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Acta Mathematica Vietnamica

On the Index of Depth Stability of Symbolic Powers of Cover Ideals of Graphs

S. A. Seyed Fakhari , icon-email S. Yassemi

Abstract

Let $G$ be a graph with $n$ vertices and let $S=\mathbb {K}[x_1,\dots ,x_n]$ be the polynomial ring in $n$ variables over a field $\mathbb {K}$. Assume that $I(G)$ and $J(G)$ denote the edge ideal and the cover ideal of $G$, respectively. We provide a combinatorial upper bound for the index of depth stability of symbolic powers of $J(G)$. As a consequence, we compute the depth of symbolic powers of cover ideals of fully clique-whiskered graphs. Meanwhile, we determine a class of graphs $G$ with the property that the Castelnuovo–Mumford regularity of $S/I(G)$ is equal to the induced matching number of $G$.