Published online by Cambridge University Press: 16 October 2012
Let $R$ be a commutative ring. The regular digraph of ideals of
$R$, denoted by
$\Gamma (R)$, is a digraph whose vertex set is the set of all nontrivial ideals of
$R$ and, for every two distinct vertices
$I$ and
$J$, there is an arc from
$I$ to
$J$ whenever
$I$ contains a nonzero divisor on
$J$. In this paper, we study the connectedness of
$\Gamma (R)$. We also completely characterise the diameter of this graph and determine the number of edges in
$\Gamma (R)$, whenever
$R$ is a finite direct product of fields. Among other things, we prove that
$R$ has a finite number of ideals if and only if
$\mathrm {N}_{\Gamma (R)}(I)$ is finite, for all vertices
$I$ in
$\Gamma (R)$, where
$\mathrm {N}_{\Gamma (R)}(I)$ is the set of all adjacent vertices to
$I$ in
$\Gamma (R)$.