
doi: 10.1007/bf01951330
A quasi-ideal Q of a ring A is an additive subgroup of A such that A\(Q\cap QA\subseteq Q\). The intersection of a left ideal and a right ideal is always a quasi-ideal but the converse is not true (a counterexample was constructed by A. H. Clifford [see \textit{O. Steinfeld}, Quasi-ideals in rings and semigroups (1978; Zbl 0403.16001), p. 8]). A quasi-ideal Q is said to have the intersection property if it is the intersection of a left and a right ideal. The main results of the present paper exhibit for various rings that they possess quasi-ideals which do not have the intersection property. Such is for instance the contracted semigroup ring \(R_ 0[S]\) where R is an arbitrary ring with identity and S is a semigroup with zero satisfying a condition which is too technical to be reproduced here. The author also constructs a skew polynomial ring without zero divisors in which not every quasi-ideal has the intersection property although every minimal quasi-ideal has it. Similar examples of contracted semigroup rings are also presented.
intersection property, quasi-ideals, Semigroup rings, multiplicative semigroups of rings, contracted semigroup rings, skew polynomial ring, Modules, bimodules and ideals in associative algebras, Valuations, completions, formal power series and related constructions (associative rings and algebras), minimal quasi- ideal
intersection property, quasi-ideals, Semigroup rings, multiplicative semigroups of rings, contracted semigroup rings, skew polynomial ring, Modules, bimodules and ideals in associative algebras, Valuations, completions, formal power series and related constructions (associative rings and algebras), minimal quasi- ideal
| citations This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 10 | |
| popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Average | |
| influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Top 10% | |
| impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Average |
