medium, the model for compressible reactive gases, the model of population dynamics, and the model of biological species with humancontrolled distribution (see [2,1114] and references therein). From a physics point of view, equation (1.5) with , and appears in the theory of nuclear reactor dynamics in which case the nonlocal term with timeintegral is called the memory term [15]. In fact, there are some important phenomena formulated as parabolic equations which are coupled with weighted nonlocal boundary conditions in mathematical models, such as thermoelasticity theory. In this case, the solution describes the entropy per volume of the materia1 (see [16,17]).
Our main goal is to find the effects of weight function on global or nonglobal existence of solutions for problem (1.5)(1.7), the suitable range of nonlinear exponent, and to give the blowup rate estimate under some suitable conditions. In addition, we treat the nonlocal nonlinearity Hölder (nonLipschitz) cases m or , as well as the Lipschitz cases in this paper. We get our main results by establishing a modified comparison principle, constructing the suitable upper and lower solutions (including the selfsimilar lower solutions, the eigenfunction argument and the technique of ordinary differential equation and so on) and the auxiliary function. Moreover, our results extend part of or all results in [810]. The detailed results are stated as follows.
• For arbitrary . If , then the solution of problem (1.5)(1.7) blows up in finite time for sufficiently large initial data.
• If , for . If , then the solution of problem (1.5)(1.7) blows up in finite time for all strictly positive initial dates with T sufficiently large.
• If , for . , , the initial value satisfies conditions (H_{1})(H_{2}) (see Section 3) and is the blowup solution of problem (1.2)(1.4), then the blowup rate is
(i) If , then the solution of problem (1.5)(1.7) exists globally for small initial data.
(ii) If , and , then the solution of problem (1.5)(1.7) exists globally for small initial data.
(iii) If , then the solution of problem (1.5)(1.7) exists globally for small enough initial data.
The rest of the paper is organized as follows. In Section 2, we give the preliminaries for our research. The proofs of blowup results and blowup rate of solutions are given in Section 3. In Section 4, we will deduce the results of global existence.
2 Comparison principle and local existence
Since equation (1.2) is degenerate when , there is no classical solution in general. Hence, it is reasonable to find a weak solution. To this end, we first give the following definition of nonnegative weak solution of problem (1.5)(1.7).
Definition 1 If the nonnegative function satisfies the following conditions:
then is called the weak solution of problem (1.5)(1.7).
If the equalities in equations (2.1)(2.3) are replaced by ‘≤’ and ‘≥’, we can get and which are called the lower solution and upper solution of problem (1.5)(1.7), respectively.
The following modified comparison principle plays a crucial role in our proofs, which can be obtained by establishing a suitable test function and Gronwall’s inequality.
Proposition 1 (Comparison principle)
Suppose thatandare the lower and upper solutions of problem (1.2)(1.4), respectively. If, and, whereεis any positive constant, thenin.
Proof For , since and are the lower and upper solutions of problem (1.5)(1.7), respectively, it follows that
Choose a test function for , where is a characteristic function defined on , then we have
where
By Lemma 4.10 in [18], we know for . Moreover, it follows from , , that () is bounded, and if , or , we have , since , . Furthermore, because and are bounded functions, we can get
That is,
By Gronwall’s inequality, we can deduce that , and so in .
in the case of in Ω. Therefore, we obtain on , and in . □
Next, we state the theorem of local existence and uniqueness without proof.
Theorem (Local existence and uniqueness)
Suppose that, , , and, the nonnegative initial datasatisfies the compatibility conditionsforandfor. Then there exists a constantsuch that problem (1.5)(1.7) admits a nonnegative solutionfor each. Furthermore, eitheror
Remark 1 The existence of local nonnegative solutions in time to problem (1.5)(1.7) can be obtained by combining Theorem 1.2 in [4] with Theorem A4′ in [19]. By the comparison principle above, we can get the uniqueness of the solutions to problem (1.5)(1.7) with , .
3 Blowup solutions and blowup rate
Comparing with the problem under a general homogeneous Dirichlet boundary condition, the existence of weight function in the boundary condition has a great influence on the global and nonglobal existence of solutions.
Theorem 1Suppose that, then the solution of problem (1.5)(1.7) blows up in finite time for arbitraryand sufficiently large initial data.
Proof In order to prove the blowup result, we need to establish a selfsimilar blowup solution. Let
It is obvious that blows up at as t approaches T. Set
An explicit calculation yields
and
Therefore we have
and
In view of the above, this gives
We will discuss the problem for two cases.
Case 1. , . We need to show that for sufficiently small T,
That is,
Let δ be sufficiently large, satisfying . By the condition , , and , we just have to make the following equality hold:
It is obvious that it holds for .
Case 2. , choose and we can get
and
Since , choose and to satisfy . However,
thus we find
Then
In order to get the result, we have to show that
in which case we can get the result.
(ii) ; we have and . Since and , we know that , and
Let , , it is obvious that and . Substituting equation (3.2) into equation (3.1) gives
However, since and , it follows that
Finally, we need to show that
In other words, we just need the following inequality:
to hold. So choose T to be small enough, and we can get
choose , then is the lower solution of problem (1.5)(1.7). This implies that the solution blows up in finite time for large enough initial data. □
Theorem 2Suppose thatfor. If, then the solution of problem (1.5)(1.7) blows up in finite time for all strictly positive initial dates withTsufficiently large.
Proof Consider the following problem:
As , we know , and . Therefore, the solution of equation (3.3) is an upper solution of the following problem:
Since and , the solution of this problem blows up in finite time if .
It is obvious that the solution of problem (3.3) is a lower solution of problem (1.5)(1.7) when and . By Proposition 1, is a blowup solution. □
Suppose that the solution of problem (1.5)(1.7) with blows up in finite time, and let . We suppose that the initial data satisfies the following assumptions:
(H_{2}) There exists a constant such that .
Theorem 3Suppose thatfor. If, satisfies condition (H_{1})(H_{2}), andis the blowup solution of problem (1.5)(1.7) in finite timeTwith, then the blowup rate is
Remark 2 Choose , , , and , one can easily verify that satisfies (C_{1})(C_{2}), conditions in Theorem 3 are thus valid.
Lemma 1Ifsatisfies condition (H_{1})(H_{2}), , then there exists a positive constantsuch that.
Proof It is obvious that is Lipschitz continuous and differentiable almost everywhere. By equation (1.5) with and , it yields
and thus
Integrating the result above over , we can obtain the conclusion. □
Proof of Theorem 3 Let , where is sufficiently small. Since , we have
so we can choose to be small enough and thus obtain
On the other hand, as , we get
Let , By Jensen’s inequality, this gives
and
It follows from the assumptions of (H_{1})(H_{2}) that . Therefore, it is easy to deduce that for . That is, and integrating this over yields . Combining the results with Lemma 1, we obtain the desired result. □
4 Global existence of solutions
In this section, we give sufficient conditions of the global existence of solutions.
Theorem 4Suppose thatfor. If, then the solution of problem (1.5)(1.7) exists globally for small initial data.
Proof Let , where are determined later, and solves the following problem:
we can infer that
Selecting , we can deduce that the result holds. □
Theorem 5Suppose thatfor. If, and, then the solution of problem (1.5)(1.7) exists globally for small initial data.
Proof Suppose that solves the following problem:
and
For , we choose such that and . It follows that
and
and
we can get
On the other hand, for and sufficiently large A, we have
Choosing to be sufficiently small such that , we can conclude that is an upper solution of problem (1.5)(1.7). The proof is completed. □
Theorem 6Suppose thatfor. If, then the solution of problem (1.5)(1.7) exists globally for small enough initial data.
Proof Choosing and , it is easy to see that the result holds. □
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
All authors contributed equally to the manuscript and read and approved the final manuscript.
Acknowledgements
This work is supported by the Natural Science Foundation of Shandong Province of China (ZR2012AM018) and the Fundamental Research Funds for the Central Universities (No. 201362032). The authors would like to warmly thank all the reviewers for their insightful and constructive comments.
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