Representation of ax+b group and Dirichlet Series

Abstract

Let $G$ be the $ax+b$ group. There are essentially two irreducible infinite dimensional unitary representations of $G$, $(\hat{I}¼,L^2({\mathbb{R}}^{+}))$ and $(\hat{I}{¼}^{\ast },L^2({\mathbb{R}}^{+}))$. In this paper, we give various characterizations about smooth vectors of $\hat{I}¼$ and their Mellin transforms. Let $\f d$ be a linear sum of delta distributions supported on the the positive integers ${\mathbb{Z}}^{+}$. We study the Mellin transform of the matrix coefficients $μ_{ \f d, f}(a)$ with $f$ smooth. We express these Mellin transforms in terms of the Dirichlet series $L(s, \f d)$. We determine a sufficient condition such that the generalized matrix coefficient $μ_{\f d, f}$ is a locally integrable function and estimate the $L^2$-norms of $μ_{\f d, f}$ over the Siegel set. We further derive an inequality which may potentially be used to study the Dirichlet series $L(s, \f d)$.

14 pages, 0 figure