Simplicial Resolutions of Powers of Square-free Monomial Ideals

Fuente: arXiv
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Autores principales: Cooper, Susan M., Khoury, Sabine El, Faridi, Sara, Mayes-Tang, Sarah, Morey, Susan, Sega, Liana M., Spiroff, Sandra
Formato: Preprint
Publicado: 2022
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author Cooper, Susan M.
Khoury, Sabine El
Faridi, Sara
Mayes-Tang, Sarah
Morey, Susan
Sega, Liana M.
Spiroff, Sandra
author_facet Cooper, Susan M.
Khoury, Sabine El
Faridi, Sara
Mayes-Tang, Sarah
Morey, Susan
Sega, Liana M.
Spiroff, Sandra
contents The Taylor resolution is almost never minimal for powers of monomial ideals, even in the square-free case. In this paper we introduce a smaller resolution for each power of any square-free monomial ideal, which depends only on the number of generators of the ideal. More precisely, for every pair of fixed integers $r$ and $q$, we construct a simplicial complex that supports a free resolution of the $r$-th power of any square-free monomial ideal with $q$ generators. The resulting resolution is significantly smaller than the Taylor resolution, and is minimal for special cases. Considering the relations on the generators of a fixed ideal allows us to further shrink these resolutions. We also introduce a class of ideals called "extremal ideals", and show that the Betti numbers of powers of all square-free monomial ideals are bounded by Betti numbers of powers of extremal ideals. Our results lead to upper bounds on Betti numbers of powers of any square-free monomial ideal that greatly improve the binomial bounds offered by the Taylor resolution.
format Preprint
id arxiv_https___arxiv_org_abs_2204_03136
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Simplicial Resolutions of Powers of Square-free Monomial Ideals
Cooper, Susan M.
Khoury, Sabine El
Faridi, Sara
Mayes-Tang, Sarah
Morey, Susan
Sega, Liana M.
Spiroff, Sandra
Commutative Algebra
Combinatorics
13D02, 13F55
The Taylor resolution is almost never minimal for powers of monomial ideals, even in the square-free case. In this paper we introduce a smaller resolution for each power of any square-free monomial ideal, which depends only on the number of generators of the ideal. More precisely, for every pair of fixed integers $r$ and $q$, we construct a simplicial complex that supports a free resolution of the $r$-th power of any square-free monomial ideal with $q$ generators. The resulting resolution is significantly smaller than the Taylor resolution, and is minimal for special cases. Considering the relations on the generators of a fixed ideal allows us to further shrink these resolutions. We also introduce a class of ideals called "extremal ideals", and show that the Betti numbers of powers of all square-free monomial ideals are bounded by Betti numbers of powers of extremal ideals. Our results lead to upper bounds on Betti numbers of powers of any square-free monomial ideal that greatly improve the binomial bounds offered by the Taylor resolution.
title Simplicial Resolutions of Powers of Square-free Monomial Ideals
topic Commutative Algebra
Combinatorics
13D02, 13F55
url https://arxiv.org/abs/2204.03136