Article in volume
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Title:
A new upper bound for the perfect Italian domination number of a tree
PDFSource:
Discussiones Mathematicae Graph Theory 42(3) (2022) 1005-1022
Received: 2019-09-03 , Revised: 2020-04-08 , Accepted: 2020-04-10 , Available online: 2020-05-11 , https://doi.org/10.7151/dmgt.2324
Abstract:
A perfect Italian dominating function (PIDF) on a graph $G$ is a function
$f:V(G)\rightarrow\{0,1,2\}$ satisfying the condition that for every vertex
$u$ with $f(u)=0$, the total weight of $f$ assigned to the neighbors of $u$ is
exactly two. The weight of a PIDF is the sum of its functions
values over all vertices. The perfect Italian domination number of $G$,
denoted $\gamma_{I}^{p}(G)$, is the minimum weight of a PIDF of $G$. In this
paper, we show that for every tree $T$ of order $n\geq3$, with $\ell(T)$
leaves and $s(T)$ support vertices, $\gamma_{I}^{p}(T)\leq\frac{4n-\ell
(T)+2s(T)-1}{5}$, improving a previous bound given by T.W. Haynes and M.A.
Henning in [Perfect Italian domination in trees, Discrete Appl. Math. 260
(2019) 164–177].
Keywords:
Italian domination, Roman domination, perfect Italian domination
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