Communications on Applied Mathematics and Computation ›› 2025, Vol. 7 ›› Issue (6): 2339-2384.doi: 10.1007/s42967-024-00380-3

• ORIGINAL PAPERS • Previous Articles     Next Articles

Numerical Algorithms for Ultra-slow Diffusion Equations

Min Cai, Changpin Li, Yu Wang   

  1. Department of Mathematics, Shanghai University, and Newtouch Center for Mathematics of Shanghai University, Shanghai 200444, China
  • Received:2023-08-17 Revised:2024-01-30 Published:2025-12-24
  • Contact: Changpin Li, E-mail:lcp@shu.edu.cn E-mail:lcp@shu.edu.cn
  • Supported by:
    MC was supported in part by the National Natural Science Foundation of China under Grant No. 12201391 and Chunhui Project from Education Ministry of China under Grant No. HZKY20220092. CL was supported in part by the National Natural Science Foundation of China under Grant No. 12271339.

Abstract: In this article, numerical algorithms are derived for ultra-slow (or superslow) diffusion equations in one and two space dimensions, where the ultra-slow diffusion is characterized by the Caputo-Hadamard fractional derivative of order $ \alpha \in (0,1) $. To describe the non-locality in spatial interaction, the Riesz fractional derivative and the fractional Laplacian are used in one and two space dimensions, respectively. The Caputo-Hadamard derivative is discretized by two typical approximate formulae, i.e., $ \textrm{L2-1}_{\sigma } $ and L1-2 ones. The spatial fractional derivatives are discretized by the second order finite difference methods. When the $ \textrm{L2-1}_{\sigma } $ discretization is used, the derived numerical schemes are unconditionally stable, with both theoretical and numerical convergence order $ \mathcal {O}(\tau ^{2}+h^{2}) $ for all $ \alpha \in (0, 1) $, in which $ \tau $ and h are temporal and spatial stepsizes, respectively. When the L1-2 discretization is used, the derived numerical schemes are proved to be stable with the error estimate $ \mathcal {O}(\tau ^{2}+h^{2}) $ for $ \alpha \in (0, 0.373\,8) $, and numerically exhibit the stability for all $ \alpha \in (0, 1) $ with the numerical error being $ \mathcal {O}(\tau ^{3-\alpha }+h^2) $. The illustrative examples displayed are in line with the theoretical analysis.

Key words: Ultra-slow diffusion equation, Caputo-Hadamard derivative, Riesz derivative, Fractional Laplacian, $ \textrm{L2-1}_{\sigma } $ formula, L1-2 formula

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