Advances in Mathematical Physics

Volume 2017 (2017), Article ID 1620417, 18 pages

https://doi.org/10.1155/2017/1620417

## Global Well-Posedness for a Class of Kirchhoff-Type Wave System

Department of Mathematics, Bohai University, Jinzhou, Liaoning 121013, China

Correspondence should be addressed to Xiaoli Jiang

Received 6 June 2017; Revised 9 August 2017; Accepted 8 November 2017; Published 7 December 2017

Academic Editor: Rehana Naz

Copyright Â© 2017 Xiaoli Jiang and Xiaofeng Wang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

In recent years, the small initial boundary value problem of the Kirchhoff-type wave system attracts many scholarsâ€™ attention. However, the big initial boundary value problem is also a topic of theoretical significance. In this paper, we devote oneself to the well-posedness of the Kirchhoff-type wave system under the big initial boundary conditions. Combining the potential well method with an improved convex method, we establish a criterion for the well-posedness of the system with nonlinear source and dissipative and viscoelastic terms. Based on the criteria, the energy of the system is divided into different levels. For the subcritical case, we prove that there exist the global solutions when the initial value belongs to the stable set, while the finite time blow-up occurs when the initial value belongs to the unstable set. For the supercritical case, we show that the corresponding solution blows up in a finite time if the initial value satisfies some given conditions.

#### 1. Introduction

This paper studies the initial boundary value problem for the following Kirchhoff-type wave system:where is a bounded domain in () with a smooth boundary , , , is a nonnegative function like , with , and : : , are given functions which will be specified later.

##### 1.1. Historical Research

Kirchhoff-type wave system with nonlinear source and dissipative and viscoelastic terms have various applications in the field of physics and mechanics, which is the model to describe the motion of deformable solids. A single Kirchhoff-type wave equation is proposed:and (6) has its roots for the small amplitude vibrations of a string when and , but the tension of the string can not be ignored (see, e.g., Carrier et al. [1]). While (6) is used to describe the dynamics of an elastic string with fading memory when , this equation shows that the dynamic equilibrium of the object depends on both the present state of deformation and the history of the deformation gradient. Pohozaev and Tesei [2] proved that the solution exists in time if the datum satisfy an analytic-type condition for the case . This result of the case was extended by Torrejon and Yong [3]; they obtained the existence of weakly asymptotic stable solution. Later, Munoz Rivera [4] showed the existence of global solutions for small initial value and the exponential decay of the total energy. Then Wu and Tsai [5] established the global existence and energy decay under the assumption . Recently, this decay estimate was improved for a weaker condition on in [6].

Problem (6) is simplified to the following format without viscoelastic term:and some results of (7) concerning global well-posedness have been established in [7â€“11] for the case of . The above problem without source and dissipative terms is called Kirchhoff-type equation when is not a constant function, which was first introduced by Kirchhoff [12]; it describes the nonlinear vibrations of an elastic string. up to now, there are numerous results related to global well-posedness, including global existence, decay result, and blow-up properties; we refer the reader to [13â€“17].

Most recently Xu and Yang considered the initial boundary value problem of the following equation in [18]; they gave a blow-up result under supercritical energy:

Wave system such as (1) and (2) goes back to Reed [19] who proposed a similar system, but it does not contain and the viscoelastic terms . Subsequently, concerning blow-up and nonexistence, results in wave systems were discussed. Agre and Rammaha [20] studied the following concrete system:in with initial and boundary conditions of Dirichlet type, where and satisfy (**A1**) and (**A2**). They obtained several results concerning global well-posedness of a weak solution and showed that any weak solution blows up in finite time at negative initial energy. Afterwards, Alives et al. made further efforts as regards (9) in [21]. They obtained the global existence, uniform decay rates, and blow-up of solutions in finite time by involving the Nehari manifold when the initial energy is nonnegative and less than the mountain pass level value. And this blow-up result was improved by Said-Houari [22] when the initial data are large enough. In [23], Rammaha and Sakuntasathien studied a more general case of (9) by degenerating damping terms. Several results on the existence of local and global solutions as well as uniqueness are obtained by considering the constraint on the parameters of the system. Furthermore, they proved that the weak solutions blow up in finite time whenever the initial energy is negative and the exponent of the source term is more dominant than the exponents of both damping terms. Moreover, many studies of the global well-posedness for wave systems with dissipative terms have been researched in [24â€“28].

Wave systems with viscoelastic terms and dissipative terms have not been fully studied. In [29] the following coupled nonlinear wave equations with dispersive terms, viscoelastic dissipative terms, and nonlinear weak damping terms are considered:A global nonexistence theorem for certain solutions with positive initial energy is proved. Reference [30] further considered a fourth-order wave system similar to (10). In that case, the energy increases exponentially when time goes to infinity and the initial data are large enough.

Recently [31] considered a system of two coupled wave equations with dispersive and strong dissipative terms under Dirichlet boundary conditions:where The global existence of weak solutions and uniform decay rates (exponential one) of the solution energy were established.

Many researches considered the initial boundary value problem with global existence and blow-up of solutions for the nonlinear wave equations as follows:where is a bounded domain in () with a smooth boundary . When the viscoelastic terms are absent in (13), [20] showed local and global existences of a weak solution that any weak solution blows up in finite time with negative initial energy as the same way used in [22]. Later, Said-Houari extended this blow-up result to positive initial energy. At the same time, Liu [32] studied the following Cauchy problem for the coupled system of nonlinear Klein-Gordon equations with damping terms:and the existence of standing wave with ground state was stated and a sharp criterion for global existence and blow-up of solutions when was established. The author introduced a family of potential wells and the invariant sets and vacuum isolating behavior of solutions for and , respectively. Furthermore, he proved the global existence and asymptotic behavior of solutions when the condition is . Finally, a blow-up result with arbitrarily positive initial energy was obtained.

Conversely, in the presence of the memory term (), some results related to the asymptotic behavior and blow-up of solutions of viscoelastic systems were discussed. For example, [33] studied problem (13) with and and obtained the fact that the decay rate of the energy function is exponential under suitable conditions on the functions , certain initial data in the stable set. On the contrary, when the initial data is in the unstable set, the solutions blow up in finite time under positive initial energy. For and , [26] established local and global existence as well as finite time blow-up (the initial energy ). The latter blow-up result has been improved by [29] by considering a class of positive initial data. On the other hand, Messaoudi and Tatar [34] considered the following similar wave equations without considering coupling coefficient of and :where the functions and satisfy the following assumptions: and for some constant and , the solution goes to zero with an exponential or polynomial rate which depending on the decay rate of the relaxation functions was obtained. This result was improved in [35] to weaker conditions on the relaxation functions and more general coupling functions.

Additionally, Liu and Wang [36] considered the following nonlinear hyperbolic systems with damping and source termsThe author defined potential well and the outer manifold of the potential well associated with system (17) and got the global existence in the case of and discussed the global nonexistence of solutions for problem (1)â€“(5) in the case of and on page 88 of [36]. In [37], (1)â€“(5) was considered with and without imposing the memory terms (). The rate of decay of the exponential or polynomial energy of the damping terms was obtained.

Recently, Wu [38] considered the initial boundary value problem for system (1)â€“(5) with . The assumptions for problem (1)â€“(5) are as follows:**(A1)**The nonlinear source terms , satisfyâ€‰where with .**(A2)** is a nonnegative function for satisfying **(A3)**The nonlinearity of satisfies**(A4)**For the relaxation functions and are of class and satisfy The solutions are global in time when the functions , , and , satisfy suitable conditions and certain initial data is in the stable set. The author established the rate of decay of solutions by a difference inequality given by Nakao [39] and intended to study the blow-up phenomena of problem (1)â€“(5). The blow-up of solutions when the energy is negative or subcritical case was proved by adopting and modifying the methods used in [29]. In this way, the above results in [38] allowed a bigger region for the blow-up results and improved the results of Messaoudi and Said-Houari [29]. More specifically, the decay result in [38] extends the one in [16, 37] to problem (1)â€“(5), where is not a constant function and the equations considered in [38] have more dissipations.

##### 1.2. Unsolved Problems

It is well known that in the absence of the nonlinear source term the damping term ensures global existence. In addition, without the dissipative term, the nonlinear source term causes finite time blow-up of solution. Moreover, the viscoelastic materials possess a capacity of storage and dissipation of mechanical energy; therefore, it is interesting to investigate the well-posedness of solution for the viscoelastic equation with dissipative term and nonlinear source term.

We can see that problem (1)â€“(5) contains system (9) (), systems (10), (13), and (15) (), system (11) (), and system (17) () as special cases. In fact, the viscoelastic terms change the frame of the equations comparing without those viscoelastic conditions, which makes the structure of the equations and solutions more complex and which also makes energy decay faster. So the classical methods can not be applied to investigate properties of solutions. Therefore, much less is known for (1)â€“(5) with viscoelastic terms. We can note that in all of the above studies except [38] only the global well-posedness of solutions was proved in a relatively rough variational framework, but the global existence and finite time blow-up for problem (1)â€“(5) at the other initial energy levels have not been discussed yet. The global existence and blow-up results in [38] are under the assumption of negative initial energy or . In other words, to our knowledge there are no results on global well-posedness of solutions to the initial boundary value problem for a couple of nonlinear wave equations with coupling coefficient of and , viscoelastic terms , and nonlinear weak dissipative terms , . It is natural to ask a question of how the solution behaves for problem (1)â€“(5), which is what we want to deal with in this paper. Moreover, regarding the initial energy level, the present paper is also a comprehensive study for low energy case and high energy situation. To our knowledge this is the first try to consider this problem. The most attractive one is that we attain a blow-up result with arbitrary positive initial energy for a wave system of Kirchhoff type.

By reviewing above known results and also [19â€“38], we will face the fact that the following unsolved problems arise naturally. Firstly, from [38] we know the global existence for the definitely positive energy, but we know less for the initial energy which may be negative. Secondly, for general initial energy, which means the initial energy is not necessarily definitely positive, what will happen for the solution when the initial energy or ?

We restricts our attention to considering the global existence and blow-up at two different initial energy levels. Since the initial energy level plays a crucial role in dealing with the well-posedness of problem (1)â€“(5), the two cases are, respectively, tackled with different tools. For the subcritical case , there have been many tools tackling the hyperbolic problem without viscoelastic terms in [16, 17]. We may refer the tools to deal with (1)â€“(5) with viscoelastic terms. By the well-known works [40â€“44], we see that the supercritical case is not easy to deal with. Filippo and Marco [45] made the initial attempt to consider the global well-posedness of hyperbolic problem at high initial energy level . However, they focused on particular source term , and our work is on the viscoelastic terms condition and the complex source term . Based on the general comparison principle in [9], we try to resolve the above open problems with variational methods. In this paper, we consider the initial boundary value problem for system (10) with and the nonlinear source terms, coupling coefficient , the nonlinearity of , and the relaxation functions and satisfying the assumptions (**A1**)â€“(**A4**), respectively. In addition, we consider nonlinear damping terms of the form and as in the first equation and in the second equation of (10), respectively.

##### 1.3. The Main Results and Organization of the Paper

In this paper, we mainly discuss the following problems.(1)Case : different from the method applied in [38], we introduce a family of potential wells to obtain the results: invariant sets, global existence, and finite time blow-up.(2)Case : we obtain the finite time blow-up of solutions for problem (1)â€“(5) whose initial data have arbitrarily high initial energy.

We can summarize our main conclusions in Table 1 and use the question mark â€ś?â€ť to indicate the open problem.