Posets for $F$-polynomials in cluster algebras from surfaces

Fuente: arXiv
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Main Authors: Pilaud, Vincent, Reading, Nathan, Schroll, Sibylle
Format: Preprint
Published: 2023
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author Pilaud, Vincent
Reading, Nathan
Schroll, Sibylle
author_facet Pilaud, Vincent
Reading, Nathan
Schroll, Sibylle
contents We prove a simple formula for arbitrary cluster variables in the marked surfaces model. As part of the formula, we associate a labeled poset to each tagged arc, such that the associated $F$-polynomial is a weighted sum of order ideals. Each element of the poset has a weight, and the weight of an ideal is the product of the weights of the elements of the ideal. In the unpunctured case, the weight on each element is a single $\hat{y}_i$, in the usual sense of principal coefficients. In the presence of punctures, some elements may have weights of the form $\hat{y}_i/\hat{y}_j$. Our search for such a formula was inspired by the Fundamental Theorem of Finite Distributive Lattices combined with work of Gregg Musiker, Ralf Schiffler, and Lauren Williams that, in some cases, organized the terms of the $F$-polynomial into a distributive lattice. The proof consists of a simple and poset-theoretically natural argument in a special case, followed by a hyperbolic geometry argument using a cover of the surface to prove the general case.
format Preprint
id arxiv_https___arxiv_org_abs_2311_06033
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Posets for $F$-polynomials in cluster algebras from surfaces
Pilaud, Vincent
Reading, Nathan
Schroll, Sibylle
Combinatorics
Representation Theory
We prove a simple formula for arbitrary cluster variables in the marked surfaces model. As part of the formula, we associate a labeled poset to each tagged arc, such that the associated $F$-polynomial is a weighted sum of order ideals. Each element of the poset has a weight, and the weight of an ideal is the product of the weights of the elements of the ideal. In the unpunctured case, the weight on each element is a single $\hat{y}_i$, in the usual sense of principal coefficients. In the presence of punctures, some elements may have weights of the form $\hat{y}_i/\hat{y}_j$. Our search for such a formula was inspired by the Fundamental Theorem of Finite Distributive Lattices combined with work of Gregg Musiker, Ralf Schiffler, and Lauren Williams that, in some cases, organized the terms of the $F$-polynomial into a distributive lattice. The proof consists of a simple and poset-theoretically natural argument in a special case, followed by a hyperbolic geometry argument using a cover of the surface to prove the general case.
title Posets for $F$-polynomials in cluster algebras from surfaces
topic Combinatorics
Representation Theory
url https://arxiv.org/abs/2311.06033