Computation and structure of character polylogarithms with applications to character Mordell{Tornheim{Witten sums D. H. Bailey∗ J. M. Borwein.y June 9, 2014 Abstract This paper extends tools developed in [10,8] to study character polylogarithms. These objects are used to compute Mordell-Tornheim-Witten character sums and to explore their connections with multiple-zeta values (MZVs) and with their character analogues [17]. 1 Introduction In [10] we defined an ensemble of extended Mordell{Tornheim{Witten (MTW) zeta func- tion values [18, 34, 24, 25,7, 12, 36, 38, 32]. There is by now a huge literature on these sums; in part because of the many connections with fields such as combinatorics, number theory, and mathematical physics. Unlike previous authors we included derivatives with re- spect to the order of the terms. We investigated interrelations amongst MTW evaluations, and explored some deeper connections with multiple-zeta values (MZVs). In this article we continue the research in [8, 10] by studying character polylogarithms and applying them to analyze the relations between MTW character sums defined by X χd1(m) χd2(n) 1 µ (q; r; s) := ; (1) d1;d2 mq nr (m + n)s n;m>0 ±d n−1 where for d > 2, χ±d(n) := n ; and χ−2(n) := (−1) ; χ1(n) = 1: When d1 = d2 = 1 these devolve to classical Mordell{Tornheim{Witten (MTW) sums, as defined in (2) below for K = 2. ∗Lawrence Berkeley National Lab (retired), Berkeley, CA 94720, and University of California, Davis, Dept. of Computer Science, Davis, CA 95616, USA. E-mail:
[email protected].