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Abstract and Applied Analysis

Volume 2012 (2012), Article ID 327572, 15 pages

http://dx.doi.org/10.1155/2012/327572

## On the Global Well-Posedness of the Viscous Two-Component Camassa-Holm System

School of Mathematics and Statistics, Changshu Institute of Technology, Changshu 215500, China

Received 3 January 2012; Accepted 15 February 2012

Academic Editor: Valery Covachev

Copyright © 2012 Xiuming Li. 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

We establish the local well-posedness for the viscous two-component Camassa-Holm system. Moreover, applying the energy identity, we obtain a global existence result for the system with .

#### 1. Introduction

We are interested in the global well-pose dness of the initial value problesm associated to the viscous version of the two-component Camassa-Holm shallow water system [1–3], namely, where the variable represents the horizontal velocity of the fluid or the radial stretch related to a prestressed state, and is related to the free surface elevation from equilibrium or scalar density with the boundary assumptions, and as . The parameter characterizes a linear underlying shear flow, so that (1.1) models wave-current interactions [4–6]. All of those are measured in dimensionless units.

Set , . Then for all , where denotes the spatial convolution. Let , (1.1) can be rewritten as a quasilinear nonlocal evolution system of the type

The system (1.1) without vorticity, that is, , was also rigorously justified by Constantin and Ivanov [1] to approximate the governing equations for shallow water waves. The multipeakon solutions of the same system have been constructed by Popivanov and Slavova [7], and the corresponding integral surface is partially ruled. Chen et al. [8] established a reciprocal transformation between the two-component Camassa-Holm system and the first negative flow of AKNS hierarchy. More recently, Holm et al. [9] proposed a modified two-component Camassa-Holm system which possesses singular solutions in component . Mathematical properties of (1.1) with have been also studied further in many works. For example, Escher et al. [10] investigated local well-posedness for the two-component Camassa-Holm system with initial data with and derived some precise blow-up scenarios for strong solutions to the system. Constantin and Ivanov [1] provided some conditions of wave breaking and small global solutions. Gui and Liu [11] recently obtained results of local well-posedness in the Besov spaces and wave breaking for certain initial profiles. More recently, Gui and Liu [12] studied global existence and wave-breaking criteria for the system (1.2) with initial data with .

In this paper, we consider the global well-posedness of the viscous two-component Camassa-Holm system

The goal of the present paper is to study global existence of solutions for (1.3) to better understand the properties of the two-component Camassa-Holm system (1.2). We state the main result as follows.

Theorem 1.1. *For , there exists a unique global solution of (1.3) such that
*

To proof Theorem 1.1, we will first establish global well-posedness of the following regularized two-component system with given:

that is, Due to the Duhamel’s principle, we can also rewrite (1.6) as an integral equation where, , , here and in what follows, we denote the Fourier (or inverse Fourier) transform of a function by (or ).

The remainder of the paper is organized as follows. In Section 2, we will set up and introduce some estimates for the nonlinear part of (1.5). In Section 3, we will get the local well-posedness of (1.3) by constructing the global well-posedness of (1.5) using the contraction argument and energy identity. The last section is devoted to the proof of Theorem 1.1.

#### 2. Preliminaries

We will list some lemmas needed in Section 3. First, we state the following lemma which consists of the crucial inequality involving the operator .

Lemma 2.1 (see [13]). *For ,
**
or more generally
**
for all .*

The next two lemmas are regarding the nonlinear part of (1.5).

Lemma 2.2. *Consider the following: *

*Proof. *Let us prove (2.3) firstly. Thanks to Lemma 2.1, the Sobolev embedding theorem , and the Hölder’s inequality, we have
which yields that
Similarly, we can get
and then
which implies (2.4).

Lemma 2.3. *Consider the following: *

*Proof. *We mainly prove (2.9). For this, we have that
Therefore, applying Lemma 2.2, we can easily obtain (2.9).

Similarly, we can also obtain (2.10).

Let us state the following lemma, which was obtained in [13] (up to a slight modification).

Lemma 2.4. *For any and , there exists such that
**
For any , , and , there exists such that
*

Next, we consider the nonlinear part of (1.7). When written as , , then we have that is,

First, we have the following basic estimates.

Lemma 2.5. *Consider the following: *

*Proof. *First, let us prove (2.16),
which implies
then we can get that
where we applied Lemma 2.1, Sobolev embedding theorem , and Hölder’s inequality. This proves (2.16).

Next, we prove (2.17),
which yields that
and this ends the proof of (2.17).

Then we have some estimates for and .

Lemma 2.6. *Consider the following: *

*Proof. *We mainly prove (2.24). We have that

Multiply to the second equation of (2.14) and integrate with respect to over . After integration by parts, we have
for any , which implies
By (2.25), together with (2.27), we have that
By Lemma 2.5, (2.24) follows.

Similarly, we can also obtain (2.23).

#### 3. Local Well-Posedness

Let , , and define the mapping by

Theorem 3.1. *For any , there exist and such that . In addition, is a contraction mapping.*

*Proof. *We first need to show that the map is well defined for some appropriate and . Let , then we have

Considering the terms in (3.3) one by one, from Lemma 2.2, the first term in (3.3) can be estimated as follows:
From Lemma 2.3, the second term in (3.3) can be estimated as follows:
which implies
From Lemma 2.6, the third term in (3.3) can be estimated as follows:
Combining (3.4)–(3.7), we have that

With appropriate values of , , and , we are able to have that , that is, is well defined.

Similar to the above argument, we can show that is a contraction mapping,
where can be chosen as with appropriate values of and .

Theorem 3.2. *For any and , there exist a and a unique solution of (1.5) such that
*

*Proof. *Theorem 3.2 is merely Theorem 3.1 with a standard uniqueness argument.

Theorem 3.3. *For any and , there exists a unique global solution of (1.5) such that
*

*Proof. *To prove Theorem 3.3, we need only to establish the *a priori* energy identity. Multiplying the first equation in (1.6) by and integrating by parts (with respect to over ), we have that
where we used the relation and . Multiplying the first equation in (1.6) by and integrating by parts (with respect to over ), we have that
From (3.12) and (3.13), we obtain the energy identity
which gives rise to the following inequality independent of and :
According to Theorem 3.2 and the energy inequality (3.15), one can extend the local solution to the global one by a standard contradiction argument, which completes the proof of Theorem 3.3.

From Theorem 3.3, one has the local well-posedness of system (1.3).

Theorem 3.4. *For , there exist a and a unique local solution of (1.3) such that
*

Similar to the proof of Theorem 4.1 in [12] (up to a slight modification), we may get the following.

Theorem 3.5. *Let , , and let be the corresponding solution to (1.3). Assume that is the maximal time of existence, then
*

#### 4. Proof of Theorem 1.1

*Proof of Theorem 1.1. *From Theorem 3.4, we have got the local solution of (1.3). On the other hand, according to the second equation of (1.3), we have
An application of Gronwall’s inequality yields
Similar to the proof of Theorem 3.3, we may get the energy identity
which implies
Due to the Sobolev embedding theorem and (4.4), we obtain that for any ,
Therefore, from Theorem 3.5, we deduce that the maximal existence time . This proves Theorem 1.1.

#### Acknowledgments

The work of the author is supported in part by the NSF of China under Grant no. 11001111 and no. 11141003. The author would like to thank the referees for constructive suggestions and comments.

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