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hp-version C1-continuous Petrov–Galerkin method for nonlinear second-order initial value problems with application to wave equations 非线性二阶初值问题的 hp 版本 C1 连续 Petrov-Galerkin 方法在波方程中的应用
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-06-21 DOI: 10.1093/imanum/drae036
Lina Wang, Mingzhu Zhang, Hongjiong Tian, Lijun Yi
We introduce and analyze an $hp$-version $C^{1}$-continuous Petrov–Galerkin (CPG) method for nonlinear initial value problems of second-order ordinary differential equations. We derive a-priori error estimates in the $L^{2}$-, $L^{infty }$-, $H^{1}$- and $H^{2}$-norms that are completely explicit in the local time steps and local approximation degrees. Moreover, we show that the $hp$-version $C^{1}$-CPG method superconverges at the nodal points of the time partition with regard to the time steps and approximation degrees. As an application, we apply the $hp$-version $C^{1}$-CPG method to time discretization of nonlinear wave equations. Several numerical examples are presented to verify the theoretical results.
我们介绍并分析了用于二阶常微分方程非线性初值问题的 $hp$ 版本 $C^{1}$-continuous Petrov-Galerkin (CPG) 方法。我们推导出$L^{2}$-、$L^{infty }$-、$H^{1}$-和$H^{2}$-规范中的先验误差估计值,这些误差估计值在局部时间步长和局部逼近度中是完全显式的。此外,我们还证明了 $hp$ 版本的 $C^{1}$-CPG 方法在时间分区的结点处超收敛,与时间步长和近似度有关。作为应用,我们将$hp$版$C^{1}$-CPG方法应用于非线性波方程的时间离散化。我们给出了几个数值示例来验证理论结果。
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引用次数: 0
Erratum to ‘Pressure robust SUPG-stabilized finite elements for the unsteady Navier–Stokes equation’ 用于非稳态纳维-斯托克斯方程的压力鲁棒 SUPG 稳定有限元》的勘误
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-06-12 DOI: 10.1093/imanum/drae035
L. da Veiga, F. Dassi, G. Vacca
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引用次数: 0
Precise error bounds for numerical approximations of fractional HJB equations 分数 HJB 方程数值近似的精确误差范围
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-06-12 DOI: 10.1093/imanum/drae030
Indranil Chowdhury, Espen R Jakobsen
We prove precise rates of convergence for monotone approximation schemes of fractional and nonlocal Hamilton–Jacobi–Bellman equations. We consider diffusion-corrected difference-quadrature schemes from the literature and new approximations based on powers of discrete Laplacians, approximations that are (formally) fractional order and second-order methods. It is well known in numerical analysis that convergence rates depend on the regularity of solutions, and here we consider cases with varying solution regularity: (i) strongly degenerate problems with Lipschitz solutions and (ii) weakly nondegenerate problems where we show that solutions have bounded fractional derivatives of order $sigma in (1,2)$. Our main results are optimal error estimates with convergence rates that capture precisely both the fractional order of the schemes and the fractional regularity of the solutions. For strongly degenerate equations, these rates improve earlier results. For weakly nondegenerate problems of order greater than one, the results are new. Here we show improved rates compared to the strongly degenerate case, rates that are always better than $mathcal{O}big (h^{frac{1}{2}}big )$.
我们证明了分数和非局部 Hamilton-Jacobi-Bellman 方程单调逼近方案的精确收敛率。我们考虑了文献中的扩散校正差分二次方程方案和基于离散拉普拉斯幂的新近似方案,这些近似方案(形式上)是分数阶和二阶方法。众所周知,数值分析的收敛率取决于解的正则性,在此我们考虑了解的正则性不同的情况:(i) 具有 Lipschitz 解的强退化问题;(ii) 弱非退化问题,在这些问题中,我们证明解具有阶为 $sigma in (1,2)$ 的有界分数导数。我们的主要结果是最优误差估计,其收敛率精确地捕捉到了方案的分数阶和解的分数正则性。对于强退化方程,这些收敛率改进了之前的结果。对于阶数大于 1 的弱非退化问题,这些结果是全新的。在这里,我们展示了与强退化情况相比的改进率,这些率总是优于 $mathcal{O}big (h^{frac{1}{2}}big )$。
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引用次数: 0
CIP-stabilized virtual elements for diffusion-convection-reaction problems 扩散-对流-反应问题的 CIP 稳定虚拟元素
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-05-31 DOI: 10.1093/imanum/drae020
L Beirão da Veiga, C Lovadina, M Trezzi
The Virtual Element Method (VEM) for diffusion-convection-reaction problems is considered. In order to design a quasi-robust scheme also in the convection-dominated regime, a Continuous Interior Penalty approach is employed. Due to the presence of polynomial projection operators, typical of the VEM, the stability and the error analysis requires particular care—especially in treating the advective term. Some numerical tests are presented to support the theoretical results.
研究考虑了针对扩散-对流-反应问题的虚拟元素法(VEM)。为了在对流主导机制中也能设计出准稳健的方案,采用了连续内部惩罚法。由于存在多项式投影算子(VEM 的典型特征),稳定性和误差分析需要特别小心,尤其是在处理平流项时。本文介绍了一些数值测试,以支持理论结果。
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引用次数: 0
Stochastic modified equations for symplectic methods applied to rough Hamiltonian systems 适用于粗糙哈密顿系统的交映法随机修正方程
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-05-24 DOI: 10.1093/imanum/drae019
Chuchu Chen, Jialin Hong, Chuying Huang
We investigate stochastic modified equations to explain the mathematical mechanism of symplectic methods applied to rough Hamiltonian systems. The contribution of this paper is threefold. First, we construct a new type of stochastic modified equation. For symplectic methods applied to rough Hamiltonian systems, the associated stochastic modified equations are proved to have Hamiltonian formulations. Secondly, the pathwise convergence order of the truncated modified equation to the numerical method is obtained by techniques in rough path theory. Thirdly, if increments of noises are simulated by truncated random variables, we show that the error can be made exponentially small with respect to the time step size.
我们研究了随机修正方程,以解释将对称方法应用于粗糙哈密顿系统的数学机制。本文有三方面的贡献。首先,我们构建了一种新型随机修正方程。对于应用于粗糙哈密顿系统的交点法,相关的随机修正方程被证明具有哈密顿形式。其次,通过粗糙路径理论的技术获得了截断修正方程对数值方法的路径收敛阶数。第三,如果用截断随机变量模拟噪声的增量,我们证明误差可随时间步长呈指数级减小。
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引用次数: 0
Discrete anisotropic curve shortening flow in higher codimension 高标度离散各向异性曲线缩短流
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-05-24 DOI: 10.1093/imanum/drae015
Klaus Deckelnick, Robert Nürnberg
We introduce a novel formulation for the evolution of parametric curves by anisotropic curve shortening flow in ${{mathbb{R}}}^{d}$, $dgeq 2$. The reformulation hinges on a suitable manipulation of the parameterization’s tangential velocity, leading to a strictly parabolic differential equation. Moreover, the derived equation is in divergence form, giving rise to a natural variational numerical method. For a fully discrete finite element approximation based on piecewise linear elements we prove optimal error estimates. Numerical simulations confirm the theoretical results and demonstrate the practicality of the method.
我们为参数曲线在 ${{{mathbb{R}}}^{d}$, $dgeq 2$ 的各向异性曲线缩短流中的演变引入了一种新的公式。重述的关键在于对参数化切线速度的适当处理,从而得出严格的抛物线微分方程。此外,推导出的方程是发散形式的,从而产生了一种自然的变分数值方法。对于基于片线性元素的完全离散有限元近似,我们证明了最佳误差估计值。数值模拟证实了理论结果,并证明了该方法的实用性。
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引用次数: 0
High-order Lagrange-Galerkin methods for the conservative formulation of the advection-diffusion equation 用于平流扩散方程保守公式的高阶拉格朗日-加勒金方法
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-05-18 DOI: 10.1093/imanum/drae018
Rodolfo Bermejo, Manuel Colera
We introduce in this paper the numerical analysis of high order both in time and space Lagrange-Galerkin methods for the conservative formulation of the advection-diffusion equation. As time discretization scheme we consider the Backward Differentiation Formulas up to order $q=5$. The development and analysis of the methods are performed in the framework of time evolving finite elements presented in C. M. Elliot and T. Ranner, IMA Journal of Numerical Analysis41, 1696–1845 (2021). The error estimates show through their dependence on the parameters of the equation the existence of different regimes in the behavior of the numerical solution; namely, in the diffusive regime, that is, when the diffusion parameter $mu $ is large, the error is $O(h^{k+1}+varDelta t^{q})$, whereas in the advective regime, $mu ll 1$, the convergence is $O(min (h^{k},frac{h^{k+1} }{varDelta t})+varDelta t^{q})$. It is worth remarking that the error constant does not have exponential $mu ^{-1}$ dependence.
本文介绍了针对平流-扩散方程保守公式的高阶时间和空间拉格朗日-加勒金方法的数值分析。作为时间离散化方案,我们考虑了最高阶数为 $q=5$ 的后向微分公式。方法的开发和分析是在 C. M. Elliot 和 T. Ranner, IMA Journal of Numerical Analysis41, 1696-1845 (2021) 中提出的时间演化有限元框架内进行的。误差估计值通过其对方程参数的依赖性显示出数值解的行为存在不同的体制;即在扩散状态下,即扩散参数 $mu $ 较大时,误差为 $O(h^{k+1}+varDelta t^{q})$ ;而在平流状态下,即 $mu ll 1$,收敛为 $O(min(h^{k},frac{h^{k+1}}{varDelta t})+varDelta t^{q})$ 。值得注意的是,误差常数与 $mu ^{-1}$不呈指数关系。
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引用次数: 0
An equilibrated estimator for mixed finite element discretizations of the curl-curl problem 卷曲问题混合有限元离散的均衡估计器
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-05-17 DOI: 10.1093/imanum/drae007
T Chaumont-Frelet
We propose a new a posteriori error estimator for mixed finite element discretizations of the curl-curl problem. This estimator relies on a Prager–Synge inequality, and therefore leads to fully guaranteed constant-free upper bounds on the error. The estimator is also locally efficient and polynomial-degree-robust. The construction is based on patch-wise divergence-constrained minimization problems, leading to a cheap embarrassingly parallel algorithm. Crucially, the estimator operates without any assumption on the topology of the domain, and unconventional arguments are required to establish the reliability estimate. Numerical examples illustrate the key theoretical results, and suggest that the estimator is suited for mesh adaptivity purposes.
我们为卷曲问题的混合有限元离散化提出了一种新的后验误差估算器。该估计器依赖于普拉格-辛格不等式,因此能完全保证误差的无常数上界。该估计器还具有局部高效性和多项式度稳健性。其构造基于片断式发散约束最小化问题,从而产生了一种廉价的令人尴尬的并行算法。最重要的是,估计器的运行不需要对域的拓扑结构做任何假设,而且需要非常规的论证来建立可靠性估计。数值示例说明了关键的理论结果,并表明该估计器适用于网格自适应目的。
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引用次数: 0
Optimal convergence analysis of two RPC-SAV schemes for the unsteady incompressible magnetohydrodynamics equations 针对非稳态不可压缩磁流体动力学方程的两种 RPC-SAV 方案的最佳收敛性分析
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-05-15 DOI: 10.1093/imanum/drae016
Xiaojing Dong, Huayi Huang, Yunqing Huang, Xiaojuan Shen, Qili Tang
In this paper, we present and analyze two linear and fully decoupled schemes for solving the unsteady incompressible magnetohydrodynamics equations. The rotational pressure-correction (RPC) approach is adopted to decouple the system, and the recently developed scalar auxiliary variable (SAV) method is used to treat the nonlinear terms explicitly and keep energy stability. One is the first-order RPC-SAV-Euler and the other one is generalized Crank–Nicolson-type scheme: GRPC-SAV-CN. For the RPC-SAV-Euler scheme, both unconditionally energy stability and optimal convergence are derived. The new GRPC-SAV-CN is constructed and can be regarded as a parameterized scheme, which includes PC-SAV-CN when the parameter $beta =0$ and RPC-SAV-CN when $beta in (0,frac {1}{2}]$; see Algorithm 3.2. However, Jiang and Yang (Jiang, N. & Yang, H. (2021) SIAM J. Sci. Comput., 43, A2869–A2896) point out that the SAV method has low accuracy by several commonly tested benchmark flow problem when solving Navier–Stokes equations. To improve the accuracy, we added two stabilization $-alpha _{1}varDelta tnu varDelta (widetilde {textbf {u}}^{n+1}-{textbf {u}}^{n})$ and $alpha _{2}varDelta tsigma ^{-1}mbox {curl}mbox {curl} (textbf {H}^{n+1}-textbf {H}^{n})$ in the GRPC-SAV-CN scheme, which play decisive roles in giving optimal error estimates. The unconditionally energy stability of the proposed scheme is given. We prove that the PC-SAV-CN scheme has second-order convergence speed, and the RPC-SAV-CN one has 1.5-order convergence rate. Finally, some numerical examples are presented to verify the validity and convergence of the numerical schemes.
本文提出并分析了两种线性完全解耦方案,用于求解非稳态不可压缩磁流体动力学方程。采用旋转压力校正(RPC)方法来解耦系统,并使用最近开发的标量辅助变量(SAV)方法来显式处理非线性项并保持能量稳定性。其中一个是一阶 RPC-SAV-Euler 方案,另一个是广义 Crank-Nicolson-type 方案:GRPC-SAV-CN。对于 RPC-SAV-Euler 方案,推导出了无条件能量稳定性和最优收敛性。新的 GRPC-SAV-CN 被构建并可视为参数化方案,其中包括当参数 $beta =0$ 时的 PC-SAV-CN 和当 $betain (0,frac {1}{2}]$ 时的 RPC-SAV-CN;见算法 3.2。然而,Jiang 和 Yang(Jiang, N. & Yang, H. (2021) SIAM J. Sci. Comput.为了提高精度、我们添加了两个稳定 $-alpha _{1}varDelta tnu varDelta (widetilde {textbf {u}}^{n+1}- {textbf {u}}^{n+1}){和 $alpha _{2}varDelta tsigma ^{-1}mbox {curl}mbox {curl} (textbf {H}^{n+1}-textbf {H}^{n})$ 在 GRPC-SAV-CN 方案中、在给出最佳误差估计值方面起着决定性作用。我们给出了所提方案的无条件能量稳定性。我们证明 PC-SAV-CN 方案具有二阶收敛速度,而 RPC-SAV-CN 方案具有 1.5 阶收敛速度。最后,我们给出了一些数值示例来验证数值方案的有效性和收敛性。
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引用次数: 0
Efficient function approximation in enriched approximation spaces 丰富近似空间中的高效函数近似
IF 2.1 2区 数学 Q1 Mathematics Pub Date : 2024-05-12 DOI: 10.1093/imanum/drae017
Astrid Herremans, Daan Huybrechs
An enriched approximation space is the span of a conventional basis with a few extra functions included, for example to capture known features of the solution to a computational problem. Adding functions to a basis makes it overcomplete and, consequently, the corresponding discretized approximation problem may require solving an ill-conditioned system. Recent research indicates that these systems can still provide highly accurate numerical approximations under reasonable conditions. In this paper we propose an efficient algorithm to compute such approximations. It is based on the AZ algorithm for overcomplete sets and frames, which simplifies in the case of an enriched basis. In addition, analysis of the original AZ algorithm and of the proposed variant gives constructive insights on how to achieve optimal and stable discretizations using enriched bases. We apply the algorithm to examples of enriched approximation spaces in literature, including a few nonstandard approximation problems and an enriched spectral method for a 2D boundary value problem, and show that the simplified AZ algorithm is indeed stable, accurate and efficient.
丰富近似空间是在传统基础的跨度上加入一些额外的函数,例如为了捕捉计算问题解法的已知特征。在基上添加函数会使其过于完整,因此,相应的离散化近似问题可能需要求解一个条件不良的系统。最近的研究表明,在合理条件下,这些系统仍能提供高精度的数值近似。在本文中,我们提出了一种计算此类近似值的高效算法。该算法基于针对过完备集和框架的 AZ 算法,并在丰富基础的情况下进行了简化。此外,对原始 AZ 算法和所提变体的分析为如何利用丰富基实现最优和稳定离散提供了建设性见解。我们将该算法应用于文献中的富集近似空间实例,包括一些非标准近似问题和二维边界值问题的富集谱方法,结果表明简化的 AZ 算法确实稳定、精确且高效。
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引用次数: 0
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IMA Journal of Numerical Analysis
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