随机扰动KdV方程的Khasminski-Whitham平均
Khasminskii--Whitham averaging for randomly perturbed KdV equation
摘要:
考虑阻尼驱动的KdV方程$$ \dot u-ν{u_{xx}}+u_{xxx}-6uu_x=\sqrtνη(t,x), x\in S^1, \int u dx\equiv \intηdx\equiv0, $$,其中$0<ν\le1$和随机过程$η$在$x$中是光滑的,在$t$中是白色的.对于任何周期函数$u(x)$,令$ I=(I_1,I_2,...) $为矢量,由运动的KdV积分形成,为势$u(x)$计算。我们证明,如果$u(t,x)$是上述方程的解,那么对于$0\le t\lesssimν^{-1}$和$ν\to0$,矢量$ I(t)=(I_1(u(t,\cdot)),I_2(u(t,\cdot)),...) $满足(Whitham)平均方程。
英文摘要:
We consider the damped-driven KdV equation $$ \dot u-ν{u_{xx}}+u_{xxx}-6uu_x=\sqrtνη(t,x), x\in S^1, \int u dx\equiv \intηdx\equiv0, $$ where $0<ν\le1$ and the random process $η$ is smooth in $x$ and white in $t$. For any periodic function $u(x)$ let $ I=(I_1,I_2,...) $ be the vector, formed by the KdV integrals of motion, calculated for the potential $u(x)$. We prove that if $u(t,x)$ is a solution of the equation above, then for $0\le t\lesssimν^{-1}$ and $ν\to0$ the vector $ I(t)=(I_1(u(t,\cdot)),I_2(u(t,\cdot)),...) $ satisfies the (Whitham) averaged equation.
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