A decoupled meshless Nyström scheme for 2D Fredholm integral equations of the second kind with smooth kernels
Status: in preparation. Last update: October 2025
Abstract: The Nyström method for the numerical solution of Fredholm integral equations of the second kind is generalized by decoupling the set of solution nodes from the set of quadrature nodes. The accuracy and efficiency of the new method is investigated for smooth kernels and complex 2D domains using recently developed moment-free meshless quadrature formulas on scattered nodes. Compared to the classical Nyström method, our variant has a clear performance advantage, especially for narrow kernels. The decoupled Nyström method requires the choice of a reconstruction scheme to approximate values at quadrature nodes from values at solution nodes. We prove that, under natural assumptions, the overall order of convergence is the minimum between that of the quadrature scheme and of the reconstruction scheme. For interpolatory reconstructions, we prove that decoupled Nyström methods are equivalent to collocation schemes using the corresponding cardinal functions. In terms of applications, we compute equilibrium states of various Fredholm integro-differential equations, including one that models nonlocal population dynamics subject to logistic growth on an island.
I have recently given a talk on this topic at the SMART 2025 conference in Reggio Calabria, Italy. Slides are available for download.