Let $R$ be an Archimedean partially ordered ring in which the square of every element is positive, and $N(R)$ the set of all nilpotent elements of $R$. It is shown that $N(R)$ is the unique nil radical of $R$, and that $N(R)$ is locally nilpotent and even nilpotent with exponent at most $3$ when $R$ is 2-torsion-free. $R$ is without non-zero nilpotents if and only if it is 2-torsion-free and has zero annihilator. The results are applied on partially ordered rings in which every element $a$ is expressed as $a=a_1-a_2$ with positive $a_1$, $a_2$ satisfying $a_1a_2=a_2a_1=0$.
@article{118661, author = {Boris Lavri\v c}, title = {The nil radical of an Archimedean partially ordered ring with positive squares}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {35}, year = {1994}, pages = {231-238}, zbl = {0805.06017}, mrnumber = {1286569}, language = {en}, url = {http://dml.mathdoc.fr/item/118661} }
Lavrič, Boris. The nil radical of an Archimedean partially ordered ring with positive squares. Commentationes Mathematicae Universitatis Carolinae, Tome 35 (1994) pp. 231-238. http://gdmltest.u-ga.fr/item/118661/
Almost $f$-algebras and $d$-algebras, Proc. Cambridge Philos. Soc. 107 (1990), 287-308. (1990) | MR 1027782 | Zbl 0707.06009
Lattice-ordered rings, An. Acad. Brasil Ci\^enc. 28 (1956), 41-69. (1956) | MR 0080099 | Zbl 0070.26602
A radical for lattice-ordered rings, Pacific J. Math. 25 (1968), 71-82. (1968) | MR 0227068 | Zbl 0157.08004
Rings and Radicals, Allen, London, 1965. | MR 0197489 | Zbl 0138.26303
Partially Ordered Algebraic Systems, Pergamon Press, Oxford-London-New YorkParis, 1963. | MR 0171864 | Zbl 0137.02001
A characterization of $f$-rings without non-zero nilpotents, J. London Math. Soc. 39 (1964), 706-707. (1964) | MR 0167501 | Zbl 0126.06502
Structure of Rings, Colloquium Publication 37, Amer. Math. Soc., Providence, 1956. | MR 0081264 | Zbl 0098.25901
On lattice-ordered rings in which the square of every element is positive, J. Austral. Math. Soc. Ser. A 22 (1976), 362-370. (1976) | MR 0427198 | Zbl 0352.06017
Radicals of Rings, Akademiai Kiado - John Wiley & Sons, Budapest-ChichesterNew York-Brisbane-Toronto, 1981. | MR 0636787