English

A Dirichlet character analogue of Ramanujan's formula for odd zeta values

Number Theory 2023-10-02 v2

Abstract

In 2001, Kanemitsu, Tanigawa, and Yoshimoto studied the following generalized Lambert series, n=1nN2hexp(nNx)1, \sum_{n=1}^{\infty} \frac{n^{N-2h} }{\exp(n^N x)-1}, for NNN \in \mathbb{N} and hZh\in \mathbb{Z} with some restriction on hh. Recently, Dixit and the last author pointed out that this series has already been present in the Lost Notebook of Ramanujan with a more general form. Although, Ramanujan did not provide any transformation identity for it. In the same paper, Dixit and the last author found an elegant generalization of Ramanujan's celebrated identity for ζ(2m+1)\zeta(2m+1) while extending the results of Kanemitsu et al. In a subsequent work, Kanemitsu et al. explored another extended version of the aforementioned series, namely, r=1qn=1χ(r)nN2hexp(rqnNx)1exp(nNx),\sum_{r=1}^{q}\sum_{n=1}^{\infty} \frac{\chi(r)n^{N-2h}{\exp\left(-\frac{r}{q}n^N x\right)}}{1-\exp({-n^N x})}, where χ\chi denotes a Dirichlet character modulo qq, N2NN\in 2\mathbb{N} and with some restriction on the variable hh. In the current paper, we investigate the above series for {\it any} NNN \in \mathbb{N} and hZh \in \mathbb{Z}. We obtain a Dirichlet character analogue of Dixit and the last author's identity and there by derive a two variable generalization of Ramanujan's identity for ζ(2m+1)\zeta(2m+1). Moreover, we establish a new identity for L(1/3,χ)L(1/3, \chi) analogous to Ramanujan's famous identity for ζ(1/2)\zeta(1/2).

Keywords

Cite

@article{arxiv.2308.08988,
  title  = {A Dirichlet character analogue of Ramanujan's formula for odd zeta values},
  author = {Anushree Gupta and Md Kashif Jamal and Nilmoni Karak and Bibekananda Maji},
  journal= {arXiv preprint arXiv:2308.08988},
  year   = {2023}
}

Comments

24 pages, comments are welcome!