English

The intersection graph of ideals of $\mathbb{Z}_n$ is\\ weakly perfect

Commutative Algebra 2013-05-28 v1 Combinatorics

Abstract

A graph is called weakly perfect if its vertex chromatic number equals its clique number. Let RR be a ring and I(R)I(R)^* be the set of all left proper non-trivial ideals of RR. The intersection graph of ideals of RR, denoted by G(R)G(R), is a graph with the vertex set I(R)I(R)^* and two distinct vertices II and JJ are adjacent if and only if IJ0I\cap J\neq 0. In this paper, it is shown that G(Zn)G(\mathbb{Z}_n), for every positive integer nn, is a weakly perfect graph. Also, for some values of nn, we give an explicit formula for the vertex chromatic number of G(Zn)G(\mathbb{Z}_n). Furthermore, it is proved that the edge chromatic number of G(Zn)G(\mathbb{Z}_n) is equal to the maximum degree of G(Zn)G(\mathbb{Z}_n) unless either G(Zn)G(\mathbb{Z}_n) is a null graph with two vertices or a complete graph of odd order.

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Cite

@article{arxiv.1305.6287,
  title  = {The intersection graph of ideals of $\mathbb{Z}_n$ is\\ weakly perfect},
  author = {R. Nikandish and M. J. Nikmehr},
  journal= {arXiv preprint arXiv:1305.6287},
  year   = {2013}
}

Comments

8 pages