In this article, necessary and sufficient conditions are determined in order that (Γ(R)) c (that is, the complement of the zero-divisor graph of R) is planar. It is noted that, if (Γ(R)) c is planar, then the number of maximal N -primes of (0) in R is at most three. Firstly, we consider rings R admitting exactly three maximal N -primes of (0) and present a characterization of such rings in order that the complement of their zero-divisor graphs be planar. Secondly, we consider rings R admitting exactly two maximal N -primes of (0) and investigate the problem of when the complement of their zero-divisor graphs is planar. Thirdly, we consider rings R admitting only one maximal N -prime of (0) and determine necessary and sufficient conditions in order that the complement of their zero-divisor graphs be planar.
Introduction.All rings considered in this article are nonzero commutative rings with identity. Unless otherwise specified, we consider rings which admit at least two nonzero zero-divisors. For any ring R, and for any R-module M , the set of zero-divisors of M as an R-module denoted by Z R (M ) is defined as Z R (M ) = {r ∈ R | rm = 0 for some m ∈ M \ {0}}. In the special case when M = R, Z R (R) is simply denoted by Z(R). We denote by Z(R) * the set of all nonzero zero-divisors of R.Let R be a ring which is not an integral domain. Recall from [5] that the zero-divisor graph of R, denoted by Γ(R), is defined as the graph whose vertex set is Z(R) * and distinct x, y ∈ Z(R) * are joined by an edge in this graph if and only if xy = 0. Many interesting and inspiring theorems are known about zero-divisor graphs. Several researchers investigated in the area of zero-divisor graphs, and the theorems proved 2010 AMS Mathematics subject classification. Primary 13A15. Keywords and phrases. The complement of the zero-divisor graph, maximal N -primes of (0).