A spectral method for nonlocal diffusion operators on the sphere
Provides a high-precision numerical method for nonlocal diffusion models on the sphere, relevant for geophysics and materials science.
Developed spectrally accurate algorithms for nonlocal diffusion on the sphere using spherical harmonics, achieving high relative accuracy in eigenvalue computation and enabling efficient time integration. Demonstrated on nonlocal Poisson, Allen-Cahn, and Brusselator equations.
We present algorithms for solving spatially nonlocal diffusion models on the unit sphere with spectral accuracy in space. Our algorithms are based on the diagonalizability of nonlocal diffusion operators in the basis of spherical harmonics, the computation of their eigenvalues to high relative accuracy using quadrature and asymptotic formulas, and a fast spherical harmonic transform. These techniques also lead to an efficient implementation of high-order exponential integrators for time-dependent models. We apply our method to the nonlocal Poisson, Allen--Cahn and Brusselator equations.