ON PRIME RINGS AND THE RADICALS ASSOCIATED WITH THEIR DEGREES OF PRIMENESS

Abstract

Prime ringsMaybe classified by the sizes of the sets that ‘insulate’ their elements from annihilation. For a cardinal m > 0, the class [Pbar]_r,(m) of all rings that are right prime of ‘bound at most m’ is studied, with particular reference to its closure under constructions such as matrix rings, semigoup rings, orders and extensions. The classes [Pbar]_r,(m) are special in the sense of radical theory for each m > 0. The attendant upper radicals υ[Pbar]_r,(m) are right (and not left) strong; their compatibility with certain ring constructions is examined. In the lattice of radicals (where they form a strictly descending chain), their positions are described, relative to various familiar radicals.     

*—BI—IDEALS IN RADICAL THEORY OF INVOLUTION RINGS

Abstract

If a radical class is closed under involution in every ring with involution then the radical theoretic conditions involving *-bi-ideals are equivalent to the corresponding conditions concerning bi-ideals without involution.     

CHARACTERIZING THE NIL RADICAL OF A GAMMA RING

ABSTRACT

The nil radical, N(M) of a Γ-ring M was defined by Coppage and Luh [3], and shown by Groenewald [4] to be a special radical. We define s-prime ideals of M and show that N(M) is equal to the intersection of the s-prime ideals of M. If R is a ring, the nil radical of R considered as a Γ-ring with Γ = R is equal to the upper nil radical of R. We also give a sufficient condition for the equality N(R)* = N(M), where R is the right operator ring of M, and N(R) is its upper nil radical.     

ON THE STRUCTURE OF THE JACOBSON RADICAL OF GRADED RINGS

Abstract

We introduce a new large class of semigroups S including all locally finite, completely regular and strongly π-regular linear semigroups. For any semigroup S in the class and any S-graded ring R, the structure of the Jacobson radical of R is reduced to the radicals of subrings graded by the maximal subgroups of S. Many results on radicals follow from this reduction in a unified way. In two special cases the reduction is simplified.     

RADICAL THEORY FOR SEMIRINGS

Abstract

In this article we continue investigations on a Kurosh-Amitsur radical theory for a universal class U of hemirings as introduced by O.M. Olson et al. We give some necessary and sufficient conditions that such a universal class U consists of all hemirings. Further we consider special and weakly special subclasses M of U which yield hereditary radical classes P = um of U. In this context we correct some statements in the papers of Olson et al. Moreover, a problem posed there concerning the equality of two radicals ?_∞(S) and ?^ε(S) and two similar ideals β_∞ (S) and β^ε(S) is widely solved. We prove ?_∞(S) ? ?^ε(S) = β^∞(S) = β^ε(S) and give necessary and sufficient conditions for equality in the first inclusion. This yields in particular that the weakly special class M_ε(U) is always semisimple, a result which is not true for the special class M_∞(U).     

ON ANTISIMPLE GAMMA RINGS

ABSTRACT

In this note, we define the antisimple radical, A(M), of a Γ-ring M. A(M) is shown to be a special radical, and two characterizations of antisimple rings due to Szész are extended to Γ-rings. If R is the right operator ring of M, then A(R)* = A(M), where A(R) is the antisimple radical of R. If m,n are positive integers, then A(M_mn) = (A(M))_mn, where M_mn denotes the group m x n matrices over M, considered as a Γ_nm -ring with the operations of matrix addition and multiplication.     

REGULARITIES AND SUBDIRECT PRODUCTS OF RINGS

Abstract

Structure theorems are obtained for certain radical classes of rings (including the Brown-McCoy radical class, the class of λ-rings, the class of E ₅-rings, the class of E ₆-rings and the class of f-regular rings) by generalizing the concept of a prime ideal.     

ON SOME SPECIAL CLASSES OF PRIME RINGS

Abstract

Given a non-zero cardinal α, a ring R is said to be SP(α) if a is the first cardinal for which every non-zero element of R has an insulator of cardinality less than α + 1.

It is shown that the class of SP(α) rings is a special class (in the sense of Andrunakievi?) for each α. A theorem of Groenewald and Heyman (also Desale and Varadarajan) to the effect that the class of all strongly prime rings is a special class is obtained as a corollary. Every SP(α) ring has an SP(α) rational extension ring with identity.     

MODULO-CONSTANT IDEAL-HEREDITARY RADICALS OF NEAR-KINGS

ABSTRACT

It is known that no “good” radical of (not necessarily o-symmetric) near-rings can be ideal-hereditary. Using the results of the o-symmetric case, we show that the situation is not as bad as on first appearances and we give several examples of (Kurosh-Amitsur) radicals of near-rings for which the semisimple class is hereditary and the radical class is hereditary on left invariant ideals. We also extend some recent results on left strong radicals from the o-symmetric case to the general case.     

ON THE EXISTENCE AND NON-EXISTENCE OF COMPLEMENTARY RADICAL AND SEMISIMPLE CLASSES

ABSTRACT

In certain categories of mathematical structures, non-trivial complementary radical classes (torsion classes or connectednesses) can be found. The question is why this is true for some but not for all categories. The answer depends on the embedding of trivial objects into nontrivial objects and is given by our main result: Any ‘reasonable’ category has no non-trivial complementary radical and semisimple classes if and only if for every trivial object T and every non-trivial object A there is a morphism T → A. Roughly, a ‘reasonable’ category in our sense is one with at least one object into which a terminal object can be embedded and has finite products, coproducts or lexicographic products.     

A note on Brown—McCoy radicals ofΓ-rings

In [1] we defined the Brown—McCoy radical,B(M), of a-ringM. In this note we show thatB is a special radical. The simplicial radical, defined by Kyuno [4] for-rings with left and right unities, is extended to arbitrary-rings. The simplicial radicalS is shown to be a generalization of the Brown—McCoy radical of a ring. In general,B(M) S(M). This work is supported financially by the Technikon Natal.     

ALHOST M-RINGS AND M*-RINGS

ABSTRACT

For a class C of rings, Olson in 1982, and Le Roux and Heyman in 1980, introduced the definitions of classes C ₁ and C* of rings respectively. The aim of this paper is to show the equivalence of these two definitions if C satisfies certain properties. Furthermore the relation between C ₁ and C*, and UC and UC* will be investigated if C does not necessarily satisfy these restricted properties.     

UNIFORMLY STRONGLY PRIME RADICALS

Abstract

In this article different characterizations for a uniformly strongly prime ring are given as well as a way of constructing a uniformly strongly prime ring. Uniformly strongly prime rings of bound one as well as the upper radical determined by this special class of rings are also investigated.     

A NOTE ON THE g-PRIME RADICAL IN GAMMA RINGS

ABSTRACT

The g-prime radical of a Γ-ring M is equal to either the zero ideal or the prime radical of M. If the prime radical of M is a non-zero ideal, then the following three conditions are equivalent; (i) g-prime radical of M is equal to the prime radical of M; (ii) every g-prime ideal is a prime ideal; and (iii) every g-semiprime ideal is a semiprime ideal.     

ON THE GROENEWALD-HEYMAN STRONGLY PRIME RADICAL

Strongly prime rings were introduced by Handelman and Lawrence [6], and in a recent paper [5] Groenewald and Heyman investigated the upper radical determined by the class of all strongly prime rings. In this paper we continue this investigation. Section 1 provides some alternative characterizations of the radical and in section 2 we discuss general properties of the radical and compare it with other well-known radicals. Finally, combinatorial results on polynomial identities are presented which, combined with our results in section 2. yield some new comnutativity theorems.

All rings considered are associative, but do not necessarily have an identity. As usual, I Δ A means that I is an ideal of the ring A. The notation <x₁,x₂,…> and (x_l,x₂,…) will stand for the subring and ideal, respectively, generated by the elements x₁,x₂,…. The rignt annihirator of a subset S of a ring A will be denoted by ann_A(S).

This work was supported in part by NSERC grants A-8775 and A-8789. and was completed while the first and third authors were visiting Dalhousie University. These authors would like to thank the Department of Mathematics, Statistics and Computing Science at Oalhousie University for its generous hospitality.     

ON CERTAIN NEW RADICALS ARISING FROM A GIVEN RADICAL

Abstract

If R is a ring and n is an integer weMaydefine a ring T_n (R) on the same underlying additive abelian group by using the formula a * b = nab to define a new multiplication. T_n , is a functor on the category of associative rings. If C is a class of rings then, for each n, the class C_n , is defined to consist of all rings R such that T_n (R) is in C. If C is a radical class then each class C_n , is also a radical class. We consider the properties of the radical class C which are inherited by C_n , and relationships between these classes C _n as n varies.     

ASPECTS OF BOUNDED PERTURBATION THEORY

1. Abstract

This paper is concerned with the stability of certain properties of linear operators in locally convex topological vector spaces under perturbations by operators which are small in some sense. Section 3 deals with the very useful concept of Banach balls which was introduced by Ra?kov [9]. Some properties are discussed. The following section investigates the invertibility of certain operators generalizing results of Robert [10] and de Bruyn [2],[3]. These results are used extensively in the sequel. We go on to discuss Riesz operators. We obtain results stronger than those of de Bruyn [1] with regard to asymptotically quasi-compact operators in locally convex spaces. The proofs are basically adaptations of those from [1]. In the final section we observe some results concerning the range ad null space of an operator perturbed by bounded operators. We obtain a result very similar to an unproved theorem of Vladimirski? [a] and point out their differences. MOS codes 4601, 4710, 4745, 4768, 4755.

This work was undertaken at Cambridge University and I would like to thank my research supervisor Dr. F. Smithies for his help and encouragement. I wish also to thank Dr. G.F.C. de Bruyn ad Dr. J.H. Webb for their interesting discussions on this subject. During my research I was financed by a Sir Henry Strakosch Memorial Scholarship and a grant from the South African Council for Scientific and Industrial Research.     

A BROWN-McCOY RADICAL FOR T-RINGS

Abstract

A notion of G-regularity is introduced for a Γ-ring M, and from this notion a Brown-McCoy radical, B(M) is defined. B(M) is shown to be a radical in the sense of Kurosh and Amitsur, and analogies of various well-known results on the Brown-McCoy radical of a ring are proved. A “right” Brown McCoy radical, B'(M) can also be defined. In general, B(M) ? B'(M).     

STRONGLY EQUIPRIME NEAR-RINGS

Abstract

Strongly equiprime near-rings are defined which generalize strongly prime rings to near-rings. These near-rings determine an ideal-hereditary Kurosh-Amitsur radical in the variety of 0-symmetric near-rings. In the same variety, the uniformly strongly equiprime near-rings also determine an ideal-hereditary Kurosh-Amitsur radical which is not comparable with the Jacobson-type radicals nor with the Brown-McCoy-type radicals.     

EQUIPRIME Γ-NEAR-RINGS

Abstract

Equiprime and strongly equiprime near-rings were recently defined by the present authors, together with S. Veldsman. In the present paper, the concepts are introduced for Γ-near-rings, and give rise to Kurosh- Amitsur radicals. If M is a Γ-near-ring and L is its left operator near-ring, then R(L)⁺ = R(M), where R(—) in both cases denotes either the equiprime or the strongly equiprime radical.