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A positive solution of a p-Laplace-like equation with critical growth
Journal of Inequalities and Applications volume 2012, Article number: 218 (2012)
Abstract
The existence of a positive solution of a p-Laplace-like equation with critical growth is established by the generalization to the concentration-compactness principle and the Sobolev inequality under some proper assumptions. Moreover, we achieve some regularity results of the solution.
MSC:35J65.
1 Introduction
This paper is devoted to the existence of a positive solution of the following p-Laplace-like problem with critical growth:
where Ω is a smooth bounded domain in , , and the functions a, f satisfy some proper conditions, the details of which are described later.
There were many papers about the existence of the solution of p-Laplacian problems involving critical growth such as [1–6]. In them, and f are some concrete functions with critical growth, which means that does not converge to zero as , where is the critical exponent, i.e., . The concentration-compactness principle, which was built by Lions in [7, 8], plays an important role in achieving the existence of a nontrivial solution of the problems in them.
The authors proved the existence of a nonnegative and nontrivial solution for a Dirichlet problem for p-mean curvature operate with critical growth in [9], where , , and f is some concrete function involving a critical exponent. Since the function a has an explicit form, the authors can use the concentration-compactness principle to achieve their results, too. But if a is an abstract function in problem (1.1), then the problem becomes more complicated and interesting, and Lions’ C-C principle cannot be directly applied to it. Thanks to the generalization of the C-C principle in [10], we can establish the existence of a nonnegative and nontrivial solution of equation (1.1) if we impose some proper conditions on the functions a and f and make more careful estimates. Moreover, we achieve some regularity result of the solution and prove the solution is positive under some proper assumptions. The results can be easily extended to a more general p-Laplace-like equation with critical growth and singular weights by the Caffarelli-Kohn-Nirenberg inequality and the method in [11].
Recently, there have been some articles on stochastic partial differential equations (SPDEs) involving p-Laplace operator; see [12, 13]. Some estimates and properties of the solution of the corresponding elliptic equations are important to the research on SPDEs. So, the results in this paper may be useful in the study of p-Laplace SPDEs with critical growth.
In this paper, we suppose that the potential satisfies the following assumptions.
Let be of continuous derivative with respect to ξ with and satisfy the following conditions:
(A1) ,
(A2) there are and , three positive constants , and such that
(A3) is strictly convex in ξ, that is, for any ,
(A4) there exists a positive number such that .
We impose some assumptions on the critical nonlinear term , which is continuous, as follows:
(B1) ,
(B2) there is a function such that
(B3) there are two positive numbers and such that
(B4) denote , which satisfies
Moreover, we suppose a and f satisfy the next correlation.
(C1) there exists a such that
where X is , i.e., the completion of with the norm .
It is not difficult to see that both and with satisfy (A1)-(A4), and the problems in [9] and [6] are concrete examples of problem (1.1). Moreover, we can consider some more generalized problem with a singular nonlinear term with critical growth by the similar method in this paper and [11]. Then we can achieve more generalized results than those in [2] and [5], which will be considered in another paper. Since is not an explicit function, we need to use the generalization of the C-C principle in [10] and more subtle estimates to study problem (1.1).
It is clear that the solution of problem (1.1) is the critical point of the variational functional
Moreover, is continuous differentiable in X, and its Fréchet derivation is
The first main result in this paper is
Theorem 1.1 Suppose problem (1.1) satisfies assumptions (A1)-(A4), (B1)-(B4) and (C1). Moreover, there exists a nontrivial such that and
(C2) , where , with ().
Then problem (1.1) has a nonnegative and nontrivial solution.
Since the condition (C2) is difficult to check, we give another easily checked theorem.
Theorem 1.2 Assume conditions (A1)-(A4), (B1)-(B4) and (C1) are satisfied and
(A5) for any ,
(B5) there exists a nonempty set such that for any ,
(C3) , where , with
Then problem (1.1) has a nonnegative and nontrivial solution in X.
To establish the regularity of the solution u and prove in Ω, we need to impose stronger assumptions on the potential a and the nonlinear term f, which are as follows:
(D1) with and there exist positive numbers c and C, such that for any and ,
(D2) a admits the form . Moreover, for any .
Theorem 1.3 Assume the assumptions in Theorem 1.1 or those in Theorem 1.2 hold, then there exists a constant such that the solution if assumption (D1) holds. Moreover, if assumption (D2) is satisfied, then in Ω.
In Section 2, we will prove the main results. Some corollaries and examples are shown in Section 3.
2 The proof of the main results
First, we present the main tool in this paper - the generalized concentration-compactness principle, which is easily deduced from Theorem 2.1 in [10].
Lemma 2.1 Suppose assumptions (A1), (A2) and (A3) hold, weakly converges to u in X and , converge to μ, ν weakly in the sense of measures, respectively.
Then there exist some at most countable set J, a family of distinct points in Ω, and two families , of positive numbers such that
where denotes the Dirac measure at the point .
Second, we deduce some properties of a and f by the similar method as in [11] or [6]. According to assumptions (A1)-(A4) and (B1)-(B4), we conclude that for any , , there exist some constants , , C such that for any , , ,
To obtain a nonnegative solution, we first consider the following variational functional and its Fréchet derivation:
It is clear that if . Next, we deduce satisfies the geometrical result of the mountain pass theorem without the (PS) condition, i.e.,
Lemma 2.2 and there exist two constants , and a function such that
where , denotes the boundary of .
Proof Let in (2.6), and we have .
Choosing , in (2.3) (where is the best embedding constant from X to ), and combining assumptions (C1), (A2), we have
Hence, if is small enough. So, we have showed the existence of and in (2.8).
Next, we construct satisfying (2.8). In fact, fixing a nonnegative and nontrivial function , recalling assumption (A2) and (2.3), we deduce that there are positive constants , , such that
Hence, if t is large enough, then we can set satisfying (2.8). □
According to the Ambrosetti-Rabinowitz mountain pass theorem without the (PS) condition, there exists a function sequence such that as ,
Γ denotes the class of continuous paths joining 0 to in X, denotes the dual space of X.
Lemma 2.3 The sequence is bounded in X.
Proof Let in (2.7) and combine (2.6), (2.9). We see that as ,
In the last inequality, we have used (2.2) and (2.5). If we fix a small enough σ such that in the above inequality, then the conclusion in this lemma is obvious. □
As a result of the above preparations, we can prove Theorem 1.1.
Proof of Theorem 1.1 Since is bounded in X, it is easy to see there are a and a subsequence of , still denoted by itself , such that
By the Helly theorem, there exist a subsequence, still denoted by itself, and two nonnegative measures μ and ν such that as ,
Applying Lemma 2.1, we have the corresponding conclusions of Lemma 2.1.
Next, we establish the lower-bound of and
Denote φ as the cutoff function of the ball in , i.e., which satisfies
Define for every and for any . Recalling Lemma 4 in [6], we have the following estimate:
Hence, is still bounded in X and the boundary is independent of ε, j.
Let , in (2.6) and combine (2.2), (2.4), (2.10), (2.15). Then we obtain as ,
In the above inequality, first letting , then taking , and finally taking , we deduce . So, (2.1) implies (2.13). Since ν is a bounded measure, J is at most finite.
In the following, we prove that , and it is the solution of problem (1.1). If J is empty, then the proof is similar to that when J is nonempty, which we omit. Next, we suppose J is nonempty and denote , . Fix a large enough R and a sufficiently small so that
Define with , . It is not difficult to deduce that is bounded in X and the bound is independent of ε from (2.15). According to (2.9) and (2.10), it is clear that as ,
where , and . Applying the method as in (2.16), we see that converges to 0 as . Moreover, the definition of and (2.12) imply
Recalling (2.10), we see in . In view of (2.4), we obtain
According to (2.17), (2.18), we deduce that converges to 0 a.e. in Ω as , maybe extracting a subsequence. Since is strictly convex, by the same method as [14], we claim a.e. in Ω, and there exists a subsequence, still denoted by itself, such that weakly converges to in . Hence, (2.7), (2.9) and (2.11) imply that weakly converges to in and . So, it is not difficult to see that and , which means that u is a weakly solution of equation (1.1).
Next, we prove u is nontrivial, i.e., if assumption (C2) holds. According to the definition of and the properties of , we conclude that as ,
where converges to 0 as , and it has been proved in (2.16) that converges to 0 as . Moreover, as ,
Combining (2.12), (2.13) and the above inequalities and equalities, firstly taking , then taking , and finally taking in (2.19), we have
According to the definition of and assumption (C2), we have , which means . □
Before proving Theorem 1.2, we need to introduce the function family which approximates the best embedding constant S from X to . Without loss of generalization, we suppose , . Denote
where φ is defined in (2.14), and U is the extremal function reaching S. It is easy to check that as ,
As a result of the preparations, we can prove Theorem 1.2 as follows.
Proof of Theorem 1.2 Without loss of generalization, we suppose . For convenience, let A and B denote some positive constants which may be different in different places.
Applying the method in the proof of Lemma 2.2, we deduce that as , which implies there exists a such that and
Let and in (2.4), combining (2.23), (A1), (A3) and (A5), we obtain
Recalling (2.22), we see that is positive and bounded away from zero as . Moreover, according to assumption (A2) and (2.4), we infer
Hence, (2.22) implies is bounded, and the bound is independent of ε.
Set
In view of (2.22), we have
It is noted that is increasing with according to assumption (C3). Hence, we deduce
Next, we handle the last two terms on the right-hand side of (2.24). Since is nonnegative and increasing, we can utilize the properties of and to calculate
where is defined in assumption (C3). Without loss of generalization, suppose and . According to the definition of ϕ and assumption (A2), it is clear that , then we have
We have used (2.20) and (2.21) in the last equality. Furthermore, (2.3) and the definition of imply that . Repeating the above argument, we obtain
Remembering assumption (A5), we see . Combining (2.24)-(2.28), we obtain
So, assumption (C3) implies that assumption (C2) holds if we choose ε small enough, and the conclusion in Theorem 1.2 follows from Theorem 1.1. □
Proof of Theorem 1.3 We firstly prove by the Moser iteration. Since the problem involves critical growth, we need some preparation before making the Moser iteration. Set and
It is not difficult to check that and if , and for any ,
Let in (1.3), where and φ is defined in (2.14), , . Denote , , then we compute
Denote the first term and the second term on the left-hand side and on the right-hand side of (2.30) as and , , respectively. Now, we estimate them as follows:
where σ is a positive number defined later and
Set in view of (2.30) and the above equalities. If we firstly fix a small enough σ, then a small enough , then we can obtain
where C is a constant independent of M. Taking , then we deduce . Applying a simple covering argument, we achieve that . Finally, repeating the same argument, we derive that . As a result of the preparations, we can use the Moser iteration to prove . Let in (1.3), and we calculate
where C is a constant independent of M and k. If we set , then the above inequality implies
Thus, follows from the standard Moser iteration method.
Applying Theorem 1 in [15], we see that there exists a constant such that . If we rewrite as , then with . Employing Theorem 6 in [16], it is obvious that in Ω. □
3 Some corollaries and examples
In this section, we firstly consider when (C3) is true through analyzing and , then we give some concrete examples and corollaries.
Firstly, we analyze the effect of to :
Lemma 3.1 Suppose satisfies assumptions (A1)-(A5) and
(A6) There exist positive numbers , , A, B such that for any and for any .
Then as , where is defined in Theorem 1.2 and
Proof Repeating the argument similar to (2.26), we compute
□
Secondly, we analyze how affects . The proof is similar to the above, and we omit it.
Lemma 3.2 Suppose defined in Theorem 1.2 satisfies
(B6) There are positive numbers A, B and such that when .
Then we have as , where
Lemma 3.3 Suppose defined in Theorem 1.2 satisfies
(B7) There exist positive numbers A, B and such that if .
Then as , where
In the following, we can utilize Theorem 1.2 and Lemmas 3.1-3.3 to prove the following results about some concrete problems. The proof is trivial and we omit it.
Corollary 3.4 Assume , in problem (1.1), and assumptions (B1)-(B5), (C1) hold, defined in assumption (B5) satisfies
Then problem (1.1) possesses a nontrivial solution.
Proof Take and in Lemma 3.1, and we can deduce the conclusion. □
Example 3.1 Next, we consider the following equation:
Corollary 3.5 Suppose the parameters and , the functions with , and with , . Moreover,
Then problem (3.1) possesses a positive solution in ().
Example 3.2 Next, we consider the following equation:
Corollary 3.6 Suppose the parameters and , , the functions with , and with , . Moreover,
Then problem (3.2) possesses a positive solution in ().
Proof Letting and in Lemma 3.1, and combining Lemma 3.2, Lemma 3.3 and Theorem 1.3, we can derive the conclusion. □
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Acknowledgements
The project is supported by National Natural Science Foundation of China (No. 11271143, 10901060, 10971073), the Natural Science Foundation of Zhejiang Province (No. Y6110775, Y6110789).
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Authors’ contributions
ZY brought out the problem and gave the proof of the existence of a nontrivial solution. GD suggested that the generalized C-C principle could be applied to this problem and proved the non-trivial solution could be a positive solution. HY improved the regularity of the solution and checked all of the proof.
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Yang, Z., Geng, D. & Yan, H. A positive solution of a p-Laplace-like equation with critical growth. J Inequal Appl 2012, 218 (2012). https://doi.org/10.1186/1029-242X-2012-218
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DOI: https://doi.org/10.1186/1029-242X-2012-218