Multiple Fourier series and lattice point problems

Abstract

For the multiple Fourier series of the periodization of some radial functions on Rd, we investigate the behavior of the spherical partial sum. We show the Gibbs-Wilbraham phenomenon, the Pinsky phenomenon and the third phenomenon for the multiple Fourier series, involving the convergence properties of them. The third phenomenon is closely related to the lattice point problems, which is a classical theme of the analytic number theory. We also prove that, for the case of two or three dimensions, the convergence problem on the Fourier series is equivalent to the lattice point problems in a sense. In particular, the convergence problem at the origin in two dimensions is equivalent to Hardy's conjecture on Gauss's circle problem.