In this paper, we investigate when symbolic and ordinary powers of the parity binomial edge ideal of a graph fail to be equal. It turns out that if $\mathcal{ I}_{ G}$ is the parity binomial edge ideal of a graph $G$, then in each of the following cases the symbolic power $\mathcal{ I}_{ G}^{ (t)}$ and the ordinary power $\mathcal{ I}_{ G}^t$ are not equal for some $t$: (i) the clique number of $G$ is greater than 3; (ii) $G$ has a net; or (iii) $G$ has a PT as an induced subgraph.
Categories: math.AC math.CO