Ambiguities in nonpolynomial lagrangian theories

Abstract

During the last few years there has been an increasing interest in nonlinear Lagrangians and, as a consequence, attention has been focussed on expressions like Σn C/(n) Δn, n trying to give a meaning to them or to their Fourier transforms. Different methods have been proposed to achieve these aims and specific results have been obtained in some particular examples. Serious doubts have arisen about the uniqueness of these results. It seems natural to put to the test those methods in eases where the result of the series can be evaluated by other means.