The concept of an Asymptotic-Preserving (AP) method makes a breakthrough in the numerical resolution of asymptotic perturbations of Partial-Differential Equations. The general principle of an Asymptotic-Preserving method is as follows. Consider a singular perturbation problem Peps whose solutions converge to those of a limit problem P0 when the perturbation parameter 'eps' tends to zero. A scheme Peps,h for problem Peps with discretization parameters 'h' is called Asymptotic Preserving (or AP) if its stability requirement on h is independent of 'eps' and if its limit P0,h when 'eps' tends to zero is consistent with the limit problem P0. This property is illustrated by the commutative diagram below:
AP schemes are extremely powerful tools as they permit the use of the same scheme to discretize a perturbation problem and its limit problem, with fixed discretization parameters.