Convolution and Cross-Correlation of Ramanujan-Fourier Series
arXiv:0805.0284
Abstract
This paper uses the machinery of almost periodic functions to prove that even without uniform convergence the connection between a pair of almost periodic functions and the constants of the associated Fourier series exists for both the convolution and cross-correlation. The general results for two almost periodic functions are narrowed and applied to Ramanujan sums and finally applied to support the specific relation of the Wiener-Khinchin formula for arithemic functions with a Ramanujan-Fourier Series.
The paper fails to establish the continuity of the a.p. functions involved required to uniformly approximate the a.p. function with the Bochner-Fejer polynomials. Without this uniform convergence the key interchange of limits is not justified