We study when the modifications of the Cohen-Macaulay vertex cover ideal of a graph are Cohen-Macaulay.

Recently, motivated by Anderson, Dumitrescu’s $S$-finiteness, D. Bennis, M. El Hajoui (2018) introduced the notion of $S$-coherent rings, which is the $S$-version of coherent rings. Let $R={⨁}_{\alpha \in G}{R}_{\alpha }$ be a commutative ring with unity graded by an arbitrary commutative monoid $G$, and $S$ a multiplicatively closed subset of nonzero homogeneous elements of $R$. We define $R$ to be graded-$S$-coherent ring if every finitely generated homogeneous ideal of $R$ is $S$-finitely presented. The purpose of this paper is to give the graded...