Cohen-Macaulay squares of edge ideals

Abstract: Let $G$ be a finite graph and $I(G)$ its edge ideal. The question in which we are interested is when the square $I(G)^2$ is Cohen--Macaulay. Via the polarization technique together with Reisner's criterion, it is shown that, if $G$ belongs to the class of finite graphs which consists of cycles, whisker graphs, trees, connected chordal graphs and connected Cohen--Macaulay bipartite graphs, then the square $I(G)^2$ is Cohen--Macaulay if and only if either $G$ is the pentagon, the cycle of length $5$, or $G$ consists of exactly one edge.