English

Asymptotic formulae for Eulerian series

Number Theory 2017-09-26 v1 Classical Analysis and ODEs

Abstract

Let (a;q)(a;q)_{\infty} be the qq-Pochhammer symbol and li2(x)\mathrm{li}_2(x) be the dilogarithm function. Let α,β,γ\prod_{\alpha,\beta,\gamma} be a finite product with every triple (α,β,γ)(R>0)3(\alpha,\beta,\gamma)\in(\mathbb{R}_{>0})^3 and SαβγRS_{\alpha\beta\gamma}\in\mathbb{R}. Also let the triple (A,B,v)(R>0×R2)({0}2×R>0)({0}×R<0×R)(A,B,v)\in\left(\mathbb{R}_{>0}\times\mathbb{R}^2\right)\cup\left(\{0\}^2\times\mathbb{R}_{>0}\right)\cup\left(\{0\}\times\mathbb{R}_{<0}\times\mathbb{R}\right). In this work, we let z=evz=e^v, denote by H1(u)=vuAu2+αli2(eαu)β,γβ1SαβγH_{-1}(u)=vu-Au^2+\sum_{\alpha}\mathrm{li}_2(e^{-\alpha u})\sum_{\beta,\gamma} \beta^{-1}S_{\alpha\beta\gamma} and consider the Eulerien series H(z;q)=m=0qAm2+Bmzmα,β,γ(qαm+γ;qβ)Sαβγ.\mathcal{H}(z;q)=\sum_{m=0}^{\infty}\frac{q^{Am^2+Bm}z^{m}}{\prod\limits_{\alpha,\beta,\gamma}(q^{\alpha m+\gamma};q^{\beta})_{\infty}^{S_{\alpha\beta\gamma}}}. We prove that if there exist an ε>0\varepsilon>0 such that H1(u)H_{-1}(u) is an increasing function on [0,ε)[0,\varepsilon), then as q1q\rightarrow 1^-, H(z;q)=(1+o(logqp))0qAx2+Bxzxα,β,γ(qαx+γ;qβ)Sαβγdx\mathcal{H}(z;q)=\left(1+o\left(|\log q|^p\right)\right)\int\limits_{0}^{\infty}\frac{q^{Ax^2+Bx}z^{x}}{\prod\limits_{\alpha,\beta,\gamma}(q^{\alpha x+\gamma};q^{\beta})_{\infty}^{S_{\alpha\beta\gamma}}}\,dx holds for each p0p\ge 0. We also obtain full asymptotic expansions for H(z;q)\mathcal{H}(z;q) which satisfy above condition as q1q\rightarrow 1^{-}. The complete asymptotic expansions for related basic hypergeometric series could be derived as special cases.

Keywords

Cite

@article{arxiv.1709.08550,
  title  = {Asymptotic formulae for Eulerian series},
  author = {Nian Hong Zhou},
  journal= {arXiv preprint arXiv:1709.08550},
  year   = {2017}
}

Comments

3^3 pages

R2 v1 2026-06-22T21:53:58.592Z