## Tokyo Journal of Mathematics

- Tokyo J. Math.
- Volume 41, Number 1 (2018), 1-20.

### Fundamental Solutions of the Knizhnik-Zamolodchikov Equation of One Variable and the Riemann-Hilbert Problem

Shu OI and Kimio UENO

#### Abstract

In this article, we show that the generalized inversion formulas of the multiple polylogarithms of one variable, which are generalizations of the inversion formula of the dilogarithm, characterize uniquely the multiple polylogarithms under certain conditions. This means that the multiple polylogarithms are constructed from the multiple zeta values. We call such a problem of determining certain functions a recursive Riemann-Hilbert problem of additive type. Furthermore we show that the fundamental solutions of the KZ equation of one variable are uniquely characterized by the connection relation between the fundamental solutions of the KZ equation normalized at $z=0$ and $z=1$ under some assumptions. Namely the fundamental solutions of the KZ equation are constructed from the Drinfel'd associator. We call this problem a Riemann-Hilbert problem of multiplicative type.

#### Article information

**Source**

Tokyo J. Math., Volume 41, Number 1 (2018), 1-20.

**Dates**

First available in Project Euclid: 26 January 2018

**Permanent link to this document**

https://projecteuclid.org/euclid.tjm/1516935614

**Mathematical Reviews number (MathSciNet)**

MR3830806

**Zentralblatt MATH identifier**

06966856

**Subjects**

Primary: 34M50: Inverse problems (Riemann-Hilbert, inverse differential Galois, etc.) 11G55: Polylogarithms and relations with $K$-theory

Secondary: 30E25: Boundary value problems [See also 45Exx] 11M06: $\zeta (s)$ and $L(s, \chi)$ 32G34: Moduli and deformations for ordinary differential equations (e.g. Knizhnik-Zamolodchikov equation) [See also 34Mxx]

#### Citation

OI, Shu; UENO, Kimio. Fundamental Solutions of the Knizhnik-Zamolodchikov Equation of One Variable and the Riemann-Hilbert Problem. Tokyo J. Math. 41 (2018), no. 1, 1--20. https://projecteuclid.org/euclid.tjm/1516935614