Necessary condition for measures which are multipliers
Let be a locally compact group and the left Haar measure on . Given a non-negative Radon measure , we establish a necessary condition on the pairs for which is a multiplier from to . Applied to , our result is stronger than the necessary condition established by Oberlin in [14] and is closely related to a class of measures defined by Fofana in [7].When is the circle group, we obtain a generalization of a condition stated by Oberlin [15] and improve on it in some cases.