Cohen-Macaulay Weighted Oriented Edge Ideals and its Alexander Dual

Abstract

The study of the edge ideal $I(D_G)$ of a weighted oriented graph $D_G$ with underlying graph $G$ started in the context of Reed-Muller type codes. We generalize a Cohen-Macaulay construction for $I(D_G)$, which Villarreal gave for edge ideals of simple graphs. We use this construction to classify all the Cohen-Macaulay weighted oriented edge ideals, whose underlying graph is a cycle. We show that the conjecture on Cohen-Macaulayness of $I(D_G)$, proposed by Pitones et al. (2019), holds for $I(D_{C_n})$, where $C_n$ denotes the cycle of length $n$. Miller generalized the concept of Alexander dual ideals of square-free monomial ideals to arbitrary monomial ideals, and in that direction, we study the Alexander dual of $I(D_G)$ and its conditions to be Cohen-Macaulay.

26 pages