Approximation Methods

Abstract

Only very few problems of Theoretical Physics can be really solved in a mathematically rigorous sense. In order to be able to understand experimental observations and to describe them realistically the theoretician needs an as wide as possible repertoire of approximation methods. He (she) is obliged to replace not achievable exact solutions by well-founded approximations, which do not adulterate the essential physical aspects. He (she) will therefore try to free the original problem from unnecessary ‘baggage’. i.e., to stress the important facts, and to suppress marginal phenomena in favor of mathematical simplicity. It would be desirable, but unfortunately not always satisfactorily accessible, to find a way to estimate the error, which by definition is always associated with such an approximation.