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arXiv · 2503.13295

Noncommutative factorizations of higher sine functions in positive characteristic

Nathan Green·Federico Pellarin
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Abstract

In this paper we describe new noncommutative factorizations of functions related to $d$-th tensor powers of Carlitz's $\mathbb F_q[\theta]$-module for $d\geq 1$, called higher sine functions. In recent work by the second author, factorizations of this type have been constructed for operators which are combinations of powers of a Frobenius endomorphism with coefficients ``in $\operatorname{End}(\operatorname{End}(\mathbb G_a^d))$''. In the present paper we succeed in determining factorizations with coefficients ``in $\operatorname{End}(\mathbb G_a^d)$'' which are not easily deducible from previous work. One key ingredient in obtaining this is an application of a ``motivic pairing'' that the first author introduced in recent work. Another key ingredient is the notion of ``$\Delta$-matrix'' which comes into play in the analysis of the coefficients of the factorizations. Our results can be applied to explicitly describe analogues of shuffle $q^n$-powers for multiple polylogarithms at one, and to multiple zeta values of Thakur. All the identities we prove occur at the finite level.

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Nathan Green, Federico Pellarin. 2025-03-17. Noncommutative factorizations of higher sine functions in positive characteristic. https://arxiv.org/abs/2503.13295

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