An asymptotic analysis of the Fourier-Laplace transforms of certain oscillatory functions

Abstract

We study the family of Fourier-Laplace transformsFα,β(z)=F.p.∫0∞tβexp⁡(itα−izt)dt,Imz<0, for α>1 and β∈C, where Hadamard finite part is used to regularize the integral when Reβ≤−1. We prove that each Fα,β has analytic continuation to the whole complex plane and determine its asymptotics along any line through the origin. We also apply our ideas to show that some of these functions provide concrete extremal examples for the Wiener-Ikehara theorem and a quantified version of the Ingham-Karamata theorem, supplying new simple and constructive proofs of optimality results for these complex Tauberian theorems.