在空间Rn中,若p∈[2, ∞), α∈(0, n),Ma和Zhao[1]给出了分数阶薛定谔方程的一般形式有
$ \begin{array}{*{20}{c}} {i{\varphi _t} + \Delta \varphi + p\varphi {{\left| \varphi \right|}^{p - 2}}\left( {\frac{1}{{{{\left| x \right|}^{n - \alpha }}}} * {{\left| \varphi \right|}^p}} \right) = 0}\\ {x \in {{\bf{R}}^n}, t > 0} \end{array} $ | (1) |
式中φ(t, x)为波函数,其在激光物理、量子力学等不同领域均有着广泛的应用。为了得到方程(1)的解,可以令φ(x, t)=eiωtu(x), 则方程(1)可转化为Choquard方程
$ \begin{array}{*{20}{c}} {\Delta u - \omega u + pu{{\left| u \right|}^{p - 2}}\left( {\frac{1}{{{{\left| x \right|}^{n - \alpha }}}} * {{\left| u \right|}^p}} \right) = 0}\\ {u \in {H^1}\left( {{{\bf{R}}^n}} \right)} \end{array} $ | (2) |
关于方程(2)的正解性质,Lions[2, 3]和Lieb[4]等学者进行了广泛的研究。令ω=1,v=
$ \left( {I - \Delta } \right)u = pu{\left| u \right|^{p - 2}}v $ |
也可转为积分形式
$ \left\{ \begin{array}{l} u\left( x \right) = \int_{{{\bf{R}}^n}} {{G_2}\left( {x - y} \right){{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right)v\left( y \right){\rm{d}}y} \\ v\left( x \right) = \int_{{{\bf{R}}^n}} {\frac{{{u^p}\left( y \right)}}{{{{\left| {x - y} \right|}^{n - \alpha }}}}{\rm{d}}y} \end{array} \right. $ | (3) |
其中G2是二阶的Bessel位势核,Ma和Zhao[1]研究了方程(3)在Rn上正解的径向对称性与单调性。
偏微分方程的对称解问题的研究最早可追溯到20世纪70年代。Serrin[5]在边界条件
$ \left\{ {\begin{array}{*{20}{c}} {u\left( x \right) = 0}&{x \in \partial \mathit{\Omega }}\\ {\frac{{\partial u}}{{\partial n}} = {\rm{Constant}}}&{x \in \partial \mathit{\Omega }} \end{array}} \right. $ |
下,利用移动平面法,研究了Laplace方程-Δu(x)=1, x∈Ω解的径向对称性。接下来的几十年里,文献[6, 7]对此类问题进行了更深入的研究。在此基础上,文献[8]利用Hardy-Littlewood-Sobolev不等式研究了Rn中积分方程的对称解问题。进一步地,Li和Wang[9]在有界区域上研究了积分方程解的对称性。
假设Ω1⊂Ω2⊂Rn是一有界开区域,其中∂Ω1, ∂Ω2∈C1,并且∂Ω1∩∂Ω2为空集。分数阶薛定谔方程(1)可转化为包括二阶Bessel位势和分数阶Riesz位势的积分方程组(3)。本文尝试在环形区域上研究以下包含分数阶Bessel位势和分数阶Riesz位势的积分方程组
$ \left\{ \begin{array}{l} u\left( x \right) = \int_{{{\bf{R}}^n}} {{G_\alpha }\left( {x - y} \right){{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right)v\left( y \right){\rm{d}}y} \\ \;\;\;\;\;\;\;x \in \mathit{\Omega }: = {\mathit{\Omega }_2}\backslash {{\mathit{\bar \Omega }}_1}\\ v\left( x \right) = \int_{{{\bf{R}}^n}} {\frac{{{u^p}\left( y \right)}}{{{{\left| {x - y} \right|}^{n - \alpha }}}}{\rm{d}}y} \\ \;\;\;\;\;\;\;x \in \mathit{\Omega }: = {\mathit{\Omega }_2}\backslash {{\mathit{\bar \Omega }}_1} \end{array} \right. $ | (4) |
其中p≥2, 0 < α < n。本文将证明如下定理。
定理1 假设常数t, e, s, q满足
$ \frac{1}{t} \in \left[ {\frac{1}{s}, \frac{1}{s} + \frac{\alpha }{n}} \right] \cap \left[ {\frac{\alpha }{n}, 1} \right] $ | (5) |
$ \frac{1}{e} \in \left[ {\frac{1}{q}, \frac{1}{q} + \frac{\alpha }{n}} \right] \cap \left[ {\frac{\alpha }{n}, 1} \right] $ | (6) |
且
$ s, q > 1, \frac{1}{q} + \frac{{p - 1}}{s} = \frac{1}{t}, \frac{{p - 1}}{s} = \frac{1}{e} $ | (7) |
若(u, v)∈Ls(Ω)×Lq(Ω)是方程(4)的正解,且满足边界条件
$ \left\{ \begin{array}{l} u\left( x \right) = {C_1} > 0, v\left( x \right) = {C_2} > 0, \;\;\;\;\;\;x \in {{\mathit{\bar \Omega }}_1}\\ u\left( x \right) = v\left( x \right) = 0\;\;\;\;\;\;\;\;\;x \in {{\bf{R}}^n}\backslash {\mathit{\Omega }_2} \end{array} \right. $ |
则Ω1和Ω2一定为同心球,(u, v)是径向对称的,且随着对称点的距离增加而单调递减。
推论1 当Ω1为空集时,由定理1可得方程(4)在有界区域Ω2上正解的径向对称性和单调性。
容易验证,满足条件式(5-7)的常数t, e, s, q是存在的。比如在R3中,方程(1)为非线性Choquard方程
$ \begin{array}{*{20}{c}} {i{\varphi _t} + \Delta \varphi + 2\varphi \left( {\frac{1}{{\left| x \right|}} * {{\left| \varphi \right|}^2}} \right) = 0}&{x \in {{\bf{R}}^3}, t > 0} \end{array} $ |
类似引言推导,令φ(x, t)=eiωtu(x),上述方程可转化为
$ \left\{ \begin{array}{l} \Delta u - u + 2uv = 0\\ \Delta v = {u^2} \end{array} \right. $ |
即n=3, p=2, α=2。此时可取q=3, s=
下面给出后续证明中需要用到的Bessel位势和Riesz位势的Hardy-Littlewood-Sobolev不等式。Cheng,Huang和Li在文献[10]的式(1.2)中给出了关于Riesz位势的H-L-S不等式。
引理1 (Riesz位势的H-L-S不等式)令0 < α < n,1 < p < q < +∞,对任意的f∈Lp(Rn),有
$ {\left\| {\int_{{{\bf{R}}^n}} {\frac{{f\left( y \right)}}{{{{\left| {x - y} \right|}^{n - \alpha }}}}{\rm{d}}y} } \right\|_{{L^q}\left( {{{\bf{R}}^n}} \right)}} \le C{\left\| f \right\|_{{L^p}\left( {{{\bf{R}}^n}} \right)}} $ |
其中
Huang,Li和Wang在文献[11]的定理2.3中给出了关于Bessel位势的H-L-S不等式,也可参考文献[1]的式(8)。
引理2 (Bessel位势的H-L-S不等式)令0 < α < n,1 < p < r < +∞,对任意的f∈Lp(Rn),有
$ {\left\| {\int_{{{\bf{R}}^n}} {{G_\alpha }\left( {x - y} \right)f\left( y \right){\rm{d}}y} } \right\|_{{L^r}\left( {{{\bf{R}}^n}} \right)}} \le C{\left\| f \right\|_{{L^p}\left( {{{\bf{R}}^n}} \right)}} $ |
其中
$ {G_\alpha }\left( x \right) = \frac{1}{{\gamma \left( \alpha \right)}}\int_0^\infty {\exp \left( { - \frac{{{\rm{ \mathit{ π} }}{{\left| x \right|}^2}}}{\delta }} \right)\exp \left( { - \frac{\delta }{{4{\rm{ \mathit{ π} }}}}} \right){\delta ^{\frac{{\alpha - n}}{2}}}\frac{{{\rm{d}}\delta }}{\delta }} $ |
下面用移动平面法来证明本文的主要结果。对任意的λ∈ R,定义Tλ:={(x1, …, xn)∈Ω, x1=λ}作为移动平面。下面给出一些符号说明:
$ \begin{array}{*{20}{c}} {{x^\lambda } = \left( {2\lambda - {x_1}, \cdots , {x_n}} \right), {u_\lambda }\left( x \right) = }\\ {u\left( {{x^\lambda }} \right), {v_\lambda }\left( x \right) = v\left( {{x^\lambda }} \right), } \end{array} $ |
$ {A_\lambda } = \left\{ {x:{x_1} > \lambda } \right\} $ |
$ {\mathit{\Sigma} _\lambda } = \left\{ {x:{x_1} > \lambda ,x \in {\mathit{\Omega }_2}\backslash {\mathit{\Omega }_1},{x^\lambda } \in {\mathit{\Omega }_2}\backslash {\mathit{\Omega }_1}} \right\} $ |
$ {{\mathit{\Sigma} '}_\lambda } = \left\{ {x:{x^\lambda } \in {\mathit{\Sigma} _\lambda }} \right\} $ |
$ {E_\lambda } = \left\{ {x:{x_1} > \lambda ,x \in {{\bf{R}}^n}\backslash {\mathit{\Omega }_2},{x^\lambda } \in {{\bf{R}}^n}\backslash {\mathit{\Omega }_2}} \right\} $ |
$ {{E'}_\lambda } = \left\{ {x:{x^\lambda } \in {E_\lambda }} \right\} $ |
$ {\mathit{\Omega }_\lambda } = \left\{ {x:{x_1} > \lambda ,x \in {{\bf{R}}^n}\backslash {\mathit{\Omega }_2},{x^\lambda } \in {\mathit{\Omega }_2}} \right\} $ |
$ {{\mathit{\Omega '}}_\lambda } = \left\{ {x:{x^\lambda } \in {\mathit{\Omega }_\lambda }} \right\} $ |
$ {D_\lambda } = \left\{ {x:{x_1} > \lambda ,x \in {\mathit{\Omega }_2}\backslash {\mathit{\Omega }_1},{x^\lambda } \in {\mathit{\Omega }_1}} \right\} $ |
$ {{D'}_\lambda } = \left\{ {x:{x^\lambda } \in {\mathit{D}_\lambda }} \right\} $ |
$ {P_\lambda } = \left\{ {x:{x_1} > \lambda ,x \in {\mathit{\Omega }_1},{x^\lambda } \in {\mathit{\Omega }_1}} \right\} $ |
$ {{P'}_\lambda } = \left\{ {x:{x^\lambda } \in {\mathit{P}_\lambda }} \right\} $ |
将平面Tλ从λ=+∞移向λ=-∞,在这个过程中,比较u(x)和u(xλ),v(x)和v(xλ)的大小。记λ0为Tλ第一次和∂Ω2相切时的λ的值。由边界条件,很显然,对任意的λ≥λ0,有u(xλ)≥u(x), v(xλ)≥v(x), ∀x∈Aλ。
接下来把Tλ从λ=λ0向λ=-∞移动,当出现下列4种情况之一时,停止移动,并记此时的λ为
由λ的定义,对任意的λ∈[
首先,给出一个在移动平面法中起着非常重要作用的引理。
引理3 对任意的
$ \begin{array}{*{20}{c}} {u\left( {{x^\lambda }} \right) - u\left( x \right) = \int_{{A_\lambda }} {{g_\alpha }\left( {x - y} \right)\left[ {{{\left| {u\left( {{y^\lambda }} \right)} \right|}^{p - 2}}u\left( {{y^\lambda }} \right) \cdot } \right.} }\\ {\left. {v\left( {{y^\lambda }} \right) - {{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right)v\left( y \right)} \right]{\rm{d}}y} \end{array} $ | (8) |
$ \begin{array}{*{20}{c}} {v\left( {{x^\lambda }} \right) - v\left( x \right) = \int_{{A_\lambda }} {\left( {\frac{1}{{{{\left| {x - y} \right|}^{n - \alpha }}}} - \frac{1}{{{{\left| {{x^\lambda } - y} \right|}^{n - \alpha }}}}} \right)} \cdot }\\ {\left[ {{u^p}\left( {{y^\lambda }} \right) - {u^p}\left( y \right)} \right]{\rm{d}}y} \end{array} $ | (9) |
其中Aλ=Σλ∪Dλ∪Ωλ∪Eλ∪Pλ,且gα(x-y)=Gα(x-y)-Gα(xλ-y)。这是因为对任意的λ∈[
把定理1的证明分为以下几步。首先,证明当Tλ移动一小段距离后,也就是存在常数λ1,当λ∈[λ1, λ0),有
$ u\left( {{x^\lambda }} \right) \ge u\left( x \right), v\left( {{x^\lambda }} \right) \ge v\left( x \right), \forall x \in {A_\lambda } $ | (10) |
引理4 存在常数λ1,使得对任意的λ∈[λ1, λ0),有u(xλ)≥u(x), v(xλ)≥v(x), ∀x∈Aλ。
证明 对任意的λ∈[λ1, λ0),由边界条件u(x)=C1, x∈Ω1; u(x)=0, x∈ Rn\Ω2,v(x)=C2, x∈Ω1; v(x)=0, x∈ Rn\Ω2有
$ \left\{ \begin{array}{l} u\left( {{x^\lambda }} \right) \equiv u\left( x \right) = {C_1}\;\;\;\;\forall x \in {P_\lambda }\\ u\left( {{x^\lambda }} \right) > u\left( x \right) \equiv 0\;\;\;\;\forall x \in {\mathit{\Omega }_\lambda }\\ u\left( {{x^\lambda }} \right) \equiv u\left( x \right) \equiv 0\;\;\;\;\forall x \in {E_\lambda }\\ u\left( {{x^\lambda }} \right) \equiv {C_1} > u\left( x \right)\;\;\;\;\forall x \in {D_\lambda } \end{array} \right. $ |
类似地,v(x)也有相同的边界情况。仅需考虑x∈Σλ这种情况。定义Σλu={x∈Σλ:u(x)>u(xλ)}, Σλv={x∈Σλ: v(x)>v(xλ)},则对任意的x∈Σλu,有
$ \begin{array}{*{20}{c}} {u\left( x \right) - u\left( {{x^\lambda }} \right) \le \int_{{\Sigma _\lambda }} {{g_\alpha }\left( {x,y} \right)\left[ {{{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right) \cdot } \right.} }\\ {\left. {v\left( y \right) - {{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( {{y^\lambda }} \right)v\left( {{y^\lambda }} \right)} \right]{\rm{d}}y} \end{array} $ |
且
$ \begin{array}{*{20}{c}} {v\left( x \right) - v\left( {{x^\lambda }} \right) \le \int_{{\Sigma _\lambda }} {\frac{1}{{{{\left| {x - y} \right|}^{n - \alpha }}}}\left( {{u^p}\left( y \right) - } \right.} }\\ {\left. {{u^p}\left( {{y^\lambda }} \right)} \right){\rm{d}}y} \end{array} $ |
由引理2
$ \begin{array}{l} u\left( x \right) - u\left( {{x^\lambda }} \right) \le \int_{{\Sigma _\lambda }} {{g_\alpha }\left( {x,y} \right)\left[ {{{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right) \cdot } \right.} \\ \left. {v\left( y \right) - {{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( {{y^\lambda }} \right)v\left( {{y^\lambda }} \right)} \right]{\rm{d}}y \le \\ \int_{{\Sigma _\lambda }} {{g_\alpha }\left( {x - y} \right)\left[ {{u^{p - 1}}\left( y \right)v\left( y \right) - {u^{p - 1}}\left( {{y^\lambda }} \right) \cdot } \right.} \\ \left. {v\left( {{y^\lambda }} \right)} \right]{\rm{d}}y \le \int_{{\Sigma _\lambda }} {{G_\alpha }\left( {x - y} \right)\left[ {{u^{p - 1}}\left( {{y^\lambda }} \right) \cdot } \right.} \\ \left. {{{\left( {v\left( y \right) - v\left( {{y^\lambda }} \right)} \right)}^ + } + v\left( y \right){{\left( {{u^{p - 1}}\left( y \right) - {u^{p - 1}}\left( {{y^\lambda }} \right)} \right)}^ + }} \right]{\rm{d}}y \end{array} $ |
由Hardy-Littlewood-Sobolev不等式,得‖u-uλ‖Ls(Σλu)≤‖u-uλ‖Ls(Σλ)≤C‖uλp-1(v-vλ)++v(up-1-uλp-1)+‖Lt(Σλ)≤C‖uλp-1(v-vλ)‖Lt(Σλv)+C‖v(up-1-uλp-1)‖Lt(Σλu)其中
由Hölder不等式
$ \begin{array}{*{20}{c}} {{{\left\| {u - {u_\lambda }} \right\|}_{{L^s}\left( {\Sigma _\lambda ^u} \right)}} \le C{{\left\| {u_\lambda ^{p - 1}\left( {v - {v_\lambda }} \right)} \right\|}_{{L^t}\left( {\Sigma _\lambda ^v} \right)}} + }\\ {C{{\left\| {v{u^{p - 2}}\left( {u - {u_\lambda }} \right)} \right\|}_{{L^t}\left( {\Sigma _\lambda ^u} \right)}} \le }\\ {C\left\| u \right\|_{{L^s}\left( {{{\Sigma '}_\lambda }} \right)}^{p - 1}{{\left\| {v - {v_\lambda }} \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}} + C{{\left\| v \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}} \cdot }\\ {\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^v} \right)}^{p - 2}{{\left\| {u - {u_\lambda }} \right\|}_{{L^s}\left( {\Sigma _\lambda ^u} \right)}}} \end{array} $ |
其中
类似地,有
$ \begin{array}{*{20}{c}} {{{\left\| {v - {v_\lambda }} \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}} \le C{{\left\| {{u^p} - u_\lambda ^p} \right\|}_{{L^e}\left( {\Sigma _\lambda ^u} \right)}} \le }\\ {C\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 1}{{\left\| {u - {u_\lambda }} \right\|}_{{L^s}\left( {\Sigma _\lambda ^u} \right)}}} \end{array} $ |
其中
将上述两个不等式结合起来,可以得到
$ \begin{array}{*{20}{c}} {{{\left\| {u - {u_\lambda }} \right\|}_{{L^s}\left( {\Sigma _\lambda ^u} \right)}} \le C\left( {\left\| u \right\|_{{L^s}\left( {{{\Sigma '}_\lambda }} \right)}^{p - 1}\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 1} + } \right.}\\ {\left. {{{\left\| v \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}}\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 2}} \right){{\left\| {u - {u_\lambda }} \right\|}_{{L^s}\left( {\Sigma _\lambda ^u} \right)}}} \end{array} $ | (11) |
$ \begin{array}{*{20}{c}} {{{\left\| {v - {v_\lambda }} \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}} \le \frac{{C\left\| u \right\|_{{L^s}\left( {{{\Sigma '}_\lambda }} \right)}^{p - 1}\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 1}}}{{1 - C\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 2}{{\left\| v \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}}}} \cdot }\\ {{{\left\| {v - {v_\lambda }} \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}}} \end{array} $ |
由u∈Ls(Ω)和v∈Lq(Ω)可知, 存在常数λ1,满足λ0-λ1>0,对任意的λ∈[λ1, λ0),使得|Σ'λ|, |Σλu|, |Σλv|充分小,且满足
$ \begin{array}{*{20}{c}} {C\left( {\left\| u \right\|_{{L^s}\left( {{{\Sigma '}_\lambda }} \right)}^{p - 1}\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^v} \right)}^{p - 1} + } \right.}\\ {\left. {{{\left\| v \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}}\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 2}} \right) \le \frac{1}{2}}\\ {\frac{{C\left\| u \right\|_{{L^s}\left( {{{\Sigma '}_\lambda }} \right)}^{p - 1}\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 1}}}{{1 - C\left\| u \right\|_{{L^s}\left( {\Sigma _\lambda ^u} \right)}^{p - 2}{{\left\| v \right\|}_{{L^q}\left( {\Sigma _\lambda ^v} \right)}}}} \le \frac{1}{2}} \end{array} $ |
这就意味着对任意的λ∈[λ1, λ0),‖u-uλ‖Ls(Σλu)=0, ‖v-vλ‖Lq(Σλv)=0。因此Σλu和Σλv一定是空集,这就完成了该引理的证明。
在保持式(10)成立的同时,一直向左移动,将证明平面Tλ能被移动到λ=
引理5 定义
证明 同样仅需考虑x∈Σλ的这种情况。假设Tλ能一直移动,直到
$ \begin{array}{*{20}{c}} {u\left( {{x^\lambda }} \right) \ge u\left( x \right), v\left( {{x^\lambda }} \right) \ge v\left( x \right)}\\ {x \in {\Sigma _\lambda }, \forall \lambda \ge \bar \lambda - \varepsilon > \hat \lambda } \end{array} $ | (12) |
这就与λ的定义矛盾。
定义
$ \left| {\mathit{\Sigma} _{\bar \lambda }^u} \right| = 0, \mathop {\lim }\limits_{\lambda \to {{\bar \lambda }^ + }} \Sigma _\lambda ^u \subset \Sigma _{\bar \lambda }^u, \left| {\Sigma _{\bar \lambda }^v} \right| = 0, \mathop {\lim }\limits_{\lambda \to {{\bar \lambda }^ + }} \Sigma _\lambda ^v \subset \Sigma _{\bar \lambda }^v $ | (13) |
因此可以选择足够小的ε>0,满足
即对任意的λ∈[λ -∈, λ),Σλu和Σλv是空集。完成该引理的证明。
最后, 证明环形区域(4)的解是关于
引理6
证明 首先证明Ω1和Ω2关于
在情况①和③中,有
$ \begin{array}{*{20}{c}} {{u_{\hat \lambda }}\left( {\hat x} \right) - u\left( {\hat x} \right) \ge \int_{{D_{\hat \lambda }}} {{g_\alpha }\left( {\hat x,y} \right)\left[ {C_1^{p - 1}{C_2} - } \right.} }\\ {\left. {{{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right)v\left( y \right)} \right]{\rm{d}}y + }\\ {\int_{{\Omega _{\hat \lambda }}} {{g_\alpha }\left( {\hat x,y} \right){{\left| {{u_{\hat \lambda }}\left( y \right)} \right|}^{p - 2}}{u_{\hat \lambda }}\left( y \right){v_{\hat \lambda }}\left( y \right){\rm{d}}y} > 0} \end{array} $ |
$ \begin{array}{*{20}{c}} {{v_{\hat \lambda }}\left( {\hat x} \right) - v\left( {\hat x} \right) \ge \int_{{D_{\hat \lambda }}} {\left( {\frac{1}{{{{\left| {\hat x - y} \right|}^{n - \alpha }}}} - \frac{1}{{{{\left| {{{\hat x}^{\hat \lambda }} - y} \right|}^{n - \alpha }}}}} \right)} \times }\\ {\left( {C_1^p - {u^p}\left( y \right)} \right){\rm{d}}y + }\\ {\int_{{\Omega _{\hat \lambda }}} {\left( {\frac{1}{{{{\left| {\hat x - y} \right|}^{n - \alpha }}}} - \frac{1}{{{{\left| {{{\hat x}^{\hat \lambda }} - y} \right|}^{n - \alpha }}}}} \right)u_{\hat \lambda }^p\left( y \right)} > 0} \end{array} $ |
但是由边界条件,u(x)=C1, x∈Ω1, u(x)=0, x∈ Rn\Ω2, v(x)=C2, x∈Ω1, v(x)=0, x∈ Rn\Ω2得
在情况②和④中,假设
$ {\partial _\nu }u\left( {\hat x} \right) = 0, {\partial _\nu }v\left( {\hat x} \right) = 0 $ | (14) |
令
$ \left( {{x^m}} \right)_1^{\hat \lambda } - {y_1} \ge \varepsilon $ |
对任意的y∈B,若
$ \begin{array}{*{20}{c}} {{G_\alpha }\left( {{{\left( {{x^m}} \right)}^{\hat \lambda }} - y} \right) - {G_\alpha }\left( {{x^m} - y} \right) = }\\ {\frac{1}{{\gamma \left( \alpha \right)}}\int_0^\infty {\left[ {\exp \left( { - \frac{{{\rm{ \mathsf{ π} }}{{\left| {{{\left( {{x^m}} \right)}^{\hat \lambda }} - y} \right|}^2}}}{\delta }} \right) - } \right.} }\\ {\left. {\exp \left( { - \frac{{{\rm{ \mathsf{ π} }}{{\left| {{x^m} - y} \right|}^2}}}{\delta }} \right)} \right]\exp \left( { - \frac{\delta }{{4{\rm{ \mathsf{ π} }}}}} \right){\delta ^{\frac{{\alpha - n}}{2}}}\frac{{{\rm{d}}\delta }}{\delta } = }\\ {\frac{1}{{\gamma \left( \alpha \right)}}\int_0^\infty {\exp \left( { - \frac{{{\rm{ \mathsf{ π} }}{{\left| {{{\bar x}^m} - y} \right|}^2}}}{\delta }} \right)} \cdot }\\ {\frac{{ - 2{\rm{ \mathsf{ π} }}\left( {{{\bar x}^m} - y} \right)\left[ {{{\left( {{x^m}} \right)}^{\hat \lambda }} - {x^m}} \right]}}{\delta }\exp \left( { - \frac{\delta }{{4{\rm{ \mathsf{ π} }}}}} \right){\delta ^{\frac{{\alpha - n}}{2}}}\frac{{{\rm{d}}\delta }}{\delta }} \end{array} $ |
因为
$ \begin{array}{*{20}{c}} {\left( {{{\bar x}^m} - y} \right)\left[ {{x^m} - {{\left( {{x^m}} \right)}^{\hat \lambda }}} \right] = \left( {\bar x_1^m - {y_1}} \right)\left[ {x_1^m - \left( {{x^m}} \right)_1^{\hat \lambda }} \right] \ge }\\ {\varepsilon \left[ {x_1^m - \left( {{x^m}} \right)_1^{\hat \lambda }} \right] = \varepsilon \left| {{x^m} - {{\left( {{x^m}} \right)}^{\hat \lambda }}} \right|} \end{array} $ |
则
$ \begin{array}{*{20}{c}} {{\mu _{\hat \lambda }}\left( {{x^m}} \right) - u\left( {{x^m}} \right) \ge }\\ {\int_{{D_{\hat \lambda }}} {{g_\alpha }\left( {{x^m},y} \right)\left[ {C_1^{p - 1}{C_2} - {{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right)v\left( y \right)} \right]{\rm{d}}y} + }\\ {\int_{{\Omega _{\hat \lambda }}} {{g_\alpha }\left( {{x^m},y} \right){{\left| {{u_{\hat \lambda }}\left( y \right)} \right|}^{p - 2}}{u_{\hat \lambda }}\left( y \right){v_{\hat \lambda }}\left( y \right){\rm{d}}y{\rm{d}}y} \ge }\\ {\frac{{2{\rm{ \mathsf{ π} }}\varepsilon }}{{\gamma \left( \alpha \right)}}\int_{{D_{\hat \lambda }}} {\left[ {C_1^{p - 1}{C_2} - {{\left| {u\left( y \right)} \right|}^{p - 2}}u\left( y \right)v\left( y \right)} \right]M{\rm{d}}y} + }\\ {\frac{{2{\rm{ \mathsf{ π} }}\varepsilon }}{{\gamma \left( \alpha \right)}}\int_{{\Omega _{\hat \lambda }}} {{{\left| {{u_{\hat \lambda }}\left( y \right)} \right|}^{p - 2}}{u_{\hat \lambda }}\left( y \right){v_{\hat \lambda }}\left( y \right)\mathit{M}{\rm{d}}y} } \end{array} $ |
其中
$ \begin{array}{*{20}{c}} {M = \int_0^\infty {\exp \left( {\frac{{ - {\rm{ \mathsf{ π} }}{{\left| {{{\bar x}^m} - y} \right|}^2}}}{\delta }} \right)\left| {{x^m} - {{\left( {{x^m}} \right)}^{\hat \lambda }}} \right|} \cdot }\\ {\exp \left( {\frac{{ - \delta }}{{4{\rm{ \mathsf{ π} }}}}} \right){\delta ^{\frac{{\alpha - n}}{2}}}\frac{{{\rm{d}}\delta }}{\delta }} \end{array} $ |
这意味着
$ \mathop {\lim \inf }\limits_{m \to \infty } \frac{{{u_{\hat \lambda }}\left( {{x^m}} \right) - u\left( {{x^m}} \right)}}{{\left| {{{\left( {{x^m}} \right)}^{\hat \lambda }} - {x^m}} \right|}} > 0 $ |
这与式(14)矛盾。
类似地,对任意的y∈B,若
$ \begin{array}{*{20}{c}} {\frac{1}{{{{\left| {{x^m} - y} \right|}^{n - \alpha }}}} - \frac{1}{{{{\left| {{{\left( {{x^m}} \right)}^{\hat \lambda }} - y} \right|}^{n - \alpha }}}} = }\\ {\frac{{ - \left( {n - \alpha } \right)\left( {{{\bar x}^m} - y} \right)}}{{{{\left| {{{\bar x}^m} - y} \right|}^{n - \alpha + 2}}}}\left[ {{x^m} - {{\left( {{x^m}} \right)}^{\hat \lambda }}} \right]} \end{array} $ |
则
$ \begin{array}{*{20}{c}} {{v_{\hat \lambda }}\left( {{x^m}} \right) - v\left( {{x^m}} \right) \ge }\\ {\int_{{D_{\hat \lambda }}} {\left( {\frac{1}{{{{\left| {{x^m} - y} \right|}^{n - \alpha }}}} - \frac{1}{{{{\left| {{{\left( {{x^m}} \right)}^{\hat \lambda }} - y} \right|}^{n - \alpha }}}}} \right)} \cdot }\\ {\left( {C_1^p - {u^p}\left( y \right)} \right){\rm{d}}y + }\\ {\int_{{\Omega _{\hat \lambda }}} {\left( {\frac{1}{{{{\left| {{x^m} - y} \right|}^{n - \alpha }}}} - \frac{1}{{{{\left| {{{\left( {{x^m}} \right)}^{\hat \lambda }} - y} \right|}^{n - \alpha }}}}} \right)u_{\hat \lambda }^p\left( y \right){\rm{d}}y} = }\\ {\int_{{D_{\hat \lambda }}} {\frac{{\left( {n - \alpha } \right)\left( {{{\bar x}^m} - y} \right)}}{{{{\left| {{{\bar x}^m} - y} \right|}^{n - \alpha + 2}}}}\left[ {{{\left( {{x^m}} \right)}^{\hat \lambda }} - {x^m}} \right]} \cdot }\\ {\left( {C_1^p - {u^p}\left( y \right)} \right){\rm{d}}y + }\\ {\int_{{\Omega _{\hat \lambda }}} {\frac{{\left( {n - \alpha } \right)\left( {{{\bar x}^m} - y} \right)}}{{{{\left| {{{\bar x}^m} - y} \right|}^{n - \alpha + 2}}}}\left[ {{{\left( {{x^m}} \right)}^{\hat \lambda }} - {x^m}} \right]u_{\hat \lambda }^p\left( y \right){\rm{d}}y} } \end{array} $ |
这意味着
结合以上4种情况,得到
再向反方向移动Tλ,引理4—6的结果同样成立。所以,推断出u(x)和v(x)关于
最后, 由于x1的方向是任意的,则Ω1和Ω2是同心球,且u(x)和v(x)关于中心点对称,且随着距中心点的距离增大而单调递减。
3 结束语文献[1]中证明了薛定谔方程(3)的解的径向对称性和单调性,本文则进一步研究并得到了边值为常数的分数阶薛定谔方程在有界环形区域上解的径向对称性和单调性。本文的难点在于当边值为常数时,环形区域也是对称的。在得到解的对称性基础上,可以将方程转化为常微分方程,用常微分的理论进一步研究分数阶薛定谔方程。
[1] |
MA Li, ZHAO Lin.
Classification of positive solitary solutions of the nonlinear choquard equation[J]. Arch Rational Mech Anal, 2010, 195(2): 455–467.
DOI:10.1007/s00205-008-0208-3
|
[2] |
LOINS P L.
The Choquard equation and related questions[J]. Nonlinear Analysis, 1980, 4(6): 1063–1072.
DOI:10.1016/0362-546X(80)90016-4
|
[3] |
LOINS P L.
Compactness and topological methods for some nonlinear variational problems of mathematical physics[J]. North-Holland Mathematics Studies, 1982, 61: 17–34.
DOI:10.1016/S0304-0208(08)71038-7
|
[4] |
LIEB E H.
Existence and uniqueness of the minimizing solution of Choquards nonlinear equation[J]. Stud Appl Math, 1977, 57(2): 93–105.
DOI:10.1002/sapm.v57.2
|
[5] |
SERRIN J.
A symmetry problem in potential theory[J]. Arch Rational Mech Anal, 1971, 43(4): 304–318.
DOI:10.1007/BF00250468
|
[6] |
GIDAS B, NI W M, NIRENBERG L.
Symmetry and related properties via the maximum principle[J]. Comm Math Phy, 1979, 68(3): 209–243.
DOI:10.1007/BF01221125
|
[7] |
CAFFARELL L, GIDAS B, SPRUCK J.
Asymptotic symmetry and local behavior of semilinear elliptic equations with critical Sobolev growth[J]. Comm Pure Appl Math, 1989, 42(3): 271–297.
DOI:10.1002/(ISSN)1097-0312
|
[8] |
CHEN Wengxiong, LI Congming, OU B.
Classification of solutions for an integral equation[J]. Comm Pure Appl Math, 2010, 59(3): 330–343.
|
[9] |
LI Dongsheng, WANG Lihe.
Symmetry of integral equations on bounded domains[J]. Proc Amer Math Soc, 2009, 137(11): 3695–3702.
DOI:10.1090/S0002-9939-09-09987-0
|
[10] |
CHENG Ze, HUANG Gengheng, LI Congming.
On the Hardy-Littlewood-Sobolev type systems[J]. Communications on Pure & Applied Analysis, 2015, 15(6): 2059–2074.
|
[11] |
HUANG Xiaotao, LI Dongsheng, WANG Lihe.
Symmetry of integral equation systems with Bessel kernel on bounded domains[J]. Nonlinear Analysis, 2011, 74(2): 494–500.
DOI:10.1016/j.na.2010.09.004
|