Abstract
Let $G=(V,E)$ be a simple graph with vertex set $V=V(G)$, edge set $E=E(G)$ and from maximum degree $\Delta=\Delta(G)$. Also let
$f:V\rightarrow\{0,1,...,\lceil\frac{\Delta}{2}\rceil+1\}$ be a function that labels the vertices of $G$. Let $V_i=\{v\in V: f(v)=i\}$ for $i=0,1$ and let $V_2=V-(V_0\bigcup V_1)=\{w\in V: f(w)\geq2\}$. A function $f$ is called a strong Roman dominating function (StRDF) for $G$, if every $v\in V_0$ has a neighbor $w$, such that $w\in V_2$ and $f(w)\geq 1+\lceil\frac{1}{2}|N(w)\bigcap V_0|\rceil$. The minimum weight, $\omega(f)=f(V)=\Sigma_{v\in V} f(v)$, over all the strong Roman dominating functions of $G$, is called the strong Roman domination number of $G$ and we denote it by $\gamma_{StR}(G)$. An StRDF of minimum weight is called a $\gamma_{StR}(G)$-function. Let $\overline{G}$ be the complement of $G$. The complementary prism $G\overline{G}$ of $G$ is the graph formed from the disjoint union $G$ and $\overline{G}$ by adding the edges of a perfect matching between the corresponding vertices of $G$ and $\overline{G}$. In this paper, we investigate some properties of Roman, double Roman and strong Roman domination number of $G\overline{G}$.