Research Article Traveling Wave Solutions of a Generalized ...traveling wave system ( ) to get the...
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Research ArticleTraveling Wave Solutions of a Generalized Camassa-HolmEquation: A Dynamical System Approach
Lina Zhang and Tao Song
Department of Mathematics, Huzhou University, Huzhou, Zhejiang 313000, China
Correspondence should be addressed to Lina Zhang; [email protected]
Received 1 August 2015; Accepted 14 September 2015
Academic Editor: Maria Gandarias
Copyright Β© 2015 L. Zhang and T. Song. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.
We investigate a generalized Camassa-Holm equation πΆ(3, 2, 2): π’π‘+ ππ’π₯+ πΎ1π’π₯π₯π‘
+ πΎ2(π’3)π₯+ πΎ3π’π₯(π’2)π₯π₯
+ πΎ3π’(π’2)π₯π₯π₯
= 0. Weshow that the πΆ(3, 2, 2) equation can be reduced to a planar polynomial differential system by transformation of variables. We treatthe planar polynomial differential system by the dynamical systems theory and present a phase space analysis of their singularpoints. Two singular straight lines are found in the associated topological vector field. Moreover, the peakon, peakon-like, cuspon,smooth soliton solutions of the generalized Camassa-Holm equation under inhomogeneous boundary condition are obtained.Theparametric conditions of existence of the single peak soliton solutions are given by using the phase portrait analytical technique.Asymptotic analysis and numerical simulations are provided for single peak soliton, kink wave, and kink compacton solutions ofthe πΆ(3, 2, 2) equation.
1. Introduction
Mathematical modeling of dynamical systems processing in agreat variety of natural phenomena usually leads to nonlinearpartial differential equations (PDEs).There is a special class ofsolutions for nonlinear PDEs that are of considerable interest,namely, the traveling wave solutions. Such a wave may belocalized or periodic, which propagates at constant speedwithout changing its shape.
Many powerful methods have been presented for findingthe traveling wave solutions, such as the BaΜcklund trans-formation [1], tanh-coth method [2], bilinear method [3],symbolic computation method [4], and Lie group analysismethod [5]. Furthermore, a great amount of works focusedon various extensions and applications of the methods inorder to simplify the calculation procedure. The basic ideaof those methods is that, by introducing different types ofAnsatz, the original PDEs can be transformed into a set ofalgebraic equations. Balancing the same order of the Ansatzthen yields explicit expressions for the PDE waves. However,not all of the special forms for the PDE waves can be derivedby those methods. In order to obtain all possible forms ofthe PDEwaves and analyze qualitative behaviors of solutions,
the bifurcation theory plays a very important role in studyingthe evolution of wave patterns with variation of parameters[6β9].
To study the traveling wave solutions of a nonlinear PDE
Ξ¦(π’, π’π‘, π’π₯, π’π₯π₯, π’π₯π‘, π’π‘π‘, . . .) = 0, (1)
let π = π₯ β ππ‘ and π’(π₯, π‘) = π(π), where π is the wave speed.Substituting them into (1) leads the PDE to the followingordinary differential equation:
Ξ¦1(π, π, π, . . .) = 0. (2)
Here, we consider the case of (2) which can be reduced to thefollowing planar dynamical system:
ππ
ππ= π= π¦,
ππ¦
ππ= πΉ (π, π¦) ,
(3)
through integrals. Equation (3) is called the traveling wavesystem of the nonlinear PDE (1). So, we just study the
Hindawi Publishing CorporationMathematical Problems in EngineeringVolume 2015, Article ID 610979, 19 pageshttp://dx.doi.org/10.1155/2015/610979
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2 Mathematical Problems in Engineering
traveling wave system (3) to get the traveling wave solutionsof the nonlinear PDE (1).
Let us begin with some well-known nonlinear waveequations. The first one is the Camassa-Holm (CH) equation[10]
π’π‘β π’π‘π₯π₯
+ 3π’π’π₯= 2π’π₯π’π₯π₯
+ π’π’π₯π₯π₯
(4)
arising as a model for nonlinear waves in cylindrical axiallysymmetric hyperelastic rods, with π’(π₯, π‘) representing theradial stretch relative to a prestressed state where Camassaand Holm showed that (4) has a peakon of the form π’(π₯, π‘) =ππβ|π₯βππ‘|. Among the nonanalytic entities, the peakon, a
soliton with a finite discontinuity in gradient at its crest, isperhaps the weakest nonanalyticity observable by the eye [11].
To understand the role of nonlinear dispersion in theformation of patters in liquid drop, Rosenau and Hyman [12]introduced and studied a family of fully nonlinear dispersionKorteweg-de Vries equations
π’π‘+ (π’π)π₯+ (π’π)π₯π₯π₯
= 0. (5)
This equation, denoted by πΎ(π, π), owns the property that,for certainπ and π, its solitary wave solutions have compactsupport [12]. That is, they identically vanish outside a finitecore region. For instance, the πΎ(2, 2) equation admits thefollowing compacton solution:
π’ (π₯, π‘) =
{{
{{
{
4π
3cos2 (π₯ β ππ‘
4) , |π₯ β ππ‘| β€ 2π,
0, otherwise.(6)
The Camassa-Holm equation, the πΎ(2, 2) equation, andalmost all integrable dispersive equations have the sameclass of traveling wave systems which can be written in thefollowing form [13]:
ππ
ππ= π¦ =
1
π·2 (π)
ππ»
ππ¦,
ππ¦
ππ= β
1
π·2 (π)
ππ»
ππ= β
π·(π) π¦2+ π (π)
π·2 (π),
(7)
where π» = π»(π, π¦) = (1/2)π¦2π·2(π) + β«π·(π)π(π)ππ is thefirst integral. It is easy to see that (4) is actually a special case of(3) with πΉ(π, π¦) = β(1/π·2(π))(ππ»/ππ). If there is a functionπ = π
π such that π·(π
π ) = 0, then π = π
π is a vertical straight
line solution of the system
ππ
ππ= π¦π· (π) ,
ππ¦
ππ= βπ·(π) π¦2β π (π) ,
(8)
where ππ = π·(π)ππ for π ΜΈ= ππ . The two systems have
the same topological phase portraits except for the verticalstraight line π = π
π and the directions in time. Consequently,
we can obtain bifurcation and smooth solutions of thenonlinear PDE (1) through studying the system (8), if the
corresponding orbits are bounded and do not intersect withthe vertical straight line π = π
π . However, the orbits,
which do intersect with the vertical straight line π = ππ or
are unbounded but can approach the vertical straight line,correspond to the non-smooth singular traveling waves. Itis worth of pointing out that traveling waves sometimes losetheir smoothness during the propagation due to the existenceof singular curves within the solution surfaces of the waveequation.
Most of these works are concentrated on the nonlinearwave equationswith only a singular straight line [6β9]. But tillnow there have been few works on the integrable nonlinearequations with two singular straight lines or other types ofsingular curves [13β15].
In 2004, Tian and Yin [16] introduced the following fullynonlinear generalized Camassa-Holm equation πΆ(π, π, π):
π’π‘+ ππ’π₯+ πΎ1π’π₯π₯π‘
+ πΎ2(π’π)π₯+ πΎ3π’π₯(π’π)π₯π₯
+ πΎ4π’ (π’π)π₯π₯π₯
= 0,
(9)
where π, πΎ1, πΎ2, πΎ3, and πΎ
4are arbitrary real constants and π,
π, and π are positive integers. By using four direct ansatzs,they obtained kink compacton solutions, nonsymmetry com-pacton solutions, and solitary wave solutions for theπΆ(2, 1, 1)and πΆ(3, 2, 2) equations.
Generally, it is not an easy task to obtain a uniformanalytic first integral of the corresponding traveling wavesystem of (9). In this paper, we consider the cases π = 3,π = π = 2, and πΎ
3= πΎ4. Then, (9) reduces to the πΆ(3, 2, 2)
equation
π’π‘+ ππ’π₯+ πΎ1π’π₯π₯π‘
+ πΎ2(π’3)π₯+ πΎ3π’π₯(π’2)π₯π₯
+ πΎ3π’ (π’2)π₯π₯π₯
= 0.
(10)
Actually, we have already considered a special πΆ(3, 2, 2)equation in [17], namely, πΎ
1= β1, πΎ
2= β3, and πΎ
3= β1,
where the bifurcation of peakons are obtained by applyingthe qualitative theory of dynamical systems. In this work,a more general πΆ(3, 2, 2) equation (10) is studied. Differentbifurcation curves are derived to divide the parameter spaceinto different regions associated with different types of phasetrajectories. Meanwhile, it is interesting to point out that thecorresponding traveling wave system of (10) has two singularstraight lines compared with (4), which therefore gives rise toa variety of nonanalytic traveling wave solutions, for instance,peakons, cuspons, compactons, kinks, and kink-compactons.
This paper is organized as follows. In Section 2,we analyzethe bifurcation sets and phase portraits of correspondingtraveling wave system. In Section 3, we classify single peaksoliton solutions of (10) and give the parametric representa-tions of the smooth soliton solutions, peakon-like solutions,cuspon solutions, and peakon solutions. In Section 4, weobtain the kink wave and kink compacton solutions of (10).A short conclusion is given in Section 5.
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Mathematical Problems in Engineering 3
2. Bifurcation Sets and Phase Portraits
In this section, we shall study all possible bifurcations andphase portraits of the vector fields defined by (10) in theparameter space. To achieve such a goal, let π’(π₯, π‘) = π(π)with π = π₯ β ππ‘ be the solution of (10), then it follows that
(π β π) πβ πΎ1ππ
+ πΎ2(π3)
+ πΎ3π(π2)
+ πΎ3π (π2)
= 0,
(11)
where π = ππ, π = π
ππ, and π = π
πππ. Integrating (11) once
and setting the integration constant as π, we have
(π β π) π β πΎ1ππ+ πΎ2π3+ πΎ3π (π2)
= βπ. (12)
Clearly, (12) is equivalent to the planar system
ππ
ππ= π¦,
ππ¦
ππ=π½π3+ ππ¦2+ ππ + π
π β π2,
(13)
where π = ππΎ1/2πΎ3, π½ = πΎ
2/2πΎ3, π = π/2πΎ
3, and π = (πβπ)/2πΎ
3
(πΎ3
ΜΈ= 0). System (13) has the first integral
π»(π, π¦) =π½
4π4+1
2ππ2+ ππ +
1
2π2π¦2β1
2ππ¦2= β. (14)
Obviously, for π > 0, system (13) is a singular travelingwave system [14]. Such a system may possess complicateddynamical behavior and thus generate many new travelingwave solutions. Hence, we assume π > 0 in the rest of thispaper (π = 2, > 0). The phase portraits defined by thevector fields of system (13) determine all possible travelingwave solutions of (10). However, it is not convenient todirectly investigate (13) since there exist two singular straightlines π = and π = β on the right-hand side of the secondequation of (13). To avoid the singular lines temporarily, wedefine a new independent variable π by setting (ππ/ππ) =2βπ2; then, system (13) is changed to a Hamiltonian system,
written asππ
ππ= (2β π2) π¦,
ππ¦
ππ= ππ¦2+ π½π3+ ππ + π.
(15)
System (15) has the same topological phase portraits as system(13) except for the singular lines π = and π = β.
We now investigate the bifurcation of phase portraits ofthe system (15). Denote that
π (π) = π½π3+ ππ + π. (16)
Let π(ππ, π¦π) be the coefficient matrix of the linearized
system of (15) at the equilibrium point (ππ, π¦π); then,
π(ππ, π¦π) = (
β2πππ¦ππ¦2
π+ π(ππ)
2β π2
π2πππ¦π
) , (17)
and at this equilibrium point, we have
π½ (ππ, π¦π) = detπ(π
π, π¦π)
= (π2
πβ 2) π(ππ) β (3π
2
π+ 2) π¦2
π.
(18)
By the theory of planar dynamical systems, for an equilibriumpoint of a Hamiltonian system, if π½ < 0, then it is a saddlepoint, a center point if π½ > 0, and a degenerate equilibriumpoint if π½ = 0.
From the above analysis, we can obtain the bifurcationcurves and phase portraits under different parameter condi-tions.
Let
π½1(π) = β
4π3
27π2,
π½2(π) =
π β π
3,
π½3(π) =
βπ β π
3.
(19)
Clearly, for π½ > π½1(π), the function π(π) = 0 has three
real roots π1, π2, and π
3(π1
> π2
> π3); that is, system
(15) has three equilibrium points πΈπ(ππ, 0), π = 1, 2, 3 on
the π-axis. When π½ < π½3(π), (15) has two equilibrium
points π1,2(, Β±π
1) on the straight line π = βπ, where π
1=
β(βπ β (π + π½2))/. When π½ < π½2(π), system (15) has two
equilibrium points π3,4(β, Β±π
2) on the straight line π = β,
where π2= β(π β (π + π½2))/. Notice that on making the
transformation π β βπ, π β βπ, π β βπ, system (15)is invariant. This means that, for π < 0, the phase portraitsof (15) are just the reflections of the corresponding phaseportraits of (15) in the case π > 0 with respect to the π¦-axis.Thus, we only need to consider the case π β₯ 0. To knowthe dynamical behavior of the orbits of system (15), we willdiscuss two cases: π > 0 and π < 0.
2.1. Case I: π > 0
Lemma 1. Suppose that π > 0. Denote β+= π»(, Β±π
1), ββ=
π»(β, Β±π2), and β
π= π»(π
π, 0), π = 1, 2, 3.
(1) For π > 0 and π½1(π) < π½ < π½
3(π), there exists one
and only one curve π½ = π½4(π) on the (π, π½)-plane on which
β+
= β2; for π > 0 and π½
1(π) < π½ < π½
2(π), there exists one
and only one curve π½ = π½5(π) on the (π, π½)-plane on which
ββ
= β2or ββ= β3.Moreover, the curvesπ½ = π½
1(π),π½ = π½
2(π),
π½ = π½4(π), and π½ = π½
5(π) are tangent at the point (π
1π , π½1π ).
The curve π½ = π½3(π) intersects with the curves π½ = π½
1(π),
π½ = π½4(π), and π½ = π½
5(π) at the points (π
2π , π½2π ), (π3π , π½3π ),
and (π4π , π½4π ) (0 < π
4π < π3π < π2π < π1π ), respectively.
(2) For π = 0, there exists a bifurcation point π΄(0, β2π/2)on (π, π½)-plane on which β+
= ββ
= β2when π½ = β2π/2,
β+
= ββ
< β2when π½ < β2π/2, and β+
= ββ
> β2when
β2π/2< π½ < βπ/
2.
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4 Mathematical Problems in Engineering
π½2(π)
(π1s, π½1s)
π½3(π)
π½4(π)π½5(π)
π½
β2
β2
β4
β4
β6
β8
β10
β12
β14
π½1(π)
π2 4
Figure 1: The bifurcation curves in the (π, π½)-parameter plane forπ > 0.
According to the above analysis and Lemma 1, we obtainthe following proposition on the bifurcation curves of thephase portraits of system (15) for π > 0.
Proposition 2. When π > 0, for system (15), in (π, π½)-parameter plane, there exist five bifurcation curves (see Fig-ure 1):
π½ = π½1(π) = β
4π3
27π2,
π½ = π½2(π) =
π β π
3,
π½ = π½3(π) =
βπ β π
3,
π½ = π½4(π) (|π| β€ π
3π ) ,
π½ = π½5(π) .
(20)
These five curves divide the right-half (π, π½)-parameter planeinto thirty-one regions as follows:
π΄1: {(π, π½) | π1s < π < π, π½ = π½2(π)},
π΄2: {(π, π½) | π > π1s, π½5(π) < π½ < π½2(π)},
π΄3: {(π, b) | π > π1s, π½ = π½5(π)},
π΄4: {(π, π½) | π > π1s, π½1(π) < π½ < π½5(π)},
π΄5: {(π, π½) | π > π1s, π½ = π½1(π)},
π΄6: {(π, π½) | π > π2s, π½3(π) < π½ < π½1(π)},
π΄7: {(π, π½) | π < π2s, π½ = π½3(π)},
π΄8: {(π, π½) | π > 0, π½ < max{π½1(π), π½3(π)}},
π΄9: (π, π½) = (π2s, π½2s),
π΄10: {(π, π½) | 0 < π < π2s, π½ = π½1(π)},
π΄11: {(π, π½) | π < π2s, π½1(π) < π½ < min{π½3(π),
π½4(π)}},
π΄12: {(π, π½) | π < π3s, π½ = π½4(π)},
π΄13: {(π, π½) | π > 0, π½4(π) < π½ < π½5(π)},
π΄14: {(π, π½) | π < π4s, π½ = π½5(π)},
π΄15: {(π, π½) | π > 0, π½5(π) < π½ < π½3(π)},
π΄16: {(π, π½) | π = 0, π½ < β2π/2},
π΄17: (π, π½) = (0, β2π/2),
π΄18: {(π, π½) | π = 0, β2π/2 < π½ < βπ/2},
π΄19: (π, π½) = (0, βπ/2),
π΄20: {(π, π½) | 0 < π < π4s, π½ = π½3(π)},
π΄21: (π, π½) = (π4s, π½4s),
π΄22: {(π, π½) | π4s < π < π2s, π½ = π½3(π)},
π΄23: {(π, π½) | π4s < π < π1s, max{π½1(π), π½3(π)} <
π½ < π½5(π)},π΄24: {(π, π½) | π
s4 < π < π1s, π½ = π½5(π)},
π΄25: {(π, π½) | π4s < π < π1s, max{π½3(π), π½5(π)} <
π½ < π½2(π)},π΄26: {(π, π½) | 0 < π < π1s, π½ = π½2(d)},
π΄27: (π, π½) = (π1s, π½1s),
π΄28: {(π, π½) | 0 β€ π < π, π½ > π½2(π)},
π΄29: {(π, π½) | π β R, π½ > max{0, π½2(π)}},
π΄30: {(π, π½) | π > π, π½ = π½2(π)},
π΄31: {(π, π½) | π > π, 0 < π½ < π½2(π)}.
In this case, the phase portraits of system (15) can beshown in Figure 2.
2.2. Case II: π < 0. In this case, we have the following.
Proposition 3. When π < 0, for system (15), in (π, π½)-parameter plane, there exist four parametric bifurcation curves(see Figure 3):
π½ = π½1(π) = β
4π3
27π2,
π½ = π½2(π) =
π β π
3,
π½ = π½3(π) =
βπ β π
3, π = 0.
(21)
These four curves divide the right-half (π, π½)-parameter planeinto twenty-two regions:
π΅1: {(π, π½) | π1s < π < π, π½ = π½3(π)},
π΅2: {(π, π½) | π > π1s, max{0, π½3(π)} < π½ < π½1(π)},
π΅3: {(π, π½) | π > π1s, π½ = π½1(π)},
π΅4: {(π, π½) | π > π2s, π½1(π) < π½ < π½2(π)},
π΅5: (π, π½) = (π2s, π½2s),
π΅6: {(π, π½) | π > π2s, π½ = π½2(π)},
π΅7: {(π, π½) | π > 0, π½ > max{π½1(π), π½2(π)}},
π΅8: {(π, π½) | 0 < π < π2s, π½ = π½1(π)},
π΅9: {(π, π½) | 0 < π < π2s, π½2(π) < π½ < π½1(π)},
π΅10: {(π, π½) | π = 0, π½ > βπ/2},
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Mathematical Problems in Engineering 5
0 1 2 3
0
2
4
0 2 4
0
2
4
0 2 4
0
2
4
0 2 4
0
2
4
0 2 4
0
2
4
0 1
0
2
4
0.0 0.5 1.0
0
2
4
0.0 0.5 1.0
0
2
4
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0
0
2
4
6
0.0 0.5 1.0
0
2
4
0.0 0.5 1.0
0
2
4
β3
β3
β2 β2 β2β1β4
β4
β2 β2
β2
β1
β1
β4β2β4
β4 β4
β2 β2 β2
β4
β2
β4
β2
β4
β2
β1.5 β1.0 β0.5
β1.0 β0.5 β1.0 β0.5 β1.0 β0.5
β1.5 β1.0 β0.5 β1.5 β1.0 β0.5
β6
β2
β4
β2
β4
β2
β4
β2
β4
β2
β4
πππ
π π π
πππ
π π π
yy
y
y yy
yyy
y
y y
(1) (π, π½) β A1
(4) (π, π½) β A4
(7) (π, π½) β A7 (8) (π, π½) β A8 (9) (π, π½) β A9
(5) (π, π½) β A5
(2) (π, π½) β A2 (3) (π, π½) β A3
(6) (π, π½) β A6
(10) (π, π½) β A10 (11) (π, π½) β A11 (12) (π, π½) β A12
Figure 2: Continued.
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6 Mathematical Problems in Engineering
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0
0
2
4
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0
0
1
2
0.0 0.5 1.0
0
1
2
0.0 0.5 1.0
0
1
2
0.0 0.5 1.0
0
1
2
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0
0
1
2
3
β3
β2
β1
β3
β2
β1
β2
β1
β2
β1
β2
β3
β1
β2
β3
β1
β2
β3
β1
β2
β3
β1
β2
β1
β2
β1
β3
β2
β1
β1.0 β0.5
β1.0 β0.5
β1.0 β0.5
β1.0 β0.5
β1.0 β0.5
β1.0β1.5 β0.5 β1.0β1.5 β0.5
β1.0 β0.5
β1.0 β0.5 β1.0 β0.5
β1.0 β0.5 β1.0 β0.5
β2
β4
y
πππ
π π π
πππ
π ππ
yy
y yy
yy
y
yy
y
(13) (π, π½) β A13
(16) (π, π½) β A16
(19) (π, π½) β A19 (20) (π, π½) β A20
(23) (π, π½) β A23 (24) (π, π½) β A24
(21) (π, π½) β A21
(22) (π, π½) β A22
(17) (π, π½) β A17 (18) (π, π½) β A18
(14) (π, π½) β A14 (15) (π, π½) β A15
Figure 2: Continued.
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Mathematical Problems in Engineering 7
0.0 0.5 1.0 1.5
0
1
2
3
0.0 0.5 1.0 1.5
0
1
2
3
0 1 2
0
1
2
3
0 1 2
0
1
2
3
0.0 0.5 1.0 1.5
0
1
2
3
0 1 2
0
2
4
0 1 2
0
2
4
β2
β3
β1
β2
β3
β1
β2
β3
β2
β4
β1
β2
β3
β1
β2
β3
β1
β2 β1
β2β3 β1
β2
β2
β3
β4
β1
β2 β1
β1.0β1.5 β0.5 β1.0β1.5 β0.5
β1.0β1.5 β0.5
y
yyy
y y y
π
πππ
π π π
(25) (π, π½) β A25
(28) (π, π½) β A28 (29) (π, π½) β A29
(31) (π, π½) β A31
(30) (π, π½) β A30
(26) (π, π½) β A26 (27) (π, π½) β A27
Figure 2: The bifurcation of phase portraits of system (15) when π > 0 and π β₯ 0.
π΅11: (π, π½) = (0, βπ/2),
π΅12: {(π, π½) | 0 < π < π2s, π½ = π½2(π)},
π΅13: {(π, π½) | 0 < π < π1s, π½3(π) < π½ < min{π½1(π),
π½2(π)}},
π΅14: {(π, π½) | π4s < π < π1s, π½ = π½1(π)},
π΅15: (π, π½) = (π1s, π½1s),
π΅16: {(π, π½) | 0 < π < π1s, π½ = π½3(π)},
π΅17: {(π, π½) | 0 < π < π, π½ < π½3(π)},
π΅18: {(π, π½) | π = 0, π½ = βπ/2},
π΅19: {(π, π½) | π = 0, π½ < 0},
π΅20: {(π, π½) | 0 < π < π, π½ < min{0, π½3(π)}},
π΅21: {(π, π½) | π > π, π½ = π½3(π)},
π΅22: {(π, π½) | π > π, π½3(π) < π½ < 0}.
Based on Proposition 3, we obtain the phase portraits ofsystem (15) which are shown in Figure 4.
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8 Mathematical Problems in Engineering
2 4 6
5
10
15
π½2(π)
(π1s, π½1s)
(π2s, π½2s)
π½3(π)
π½
β2β4β6
π½1(π)
π
Figure 3: The bifurcation curves in the (π, π½)-parameter plane forπ < 0.
3. Single Peak Soliton Solutions
In this section, we study classification of single peak solitonsolutions of (10) by using the phase portraits given inSection 2. LetπΆπ(Ξ©) denote the set of all π times continuouslydifferentiable functions on the open setΞ©. πΏπloc(R) refer to theset of all functions whose restriction on any compact subsetis πΏπ integrable.π»1loc(R) stands forπ»
1
loc(R) = {π β πΏ2
loc(R) |
πβ πΏ2
loc(R)}.To study single peak soliton solutions, we impose the
boundary condition
limπβΒ±β
π = π΄, (22)
where π΄ is a constant. In fact, the constant π΄ is equal to thehorizontal coordinate of saddle point πΈ(π
π, 0). Substituting
the boundary condition (22) into (14) generates the followingconstant:
β = π΄(π +π΄π
2+π΄3π½
4) . (23)
So the ODE (14) becomes
(π)2
=
(π β π΄)2
(π½π2+ 2π΄π½π + 3π΄
2π½ + 2π)
2 (2 β π2). (24)
If π½(π΄2π½ + π) β€ 0, then (24) reduces to
(π)2
=π½ (π β π΄)
2
(π β π΅1) (π β π΅
2)
2 (2 β π2), (25)
where
π΅1= βπ΄ β
ββ2π½ (π΄2π½ + π)
π½,
π΅2= βπ΄ +
ββ2π½ (π΄2π½ + π)
π½.
(26)
From (26) we know that π΅1> π΅2if π½ < 0 and π΅
1< π΅2if
π½ > 0.
Definition 4. A functionπ(π) is said to be a single peak solitonsolution for the πΆ(3, 2, 2) equation (10) if π(π) satisfies thefollowing conditions:
(C1) π(π) is continuous on R and has a unique peakpoint π
0, where π(π) attains its global maximum or
minimum value.
(C2) π(π) β πΆ3(R β {π
0}) satisfies (24) on R β {π
0}.
(C3) π(π) satisfies the boundary condition (22).
Definition 5. A wave function π is called smooth solitonsolution if π is smooth locally on either side of π
0and
limπβπ0
π(π) = lim
πβπ0π(π) = 0.
Definition 6. A wave function π is called peakon if π issmooth locally on either side of π
0and lim
πβπ0π(π) =
βlimπβπ0
π(π) = π, π ΜΈ= 0, π ΜΈ= Β±β.
Definition 7. Awave functionπ is called cuspon ifπ is smoothlocally on either side of π
0and lim
πβπ0π(π) = βlim
πβπ0π(π) =
Β±β.
Without any loss of generality, we choose the peak pointπ0as vanishing, π
0= 0.
Theorem 8. Assume that π’(π₯, π‘) = π(π) = π(π₯ β ππ‘) is a singlepeak soliton solution of the πΆ(3, 2, 2) equation (10) at the peakpoint π
0= 0. Then, we have the following:
(i) If π½(π΄2π½ + π) > 0, then π(0) = or π(0) = β.
(ii) If π½(π΄2π½ + π) β€ 0, then π(0) = or π(0) = β orπ(0) = π΅
1or π(0) = π΅
2.
Proof. If π(0) ΜΈ= Β±, then π(π) ΜΈ= Β± for any π β R sinceπ(π) β πΆ
3(R β {0}). Differentiating both sides of (24) yields
π β πΆβ(R).
(i) When π½(π΄2π½ + π) > 0, if π(0) ΜΈ= and π(0) ΜΈ= β, thenπ β πΆ
β(R). By the definition of single peak soliton we have
π(0) = 0. However, by (24) we must have π(0) = π΄, which
contradicts the fact that 0 is the unique peak point.(ii) When π½(π΄2π½ + π) β€ 0, if π(0) ΜΈ= and π(0) ΜΈ= β,
by (24) we know π(0) exists and π(0) = 0 since 0 is a peakpoint. Thus, we obtain π(0) = π΅
1or π(0) = π΅
2from (25),
since π(0) = π΄ contradicts the fact that 0 is the unique peakpoint.
Now we give the following theorem on the classificationof single peak solitons of (10).The idea is inspired by the studyof the traveling waves of Camassa-Holm equation [18, 19].
Theorem 9. Assume that π’(π₯, π‘) = π(π₯ β ππ‘) is a single peaksoliton solution of the πΆ(3, 2, 2) equation (10) at the peak pointπ0= 0. Then, we have the following solution classification:(i) If |π(0)| ΜΈ= , then π(π) β πΆβ(R), and π is a smooth
soliton solution.
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Mathematical Problems in Engineering 9
0 2
0
2
4
0 2
0
2
4
0 1 2
0
2
4
0 1 2
0
2
4
0.0 0.5 1.0 1.5
0
2
4
0 1
0
2
4
6
0.0 0.5 1.0 1.5
0
2
4
0.0 0.5 1.0
0
1
2
3
0.0 0.5 1.0 1.5
0
1
2
3
0.0 0.5 1.0
0
1
2
0.0 0.5 1.0 1.5
0
1
2
0.0 0.5 1.0 1.5
0
1
2
3
β3 β1β4
β4
β2
β4
β2
β4
β2
β4
β2β4
β6
β2
β4
β2
β4
β2
β2 β4 β4β2 β2
β3
β1
β2
β1
β2
β1
β2
β3
β1
β2
β3
β1
β2
β1β2 β1β2
π
π
π
π ππ
π π
π π
π π
y
y
y
yy
y
y y
y y
y y
β1.5 β1.0 β0.5
β1.5β2.0 β1.0 β0.5
β1.5 β1.0 β0.5 β1.5 β1.0 β0.5β1.0 β0.5
β1.5 β1.0 β0.5β1.0 β0.5
(10) (π, π½) β B10 (11) (π, π½) β B11 (12) (π, π½) β B12
(1) (π, π½) β B1
(4) (π, π½) β B4
(7) (π, π½) β B7 (8) (π, π½) β B8 (9) (π, π½) β B9
(5) (π, π½) β B5 (6) (π, π½) β B6
(2) (π, π½) β B2 (3) (π, π½) β B3
Figure 4: Continued.
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10 Mathematical Problems in Engineering
0.0 0.5 1.0 1.5
0
1
2
3
0 1
0
1
2
3
0 1 2
0
2
4
0.0 0.5 1.0 1.5
0
1
2
3
0 1 2
0
1
2
3
0.0 0.5 1.0 1.5
0
1
2
0.0 0.5 1.0 1.5
0
1
2
3
0 1 2
0
1
2
3
0.0 0.5 1.0 1.5
0
2
4
0.0 0.5 1.0 1.5
0
2
4
6
β4
β2
β4
β2
β4
β6
β2
β3 β1β2
β3 β1β2
β1β2
β1β2
β3
β1
β2
β3
β1
β2
β3
β1
β2
β3
β1
β2
β3
β1
β2
β1
β2
β3
β1
β2
π π π
πππ
π ππ
π
y y y
yy
y
y yy
y
β1.5 β1.0 β0.5
β1.5β2.0 β1.0 β0.5
β1.5 β1.0 β0.5
β1.5 β1.0 β0.5
β1.5 β1.0 β0.5
β1.5 β1.0 β0.5
(13) (π, π½) β B13 (14) (π, π½) β B14 (15) (π, π½) β B15
(16) (π, π½) β B16 (17) (π, π½) β B17 (18) (π, π½) β B18
(22) (π, π½) β B22
(20) (π, π½) β B20 (21) (π, π½) β B21(19) (π, π½) β B19
Figure 4: The bifurcation of phase portraits of system (15) when π < 0 and π β₯ 0.
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Mathematical Problems in Engineering 11
(ii) If π(0) = ΜΈ= π΅1, then π is a cuspon solution and π has
the following asymptotic behavior:
π (π) β = π1
π
2/3
+ π(π
4/3
) , π β 0,
π(π) =
2
3π1
π
β1/3 sgn (π) + π (π
1/3
) ,
π β 0,
(27)
where π1= Β±(9|π½
2+ 2π΄π½ + 3π΄
2π½ + 2π|( β π΄)
2/16)1/3.
Thus, π(π) β π»1πππ(R).
(iii) If π(0) = β ΜΈ= π΅2, then π is a cuspon solution and π
has the following asymptotic behavior:
π (π) + = π2
π
2/3
+ π(π
4/3
) , π β 0,
π(π) =
2
3π2
π
β1/3 sgn (π) + π (π
1/3
) ,
π β 0,
(28)
where π2= Β±(9|π½
2β 2π΄π½ + 3π΄
2π½ + 2π|( + π΄)
2/16)1/3.
Thus, π(π) β π»1πππ(R).
(iv) If π(0) = = π΅1and π΄ ΜΈ= 0, then π is a peakon-like
solution and
π (π) β = π3
π + π (
π
2
) , π β 0,
π(π) = π
3sgn (π) + π (π
) , π β 0,
(29)
where π3= Β±|π΄ β |βπ½(π΅
2β )/4.
(v) If π(0) = β = π΅2and π΄ ΜΈ= 0, then π is a peakon-like
solution and
π (π) + = π4
π + π (
π
2
) , π β 0,
π(π) = π
4sgn (π) + π (π
) , π β 0,
(30)
where π4= Β±|π΄ + |ββπ½(π΅
1+ )/4.
(vi) If π(0) = = π΅1and π΄ = 0, then π gives the peakon
solution exp(βββπ½/2|π₯ β ππ‘|).(vii) If π(0) = β = π΅
2and π΄ = 0, then π gives the peakon
solution β exp(βββπ½/2|π₯ β ππ‘|).
Proof. (vi) and (vii) are obvious. Let us prove (i), (ii), and (iv)in order.
(i) From the process of proofing of Theorem 8, we knowthat if |π(0)| ΜΈ= , then π β πΆβ(R) and π is a smooth solitonsolution.
(ii) If π(0) = ΜΈ= π΅1, then by the definition of single peak
soliton we have π΄ ΜΈ= ; thus, π½π2 + 2π΄π½π + 3π΄2π½ + 2π doesnot contain the factor π β . From (24), we obtain
π= sgn (π΄ β )
π β π΄
β2π2 β 2
β βπ½π2 + 2π΄π½π + 3π΄2π½ + 2π
sgn (π) .
(31)
Let π1(π) = β2(π + )/|π β π΄|β|π½π2 + 2π΄π½π + 3π΄2π½ + 2π|;
then, π1() = 2β/| β π΄|β|π½
2 + 2π΄π½ + 3π΄2π½ + 2π|, and
β« π1(π)β
π β ππ = β« sgn (π΄ β ) sgn (π) ππ. (32)
Inserting π1(π) = π
1() + π(|π β |) into (32) and using the
initial condition π(0) = , we obtain
2π1()
3
π β
3/2
(1 + π (π β
)) =π ;
(33)
thus,
π β = Β±(3
2π1()
)
2/3
π
2/3
(1 + π (π β
))β2/3
= Β±(3
2π1()
)
2/3
π
2/3
(1 + π (π β
)) ,
(34)
which implies π β = π(|π|2/3). Therefore, we have
π (π) = Β± (3
2π1()
)
2/3
π
2/3
+ π(π
4/3
)
= + π1
π
2/3
+ π(π
4/3
) , π β 0,
π1= Β±(
3
2π1()
)
2/3
= Β±(
9π½2+ 2π΄π½ + 3π΄
2π½ + 2π
( β π΄)
2
16)
1/3
,
π(π) =
2
3π1
π
β1/3 sgn (π) + π (π
1/3
) , π β 0.
(35)
So, π(π) β π»1loc(R).(iii) Similar to the proof of (ii), we ignore it in this paper.(iv) If π(0) = = π΅
1and π΄ ΜΈ= 0, then from (25) we obtain
π= ββ
π½
2sgn (π΄ β ) π β π΄
βπ β π΅2
π + sgn (π) . (36)
Let π2(π) = (1/|πβπ΄|)β(π + )/(π β π΅
2); then, π
2() = (1/|β
π΄|)β2/( β π΅2) and
β« π2(π) ππ = ββ
π½
2β« sgn (π΄ β ) sgn (π) ππ. (37)
Inserting π2(π) = π
2() + π(|π β |) into (37) and using the
initial condition π(0) = , we obtain
π2() (π β ) (1 + π (
π β ))β1
= sgn (π΄ β ) π .
(38)
Sincesgn (π β ) sgn (π΄ β ) β₯ 0,
1
1 + π (π β )= 1 + π (π β ) ,
(39)
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12 Mathematical Problems in Engineering
we get
π β =
ββπ½
2
1
π2()
π (1 + π (π β )) ,
(40)
which implies |π β | = π(|π|). Therefore, we have
π (π) = + π3
π + π (
π
2
) , π β 0,
π(π) = π
3sgn (π) + π (π
) , π β 0,
(41)
where π3= Β±|π΄ β |βπ½(π΅
2β )/4.
(v) Similar to the proof of (iv), we ignore it in this paper.
By virtue of Theorem 9, any single peak soliton for theπΆ(3, 2, 2) equation (10) must satisfy the following initial andboundary values problem:
(π)2
=π½ (π β π΄)
2
(π β π΅1) (π β π΅
2)
2 (2 β π2)flπΏ (π) ,
π (0) β {, β, π΅1, π΅2} ,
lim|π|ββ
π (π) = π΄.
(42)
πΏ(π) β₯ 0 and the boundary condition (24) imply thefollowing:
(a) If π½(2 β π2) β₯ 0, then π β₯ max{π΅1, π΅2} or π β€
min{π΅1, π΅2}.
(b) Ifπ½(2βπ2) β€ 0, thenmin{π΅1, π΅2} β€ π β€ max{π΅
1, π΅2}.
Below, we will present some implicit formulas for thesingle peak soliton solutions in the case of specific π and π½.
Case 1 ((π, π½) β π΄12). In this case, we have β < π΅
2< π΄ <
π΅1= . From the standard phase analysis and Theorem 9
we know that if π is a single peak soliton of the πΆ(3, 2, 2)equation, then
π= βββ
π½
2(π β π΄)β
π β π΅2
π + sgn (π) . (43)
From the separation of variables we get
β«β (π) ππ = ββπ½
2sgn (π) ππ, (44)
where β(π) = (1/(π΄ β π))β(π + )/(π β π΅2). After a lengthy
calculation of integral, we obtain the implicit solution πdefined by
π»(π)flβπ΄ +
π΄ β π΅2
πΌ1(π) β πΌ
2(π) = ββ
π½
2
π + πΎ,
(45)
where
πΌ1(π) = ln
(π΄ + ) (π β π΅2) + (π΄ β π΅
2) (π + ) + 2β(π΄ + ) (π΄ β π΅
2) (π β π΅
2) (π + )
β(π΄ + ) (π΄ β π΅2) (π΄ + ) (π΄ β π)
,
πΌ2(π) = ln
(π + ) + (π β π΅
2) + 2β(π + ) (π β π΅
2)
,
(46)
and πΎ is an arbitrary integration constant. For π(0) = , theconstantπΎ = π»(π(0)) is defined by
πΎ = βπ΄ +
π΄ β π΅2
πΌ1() β πΌ
2() , (47)
and for π(0) = π΅2,
πΎ = βπ΄ +
π΄ β π΅2
πΌ1(π΅2) β πΌ2(π΅2) . (48)
(i) If π(0) = , then π΄ < π β€ . Since π»(π) = β(π), weknow thatπ»(π) strictly decreases on the interval (π΄, ]; thus,π»1(π) = π»|
(π΄,](π) gives a single peak solitonwithπ»
1() = πΎ
andπ»1(π΄+) = β. Therefore, π
1(π) = π»
β1
1(ββπ½/2|π| + πΎ) is
the solution satisfying
π1(0) = ,
lim|π|ββ
π1(π) = π΄,
π
1(0Β±) = Β± (π΄ β )β
π½ (π΅2β )
4.
(49)
So, π1(π) is a peakon-like solution (see Figure 5).
(ii) If π(0) = π΅2, then π΅
2β€ π < π΄. By π»(π) = π(π),
we know that π»(π) strictly increases on the interval [π΅2, π΄).
Thus,
π»2(π) = π»|
[π΅2 ,π΄)(π) (50)
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Mathematical Problems in Engineering 13
β3 β2 β1
π
β0.2
1 2 3
0.2
0.4
0.6
0.8
1.0
x
(a)
02
02
β2 β2 x
1.0
0.5
0.0
t
π
22
(b)
Figure 5: Two- and three-dimensional graphs of the peakon-like solution.
β0.3
β0.4
β0.5
1 2 3β3 β2 β1
π
β0.2
x
(a)
0
2
0
2
β2β2
β0.2
β0.3
β0.4
β0.5
β0.6
t x
π
0
2
0
2
β2β2
t x
(b)
Figure 6: Two- and three-dimensional graphs of the smooth soliton solution.
has the inverse denoted by π2(π) = π»
β1
2(ββπ½/2|π| + πΎ).
π2(π) gives a kind of smooth soliton solution (see Figure 6)
satisfying
π2(0) = π΅
2,
lim|π|ββ
π2(π) = π΄,
π
2(0) = 0.
(51)
Case 2 ((π, π½) β π΄14). In this case, we have β = π΅
2< π΄ <
< π΅1and (25) is equivalent to
π= βββ
π½
2(π β π΄)β
π β π΅1
π β sgn (π) . (52)
Let
π (π) =1
π΄ β πβπ β π΅1
π β ; (53)
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14 Mathematical Problems in Engineering
β1 1 2 3
0.2
0.4
0.6
0.8
1.0
β3 β2
π
x
(a)
02
02β2
β2
π
x t
0.0
0.5
1.0
(b)
Figure 7: Two- and three-dimensional graphs of the cuspon solution.
then, (52) is converted to
π (π) ππ =1
π΄ β πβπ β π΅1
π β ππ = ββ
π½
2sgn (π) ππ. (54)
Integrating (54) on the interval [0, π] (or [π, 0]) leads to thefollowing implicit solutions:
πΊ (π)flβπ΄ β
π΄ β π΅1
πΌ3(π) + πΌ
4(π) = ββ
π½
2
π + πΎ,
(55)
where
πΌ3(π) = ln
(π΄ β ) (π β π΅1) + (π΄ β π΅
1) (π β ) + 2β(π΄ β ) (π΄ β π΅
1) (π β ) (π β π΅
1)
β(π΄ β ) (π΄ β π΅1) (π΄ β ) (π β π΄)
,
πΌ4(π) = ln
(π β ) + (π β π΅
1) + 2β(π β ) (π β π΅
1)
.
(56)
AndπΎ is an arbitrary integration constant. It is obvious that,for π(0) = , the constantπΎ = π»(π(0)) is defined by
πΎ = βπ΄ β
π΄ β π΅1
πΌ3() + πΌ
4() , (57)
and for π(0) = β,
πΎ = βπ΄ β
π΄ β π΅1
πΌ3(β) + πΌ
4(β) . (58)
(i) If π(0) = , then π΄ < π β€ . From π(π) < 0, weknow that πΊ(π) strictly decreases on the interval (π΄, ] withπΊ() = πΎ and πΊ(π΄+) = β. Define
πΊ1(π) = πΊ|
(π΄,](π) . (59)
Since πΊ1(π) is a strictly decreasing function from (π΄, ] onto
[πΎ,β), we can solve for π uniquely from (59) and obtain
π1(π) = πΊ
β1
1(ββ
π½
2
π + πΎ) .
(60)
It is easy to check that π satisfies
π1(0) = ,
lim|π|ββ
π1(π) = π΄,
π
1(0Β±) = ββ.
(61)
Therefore, the solutionπ1defined by (60) is a cuspon solution
for the πΆ(3, 2, 2) equation (see Figure 7).
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Mathematical Problems in Engineering 15
(ii) If π(0) = β, then β β€ π < π΄. Through a similaranalysis, we get a strictly increasing function πΊ(π) on theinterval [β, π΄) satisfying
πΊ (π) = ββπ½
2
π + πΎ,
(62)
where πΊ(π) is defined by (55). Let
πΊ2(π) = πΊ|
[β,π΄)(π) , (63)
then πΊ2(π) is a strictly increasing function from [β, π΄) onto
[πΎ,β) so that we can solve for π and obtain
π2(π) = πΊ
β1
2(ββ
π½
2
π + πΎ) .
(64)
It is easy to check that π2satisfies
π2(0) = β,
lim|π|ββ
π2(π) = π΄,
π
2(0Β±) = Β± (π΄ + )ββ
π½ (π΅1+ )
4.
(65)
Therefore, the solution π2defined by (64) is a peakon-like
solution, whose graph is similar to those in Figure 5.
Case 3 ((π, π½) β π΄16). In this case, we have β < π΅
2< π΄ =
0 < π΅1< , π΅
2= βπ΅1, and
π= βββ
π½
2πβ
π β π΅2
1
π2 β 2sgn (π) . (66)
Hence from the separation of variables we have
β2 β π2
πβπ΅2
1β π2
ππ = βββπ½
2sgn (π) ππ. (67)
Integrating (67) on the interval [0, π] (or [π, 0]) leads tothe following implicit formula for the two smooth solitonsolutions:
β2 β π2 + βπ΅2
1β π2
β2 β π΅2
1
(
β(2 β π΅2
1) π2
βπ΅2
1β π2 + π΅
1β2 β π2
)
= exp(βββπ½
2|π₯ β ππ‘|) ,
(68)
where π β (π΄, π΅1]. Consider
β2 β π΅2
2
β2 β π2 + βπ΅2
2β π2
(
βπ΅2
2β π2 β π΅
2β2 β π2
β(2 β π΅2
2) π2
)
= exp(ββπ½
2|π₯ β ππ‘|) ,
(69)
where π β [π΅2, π΄).
Case 4 ((π, π½) β π΄17). In this case, we have β = π΅
2< π΄ =
0 < π΅1= , and
π= βββ
π½
2π sgn (π) . (70)
Choosing π(0) = (or β) as initial value, we get
β«
π
1
πππ = ββ«
π
0
ββπ½
2sgn (π) ππ, for π΄ < π β€ ,
β«
π
β
1
πππ = ββ«
π
0
ββπ½
2sgn (π) ππ, for β β€ π < π΄,
(71)
which immediately yield the peakon solutions
π (π₯ β ππ‘) = Β± exp(βββπ½
2|π₯ β ππ‘|) . (72)
The graphs for the peakon solution (72) are shown in Figure 8.
Remark 10. The classical peakon solution (72) and peakon-like solution (64) admit left-half derivative and right-halfderivative at their crest. But the signs of the left-half derivativeand right-half derivative are opposite, so the peakon andpeakon-like solutions admit the discontinuous first orderderivative at their crest. In comparison with classical peakonsolution (72), the expression of the peakon-like solution (64)is more complex. Moreover, by observing Figures 2(14) and2(17) we find that the phase orbits of the peakon consist ofthree straight lines, but the phase orbits of the peakon-likeconsist of two curves and a straight line. Therefore, we callthe soliton solution (64) the peakon-like solution.
4. Kink Wave and Kink Compacton Solutions
We now turn our attention to the kink wave solutions of theπΆ(3, 2, 2) equation (10). In order to study kinkwave solutions,we assume that
limπββ
π (π) = π΄1,
limπβββ
π (π) = π΄2,
(73)
-
16 Mathematical Problems in Engineering
2 4
0.2
0.4
0.6
0.8
1.0
β2β4
π
x
(a)
0 2
02
0.0
0.5
1.0
β2
π
x
t
0
2
β2
(b)
Figure 8: Two- and three-dimensional graphs of the peakon solution.
where π΄1> π΄2. Substituting the boundary condition (73)
into (14) generates
(π)2
=
π½ (π β π΄1) (π β π΄
2) [π2+ (π΄1+ π΄2) π + π΄
2
1+ π΄1π΄2+ π΄2
2+ 2π/π½]
2 (2 β π2)flπΉ (π) . (74)
The nonlinear differential equation (74) may sustaindifferent kinds of nonlinear excitations. In what follows, weconfine our attention to the cases π΄
2= βπ΄
1and π =
βπ΄2
1π½ which describe kinks and kink compactons which
play an important role in the dynamics systems. Under theseconsiderations, (74) reduces to
(π)2
=π½ (π β π΄
1)2
(π β π΄2)2
2 (2 β π2). (75)
If π΄1< , then from the phase analysis in Section 2 (see
Figure 4(10)), we know that (π΄1, 0) and (π΄
2, 0) are two saddle
points of (13) and the kink solutions can be obtained fromthe two heteroclinic orbits connecting (π, π¦) = (π΄
1, 0) and
(π΄2, 0). When π΄
1increases upon reaching , that is π΄
1= ,
(75) becomes
(π)2
= βπ½ (π β π΄
1) (π β π΄
2)
2, (76)
and the ellipse 2π¦2+π½(πβπ΄1)(πβπ΄
2) = 0 (see Figure 4(11)),
which is tangent to the singular lines π = and π = β atpoints (π΄
1, 0) and (π΄
2, 0), respectively, gives rise to two kink
compactons of (10).We next explore the qualitative behavior of kink wave
solutions to (75) and (76). If π is a kink wave solutions of (75)
or (76), we have π β 0 as π β π΄1and as π β π΄
2.
Moreover, we have πΉ(π) β₯ 0 for π΄2β€ π β€ π΄
1and π is
strictly monotonic in any interval where πΉ(π) > 0. Thus, ifπ> 0 at some points, πwill be strictly increasing until it gets
close to the next zero of πΉ. Denoting this zero π΄1, we have
π β π΄1. What will happen to the solution when it approaches
π΄1? Depending on whether the zero is double or simple, π
has a different behavior. We explore the two cases in turn.
Theorem 11. (i) If π has a simple zero at π = π΄1, so that
πΉ(π΄1) = 0 and πΉ(π΄
1) < 0, then the solution π of (75) satisfies
π (π) β π΄1=πΉ(π΄1)
4(π β π)
2
+ π ((π β π)4
)
ππ π β π,
(77)
where π(π) = π΄1.
(ii) When π approaches the double zero π΄1of πΉ(π) so that
πΉ(π΄1) = 0 andπΉ(π΄
1) > 0, then the solutionπ of (75) satisfies
π (π) β π΄1βΌ πΌ exp(βπβπΉ (π΄
1)) ππ π β β (78)
for some constant πΌ. Thus, π β π΄1exponentially as π β β.
-
Mathematical Problems in Engineering 17
Proof. (i) When π΄1= βπ΄
2= and π = βπ΄2
1π½, from (76),
πΉ(π) has a simple zero at π = π΄1. Then,
(π)2
= (π β π΄1) πΉ(π΄1) + π ((π β π΄
1)2
)
as π β π΄1.
(79)
Using the fact that (π)2 β₯ 0, we know that πΉ(π΄1) < 0.
Moreover,
ππ
ππ=
1
β(π β π΄1) πΉ (π΄
1) + π ((π β π΄
1)2
)
. (80)
Because
β(π β π΄1) πΉ (π΄
1) + π ((π β π΄
1)2
)
= βπ΄1β π(ββπΉ (π΄
1) + π (π΄
1β π)) ,
1
ββπΉ (π΄1) + π (π΄
1β π)
=1
ββπΉ (π΄1)
+ π (π΄1β π) ,
(81)
we obtainππ
ππ=
1
ββ (π΄1β π) πΉ (π΄
1)
+ π ((π΄1β π)1/2
) . (82)
Integrating (82) yields
π β π =2
ββπΉ (π΄1)
(π΄1β π)1/2
+ π((π΄1β π)3/2
) , (83)
where π satisfies π(π) = π΄1. Thus,
(π β π)2
=4
βπΉ (π΄1)(π΄1β π) + π ((π΄
1β π)2
) , (84)
which implies π((π΄1β π)2) = π((π β π)
4). Therefore, we get
π (π) = π΄1+πΉ(π΄1)
4(π β π)
2
+ π ((π β π)4
)
as π β π,(85)
where π(π) = π΄1.
(ii) When π΄1= βπ΄
2< and π = βπ΄2
1π½, from (75), πΉ(π)
has a double zero at π = π΄1. Then,
(π)2
= (π β π΄1)2
πΉ(π΄1) + π ((π β π΄
1)3
)
as π β π΄1.
(86)
Furthermore, we get
ππ
ππ=
1
β(π β π΄1)2
πΉ (π΄1) + π ((π β π΄
1)3
)
. (87)
Observing that
β(π β π΄1)2
πΉ (π΄1) + π ((π β π΄
1)3
)
= (π΄1β π) (βπΉ (π΄
1) + π (π΄
1β π)) ,
1
βπΉ (π΄1) + π (π΄
1β π)
=1
βπΉ (π΄1)
+ π (π΄1β π) ,
(88)
we obtainππ
ππ=
1
(π΄1β π) πΉ (π΄
1)+ π (1) . (89)
By a similar computation as the one that leads to (85), wearrive at (78). This completes the proof of Theorem 11.
Next we try to find the exact formulas for the kink wavesolutions. Let π΄
1= βπ΄
2< and π = βπ΄2
1π½. Then, (75)
becomes
β2 β π2
π2 β π΄2
1
ππ = ββπ½
2ππ. (90)
Integrating both sides of (90) gives the following implicitexpressions of kink and antikink wave solutions:
arctanπ
β2 β π2
+
β2 β π΄2
1
π΄1
arctanhβ2 β π΄
2
1
π΄1
π
β2 β π2
= Β±βπ½
2π.
(91)
By letting π΄1β in (91), we get two kink compactons
which are given by
Β±π =
{{{{{{{{{
{{{{{{{{{
{
sinβπ½
2π,
π β€
π
β2π½,
, π >π
β2π½,
β, π < βπ
β2π½.
(92)
The graphs for the kink wave solutions (91) and kinkcompacton solutions (92) are shown in Figures 9 and 10,respectively.
Remark 12. The two kink compacton solutions (92) aredifferent from the well-known smooth kink wave solutions.In comparison with kink wave solutions (91), the kink com-pacton solutions (92) have no exponential decay propertiesbut have compact support.That is, they minus a constant, thedifferences identically vanish outside a finite core region.
-
18 Mathematical Problems in Engineering
π
πβ1 1
0.5
β0.5
(a)
β1β1
β0.5
0.5
0.0π
x t
0
1
01
11
(b)
Figure 9: Two- and three-dimensional graphs of the kink wave solution.
1
1π
π
β1
β1
(a)
0
1
0
1
0.00.51.0
π
β1 β1
β0.5
β1.0
tx
0
1
0
1
(b)
Figure 10: Two- and three-dimensional graphs of the kink compacton solution.
5. Conclusion
In this paper, we investigate the travelingwave solutions of theπΆ(3, 2, 2) equation (10). We show that (10) can be reduced toa planar polynomial differential system by transformation ofvariables. We treat the planar polynomial differential systemby the dynamical systems theory and present a phase spaceanalysis of their singular points. Two singular straight linesare found in the associated topological vector field. Theinfluence of parameters as well as the singular lines onthe smoothness property of the traveling wave solutions isexplored in detail.
Because any traveling wave solution of (10) is determinedfrom Newtonβs equation which we write in the form π¦2 =πΉ(π), where π¦ = π
π(π), we solve Newtonβs equation π¦2 =
πΉ(π) for single peak soliton solutions and kink wave andkink compacton solutions. We classify all single peak solitonsolutions of (10). Then peakon, peakon-like, cuspon, smoothsoliton solutions of the generalized Camassa-Holm equation
(10) are obtained. The parametric conditions of existenceof the single peak soliton solutions are given by using thephase portrait analytical technique. Asymptotic analysis andnumerical simulations are provided for single peak solitonand kink wave and kink compacton solutions of theπΆ(3, 2, 2)equation.
Actually, for π = 2π + 1, π β N+ in πΆ(π, 2, 2) equation(9), the dynamical behavior of traveling wave solutions of(9) is similar to the case π = 3; for π = 2π, π β N+ inπΆ(π, 2, 2) equation (9), the dynamical behavior of travelingwave solutions of (9) is similar to the case π = 2. We areapplying the approach mentioned in this work to πΆ(2, 2, 2)equation (9) and already get some new solutions, which wewill report in another paper.
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper.
-
Mathematical Problems in Engineering 19
Acknowledgments
This work was partially supported by the National NaturalScience Foundation of China (no. 11326131 and no. 61473332)andZhejiangProvincialNatural Science Foundation ofChinaunder Grant nos. LQ14A010009 and LY13A010005.
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