The coloring of the regular graph of ideals

Abstract

The regular graph of ideals of the commutative ring $R$, denoted by ${\Gamma }_{reg}(R)$, is a graph whose vertex set is the set of all non-trivial ideals of $R$ and two distinct vertices $I$ and $J$ are adjacent if and only if either $I$ contains a $J$-regular element or $J$ contains an $I$-regular element. In this paper, it is shown that for every Artinian ring $R$, the edge chromatic number of ${\Gamma }_{reg}(R)$ equals its maximum degree. Then a formula for the clique number of ${\Gamma }_{reg}(R)$ is given. Also, it is proved that for every reduced ring $R$ with $n(\ge 3)$ minimal prime ideals, the edge chromatic number of ${\Gamma }_{reg}(R)$ is $2^{n-1}-2$. Moreover, we show that both of the clique number and vertex chromatic number of ${\Gamma }_{reg}(R)$ are $n-1$, for every reduced ring $R$ with $n$ minimal prime ideals.

AMS-LaTeX, 11 pages with no figures