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数学物理学报, 2019, 39(2): 297-306 doi:

论文

一类非线性微分-积分时滞反应扩散系统奇摄动问题的广义解

韩祥临,1, 汪维刚2, 莫嘉琪3

Generalized Solution to the Singular Perturbation Problem for a Class of Nonlinear Differential-Integral Time Delay Reaction Diffusion System

Han Xianglin,1, Wang Weigang2, Mo Jiaqi3

收稿日期: 2017-10-31  

基金资助: 国家自然科学基金.  11771005
浙江省自然科学基金.  LY13A010005
安徽省高校自然科学研究重点项目.  KJ2017A901
安徽省教育科学规划课题.  JG10068

Received: 2017-10-31  

Fund supported: the NSFC.  11771005
the Natural Science Foundation of Zhejiang Province.  LY13A010005
the Natural Science Foundation of the Education Department of Anhui Province.  KJ2017A901
the Education Science Programming Foundation of Anhui Province.  JG10068

作者简介 About authors

韩祥临,E-mail:xlhan@zjhu.edu.cn , E-mail:xlhan@zjhu.edu.cn

摘要

该文研究了一类非线性微分-积分时滞广义反应扩散系统奇摄动问题.在适当的条件下,利用奇摄动方法构造了初始-边值问题广义解的渐近展开式.建立了广义解的微分不等式理论,并证明了相应解的存在性及其解的渐近展开式的一致有效性.

关键词: 反应扩散 ; 奇摄动 ; 非线性系统

Abstract

A class of nonlinear differential-integral system for the singular perturbation generalized reaction diffusion equations with time delay is considered. Under suitable conditions, the asymptotic expansions of generalized solution to the initial boundary problem is obtained by using the singular perturbation method. And the theory of differential inequality for generalized solution is constructed. Corresponding existence and the uniformly validity of the asymptotic expansion for the solution are proved.

Keywords: Reaction diffusion ; Singular perturbation ; Nonlinear system

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本文引用格式

韩祥临, 汪维刚, 莫嘉琪. 一类非线性微分-积分时滞反应扩散系统奇摄动问题的广义解. 数学物理学报[J], 2019, 39(2): 297-306 doi:

Han Xianglin, Wang Weigang, Mo Jiaqi. Generalized Solution to the Singular Perturbation Problem for a Class of Nonlinear Differential-Integral Time Delay Reaction Diffusion System. Acta Mathematica Scientia[J], 2019, 39(2): 297-306 doi:

1 引言

非线性系统在自然科学学术界中是一个热门的研究对象[1, 2].非线性奇异摄动问题近来已有很多近似解法,包括边界层校正法、匹配法和多重尺度法.许多科学研究者,如Tian等[3], Samusenko[4], Kellogg等[5], Skrynnikov[6]和Martinez等[7]已做了很多工作.利用非线性奇摄动和微分不等式等理论和方法,莫嘉琪,韩祥临等也研究了一类非线性奇异摄动微分方程和数学物理等问题[8-18].本文是利用广义解的微分不等式等理论和方法研究一类带有广义反应扩散系统的奇异摄动问题.

考虑如下一类非线性微分-积分时滞奇摄动广义反应扩散系统初始-边值问题

ε(ψ(x),ui(t,x)\partialt)μ2(ψ(x),Liui(t,x))+(ψ(x),Tiui(tε,x))=(ψ(x),fi(x,ui(t,x))),(t,x)(0,)×Ω,  ψ(x)\inC0(Ω),  i=1,2,,N,
(1.1)

(ψ(x),ui(t,x))=(ψ(x),gi(t,x)),  xΩ,ψ(x)C0(Ω),  i=1,2,,N,
(1.2)

(ψ(x),ui(t,x))=(ψ(x),hi(x)),  t[ε,0],  ψ(x)C0(Ω), \i=1,2,,N,
(1.3)

其中μ为正的小参数, ε为小滞时数, x=(x1,x2,,xn),u=(u1,u2,,uN), Ω为有界凸域; ΩΩC1+α类的边界(α为Hölder系数), C0(Ω)C(Ω)Ω中的紧致子集, Ki,fi,gihi为关于它们的变量在C0(Ω)内的函数,积分算子Tui(t,x)=ΩKi(x)ui(t,x)dx, L是在C0(Ω)上定义的有界函数ajk的一致椭圆型的算子

Li=nj,k=1(DjajkiDk),  i=1,2,,N,

Dj=x, \Dα=Dα1Dα2Dαn, alpha=nj=1αj,

在Sobolev空间上的函数的有界模为

(v, u)为在H^{\infty}_{0}(\Omega)上的Hilbert内积.

首先假设

(H1) 0 <\mu/\varepsilon\ll 1;

(H2) \alpha^{jk}_{i}, \ f_{i}, \ g_{i}, \ h_{i}, \ K_{i},为关于其变量在相应区域内为Hölder连续的函数;

(H3)对于函数u, v, 存在常数C_{1}, C_{2},使得

|(v, L_{i}[u])|\leq C_{1}\|v\|\|u\|, \ |(u, L_{i}[u])|\geqC_{2}\|u_{i}\|, \ \ \forall v, u\in H^{\infty}_{0}(\Omega), \ \i=1, 2, \cdots, N;

(H4)系数a^{jk}_{i}\Omega上有界,且有正常数C_{3},使得|a^{jk}_{i}(x)-a^{jk}_{i}(\overline{x})|\leqC_{3}(|x-\overline{x}|), \forall x, \overline{x}\in\Omega, j, k=1, 2, \cdots, n, \ i=1, 2, \cdots, N;

(H5)存在正常数\delta_{i1}, \delta_{i2},使得

\delta_{i1}\leq(\psi, f_{iu})\leq\delta_{i2}, \ \ \forallx\in\overline{\Omega}, \ \ \forall\psi\in H^{\infty}_{0}(\Omega), \\ i=1, 2, \cdots, N;

(H6)积分方程

(\psi(x), T_{i}u_{i})=(\psi(x), f_{i}(x, u_{i})), \ \ x\in\Omega, \ \\forall\psi(x)\in H^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N

存在一组广义解U_{i}\in H^{\infty}_{0}(\Omega), \ i=1, 2, \cdots, N.

2 初始-边值问题的广义外部解

非线性微分-积分时滞奇摄动广义反应扩散系统的退化问题为

(\psi(x), T_{i}u_{i})=(\psi(x), f_{i}(x, u_{i})), \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N.
(2.1)

由假设(H4), Fredholm积分方程(2.1)有一组广义解U_{i00}\inH^{\infty}_{0}(\Omega)\ \ i=1, 2, \cdots, N.

再将T_{i}u_{i}(t-\varepsilon, x)按时滞参数的幂展开

T_{i}u_{i}(t-\varepsilon, x)=T_{i0}u_{i}(t, x)+\sum\limits^{\infty}_{j=1}\bigg[\frac{1}{j!}\frac{\partial^{j}}{\partial\varepsilon^{j}}T_{i}u_{i}(t-\varepsilon, x)\bigg]_{\varepsilon=0}\varepsilon^{j}, \ \ i=1, 2, \cdots, N,
(2.2)

并设广义初始-边值问题(1.1)-(1.3)的外部解U_{i}(t, x), \ \i=1, 2, \cdots, N

U_{i}=\sum\limits^{\infty}_{j, k=1}U_{ijk}\varepsilon^{j}\mu^{k}, \ \i=1, 2, \cdots, N.
(2.3)

将(2.1)和(2.2)式代入系统(1.1),按照\varepsilon, \mu的幂展开非线性项,合并对应\varepsilon^{j}\mu^{k}项的系数,令同次幂\varepsilon^{j}\mu^{k}\ (i, k=0, 1, \cdots)项的系数为零.取\varepsilon^{0}\mu^{0}项的系数为零时,得到的系统就是问题(1.1)-(1.3)的退化系统,故其解为U_{i00}, \i=1, 2, \cdots, N.\varepsilon^{j}, \mu^{k}, \ j, k=0, 1, \cdots, j+k\neq 0 项的系数为零时,得到

(\psi(x), TU_{ijk})=(\psi(x), L_{i}U_{ij(k-2)})-(\psi(x), L_{i}\frac{\partial U_{(j-1)k}}{\partialt})+(\psi(x), F_{ijk}), \\\ \ \forall\psi(x)\in C^{\infty}_{0}(\Omega), \ \ j, k=0, 1, \cdots, \j+k\neq 0, \ \ i=1, 2, \cdots, N.
(2.4)

上述和下面带有负下标的项均设为零,其中F_{ijk}

F_{ijk}=\sum\limits^{\infty}_{j, k=1}\bigg[\frac{1}{j!k!}\frac{\partial^{j+k}}{\partial\varepsilon^{j}\partial\mu^{k}}f_{i}(x, \sum\limits^{\infty}_{p, q=0}U_{i}\varepsilon^{p}\mu^{q})\bigg]_{\varepsilon=\mu=0}, \ \ j, k=0, 1, \cdots, j+k\neq 0

逐次已知的函数.由假设, Fredholm积分方程(2.4)可依次得到解U_{ijk}(t, x).于是由(2.1)式可得到一组广义外部解U=(U_{1}, U_{2}, \cdots, U_{N}).但是它未必满足边界条件(1.2)和初始条件(1.3),所以尚需构造在t=0附近的初始层校正项Y和在\partial\Omega附近的边界层校正项W.

3 初始层校正项

现构造初始层校正项Y.引入伸长变量\tau=t/\varepsilon,并设

\begin{equation}u_{i}=\sum\limits^{\infty}_{j, k=1}U_{ijk}\varepsilon^{j}\mu^{k}+Y_{i}, \\ i=1, 2, \cdots, N, \end{equation}
(3.1)

这里

\begin{equation}Y_{i}=\sum\limits^{\infty}_{j, k=1}y_{ijk}(\tau, x)\varepsilon^{j}\sigma^{k}, \ \ i=1, 2, \cdots, N, \end{equation}
(3.2)

其中\sigma=\mu/\varepsilon.

将(3.1), (3.2)式代入(1.1), (1.3)式,按照\varepsilon, \sigma的幂展开非线性项,合并对应的\varepsilon^{j}\sigma^{k}项的系数,并令同次幂\varepsilon^{j}\sigma^{k}\ (i, j=0, 1, \cdots)项的系数为零有

\begin{eqnarray}& (\psi(x), \frac{\partial y_{i00}(\tau, x)}{\partial\tau})+(\psi(x), T_{i}y_{i00}(\tau, x))=(\psi(x), f_{i}(x, y_{i00}(\tau, x)+U_{i00}(0, x))), \\[2mm]&\forall\psi(x)\in C^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N, \end{eqnarray}
(3.3)

\begin{equation}(\psi(x), y_{i00}(0, x))=(\psi(x), h_{i}(x)), \ \ x\in\partial\Omega, \\ \forall\psi(x)\in C^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N, \end{equation}
(3.4)

\begin{eqnarray}&&(\psi(x), \frac{\partial y_{ijk}(\tau, x)}{\partial\tau})+(\psi(x), T_{i}y_{ijk}(\tau, x))-(\psi(x), f_{iy}(x, y_{i00}(0, x)))y_{ijk}(\tau, x)\\&=&(\psi(x), L_{i}y_{ij(k-2)}(\tau, x))+\widetilde{F}_{ijk}, \ \\forall\psi(x)\in C^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N, \end{eqnarray}
(3.5)

\begin{equation}(\psi(x), y_{ijk}(0, x))=0, \ \ x\in\partial\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N, \end{equation}
(3.6)

其中\widetilde{F}_{ijk}\ (j, k=0, 1, \cdots, \ j+k\neq 0, \i=1, 2, \cdots, N)为逐次已知的函数,其结构从略.

由初值问题(3.3), (3.4)和(3.5), (3.6),可依次得到y_{ijk}, \j, k=0, 1, \cdots, \ j+k\neq 0, \ i=1, 2, \cdots, N.因此由(3.2)式,可得到在t=0邻域内的一组初始层校正项Y=(Y_{1}, Y_{2}, \cdots, Y_{N}),且不难看出

y_{ijk}=O(\exp(-\overline{k}_{ijk}\frac{t}{\varepsilon})), \ \j, k=0, 1, \cdots, \ \ i=1, 2, \cdots, N, \ \ 0 <\varepsilon\ll 1,
(3.7)

其中\overline{k}_{ijk}\ j, k=0, 1, \cdots, \ i=1, 2, \cdots, N为正常数.

4 边界层校正项

\Omega的边界\partial\Omega的邻域内构造一个局部坐标系(\rho, \phi):在\Omega的边界\partial\Omega的邻域内每一点P\rho(0\leq\rho_{0})为点P\partial\Omega的距离,这里\rho_{0}为适当小的正常数,使得在边界\partial\Omega上各点的内法线在\partial\Omega的邻域0\leq\rho\leq\rho_{0}内相互不相交.坐标\phi=(\phi_{1}, \phi_{2}, \cdots, \phi_{n-1})是边界\partial\Omega上的一个n-1维非奇异坐标系,设点P的坐标\phi是通过点P的内法线和边界\partial\Omega的交点Q的坐标\phi相同.

\partial\Omega的邻域0\leq\rho\leq\rho_{0}中,设

L=\overline{D}^{n}_{i}\overline{a}^{nn}_{i}(\rho, \phi)\overline{D}^{n}_{i}+\sum\limits^{n-1}_{j, k=1}\overline{D}^{j}_{i}\overline{a}^{jk}_{i}(\rho, \phi)\overline{D}^{k}_{i}+\overline{D}^{n}_{i}\overline{b}^{n}_{i}(\rho, \phi)+\sum\limits^{n-1}_{j=1}\overline{D}^{j}_{i}\overline{b}^{j}_{i}(\rho, \phi), \ \ i=1, 2, \cdots, N,

\overline{D}^{n}_{i}=\frac{\partial}{\partial \rho}, \ \\overline{D}^{j}_{i}=\frac{\partial}{\partial \phi_{j}}, \ \i=1, 2, \cdots, N, \ j=1, 2, \cdots, n-1,

其中\overline{a}^{jk}_{i}, \overline{a}^{j}_{i}, \overline{b}^{j}_{i}为已知函数,它们的结构从略.

再在0\leq\rho\leq\rho_{0}上引入多重尺度变量[1, 2]

\zeta_{i}=\frac{h_{i}(\rho, \phi)}{\mu}, \ \overline{\rho}=\rho, \\phi=\phi, \ \ i=1, 2, \cdots, N,
(4.1)

这里h_{i}(\rho, \phi)为待定函数.不失一般性,以下仍用\rho来代替\overline{\rho}.由(4.1)式,我们有

L=\frac{1}{\mu^{2}}K_{i0}+\frac{1}{\mu}K_{i1}+K_{i2},
(4.2)

其中K_{i0}=\overline{a}^{nn}_{i}h^{2}_{i}\frac{\partial^{2}}{\partial\zeta^{2}},而K_{i1}K_{i2}的构造从略.设积分-微分方程初-边值问题(1.1)-(1.3)的广义解(u_{1}, u_{2}, \cdots, u_{N})

u_{i}=U_{i}+W_{i}, \ \ i=1, 2, \cdots, N,
(4.3)

其中

W_{i}=\sum\limits^{\infty}_{0}w_{ijk}(t, \zeta_{i}, \phi)\varepsilon^{j}\mu^{k}, \\ i=1, 2, \cdots, N.
(4.4)

选取h_{i}(\rho, \phi)=\int^{\rho}_{0}1/\sqrt{a^{nn}_{i}(\rho)},将(2.3), (3.2), (4.3)和(4.4)式代入(1.1), (1.2)式,按\varepsilon, \mu的幂级数展开非线性项,合并\varepsilon^{j}\mu^{k}同次幂项,并令其的系数为零,得

(\psi(\rho, \phi), K_{i0}w_{i00})-(\psi(\rho, \phi), T_{i}w_{i00})=(\psi(\rho, \phi), f_{i}(\rho, \phi, U_{i00}+w_{i00})-f_{i}(\rho, \phi, U_{i00})), \\\forall\psi(\rho, \phi)\in C^{\infty}_{0}(\Omega)\ \i=1, 2, \cdots, N,
(4.5)

(\psi(\rho, \phi), w_{i00})=(\psi(\rho, \phi), g_{i}(t, 0, \phi)), ~~x\in\partial\Omega, \ \forall\psi(\rho, \phi)\in C^{\infty}_{0}(\Omega) , \ i=1, 2, \cdots, N,
(4.6)

$(\psi(\rho, \phi), K_{i0}w_{ijk})-(\psi(\rho, \phi), T_{i}w_{ijk})=(\psi(\rho, \phi), f_{iy_{i}}(\rho, \phi, U_{i00}+w_{i00})w_{ijk}+G_{ijk}), \\\forall\psi(\rho, \phi)\in C^{\infty}_{0}(\Omega), \ \j, k=0, 1, \cdots, \ j+k\neq 0, \ \ i=1, 2, \cdots, N, \ \$
(4.7)

(\psi(\rho, \phi), w_{ijk})=(\psi(\rho, \phi), U_{ijk}(t, 0, \phi)), \\x\in\partial\Omega, \ \forall\psi(\rho, \phi)\in C^{\infty}_{0}(\Omega), \ j, k=0, 1, \cdots, \ j+k\neq 0, \ \i=1, 2, \cdots, N,
(4.8)

其中G_{ijk}\ (j, k=0, 1, \cdots, \ j+k\neq 0)为逐次已知函数,其结构也从略.

由(4.5), (4.6)式以及(4.7), (4.8)式和假设,可依次得到具有衰减性质的解w_{ijk}(t, \rho, \phi)

w_{ijk}=O(\exp(-\widetilde{k}_{ijk}\zeta_{i})), \ \ j, k=0, 1, \cdots, \ \ i=1, 2, \cdots, N,
(4.9)

这里\widetilde{k}_{ijk}\ (j, k=0, 1, \cdots, i=1, 2, \cdots, N)为适当小的正常数.

再引入一个充分光滑的分割函数\overline{\psi}(\rho)

\overline{\psi}(\rho)=1, \ \ 0\leq\rho\leq (2/3)\rho_{0}; \ \ \ \\overline{\psi}(\rho)=0, \ \ (2/3)\leq\rho.

\overline{w}_{ijk}=\overline{\psi}(\rho)w_{ijk}\(j, k=0, 1, \cdots, \ i=1, 2, \cdots, N ).为了方便,以下仍将w_{ijk}来代替\overline{w}_{ijk}.w_{ijk}代入(4.4)式,便得到具有边界层校正性质的一组广义解W=(W_{1}, W_{2}, \cdots, W_{N}).

5 解的展开式的一致有效性

由上面的讨论,可得非线性微分-积分时滞奇摄动广义反应扩散系统(1.1)-(1.3)的一组广义解u(t, x)=(u_{1}(t, x), u_{2}(t, x), \cdots, u_{N}(t, x)),并有如下渐近展开式

\begin{eqnarray}u_{i}(t, x)&=&\sum^{\infty}_{j, k=0}U_{ijk}(t, x)\varepsilon^{j}\mu^{k}+\sum^{\infty}_{j, k=0}y_{ijk}(\tau, x)\varepsilon^{j}\sigma^{k}+\sum^{\infty}_{j, k=0}w_{ijk}(t, \zeta)\varepsilon^{j}\mu^{k}, \\&&~~~~ i=1, 2, \cdots, N, \ \ 0 <\varepsilon, \sigma, \mu\ll 1.\end{eqnarray}
(5.1)

下面来讨论广义解存在性及其渐近展开式(5.1)的一致有效性.

首先建立如下非线性微分-积分时滞奇摄动广义反应扩散系统的微分不等式理论.

定义  设有两组函数\overline{u}_{i}, \i=1, 2, \cdots, N\underline{u}_{i}, \ i=1, 2, \cdots, N, \\overline{u}_{i}\geq\underline{u}_{i},并分别满足不等式

\begin{eqnarray*}&&\varepsilon(\psi(x), \frac{\partial \overline{u}_{i}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\overline{u}_{i}(t, x))+(\psi(x), T_{i}\overline{u}_{i}(t-\varepsilon, x))\\&\geq&(\psi(x), f_{i}(x, \overline{u}_{i}(t, x))), \ \(t, x)\in(0, \infty)\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N, \end{eqnarray*}

(\psi(x), \overline{u}_{i}(t, x))\geq(\psi(x), A_{i}(t, x)), \ \x\in\partial\Omega, \ \ \forall\psi(x)\in C^{\infty}_{0}(\Omega) , \\ i=1, 2, \cdots, N,

(\psi(x), \overline{u}_{i}(t, x))\geq(\psi(x), B_{i}(t, x)), \ \(t, x)\in [-\varepsilon, 0]\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N

\varepsilon(\psi(x), \frac{\partial\underline{u}_{i}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\underline{u}_{i}(t, x))+(\psi(x), T_{i}\underline{u}_{i}(t-\varepsilon, x))\leq(\psi(x), f_{i}(x, \underline{u}_{i}(t, x))),

$(t, x)\in(0, \infty)\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \$

(\psi(x), \underline{u}_{i}(t, x))\leq(\psi(x), A_{i}(t, x)), \ \x\in\partial\Omega, \ \ \forall\psi(x)\in C^{\infty}_{0}(\Omega) , \ \i=1, 2, \cdots, N,

(\psi(x), \underline{u}_{i}(t, x))\leq(\psi(x), B_{i}(t, x)), \ \(t, x)\in [-\varepsilon, 0]\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N,

则分别称\overline{u}_{i}(t, x)\underline{u}_{i}(t, x)为初始-边值问题(1.1)-(1.3)的上解和下解.

现有如下定理.

定理1  在假设(H1)-(H5)下, \underline{u}_{i}(t, x), i=1, 2, \cdots, N\overline{u}_{i}(t, x), i=1, 2, \cdots, N,分别为非线性微分-积分时滞奇摄动广义反应扩散系统初始-边值问题(1.1)-(1.3)的下解和上解,则问题(1.1)-(1.3)存在一组广义解u_{i}(t, x), i=1, 2, \cdots, N,并成立\underline{u}_{i}(t, x)\leq u_{i}(t, x)\leq \overline{u}_{i}(t, x), i=1, 2, \cdots, N.

  首先按以下关系式构造迭代序列

\begin{eqnarray}&&\varepsilon(\psi(x), \frac{\partial u_{i(k+1)}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}u_{i(k+1)}(t, x))+(\psi(x), T_{i}u_{i(k+1)}(t-\varepsilon, x))\\&=&(\psi(x), f_{i}(x, u_{ik}(t, x))), \ \(t, x)\in(0, \infty)\times\Omega, \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \\end{eqnarray}
(5.2)

(\psi(x), u_{i(k+1)}(t, x))=(\psi(x), A_{i}(t, x)), \ \\forall\psi(x)\in C^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N,
(5.3)

(\psi(x), u_{i(k+1)}(t, x))=(\psi(x), B_{i}(t, x)), \\(t, x)\in [-\varepsilon, 0]\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N.
(5.4)

由(5.2)-(5.4)式,设\overline{u}_{i0}=\overline{u}_{i}\underline{u}_{i0}=\overline{u}_{i}为两组的零次函数,我们可依次地可得\overline{u}_{in}, n=1, 2\cdots\underline{u}_{in}, n=1, 2\cdots.因此能得到两组函数列\{\overline{u}_{in}\i=1, 2, \cdots, N\}\{\underline{u}_{in}\ i=1, 2, \cdots, N\}.现讨论其收敛性态.

\overline{v}_{i0}=\overline{u}_{i0}-\overline{u}_{i1},由假设和(5.2)-(5.4)式有

\begin{eqnarray*}&&\varepsilon(\psi(x), \frac{\partial\overline{v}_{i0}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\overline{v}_{i0}(t, x))+(\psi(x), T_{i}\overline{v}_{i0}(t-\varepsilon, x))\\&=&\varepsilon(\psi(x), \frac{\partial\overline{u}_{i0}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\overline{u}_{i0}(t, x))+(\psi(x), T_{i}\overline{u}_{i0}(t-\varepsilon, x))\\&&-\varepsilon(\psi(x), \frac{\partial\overline{u}_{i1}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\overline{u}_{i1}(t, x))+(\psi(x), T_{i}\overline{u}_{i1}(t-\varepsilon, x))\\&\geq& (\psi(x), f_{i}(x, \overline{u}_{i0}(t, x)))-(\psi(x), f_{i}(x, \overline{u}_{i0}(t, x)))=0, \\&&~~(t, x)\in(0, \infty)\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N, \end{eqnarray*}

(\psi(x), \overline{v}_{i0}(t, x))=(\psi(x), \overline{u}_{i0}(t, x))-(\psi(x), \overline{u}_{i1}(t, x))=0,

x\in\partial\Omega, \ \ \forall\psi(x)\in C^{\infty}_{0}(\Omega) , \\ i=1, 2, \cdots, N,

(\psi(x), \overline{v}_{i0}(0, x))=(\psi(x), \overline{u}_{i0}(0, x))-(\psi(x), \overline{u}_{i1}(0, x))=0,

(t, x)\in [-\varepsilon, 0]\times\Omega, \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N.

于是由线性问题的极值原理得到\overline{v}_{i0}\geq 0, i=1, 2, \cdots, N.

\overline{u}_{i0}\geq\overline{u}_{i1}, ~ i=1, 2, \cdots, N.

\overline{u}_{in}\geq\overline{u}_{i(n+1)},设\overline{v}_{in}=\overline{u}_{in}-\overline{u}_{i(n+1)},这时有

\begin{eqnarray*}&&\varepsilon(\psi(x), \frac{\partial\overline{v}_{in}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\overline{v}_{in}(t, x))+(\psi(x), T_{i}\overline{v}_{in}(t-\varepsilon, x))\\&=&\varepsilon(\psi(x), \frac{\partial\overline{u}_{in}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\overline{u}_{in}(t, x))+(\psi(x), T_{i}\overline{u}_{in}(t-\varepsilon, x))\\&&-\varepsilon(\psi(x), \frac{\partial\overline{u}_{i(n+1)}(t, x)}{\partial{t}})-\mu^{2}(\psi(x), L_{i}\overline{u}_{i(n+1)(t, x)})+(\psi(x), T_{i}\overline{u}_{i(n+1)}(t-\varepsilon, x))\\&\geq& (\psi(x), f_{i}(x, \overline{u}_{in}(t, x)))-(\psi(x), f_{i}(x, \overline{u}_{i(n+1)}(t, x)))\geq 0, \\&&~~(t, x)\in(0, \infty)\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N, \end{eqnarray*}

(\psi(x), \overline{v}_{in}(t, x))=(\psi(x), \overline{u}_{in}(t, x))-(\psi(x), \overline{u}_{i(n+1)}(t, x))=0,

x\in\partial\Omega, \ \ \forall\psi(x)\in C^{\infty}_{0}(\Omega) , \\ i=1, 2, \cdots, N,

(\psi(x), \overline{v}_{in}(0, x))=(\psi(x), \overline{u}_{in}(0, x))-(\psi(x), \overline{u}_{i(n+1)}(0, x))=0,

(t, x)\in [-\varepsilon, 0]\times\Omega, \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N.

于是由线性问题的极值原理得到\overline{v}_{in}\geq 0, i=1, 2, \cdots, N.

\overline{u}_{in}\geq\overline{u}_{i(n+1)}, \ \ i=1, 2, \cdots, N.

由此我们得到

\overline{u}_{i}=\overline{u}_{i0}\geq\overline{u}_{i1}\geq\cdots\geq\overline{u}_{in}\geq\overline{u}_{i(n+1)}\geq\cdots, \ \i=1, 2, \cdots, N.

类似有

\underline{u}_{i}=\underline{u}_{i0}\leq\underline{u}_{i1}\leq\cdots\leq\underline{u}_{in}\leq\underline{u}_{i(n+1)}\leq\cdots, \\ i=1, 2, \cdots, N.

同样可得

\overline{u}_{in}\geq\underline{u}_{in}, \ \ n=0, 1, \cdots, \ \i=1, 2, \cdots, N.

由上述的结果和Arzela定理,非线性微分-积分时滞奇摄动广义反应扩散系统初始-边值问题(1.1)-(1.3)存在一组广义解u(t, x)=(u_{1}(t, x), u_{2}(t, x), \cdots, u_{N}(t, x)),且成立不等式\underline{u}_{i}(t, x)\leq u_{i}(t, x)\leq\overline{u}_{i}(t, x), \ i=1, 2, \cdots, N.定理1证毕.

定理2  在假设(H1)-(H6)下,非线性微分-积分时滞奇摄动广义反应扩散系统初始-边值问题(1.1)-(1.3)存在一组广义解u(t, x)=(u_{1}(t, x), u_{t, 2}(t, x), \cdots, u_{N}(t, x)),并具有形如(5.1)式的一致有效的渐近展开式.

  构造两组辅助函数\alpha_{i}, \beta_{i}, \ i=1, 2, \cdots, N

\alpha_{i}=Z_{iM}-r_{i}\lambda, \ \ i=1, 2, \cdots, N,
(5.5)

\beta_{i}=Z_{iM}+r_{i}\lambda, \ \ i=1, 2, \cdots, N,
(5.6)

其中r_{i}为适当大的待定正常数, \lambda=\max(\varepsilon^{M}\mu^{M+1}, \varepsilon^{M}\mu^{M+1}),而

Z_{iM}(t, x)=\sum\limits^{M}_{j, k=0}U_{ijk}(t, x)\varepsilon^{j}\mu^{k}+\sum\limits^{M}_{j, k=0}y_{ijk}(\tau, x)\varepsilon^{j}\sigma^{k}+\sum\limits^{M}_{j, k=0}w_{ijk}(t, \zeta)\varepsilon^{j}\mu^{k}.

显然,选取足够大的r_{i}, i=1, 2, \cdots, N,当r_{i}\geqr_{i0}时,恒有

(\psi(x), \alpha_{i}(t, x))\leq(\psi(x), \beta_{i}(t, x)), \\(t, x)\in [-\varepsilon, \infty)\times\Omega\ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega) , \ \ i=1, 2, \cdots, N,
(5.7)

(\psi(x), \alpha_{i}(t, x))\leq(\psi(x), g_{i}(t, x))\leq(\psi(x), \beta_{i}(t, x)), \\x\in\partial\Omega, \ \ \forall\psi(x)\in C^{\infty}_{0}(\Omega), \\ i=1, 2, \cdots, N.
(5.8)

由假设,存在正常数D_{i1}

\begin{eqnarray*}(\psi(x), \alpha_{i}(t, x))&=&(\psi(x), Z_{iM}-r_{i}\lambda)\\&=&(\psi(x), \sum^{M}_{j, k=0}U_{ijk}(t, x)\varepsilon^{j}\mu^{k}+\sum^{M}_{j, k=0}y_{ijk}(\tau, x)\varepsilon^{j}\sigma^{k}+\sum^{M}_{j, k=0}w_{ijk}(t, \zeta)\varepsilon^{j}\mu^{k}-r_{i}\lambda)\\&\leq& (\psi(x), h_{i}(x))+(D_{i1}-r_{i})\lambda), \\&&(t, x)\in[-\varepsilon, 0]\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N.\end{eqnarray*}

选取r_{i}\geq D_{i1},可得

(\psi(x), \alpha_{i}(t, x))\leq(\psi(x), h_{i}(x)),

(t, x)\in[-\varepsilon, 0]\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N.

同理可得

(\psi(x), \beta_{i}(t, x))\geq(\psi(x), h_{i}(x)),

(t, x)\in[-\varepsilon, 0]\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N.

即成立

(\psi(x), \alpha_{i}(t, x))\leq(\psi(x), h_{i}(x))\leq(\psi(x), \beta_{i}(x)), \\(t, x)\in[-\varepsilon, 0]\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N.
(5.9)

下面来证明

\varepsilon(\psi(x), \frac{\partial \alpha_{i}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\alpha_{i}(t, x))+(\psi(x), T_{i}\alpha_{i}(t-\varepsilon, x))-(\psi(x), f_{i}(x, \alpha_{i}(t, x)))\leq 0, \\(t, x)\in(0, \infty)\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N,
(5.10)

\varepsilon(\psi(x), \frac{\partial \beta_{i}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\beta_{i}(t, x))+(\psi(x), T_{i}\beta_{i}(t-\varepsilon, x))-(\psi(x), f_{i}(x, \beta_{i}(t, x)))\geq 0, \\(t, x)\in (0, \infty)\times\Omega, \ \ \forall\psi(x)\inC^{\infty}_{0}(\Omega), \ \ i=1, 2, \cdots, N.
(5.11)

由假设和(3.7), (4.9)式,对足够小的\varepsilon, \mu,存在正常数D_{i2}

\begin{eqnarray*}&&\varepsilon(\psi(x), \frac{\partial \alpha_{i}(t, x)}{\partialt})-\mu^{2}(\psi(x), L_{i}\alpha_{i}(t, x))+(\psi(x), T_{i}\alpha_{i}(t-\varepsilon, x))-(\psi(x), f_{i}(x, \alpha_{i}(t, x)))\\&=&\varepsilon(\psi(x), \frac{\partial(Z_{iM}(t, x)-r_{i}\lambda)}{\partialt})-\mu^{2}(\psi(x), L_{i}(Z_{iM}(t, x)-r_{i}\lambda))\\&&+(\psi(x), T_{i}(Z_{iM}(t-\varepsilon, x)-r_{i}\lambda))-(\psi(x), f_{i}(x, (Z_{iM}(t, x))-r_{i}\lambda))\\&=&(\psi(x), T_{i}U_{i00})-(\psi(x), f_{i}(x, U_{i00}))+\sum^{M}_{j, k=0, j+k\neq0}[(\psi(x), TU_{ijk})-(\psi(x), L_{i}[U_{ij(k-2)}])\\&&+(\psi(x), L_{i}[\frac{\partial U_{(j-1)k}}{\partialt}])-(\psi(x), F_{ijk})]\varepsilon^{j}\mu^{k}+(\psi(x), \frac{\partial y_{i00}(\tau, x)}{\partial\tau})\\&&+(\psi(x), T_{i}y_{i00}(\tau, x))-(\psi(x), f_{i}(x, y_{i00}(\tau, x))+U_{i00}(0, x))\\&&+\sum^{M}_{j, k=1, j+k\neq 0}[(\psi(x), \frac{\partialy_{ijk}(\tau, x)}{\partial \tau})+(\psi(x), T_{i}y_{ijk}(\tau, x))-(\psi(x), f_{iy}(x, y_{i00}(0, x))y_{ijk}(\tau, x))\\&&-(\psi(x), L_{i}y_{ij(k-2)}(\tau, x))-\widetilde{F}_{ijk}]\varepsilon^{j}\sigma^{k}+(\psi(\rho, \phi), K_{i0}w_{i00})-(\psi(\rho, \phi), T_{i}w_{i00})\\&&-(\psi(\rho, \phi), f_{i}(\rho, \phi, U_{i00}+w_{i00})+f_{i}(\rho, \phi, U_{i00}))\\&&+\sum^{M}_{j, k=1, j+k\neq0}[(\psi(\rho, \phi), K_{i0}w_{ijk})-(\psi(\rho, \phi), T_{i}w_{ijk})\\&&-(\psi(\rho, \phi), -f_{iy_{i}}(\rho, \phi, U_{i00}+w_{i00})w_{ijk}-G_{ijk})]\varepsilon^{j}\mu^{k}+(\psi(x), D_{i2}\lambda)-(\psi(x), \sum^{N}_{i=1}\delta_{i2}r_{i}\lambda)\\&\leq&(\psi(x), D_{i2}\lambda-\sum^{N}_{i=1}\delta_{i2}r_{i}\lambda)\leq(\psi(x), (D_{i2}\lambda))-(\psi(x), \sum^{N}_{i=1}\delta_{i2}r_{i}\lambda)\\&=&(\psi(x), (D_{i2}-\sum^{N}_{i=1}\delta_{i2}r_{i})\lambda).\end{eqnarray*}

因此选取r_{i}\geq D_{i2}/\sum\limits^{N}_{i=1}\delta_{i2},不等式(5.10)成立.同理可证不等式(5.11)也成立.

综上所证,选择足够大的r_{i},并对足够小的\varepsilon, \mu,关系式(5.7)-(5.11)成立.于是由定理1,初始-边值问题(1.1)-(1.3)存在一组广义解u=(u_{1}, u_{1}, \cdots, u_{N}),且成立

\alpha_{i}(t, x)\leq u_{i}(t, x)\leq \beta_{i}(t, x), \ \(t, x)\in[0, \infty)\times(\Omega+\partial\Omega).

再由(5.5), (5.6)式知,对于i=1, 2, \cdots, N,有

u_{i}(t, x)=\sum\limits^{M}_{j, k=0}U_{ijk}(t, x)\varepsilon^{j}\mu^{k}+\sum\limits^{M}_{j, k=0}y_{ijk}(\tau, x)\varepsilon^{j}\sigma^{k}+\sum\limits^{M}_{j, k=0}w_{ijk}(t, \zeta_{i})\varepsilon^{j}\mu^{k}+O(\lambda),

\lambda=\max(\varepsilon^{M+1}\mu^{M}, \varepsilon^{M}\mu^{M+1}), \ \i=1, 2, \cdots, N, \ \ 0 <\varepsilon, \sigma, \mu\ll 1.

即非线性微分-积分时滞奇摄动广义反应扩散系统初始-边值问题(1.1)-(1.3)的解

u(t, x)=(u_{1}(t, x), u_{2}(t, x), \cdots, u_{N}(t, x))

的分量u_{i}(t, x), \ i=1, 2, \cdots, N具有形如(5.1)式的一致有效的渐近展开式.定理证毕.

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