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arXiv 2007.02619math.NAcs.NA
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随机wave equation的高阶逼近

Higher order approximation for stochastic wave equation

Xing Liu, Weihua Deng

摘要:

一个过程的无穷小生成元(分数拉普拉斯算子)是通过使一个被杀死的布朗运动从属而得到的,它抓住了波传播的幂律衰减。研究了以分数阶Laplacian算子为空间算子,噪声项为无穷维布朗运动或分数阶布朗运动(fBm)的随机波动方程的数值格式.首先,我们建立了随机分数阶波动方程温和解的正则性。然后采用谱Galerkin方法进行空间逼近,并对无穷维高斯噪声进行后处理,提高了空间收敛速度。在时间方向上,当温和解的时间导数在均方$L^p$范数意义下有界时,我们提出了一种改进的随机三角方法,得到了比已有结果更高的强收敛速度,即,时间收敛速度大于$1$。特别地,对于时间离散化,所提供的方法可以实现$2$的阶,代价是需要温和解具有一些额外的规律性。理论误差估计的数值实验证实。

英文摘要:

The infinitesimal generator (fractional Laplacian) of a process obtained by subordinating a killed Brownian motion catches the power-law attenuation of wave propagation. This paper studies the numerical schemes for the stochastic wave equation with fractional Laplacian as the space operator, the noise term of which is an infinite dimensional Brownian motion or fractional Brownian motion (fBm). Firstly, we establish the regularity of the mild solution of the stochastic fractional wave equation. Then a spectral Galerkin method is used for the approximation in space, and the space convergence rate is improved by postprocessing the infinite dimensional Gaussian noise. In the temporal direction, when the time derivative of the mild solution is bounded in the sense of mean-squared $L^p$-norm, we propose a modified stochastic trigonometric method, getting a higher strong convergence rate than the existing results, i.e., the time convergence rate is bigger than $1$. Particularly, for time discretization, the provided method can achieve an order of $2$ at the expenses of requiring some extra regularity to the mild solution. The theoretical error estimates are confirmed by numerical experiments.

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