On generalized Eisenstein series and Ramanujan's formula for periodic zeta-functions

Abstract

In this paper, transformation formulas for a large class of Eisenstein series defined by \[ G(z,s;A_α,B_β;r_{1},r_{2})=\sum\limits_{m,n=-\infty}^{\infty }\ \hspace{-0.19in}^{^{\prime}}\frac{f(αm)f^{\ast}(βn)} {((m+r_{1})z+n+r_{2})^{s}},\text{ }\operatorname{Re}(s)>2,\text{ }\operatorname{Im}(z)>0 \] are investigated for $s=1-r$, $r\in\mathbb{N}$. Here $\left\{ f(n)\right\}$ and $\left\{ f^{\ast}(n)\right\}$, $-\infty 0$, and $A_α=\left\{ f(αn)\right\} $ and $B_β=\left\{ f^{\ast}(βn)\right\}$, $α,β\in\mathbb{Z}$. Appearing in the transformation formulas are generalizations of Dedekind sums involving the periodic Bernoulli function. Reciprocity law is proved for periodic Apostol-Dedekind sum outside of the context of the transformation formulas. Furthermore, transformation formulas are presented for $G(z,s;A_α,I;r_{1},r_{2})$ and $G(z,s;I,A_{α};r_{1},r_{2})$, where $I=\left\{ 1\right\}$. As an application of these formulas, analogues of Ramanujan's formula for periodic zeta-functions are derived.