Characterizing Hilbert modular cusp forms by coefficient size
  Associated to an (adelic) Hilbert modular form is a sequence of `Fourier coefficients' which uniquely determine the form. In this paper we characterize Hilbert modular cusp forms by the size of their Fourier coefficients. This answers in the affirmative a question posed by Winfried Kohnen. 
Benjamin Linowitz
math.NT