2017/06/27 by Madani, Sara Saeedi, Kiani, Dariush · 1 citation
#Combinatorics (math.CO) #Commutative Algebra (math.AC) #FOS: Mathematics #Primary 13D02 #Secondary 05E40
paper · doi:10.48550/arxiv.1706.09002
Let JG be the binomial edge ideal of a graph G. We characterize all graphs whose binomial edge ideals, as well as their initial ideals, have regularity 3. Consequently we characterize all graphs G such that JG is extremal Gorenstein. Indeed, these characterizations are consequences of an explicit formula we obtain for the regularity of the binomial edge ideal of the join product of two graphs. Finally, by using our regularity formula, we discuss some open problems in the literature. In particular we disprove a conjecture in \citeCDI on the regularity of weakly closed graphs.