English

Linear independence criteria for generalized polylogarithms with distinct shifts

Number Theory 2023-01-06 v2

Abstract

For a given rational number xx and an integer s1s\geq 1, let us consider a generalized polylogarithmic function, often called the Lerch function, defined by Φs(x,z)=k=0zk+1(k+x+1)s.\Phi_{s}(x,z)= \sum_{k=0}^{\infty}\frac{z^{k+1}}{(k+x+1)^s}\enspace. We prove the linear independence over any number field KK of the numbers 11 and Φsj(xj,αi)\Phi_{s_j}(x_j,\alpha_i) with any choice of distinct shifts x1,,xdx_1,\ldots, x_d with 0x1<<xd<10\le x_1<\ldots<x_d<1, as well as any choice of depths 1s1r1,,1sdrd1\leq s_1\leq r_1,\ldots, 1\leq s_d\leq r_d, at distinct algebraic numbers α1,,αmK\alpha_1,\ldots,\alpha_m\in K subject to a metric condition. As is usual in the theory, the points αi\alpha_i need to be chosen sufficiently close to zero with respect to a given fixed place v0v_0 of KK, Archimedean or finite. This is the first linear independence result with distinct shifts x1,,xdx_1, \ldots, x_d that allows values at different points for generalized polylogarithmic functions. Previous criteria were only for the functions with one fixed shift or at one point. Further, we establish another linear independence criterion for values of the generalized polylogarithmic function with cyclic coefficients. Let q1q\geq 1 be an integer and a=(a1,,aq)Kq\boldsymbol{a}=(a_1,\ldots, a_q)\in K^q be a qq-tuple whose coordinates supposed to be cyclic with the period qq. Consider the generalized polylogarithmc function with coefficients Φa,s(x,z)=k=0ak+1mod(q)zk+1(k+x+1)s.\Phi_{\boldsymbol{a},s}(x,z)= \sum_{k=0}^{\infty}\frac{a_{k+1\bmod(q)}\cdot z^{k+1}}{(k+x+1)^s}\enspace. Under suitable condition, we show that the values of these functions are linearly independent over KK. Our key tool is a new non-vanishing property for a generalized Wronskian of Hermite type associated to our explicit constructions of Pad\'e approximants for this family of generalized polylogarithmic function.

Keywords

Cite

@article{arxiv.2202.13931,
  title  = {Linear independence criteria for generalized polylogarithms with distinct shifts},
  author = {Sinnou David and Noriko Hirata-Kohno and Makoto Kawashima},
  journal= {arXiv preprint arXiv:2202.13931},
  year   = {2023}
}

Comments

Corrected typos

R2 v1 2026-06-24T09:56:38.674Z