High order schemes based on operator splitting and deferred corrections for stiff time dependent PDEs

We consider quadrature formulas of high order in time based on Radau–type, L–stable implicit Runge–Kutta schemes to solve time dependent stiff PDEs. Instead of solving a large nonlinear system of equations, we develop a method that performs iterative deferred corrections to compute the solution at the collocation nodes of the quadrature formulas. The numerical stability is guaranteed by a dedicated operator splitting technique that efficiently handles the stiffness of the PDEs and provides initial and intermediate solutions to the iterative scheme. In this way the low order approximations computed by a tailored splitting solver of low algorithmic complexity are iteratively corrected to obtain a high order solution based on a quadrature formula. The mathematical analysis of the numerical errors and local order of the method is carried out in a finite dimensional framework for a general semi–discrete problem, and a time–stepping strategy is conceived to control numerical errors related to the time integration. Numerical evidence confirms the theoretical findings and assesses the performance of the method in the case of a stiff reaction–diffusion equation.