Improvement of the derivative expansion
We propose an algebraic method to improve the convergence of the derivative expansion. This method, originally designed to improve the convergence of the derivative expansion of the two-dimensional 4 field theory, can easily be adopted for field theory in any dimension. While this method may appear to be far from mathematically rigorous and unique, and the example seems to be unrealistic, it opens up the possibility that a clever technique with proper analytic continuation can turn the derivative expansion into a useful tool in studying effective low-energy phenomenology. © 1988 The American Physical Society.