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arXiv 1208.4479math.NAcs.NAmath.DS
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哈密顿半线性发展方程的辛A-稳定龙格-库塔方法的指数精确哈密顿嵌入

Exponentially accurate Hamiltonian embeddings of symplectic A-stable Runge--Kutta methods for Hamiltonian semilinear evolution equations

University of Surrey(萨里大学);Jacobs University(雅各布斯大学)

Claudia Wulff, Marcel Oliver

AI总结:

针对解析初始数据的半线性哈密顿偏微分方程,证明一类A-稳定辛龙格-库塔时间半离散化可嵌入修正哈密顿流,误差指数小,从而守恒修正哈密顿量至指数小误差。

摘要:

我们证明,对于一类在解析函数空间上适定且具有解析初始数据的半线性哈密顿偏微分方程,应用一类A-稳定辛龙格-库塔时间半离散化(包括高斯-勒让德方法)可嵌入修正哈密顿流,误差指数小。因此,此类时间半离散化守恒修正哈密顿量至指数小误差。修正哈密顿量与原始能量相差$O(h^p)$,其中$p$是方法的阶,$h$是时间步长。此类系统的例子包括具有解析非线性和周期边界条件的半线性波动方程或非线性薛定谔方程。由于修正向量场构造中出现无界算子,标准的哈密顿插值结果在此不适用。通过将偏微分方程投影到演化方程中算子有界的子空间,并将激发模式数及修正向量场展开项数与步长耦合,可处理构造中正则性的损失。由此我们得到形如$O(\exp(-c/h^{1/(1+q)}))$的指数估计,其中$c>0$,$q\geq0$;对于半线性波动方程,$q=1$;对于非线性薛定谔方程,$q=2$。我们给出一个例子,表明解析初始数据是获得指数估计的必要条件。

英文摘要:

We prove that a class of A-stable symplectic Runge--Kutta time semidiscretizations (including the Gauss--Legendre methods) applied to a class of semilinear Hamiltonian PDEs which are well-posed on spaces of analytic functions with analytic initial data can be embedded into a modified Hamiltonian flow up to an exponentially small error. As a consequence, such time-semidiscretizations conserve the modified Hamiltonian up to an exponentially small error. The modified Hamiltonian is $O(h^p)$-close to the original energy where $p$ is the order of the method and $h$ the time step-size. Examples of such systems are the semilinear wave equation or the nonlinear Schrödinger equation with analytic nonlinearity and periodic boundary conditions. Standard Hamiltonian interpolation results do not apply here because of the occurrence of unbounded operators in the construction of the modified vector field. This loss of regularity in the construction can be taken care of by projecting the PDE to a subspace where the operators occurring in the evolution equation are bounded and by coupling the number of excited modes as well as the number of terms in the expansion of the modified vector field with the step size. This way we obtain exponential estimates of the form $O(\exp(-c/h^{1/(1+q)}))$ with $c>0$ and $q \geq 0$; for the semilinear wave equation, $q=1$, and for the nonlinear Schrödinger equation, $q=2$. We give an example which shows that analyticity of the initial data is necessary to obtain exponential estimates.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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