An antiradical for near-rings

In (1), Atkinson characterized the set of Fredholm operators on a Banach space X as those bounded operators invertible modulo the two-sided ideal of compact operators on X. It follows from this characterization that the Fredholm operators can also be described as those bounded operators which are invertible modulo the two-sided ideal of bounded operators on X which have finite-dimensional range. This ideal is the socle of the algebra of all bounded operators on X. Now, if A is any ring with no nilpotent left or right ideals, then the concept of socle makes sense (the socle of A in this case is the algebraic sum of the minimal left ideals of A, or 0 if A has no minimal left ideals). Also, in this case, the socle is a two-sided ideal of A. In this paper we study the elements in a ring A which are invertible modulo the socle. We call these elements the Fredholm elements of A.

Let R be an associative ring with identity.Then the left socle of R is a direct summand of R as a right ϋNmodule if and only if it is projective as a left jR-module and contains no infinite sets of orthogonal idempotents.This implies, for example, that a ring with finitely generated left socle and no nilpotent minimal left ideals is a ring direct sum of a semisimple artinian ring and a ring with zero left socle.

The intersection ideal graph Γ(S) of a semigroup S is a simple undirected graph whose vertices are all nontrivial left ideals of S and two distinct left ideals I, J are adjacent if and only if their intersection is nontrivial. In this paper, we investigate the connectedness of Γ(S). We show that if Γ(S) is connected, then the diameter of Γ(S) is at most two. Further, we classify the semigroups S in terms of their ideals such that the diameter of Γ(S) is two. We obtain the domination number, independence number, girth and the strong metric dimension of Γ(S). We have also investigated the completeness, planarity and perfectness of Γ(S). We show that if S is a completely simple semigroup, then Γ(S) is weakly perfect. More over, in this article, we give an upper bound of the chromatic number of Γ(S). Finally, if S is the union of n minimal left ideals, then we obtain the metric dimension and the automorphism group of Γ(S).

Let A be an indiscrete locally compact primitive ring having minimal left ideals.Algebraically, A may be regarded as a dense ring of linear operators containing nonzero linear operators of finite rank on a vector space E over a division ring K, and furthermore if A is simple, then A contains only linear operators of finite rank.The topology of A induces topologies on F and A" in a natural way, so that K becomes a locally compact division ring and E a locally compact vector space over K. Theorems about locally compact division rings and locally compact vector spaces imply that if K is indiscrete, then E is necessarily finite dimensional over K, and thus A is the ring of all linear operators on a finite-dimensional vector space over a locally compact division ring.Kaplansky proved that if A has characteristic zero, then K is indeed indiscrete, but he showed by an example that E could be infinite dimensional.Kaplansky remarked [9, p. 459], however, that if A is simple, it seemed unlikely that F could be infinite dimensional, since otherwise "completeness appears to require the presence of linear transformations with infinitedimensional range."Our principal result in 1 is the verification of this conjecture; however, our argument is based not on the fact that a locally compact ring is complete, but rather on the fact that a locally compact space is a Baire space and on the symmetry between minimal left and right ideals in a simple ring.In 2 we shall present certain results about locally compact vector spaces over discrete division rings; these enable us to prove that a locally compact, indiscrete, central primitive algebra having minimal left ideals is finite dimensional provided its scalar field either is indiscrete, has characteristic zero, or is uncountably infinite.However, there is a very natural example of a locally compact, indiscrete, infinitedimensional central primitive algebra having minimal left ideals over a discrete countably infinite field of prime characteristic.1. Locally compact simple rings having minimal left ideals.We begin with a summary of the structure theory of a primitive ring A having minimal left ideals.Let e be a minimal idempotent of A, that is, an idempotent such that Ae is a minimal left ideal, or equivalently, such that eA is a minimal right ideal.Then eAe is a division ring, the additive group Ae becomes a right eAe-\tctor space by defining scalar multiplication to be the restriction of multiplication on A to

Let${\mathcal{A}}$be a semisimple Banach algebra with minimal left ideals and$\text{soc}({\mathcal{A}})$be the socle of${\mathcal{A}}$. We prove that if$\text{soc}({\mathcal{A}})$is an essential ideal of${\mathcal{A}}$, then every 2-local derivation on${\mathcal{A}}$is a derivation. As applications of this result, we can easily show that every 2-local derivation on some algebras, such as semisimple modular annihilator Banach algebras, strongly double triangle subspace lattice algebras and${\mathcal{J}}$-subspace lattice algebras, is a derivation.

In previous work, we associated to $$\text {SU(3)}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>SU(3)</mml:mtext> </mml:math> , $$\textrm{G}_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>G</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:math> , and $$\text {Spin(7)}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>Spin(7)</mml:mtext> </mml:math> -structures minimal left ideals for the Clifford algebras $$\mathbb {R}_{0,6},\mathbb {R}_{0,7}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>R</mml:mi> <mml:mrow> <mml:mn>0</mml:mn> <mml:mo>,</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msub> <mml:mo>,</mml:mo> <mml:msub> <mml:mi>R</mml:mi> <mml:mrow> <mml:mn>0</mml:mn> <mml:mo>,</mml:mo> <mml:mn>7</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> , and $$\mathbb {R}_{0,8}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>R</mml:mi> <mml:mrow> <mml:mn>0</mml:mn> <mml:mo>,</mml:mo> <mml:mn>8</mml:mn> </mml:mrow> </mml:msub> </mml:math> , respectively. In this paper, we continue to analyze the link between Berger’s classification theorem and the structure theorem of minimal left ideals for Clifford algebras of signature ( p , q ) by identifying $$\textrm{U}(n)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>U</mml:mtext> <mml:mo>(</mml:mo> <mml:mi>n</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> -structures with minimal left ideals for Clifford algebras of various signatures via the induced Kahler polynomial $$P(\omega _{0})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>P</mml:mi> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>ω</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> associated with the symplectic form $$\omega _{0}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>ω</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:math> that defines the $$\textrm{U}(n)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>U</mml:mtext> <mml:mo>(</mml:mo> <mml:mi>n</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> -structure as a stabilizer subgroup of $$\textrm{O}(n)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>O</mml:mtext> <mml:mo>(</mml:mo> <mml:mi>n</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> .

Algebras with minimal left ideals which are Hilbert spaces

The aim of this thesis is to investigate the circumstances under which group rings over fields have non-zero socle, i.e. contain minimal one-sided ideals. After an introductory chapter, we consider the special case o₊ a periodic abelian group and a non-modular field (that is, a field of characteristic prime to the orders of the elements of the group). This special case, and the background material contained in Chapter III, serve as preparation for our principal results, which concern, locally finite groups. We establish necessary and sufficient conditions on an arbitrary field K and a locally finite group 0 for the group ring KG to contain minimal one-sided ideals: the most important condition is that G should be a Cernikov group. We then examine the structure of KG when these conditions are satisfied. Vie show that KG has a finite series of ideal3 each factor of which i3 a direct sum of quasi-Frobenius rings, and characterize the socle of KG. Me also classify indecomposable KG-modules, and determine (for countable but not necessarily locally finite groups G) necessary and sufficient conditions for all indecomposable KG-modules to be irreducible. In the final chapter we consider non-locally-finite groups, conjecturing that group rings of such groups never contain minimal one-sided ideals. We establish the truth of this conjecture for several classes of groups, and also consider semiartinian group rings.

Let A be a commutative semi‐simple Banach algebra such that the set consisting of finite sums of elements from minimal left ideals coincides with that of finite sums of elements from minimal right ideals. Let S(A) (the socle of A) denote this set. Let C(A) denote the set of elements x in A such that the map a → xax is compact. It is shown that C(A) is the norm closure of S(A).

In this paper a structural similarity between a recent braid- and division algebraic description of the unbroken internal symmetries of a single generation of Standard Model (SM) fermions is identified. This unexpected connection between two independently motivated models provides the first step towards unifying them into a unified theory based on braid groups and normed division algebras (NDA).Each of the four NDAs over the reals is shown to contain a representation of a circular braid group. For the complex numbers and the quaternions, the represented circular braid groups are B2 and B3c, precisely those used to represent leptons and quarks as framed braids in the Helon model of Bilson-Thompson. It is then shown that the twist structure of these framed braids representing fermions coincides exactly with the states that span the minimal left ideals of the complex (chained) octonions, shown by Furey to describe one generation of leptons and quarks with unbroken SU(3)c and U(1)em symmetry.This identification of basis states of minimal ideals with certain framed braids is possible because the braiding in B2 and B3c in the Helon model are interchangeable. It is shown that the framed braids in the Helon model can be written as pure braid words in B3c with trivial braiding in B2, something which is not possible for framed braids in general.

Algebraic and topological equivalences in the Stone-Čech compactification of a discrete semigroup

Introduction. Let A be a strictly power-associative algebra of characteristic not two with radical N and such that the difference algebra A N is separable. Then we say that A has a Wedderburn decomposition if A has a subalgebra S _ A N with A = S + N (vector space direct sum). Since the characterization of the simple, and hence semisimple, commutative strictly power-associative algebras is nearly complete (see [10]) it is desirable to see if a Wedderburn decomposition can be given for them. In ?2 the problem is reduced to the case where A has a unity element and A N is simple. In ?3 we show that if A N is simple and does not have two as the maximum number of pairwise orthogonal primitive idempotents, then A has a Wedderburn decomposition (Corollary 3.3). The counterexample to a general decomposition theorem (?5) shows that this is the best possible result of that type. Our other major result (Theorem 4.1) is that stable algebras have Wedderburn decompositions. It is known that associative [1, Theorem 23, p. 47], alternative [12], and Jordan [2], [11] algebras have Wedderburn decompositions. In each of these cases the proof is essentially effected in two stages, namely, N2 = 0 and N2 # 0. In our results we do not have anything corresponding to the case N2 = 0 but our basic tools (Lemma 3.2 and Theorem 4.1) are conceptually based on the same idea as the usual induction proof employed in the case N2 # 0. As a matter of terminology, by an algebra we will always mean a finite dimensional vector space with a multiplication defined which satisfies both distributive laws. An algebra A is called power-associative if x'x# = x a+# for all positive integers oc and ,B and every x eA. A is called strictly power-associative if AK is power-associative for every scalar extension K of the base field. In [7] Kokoris shows that, for commutative algebras of characteristic not 2, 3, or 5, powerassociativity and strict power-associativity are equivalent concepts. The radical of a strictly power-associative algebra is the unique maximal nil ideal of A and a non-nil algebra with zero radical is called semisimple. A is called separable if AK is semisimple for every scalar extension K of the base field. The basic structure theory of commutative strictly power-associative algebras of characteristic not 2, 3, or 5 was given by Albert in [4] and extended to charac-

The structure of halfrings which are strong direct sums of minimal subtractive right ideals is studied.A class of right simple hemirings which contains both division hemirings and differential subsemirings of division rings is introduced and studied extensively as a tool in this investigation.A matrix representation is obtained for a class of halfrings which properly includes differential subsemirings of simple Artinian rings.1. Introduction.A semiring is a triple (H, +, ) such that (H, + ) is a semigroup with identity 0, (H, ) is semigroup with zero 0, and multiplication distributes over addition.If the addition is commutative, H is called a hemiring.A subsemiring S of a hemiring H is differential in HifVhEH 3s, t G S with s + h = t.A halfring is a hemiring H which is differential in some ring H, which is then uniquely determined.This paper continues the point of view of [9], and terminology introduced there will be extended without comment to hemirings generally.A hemiring is [right, left] simple if it has no nontrivial subtractive [right, left] ideals.It is [right, left] ideal-free if it has no nontrivial [right, left] ideals.A division semiring is a semiring with 1 = 0 all of whose nonzero elements have multiplicative inverse.It is clear that division hemirings may be characterized among nonzero hemirings as those which are right and left ideal-free, and among hemirings with identity as those which are right ideal-free.Grillet and Grillet [4], [5] have recently studied ideal-free and semisimple semirings very successfully using the techniques of semigroup theory.Earlier, Bourne [1], Bourne and Zassenhaus [2], [3], Steinfeld [8], and Wiegant [10] had studied semirings which are direct sums of minimal right ideals.The culmination of that study is an analogue of the Wedderburn theorem which may be paraphrased as follows:An ideal-free semiring with identity which is a strong direct sum of finitely many minimal right ideals is isomorphic to a full semiring of matrices over a division semiring.

Flat endofinite modules, prime ideals, and duality

Proof.We will prove the first part by induction on t.When r=l, u=Uy.In addition, [uk] = [u]k = [u] so u is not nilpotent.Hence, the associative algebra of all polynomials in u, denoted by F[u], is not nilpotent and thus contains an idempotent e=f(u) for fix) a polynomial.Then [e] = [/(«)] = a[u] where a=f(l) is in F. Thus a[w] = [e] = [e]2 = c72[w]2 = c72[w].Since e is not in M, a[u]^0 and a=l.Let w = Uy + u2 for r^2.Then u=w+u3+ ■ ■ ■ +ut for pairwise orthogonal idempotents [w], [u3],..., [ut].By the inductive hypothesis, there exists an idempotent e and pairwise orthogonal idempotents/ e3,...,et in Ae(l) such that