# Italian domination in trees

## Document Type

Article

## Publication Date

1-30-2017

## Abstract

The Roman domination number and Italian domination number (also known as the Roman {2}-domination number) are graph labeling problems in which each vertex is labeled with either 0, 1, or 2. In the Roman domination problem, each vertex labeled 0 must be adjacent to at least one vertex labeled 2. In the Italian domination problem, each vertex labeled 0 must have the labels of the vertices in its closed neighborhood sum to at least two. The Italian domination number, γI(G), of a graph G is the minimum possible sum of such a labeling, where the sum is taken over all the vertices in G. It is known that if T is a tree with at least two vertices, then γ(T)+1≤γI(T)≤2γ(T). In this paper, we characterize the trees T for which γ(T)+1=γI(T), and we characterize the trees T for which γI(T)=2γ(T).

## Publication Title

Discrete Applied Mathematics

## Volume

217

## First Page

557

## Last Page

564

## Digital Object Identifier (DOI)

10.1016/j.dam.2016.09.035

## ISSN

0166218X

## Citation Information

Henning, & Klostermeyer, W. F. (2017). Italian domination in trees. Discrete Applied Mathematics, 217, 557–564. https://doi.org/10.1016/j.dam.2016.09.035