#### Abstract

We study the initial boundary value problem of the general three-component Camassa-Holm shallow water system on an interval subject to inhomogeneous boundary conditions. First we prove a local in time existence theorem and present a weak-strong uniqueness result. Then, we establish a asymptotic stabilization of this system by a boundary feedback. Finally, we obtain a result of blow-up solution with certain initial data and boundary profiles.

#### 1. Introduction

It is well known that the Camassa-Holm equation has attracted much attention in the past decade. It is a nonlinear dispersive wave equation that models the propagation of unidirectional irrotational shallow water waves over a flat bed, as well as water waves moving over an underlying shear flow. It was first introduced by Fo kas and Fuchssteiner as a bi-Hamiltonian model. Cauchy problem and initial boundary value problem for Camassa-Holm equation have been studied extensively in a number of papers (see [1–15] and the references within).

Fu and Qu in [16] proposed a coupled Camassa-Holm equation, with , which has peakon solitons in the form of a superposition of multipeakons and may as well be integrable. They investigated the local well-posedness and blow-up solutions of system (1) by means of Kato’s semigroup approach to nonlinear hyperbolic evolution equation and obtained a criterion and condition on the initial data guaranteeing the development of singularities in finite time for strong solutions of system (1) by energy estimates. Recently the initial boundary value problem for the system (1) has been established in [17]; moreover, the local well-posedness and blow-up phenomena for the coupled Camassa-Holm equation were also established in [16, 18–32]. In [33], Tian and Xu obtained the compact and bounded absorbing set and the existence of the global attractor for viscous system (1) with the periodic boundary condition in by uniform prior estimate.

Recently, Fu and Qu in [34] introduced a general three-component Camassa-Holm equation as follows: where , , and . Equation (2) also has peakon solitons in the form of a superposition of multipeakons. Such system also conserves the -norm conservation law. Moreover, the well-posedness and blow-up phenomena for system (2) with peakons have been established in [35]. To our knowledge, the initial boundary value problem of (2) has not been studied yet. The first aim of this paper is to consider an initial boundary value problem of the following where .

Then, we will consider the asymptotic stabilization of (3) by means of a stationary feedback law acting on the inhomogeneous boundary condition. Following the step in [11], we convert the initial boundary value problem of (3) on the interval into an ODE system and two PDE systems. Then, we can consider the system (3) easily. Consequently, we obtain a local in time existence theorem, a weak-strong uniqueness result, asymptotic stabilization result on the interval, and a result of blow-up solution, respectively.

Our paper is organized as follows. In Section 2, we will consider an initial boundary value problem and the uniqueness of the solution to (3). By using the feedback law enjoyed by (3), the asymptotic stabilization on an interval is considered in Section 3. Finally, in Section 4, a result of blow-up solution with certain initial data and boundary profiles will be established.

First, we begin with a general remark that will be used many times later.

*Remark 1. *Let be a positive number and . Changing in, in, in, and in , and it will be more convenient for us to analysis the system, if we define the following sets

Let , then the operator can be expressed as
where . Now, let , , where is an auxiliary function which lifts the boundary values , , , , and defined by
where .

Setting , , and , we can further rewrite the system (3) as
where functions , and in are the boundary values and , and in are the initial datum.

Lemma 2. * We have and , . Moreover, we also have the bounds
*

*Proof. * can be expressed, respectively, as
Estimates (9) and (10) can be easily obtained from the above expressions.

#### 2. Initial Boundary Value Problem

First, we define what we mean by a weak solution to (8). Our test functions will be in the space:

*Definition 3. * When , the function is the weak solution to (8) if for all :

It is obvious that ; therefore, a weak solution to system (8) is also a solution to (8) in the distribution sense. And it is clear that a regular weak solution is a classical solution.

*Definition 4. *For , we consider the maximal solution satisfying

We consider that is the flow of . For , is defined on a set . Here is basically the entrance time in of the characteristic curve going through .

*Remark 5. *Obviously implies that .

In the following, we consider a partition of , which allows us to distinguish the different influence zones in .

*Definition 6. * Let such that and ,

Those points of the set are tangent to the boundary, which are precisely the singular points of and . It's obviously that the sets , and constitute a partition of . Furthermore, if , then , and if , then .

*Definition 7. * Here, we consider the case of data ; . We define the functions , and in the following way.

When , , , and , when ,
when ,
when ,

Lemma 8. * Since and satisfies (8), we immediately get that is the weak solution of (8) and . However, the functions , and satisfy the following estimates:
*

*Definition 9. * We can define operator and a domain for the system (8) by: ,
where

Obviously is convex and is compact with respect to the norm . We will endow with the norm . There exist positive numbers , and such that maps into itself.

Theorem 10. * There exists , and is a weak solution of (8) with and . Moreover, any such solution is in fact in . Furthermore, the existence time of a maximal solution , with
*

* Proof. * For , we consider , and in such that the sets and have only a finite number of connected components.

Let , where and
Now, if (see (21)), we have
For all , we have
We also define that . If , then from Lemmas 2 and 8, we derive that

Finally, to obtain , it is sufficient to show that
if we have chosen and ; it is easy to choose to satisfy the second inequality. For the above two inequalities, we just choose and sufficiently large and then close to 0. More precisely:

Maximizing the bound of , we can get minimum existence. Then, we get the result announced, where , .

Lemma 11. * The operator is continuous with respect to .*

*Proof. *The proof is omitted here; one can see a similar proof in [8, Proposition 2.4].

Now, we can apply Shauder's fixed point theorem to the operator , and we get the result that there exist fixed points such that , , and , so we know that there exists a wake solution of (9).

##### 2.1. Uniqueness

We will prove the weak-strong uniqueness of weak solution of (8) in the following.

Theorem 12. *Let be the weak solution of (7)-(8), then it is unique in .*

*Proof. *Define , , and , , , then we have
where , and is the unique weak solution of

Let
with , , and , where .

For , we have , and .

Then, we get the uniqueness result.

For , we have

For , we have

For , we have

Now since , , and bounded, we see that for some , , ,
since , and are bounded, we get that for some , , ,
We can obtain that

As a result, we get the result of the uniqueness by Gronwall's inequality when , , . Then, we complete the proof of the uniqueness results.

#### 3. Asymptotic Stabilization

##### 3.1. Preliminary Results

The equilibrium state that we want to stabilize is , , and . A natural idea is using Lyapunov indirection method to investigate whether the linearized system around the equilibrium state is stabilizable or not. Its stabilization would provide a local stabilization result on the nonlinear system. However, there is a difficulty in the stabilization problem. We have to prescribe , and we just need to make a continuous transition at , and that asymptotically converge in time. For convenience, the system (6)–(8) can rewrite in the following where