Discrete Fourier Transform and $L$-functions
D. Liu
TL;DR
This paper shows a converse to Dirichlet's theorem by generalizing Guinand's zero-indicator to Dirichlet $L$-functions. It constructs a Dirichlet polynomial $D_x(z)=\sum_{n\le x}\frac{\Lambda(n)}{n^{1/2-iz}}$ via Mellin inversion and relates it to $-\frac{L'}{L}$ through contour integration, producing a zero-indicator identity linking prime powers to zeros $\rho$. It develops a Discrete Fourier Transform decomposition across residue classes modulo $q$, with a DFT matrix $M$ satisfying $M M^{*}=\varphi(q) I$, and includes compensation terms for non-primitive characters. Numerical experiments illustrate the predicted spikes at zeros and the DC/compensation structure, validating the transform-based view of the explicit formulas.
Abstract
We give the converse to Dirichlet's theorem on primes in arithmetic progressions by generalizing an old result of Guinand.
