Stability of (1,2)-total pitchfork domination

Abstract

Let $G=(V, E)$ be a finite, simple, and undirected graph without isolated vertex. We define a dominating $D$ of $V(G)$ as a total pitchfork dominating set, if $1leq|N(t)cap V-D|leq2$ for every $t in D$ such that $G[D]$ has no isolated vertex. In this paper, the effects of adding or removing an edge and removing a vertex from a graph are studied on the order of minimum total pitchfork dominating set $gamma_{pf}^{t} (G)$ and the order of minimum inverse total pitchfork dominating set $gamma_{pf}^{-t} (G)$. Where $gamma_{pf}^{t} (G)$ is proved here to be increasing by adding an edge and decreasing by removing an edge, which are impossible cases in the ordinary total domination number.