On the Castelnuovo-Mumford regularity of squarefree powers of edge ideals

TL;DR

This paper investigates bounds on the Castelnuovo-Mumford regularity of squarefree powers of edge ideals in certain classes of graphs, establishing exact formulas for Cameron-Walker graphs and bounds for others.

Contribution

It provides new upper bounds for the regularity of squarefree powers in specific graph classes and exact regularity formulas for Cameron-Walker graphs.

Findings

For certain graph classes, regularity is bounded by match(G)+s.

Exact regularity is achieved for Cameron-Walker graphs.

The results extend understanding of algebraic invariants of edge ideals.

Abstract

Assume that $G$ is a graph with edge ideal $I(G)$ and matching number ${\rm match}(G)$. For every integer $s\geq 1$, we denote the $s$-th squarefree power of $I(G)$ by $I(G)^{[s]}$. It is shown that for every positive integer $s\leq {\rm match}(G)$, the inequality ${\rm reg}(I(G)^{[s]})\leq {\rm match}(G)+s$ holds provided that $G$ belongs to either of the following classes: (i) very well-covered graphs, (ii) semi-Hamiltonian graphs, or (iii) sequentially Cohen-Macaulay graphs. Moreover, we prove that for every Cameron-Walker graph $G$ and for every positive integer $s\leq {\rm match}(G)$, we have ${\rm reg}(I(G)^{[s]})={\rm match}(G)+s$