On single-variable Witten zeta functions of rank two and three
Kam Cheong Au
TL;DR
The paper develops a unified Mellin-transform kernel method to analyze Witten zeta functions for rank-2 and rank-3 root systems, enabling meromorphic continuation, pole-residue structure, and explicit special values. It introduces an explicit integral kernel framework, derives a rank-2 and a rank-3 convolution formalism, and applies creative telescoping to obtain closed-form integrals that determine derivatives at the origin and positive-pole residues. The main results include precise pole locations for $\xi_f(s)$, closed-form residues (often gamma-valued) at abscissas of convergence, and explicit expressions for $\xi_f(-n)$ and $\xi_f(0),\xi_f'(0)$ for rank-2 and rank-3 cases, as well as asymptotic formulas for the number of representations $r_\Phi(n)$. These findings reveal deep connections to Eisenstein series and $p$-adic phenomena, and they yield sharp asymptotics for representation counts, with potential generalization to higher rank root systems.
Abstract
By introducing a novel integration kernel for Mellin transform, we uncover many previously unknown and intriguing properties of the Witten zeta functions of rank two and three. Detailed results concerning their pole locations, residues, and special values are obtained. We propose a non-trivial conjecture regarding their derivatives at the origin, which seems to encode deep information about the root system. We also discuss their behavior at negative integers, highlighting a connection with Eisenstein series and a $p$-adic observation.
