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耦合Schrodinger系统变号解的渐进行为,王友军,杨俊,我们研究了下列耦合Schrodinger系统变号解的渐进性质 eegin{cases}-arepsilon^2Deltau+lambda_1u=mu_1u^3+eta uv^2,quad &xin Omega, onumber\-arepsilon^2Delta v+lam
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˖ڍመڙጲ
http://www.paper.edu.cn
耦合 Schrodinger 系统变号解的渐进行为
王友军,杨俊
华南理工大学数学学院,广州 510640
摘要:我们研究了下列耦合 Schrodinger 系统变号解的渐进性质
−ε
2
∆u + λ
1
u = µ
1
u
3
+ βuv
2
, x ∈ Ω,
−ε
2
∆v + λ
2
v = µ
2
v
3
+ βvu
2
, x ∈ Ω,
u = v = 0, x ∈ ∂Ω,
其中 Ω ⊂ R
N
(N ≤ 3) 是有光滑边界的有界区域,λ
1
, � λ
2
, � µ
1
,µ
2
> 0,β < 0。当 ε → 0 时,
证明了半变号解(即,解的一个分支变号,另一个分支大于零)变号的分支有唯一的正和负尖
峰,它们都收敛到 Ω 中不同的点,不变号的分支有唯一的正尖峰,它也收敛到一点。我们同
样也证明了当 ε → 0 时,这些最大值和最小值点与边界的距离除以 ε 是发散的。
关键词:耦合非线性 Schrodinger 系统;变号解;渐进行为
中图分类号: O175
The asymptotic behavior of nodal solutions for
two coupled Schrödinger system
WANG You-Jun , YANG Jun
Department of Mathematics, South China University of Technology, Guangzhou 510640
Abstract: We study the asymptotic behavior of nodal solution for the coupled nonlinear
Schrödinger system
−ε
2
∆u + λ
1
u = µ
1
u
3
+ βuv
2
, x ∈ Ω,
−ε
2
∆v + λ
2
v = µ
2
v
3
+ βvu
2
, x ∈ Ω,
u = v = 0, x ∈ ∂Ω,
where Ω ⊂ R
N
(N ≤ 3) is a smooth and bounded domain, λ
1
, λ
2
, µ
1
, µ
2
> 0 and β < 0. It is
shown that the semi-nodal solution (u, v), that is, one component changes sign and another
one is positive, has exactly one positive and one negative peaks, which converge to two
distinct points of Ω as ε → 0, and another component has exactly one positive peak, which
Foundations: NSFC (11201154),SRFDP(No.20120172120040)
Author Introduction: WANG You-Jun(1981-),male,associate professor,major research direction:Nonlinear analysis
and partial differential equations. Correspondence author:YANG Jun (1979-),female,lecturer,major research direction:
Partial differential equations.
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converge to a point of Ω as ε → 0. We also prove the distances between the local maximum
points, the local minimum points and the boundary of Ω divided by ε diverge.
Key words: coupled nonlinear Schrödinger system ; nodal solution; the asymptotic behavior
0 Introduction
In this paper, we consider the existence of nodal solution and its asymptotic behavior for
the coupled nonlinear Schrödinger system
−i
∂Φ
1
∂t
=
h
2
2m
∆Φ
1
− W
1
(x)Φ
1
+ µ
1
|Φ
1
|
2
Φ
1
+ β|Φ
2
|
2
Φ
1
, x ∈ Ω, t > 0,
−i
∂Φ
2
∂t
=
h
2
2m
∆Φ
2
− W
2
(x)Φ
2
+ µ
2
|Φ
2
|
2
Φ
2
+ β|Φ
1
|
2
Φ
2
, x ∈ Ω, t > 0,
Φ
j
= Φ
j
(x, t) ∈, j = 1, 2,
Φ
j
(x, t) = 0, x ∈ ∂Ω, t > 0, j = 1, 2.
This system models a binary mixture of Bose-Einstein condensates in two different hyperfine
states |1⟩ and |2⟩ (cf. [1]). Physically, Φ
1
and Φ
2
are the corresponding condensate amplitudes,
Ω ⊆ R
N
is the domain for condensate dwelling, h is the Planck constant, m is atom mass
and W
j
is the trapping potential for the j-th hyperfine state. µ
j
= −(N
j
− 1)U
jj
is a fixed
number of atoms in the hyperfine state |j⟩, N
1
, N
2
≥ 1, β = −N
2
U
12
and U
ij
= 4π
h
2
m
a
ij
,
where a
jj
’s and a
12
are the intraspecies and interspecies scattering lengths. The sign of the
scattering length a
12
determines whether the interactions of states |1⟩ and |2⟩ are repulsive or
attractive. When a
12
> 0, i.e., β < 0, the interactions of states |1⟩ and |2⟩ are repulsive. In
contrast, when a
12
< 0, i.e., β > 0, the interactions of states |1⟩ and |2⟩ are attractive. For
atoms of the single state |j⟩, when a
jj
< 0, i.e., µ
j
> 0, the interactions of the single state
|j⟩ are attractive. Spikes may appear in a single condensate when the s-wave scattering length
is negative and large. Due to Feshbach resonance, the s-wave scattering length of a single
condensate can be tuned over a very large range by adjusting the externally applied magnetic
field. As the s-wave scattering length of a single condensate is negative and large enough, the
interactions of atoms are strongly attractive and the associated condensate tends to contract
(see [2] and the references therein). It seems spikes may occur in a double condensate when the
intraspecies scattering lengths a
jj
’s are negative and large enough, i.e. µ
j
’s are positive and
large enough. On the other hand, the interspecies scattering length a
12
plays an important role
in a double condensate. Without the effect of trap potentials, when the interspecies scattering
length a
12
is positive and large enough, the states |1⟩ and |2⟩ may repel each other and form
segregated domains called phase separation, see [2] and the references cited therein. In [2], T.
C. Lin and J. Wei showed that spikes of states |1⟩ and |2⟩ repel each other and behave like
two separate spikes as the interspecies scattering length a
12
is positive and large enough. In
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contrast, if the interspecies scattering length a
12
is negative and large enough, spikes of states
|1⟩ and |2⟩ attract each other and behave like one single spike. More precisely, they studied
solitary wave solutions of the following elliptic system
ε
2
∆u − λ
1
u + µ
1
u
3
+ βuv
2
= 0, x ∈ Ω,
ε
2
∆v − λ
2
v + µ
2
v
3
+ βu
2
v = 0, x ∈ Ω,
u > 0, v > 0, x ∈ Ω,
u = v = 0, x ∈ ∂Ω,
(1)
where Ω ⊂ R
N
(N ≤ 3) is a smooth and bounded domain; ε > 0 is a small parameter;
λ
1
, λ
2
, µ
1
, µ
2
are positive constants; β = 0 is a coupling constant. They proved that there
exists a β
0
∈ (0,
√
µ
1
µ
2
) such that for any β ∈ (−∞, β
0
) and ε small enough, (1) has a least
energy positive solution (u
ε
, v
ε
) concentrates respectively in the local maximum point P
ε
of u
ε
and local minimum point Q
ε
of v
ε
. The result of [2] seems to be the first attempt in studying
the positive solutions for systems of singularly perturbed problems.
When ε = 1, (1) turns into the following system:
−∆u + λ
1
u = µ
1
u
3
+ βuv
2
, x ∈ Ω,
−∆v + λ
2
v = µ
2
v
3
+ βu
2
v, x ∈ Ω,
u > 0, v > 0, x ∈ Ω,
u = v = 0, x ∈ ∂Ω.
(2)
For this case, (2) has also been studied by N. Dancer, J. We and T. Weth in [3], where a priori
bounds and multiple existence of positive solutions to (2) were obtained. Their main tools are
Liouville type theorems and a variant of Lyusternik-Schnirelmann theory on a submanifold of
Nehari type.
When Ω is a unit ball B, λ
1
= λ
2
= µ
1
= µ
2
= 1, β ≤ −1, for any k ∈ N, J. Wei
and T. Weth [4] established the existence of radially symmetric positive solution (u, v) to (2)
such that u − v changing sign precisely k − 1 times in the radial variable. The genus theory
and corresponding parabolic equation theory are applied. Their results provides a theoretical
indications of phase separation into many nodal domains for Bose-Einstein double condensates
with strong repulsion. When λ
1
= λ
2
∈ R, µ
1
= µ
2
= 1, for −β large enough, the systems (2)
has an unbounded sequence of positive solutions, this was proved by B. Noris and M. Ramos
[5]. The main ideas of [5] is a suitable minimax framework and the Morse index estimates.
When Ω = R
N
(N ≤ 3), system (1) have been widely investigated by several authors. In
Sirakov [6], the least energy solitary waves for (1) were established when ε = 1. By using the
fixed point index, when ε = 1, T. Bartsch et al. [7] proved a global bifurcation theorem for
positive solutions. They also obtained further information on the set of all positive bound states
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by applying Morse theory to the associated energy functional constrained to a nonnegative
cone. A. Ambrosetti and E. Colorado [8] showed that there exist Λ
′
> Λ > 0, depending
upon λ
i
and µ
i
such that (1) has a radially symmetric positive solution provided β ∈ (0, Λ) ∪
(Λ
′
, ∞). Moreover, for β > Λ
′
, these solutions are ground states, in the sense that they have
minimal energy and their Morse index is 1. In A. Pomponio, [9], with suitable assumptions on
the potentials and for ε sufficiently small, by using finite dimensional reduction, one positive
solutions were obtained which concentrates respectively on P
ε
and Q
ε
tending toward the same
point and the distance between them divided by ε diverges. In [10], Montefusco, Pellacci and
Squassina studied the case β > 0. They showed for small ε > 0, problem (1) has a non-zero
solution (u
ε
, v
ε
) such that u
ε
(x) + v
ε
(x) has exactly one global maximum point. We refer the
readers to [11, 12, 13, 14, 15, 16] and the references cited therein for more results for the case
of Ω = R
N
.
In this paper, we consider the nodal solutions (u, v) to (3) below:
−ε
2
∆u + λ
1
u = µ
1
u
3
+ βuv
2
= 0, x ∈ Ω,
−ε
2
∆v + λ
2
v = µ
2
v
3
+ βu
2
v = 0, x ∈ Ω,
u = v = 0, x ∈ ∂Ω,
(3)
where Ω is bounded or unbounded. Here we say nodal solution (u, v), it means either u or v
or both are sing-changing. Recently, Chen and zou in [17] proved there exists β
1
> 0 such that
for β ∈ (0, β
1
), there exists a nodal solution of (3) with ε = 1. Thus, for each ε > 0, we can get
a nodal solution (u
ε
, v
ε
) for the Schrödinger system (3). The purpose of the current paper is
to study their profiles.
Theorem 0.1. For β ∈ (−
√
µ
1
µ
2
, 0) and ε sufficiently small, (3) has a semi-nodal solution
(u
ε
, v
ε
) satisfying the following properties:
(1) u
ε
has exactly one local maximum point P
1
ε
and one minimum point P
2
ε
, v
ε
has exactly
one local maximum point Q
ε
.
(2) u
ε
, v
ε
→ 0 in C
1
loc
(Ω \ {P
1
ε
, P
2
ε
, Q
ε
}). Moreover, there exist some C > 0 and 0 < σ < 1
such that
|u
ε
(x)| ≤ Ce
−(1−σ)
√
λ
1
min{|x−P
1
ε
|,|x−P
2
ε
|}/ε
,
|v
ε
(x)| ≤ Ce
−(1−σ)
√
λ
2
|x−Q
ε
|/ε
.
For single equation case, the existence of nodal solutions and its asymptotic behavior for
singularly perturbed Neuman or Dirichlet problems have been studied by some authors. We
refer the readers to [18, 19, 20, 21] and the references therein. For such case, it is easy to
check that if u belongs to the classical Nehari manifold N corresponding to the functional,
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