Ordered trees and the Geode

Fuente: arXiv
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Autore principale: Gossow, Fern
Natura: Preprint
Pubblicazione: 2025
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author Gossow, Fern
author_facet Gossow, Fern
contents In recent work of Wildberger and Rubine, it is shown that the formal power series $\mathbf{S}$ in the variables $t_1,t_2,\dots$ satisfying $\mathbf{S}=1+\sum_{n\geq 1} t_n\mathbf{S}^n$ has a factorisation $\mathbf{S}=1+(t_1+t_2+\cdots)\mathbf{G}$, where $\mathbf{G}$ is a power series with nonnegative coefficients called the Geode. In this note we give a combinatorial interpretation for the coefficients of $\mathbf{G}$ based on ordered trees. This amends the statement of a disproved conjecture of Wildberger and Rubine which suggests a similar (but incorrect) interpretation.
format Preprint
id arxiv_https___arxiv_org_abs_2507_18097
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Ordered trees and the Geode
Gossow, Fern
Combinatorics
05A19, 05C05
In recent work of Wildberger and Rubine, it is shown that the formal power series $\mathbf{S}$ in the variables $t_1,t_2,\dots$ satisfying $\mathbf{S}=1+\sum_{n\geq 1} t_n\mathbf{S}^n$ has a factorisation $\mathbf{S}=1+(t_1+t_2+\cdots)\mathbf{G}$, where $\mathbf{G}$ is a power series with nonnegative coefficients called the Geode. In this note we give a combinatorial interpretation for the coefficients of $\mathbf{G}$ based on ordered trees. This amends the statement of a disproved conjecture of Wildberger and Rubine which suggests a similar (but incorrect) interpretation.
title Ordered trees and the Geode
topic Combinatorics
05A19, 05C05
url https://arxiv.org/abs/2507.18097