On the compatibility of the Betti harmonic coproduct with cyclotomic filtrations

Fuente: arXiv
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Main Authors: Enriquez, Benjamin, Yaddaden, Khalef
Format: Preprint
Published: 2025
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_version_ 1866909739488641024
author Enriquez, Benjamin
Yaddaden, Khalef
author_facet Enriquez, Benjamin
Yaddaden, Khalef
contents In a previous paper, the second author introduced a Betti counterpart of $N$-cyclotomic double shuffle theory for any $N \geq 1$. The construction is based on the group algebra of the free group $F_2$, endowed with a filtration relative to a morphism $F_2 \to μ_N$ (where $μ_N$ is the group of $N$-th roots of unity). One of the main results therein is the construction of a complete Hopf algebra coproduct $\widehatΔ^{\mathcal{W}, \mathrm{B}}_N$ on the relative completion of a specific subalgebra $\mathcal{W}^\mathrm{B}$ of the group algebra of $F_2$. However, an explicit formula for this coproduct is missing. In this paper, we show that the discrete Betti harmonic coproduct $Δ^{\mathcal{W}, \mathrm{B}}$ defined in \cite{EF1} for the classical case ($N=1$) by the first author and Furusho remains compatible with the filtration structure on $\mathcal{W}^\mathrm{B}$ induced by the relative completion for arbitrary $N$. This compatibility suggests that the completion corresponding to $Δ^{\mathcal{W}, \mathrm{B}}$ is a candidate for an explicit realization of $\widehatΔ^{\mathcal{W}, \mathrm{B}}_N$.
format Preprint
id arxiv_https___arxiv_org_abs_2508_12208
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the compatibility of the Betti harmonic coproduct with cyclotomic filtrations
Enriquez, Benjamin
Yaddaden, Khalef
Algebraic Topology
Number Theory
Quantum Algebra
Rings and Algebras
Primary 11M32, 16W70, 16T10. Secondary 16T05
In a previous paper, the second author introduced a Betti counterpart of $N$-cyclotomic double shuffle theory for any $N \geq 1$. The construction is based on the group algebra of the free group $F_2$, endowed with a filtration relative to a morphism $F_2 \to μ_N$ (where $μ_N$ is the group of $N$-th roots of unity). One of the main results therein is the construction of a complete Hopf algebra coproduct $\widehatΔ^{\mathcal{W}, \mathrm{B}}_N$ on the relative completion of a specific subalgebra $\mathcal{W}^\mathrm{B}$ of the group algebra of $F_2$. However, an explicit formula for this coproduct is missing. In this paper, we show that the discrete Betti harmonic coproduct $Δ^{\mathcal{W}, \mathrm{B}}$ defined in \cite{EF1} for the classical case ($N=1$) by the first author and Furusho remains compatible with the filtration structure on $\mathcal{W}^\mathrm{B}$ induced by the relative completion for arbitrary $N$. This compatibility suggests that the completion corresponding to $Δ^{\mathcal{W}, \mathrm{B}}$ is a candidate for an explicit realization of $\widehatΔ^{\mathcal{W}, \mathrm{B}}_N$.
title On the compatibility of the Betti harmonic coproduct with cyclotomic filtrations
topic Algebraic Topology
Number Theory
Quantum Algebra
Rings and Algebras
Primary 11M32, 16W70, 16T10. Secondary 16T05
url https://arxiv.org/abs/2508.12208