The Graded Betti Numbers of the Skeletons of Simplicial Complexes

Fuente: arXiv
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Main Author: Namiq, Mohammed Rafiq
Format: Preprint
Published: 2025
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author Namiq, Mohammed Rafiq
author_facet Namiq, Mohammed Rafiq
contents In this paper, we study a class $\mathcal{C}$ of squarefree monomial ideals $I\subseteq R=\mathbb{K}[x_1,\dots,x_n]$ over a field $\mathbb{K}$, defined by the condition that $\dim R/I$ equals the maximum degree of the minimal generators of $I$ minus one. We show that the Stanley-Reisner ideal of every $i$-skeleton of a simplicial complex $Δ$ belongs to $\mathcal{C}$ for all $-1\le i<\dimΔ$. To investigate their homological properties, we introduce the notion of a degree resolution and prove that every ideal in $\mathcal{C}$ possesses this property. Moreover, we show that every squarefree monomial ideal admits a truncation whose regularity coincides with that of the original ideal, thereby reducing the study of degree resolutions to that of linear resolutions. Finally, we provide an explicit formula describing the relationship between the graded Betti numbers of a simplicial complex and those of its skeletons.
format Preprint
id arxiv_https___arxiv_org_abs_2510_09969
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Graded Betti Numbers of the Skeletons of Simplicial Complexes
Namiq, Mohammed Rafiq
Commutative Algebra
Combinatorics
Primary 13D02, 13F55, Secondary 13A02, 55U05
In this paper, we study a class $\mathcal{C}$ of squarefree monomial ideals $I\subseteq R=\mathbb{K}[x_1,\dots,x_n]$ over a field $\mathbb{K}$, defined by the condition that $\dim R/I$ equals the maximum degree of the minimal generators of $I$ minus one. We show that the Stanley-Reisner ideal of every $i$-skeleton of a simplicial complex $Δ$ belongs to $\mathcal{C}$ for all $-1\le i<\dimΔ$. To investigate their homological properties, we introduce the notion of a degree resolution and prove that every ideal in $\mathcal{C}$ possesses this property. Moreover, we show that every squarefree monomial ideal admits a truncation whose regularity coincides with that of the original ideal, thereby reducing the study of degree resolutions to that of linear resolutions. Finally, we provide an explicit formula describing the relationship between the graded Betti numbers of a simplicial complex and those of its skeletons.
title The Graded Betti Numbers of the Skeletons of Simplicial Complexes
topic Commutative Algebra
Combinatorics
Primary 13D02, 13F55, Secondary 13A02, 55U05
url https://arxiv.org/abs/2510.09969