Article
Keywords:
commutative rings; von Neumann regular rings; von Neumann local rings; Gelfand rings; polynomial rings; power series rings; rings of Gaussian integers (mod  $n$); prime and maximal ideals; maximal regular ideals; pure ideals; quadratic residues; Stone-Čech compactification; $C(X)$; zerosets; cozerosets; $P$-spaces
Summary:
In 1950 in volume 1 of Proc. Amer. Math. Soc., B.  Brown and N.  McCoy showed that every (not necessarily commutative) ring $R$ has an ideal $\frak M (R)$ consisting of elements $a$ for which there is an $x$ such that $axa=a$, and maximal with respect to this property. Considering only the case when $R$ is commutative and has an identity element, it is often not easy to determine when $\frak M (R)$ is not just the zero ideal. We determine when this happens in a number of cases: Namely when at least one of $a$ or $1-a$ has a von Neumann inverse, when $R$ is a product of local rings (e.g., when $R$ is $\Bbb Z_{n}$ or $\Bbb Z_{n}[i]$), when $R$ is a polynomial or a power series ring, and when $R$ is the ring of all real-valued continuous functions on a topological space.
References:
                        
[AHA04] Abu Osba E., Henriksen M., Alkam O.: 
Combining local and von Neumann regular rings. Comm. Algebra 32 (2004), 2639-2653. 
MR 2099923[AM69] Atiyah M., Macdonald J.: 
Introduction to Commutative Algebra. Addison-Wesley, Reading, Mass., 1969. 
MR 0242802 | 
Zbl 0238.13001[BM50] Brown B., McCoy N.: 
The maximal regular ideal of a ring. Proc. Amer. Math. Soc. 1 (1950), 165-171. 
MR 0034757 | 
Zbl 0036.29702[DO71] DeMarco G., Orsatti A.: 
Commutative rings in which every maximal ideal is contained in a unique maximal ideal. Proc. Amer. Math. Soc. 30 (1971), 459-466. 
MR 0282962[H77] Henriksen M.: 
Some sufficient conditions for the Jacobson radical of a commutative ring with identity to contain a prime ideal. Portugaliae Math. 36 (1977), 257-269. 
MR 0597848 | 
Zbl 0448.13002[L58] Leveque W.: 
Topics in Number Theory. Addison-Wesley, Reading, Mass., 1958. 
Zbl 1009.11001