O objetivo desta dissertação é estudar o radical de Jacobson de anéis de polinômios diferenciais. Mostramos um resultado de M. Ferrero, K. Kishimoro, K. Motose, que mostra que no caso geral, o radical de um anel de polinômios diferenciais é um anel de polinômios diferenciais sobre algum ideal do anel dos coeficientes. Assumindo que o anel dos coeficientes satisfaça uma identidade polinomial, mostramos seguindo B. Madill que este ideal é um ideal nil. Se o anel dos coeficientes é adicionalmente localmente nilpotente, seguindo J. Bell, B. Madill, F. Shinko, mostramos que o anel de polinômios diferenciais será localmente nilpotente. Ainda seguindo J. Bell et al, se o anel dos coeficientes é uma álgebra sobre um corpo de característica zero e tal álgebra satisfaz uma identidade polinomial, mostramos que o ideal nil é o radical de Köthe. Para tais demonstrações, cobriremos os tópicos preliminares necessários para entender os enunciados: radical nil, radical de Levitzki, radical de Baer, radical de Jacobson e propriedades, anéis PI, polinômios centrais, teorema de Kaplansky. / The aim of this work is to study the Jacobson radical of differential polynomial rings. We show a result of M. Ferrero, K. Kishimoto, K. Motose, which shows that in general, the radical of a differential polynomial ring is a differential polynomial ring over some ideal of the ring of coefficients. Assuming that the ring of coefficients satisfies a polynomial identity, we show following B. Madill that this ideal is nil. If the ring of coefficients is additionally locally nilpotent, following J. Bell, B. Madill, F. Shinko, we show that the differential polynomial ring is locally nilpotent. Still following J. Bell et al, if the ring of coefficients is an algebra over a field of zero characteristic and this algebra satisfies a polynomial identity, we show that the nil ideal is the Köthe radical. For the proofs, we cover the preliminary topics necessary for understanding the statements: nil radical, Levitzki radical, Baer radical, Jacobson radical and its properties, PI-rings, central polynomials, Kaplanskys theorem.

Modekonsumtion handlar idag mycket om självförverkligande och identitet och konsumenter köper ofta produkter baserat på varumärke. Därför lägger många företag stora resurser på att bygga upp starka varumärken och för att bli framgångsrika är det viktigt att de hittar en attraktiv position för det på marknaden. Om varumärket inte lyckas differentiera sig tillräckligt från sina konkurrenter eller av andra anledningar inte är starka eller tydliga nog kan de ompositionera sig. Detta innebär att de byter riktning mot en ny position som förhoppningsvis är mer lönsamt, men detta är inte helt riskfritt. Varumärken som är konsekventa i vad de förmedlar anses vara mer trovärdiga än de som hela tiden förändras. Dock är samhället under ständig förändring och ofta krävs att varumärket utvecklas tillsammans med det för att inte bli omodernt. Denna uppsats har undersökt vilka nyckelfaktorer som kan ge receptet för en lyckad ompositionering. Ett praktiskt fall av ompositionering har ställts mot teorier inom området för att se vilka likheter och skillnader som finns. Vi valde varumärket Oscar Jacobson då det är väl etablerat på marknaden. Kvalitativa, semi-strukturerade intervjuer utfördes med marknadschefen och en av butikscheferna på företaget. Resultatet av intervjuerna jämfördes sedan med teorier från en litteraturstudie och flera intressanta slutsatser kunde dras. Det finns mycket litteratur inom ämnet men denna uppsats har i huvudsak fokuserat på publikationer från David A. Aaker, Henrik Uggla och Jean-Noel Kapferer. En slutsats är att det är viktigt att ompositioneringen sker i ett långsamt tempo för att kunderna inte ska blir förvirrade om vad varumärket står för. Sker det för abrupt riskerar de att förlora trogna kunder. Innan och under ompositioneringen bör företaget även utföra marknadsundersökningar för att kunna granska och följa upp förändringsarbetes utveckling och inverkan. I Oscar Jacobson fall var det även avgörande att företagets ledning byttes ut samt att sortiment anpassades efter deras nya breddade målgrupp. Ibland skiljer sig Oscar Jacobsons tillvägagångssätt från teorierna. Exempelvis är det enligt teorin viktigt att tydligt förmedla det nya varumärket både internt och externt. Enligt vår undersökning har den interna kommunikationen på Oscar Jacobson varit något bristfällig på detta plan. Trots detta kan tilläggas att Oscar Jacobson ompositionering kan ses som ett framgångsrikt exempel och många intressanta slutsatser har kunnat dras.

by Au Yun-Nam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 133-137). / Introduction --- p.iv / Chapter 1 --- Preliminaries --- p.1 / Chapter 1.1 --- Some Semigroup Properties --- p.1 / Chapter 1.2 --- General Properties of Semigroup Algebras --- p.5 / Chapter 1.3 --- Group Algebras --- p.7 / Chapter 1.3.1 --- Some Basic Properties of Groups --- p.7 / Chapter 1.3.2 --- General Properties of Group Algebras --- p.8 / Chapter 1.3.3 --- Δ-Method for Group Algebras --- p.10 / Chapter 1.4 --- Graded Algebras --- p.12 / Chapter 1.5 --- Crossed Products and Smash Products --- p.14 / Chapter 2 --- Radicals of Graded Rings --- p.17 / Chapter 2.1 --- Jacobson Radical of Crossed Products --- p.17 / Chapter 2.2 --- Graded Radicals and Reflected Radicals --- p.18 / Chapter 2.3 --- Radicals of Group-graded Rings --- p.24 / Chapter 2.4 --- Algebras Graded by Semilattices --- p.26 / Chapter 2.5 --- Algebras Graded by Bands --- p.27 / Chapter 2.5.1 --- Hereditary Radicals of Band-graded Rings --- p.27 / Chapter 2.5.2 --- Special Band-graded Rings --- p.30 / Chapter 3 --- Radicals of Semigroup Algebras --- p.34 / Chapter 3.1 --- Radicals of Polynomial Rings --- p.34 / Chapter 3.2 --- Radicals of Commutative Semigroup Algebras --- p.36 / Chapter 3.2.1 --- Commutative Cancellative Semigroups --- p.37 / Chapter 3.2.2 --- General Commutative Semigroups --- p.39 / Chapter 3.2.3 --- The Nilness and Semiprimitivity of Commutative Semigroup Algebras --- p.45 / Chapter 3.3 --- Radicals of Cancellative Semigroup Algebras --- p.48 / Chapter 3.3.1 --- Group of Fractions of Cancellative Semigroups --- p.48 / Chapter 3.3.2 --- Jacobson Radical of Cancellative Semigroup Algebras --- p.54 / Chapter 3.3.3 --- Subsemigroups of Polycyclic-by-Finite Groups --- p.57 / Chapter 3.3.4 --- Nilpotent Semigroups --- p.59 / Chapter 3.4 --- Radicals of Algebras of Matrix type --- p.62 / Chapter 3.4.1 --- Properties of Rees Algebras --- p.62 / Chapter 3.4.2 --- Algebras Graded by Elementary Rees Matrix Semigroups --- p.65 / Chapter 3.5 --- Radicals of Inverse Semigroup Algebras --- p.68 / Chapter 3.5.1 --- Properties of Inverse Semigroup Algebras --- p.69 / Chapter 3.5.2 --- Radical of Algebras of Clifford Semigroups --- p.72 / Chapter 3.5.3 --- Semiprimitivity Problems of Inverse Semigroup Algebras --- p.73 / Chapter 3.6 --- Other Semigroup Algebras --- p.76 / Chapter 3.6.1 --- Completely Regular Semigroup Algebras --- p.76 / Chapter 3.6.2 --- Separative Semigroup Algebras --- p.77 / Chapter 3.7 --- Radicals of Pi-semigroup Algebras --- p.80 / Chapter 3.7.1 --- PI-Algebras --- p.80 / Chapter 3.7.2 --- Permutational Property and Algebras of Permutative Semigroups --- p.80 / Chapter 3.7.3 --- Radicals of PI-algebras --- p.82 / Chapter 4 --- Finiteness Conditions on Semigroup Algebras --- p.85 / Chapter 4.1 --- Introduction --- p.85 / Chapter 4.1.1 --- Preliminaries --- p.85 / Chapter 4.1.2 --- Semilattice Graded Rings --- p.86 / Chapter 4.1.3 --- Group Graded Rings --- p.88 / Chapter 4.1.4 --- Groupoid Graded Rings --- p.89 / Chapter 4.1.5 --- Semigroup Graded PI-Algebras --- p.91 / Chapter 4.1.6 --- Application to Semigroup Algebras --- p.92 / Chapter 4.2 --- Semiprime and Goldie Rings --- p.92 / Chapter 4.3 --- Noetherian Semigroup Algebras --- p.99 / Chapter 4.4 --- Descending Chain Conditions --- p.107 / Chapter 4.4.1 --- Artinian Semigroup Graded Rings --- p.107 / Chapter 4.4.2 --- Semilocal Semigroup Algebras --- p.109 / Chapter 5 --- Dimensions and Second Layer Condition on Semigroup Algebras --- p.119 / Chapter 5.1 --- Dimensions --- p.119 / Chapter 5.1.1 --- Gelfand-Kirillov Dimension --- p.119 / Chapter 5.1.2 --- Classical Krull and Krull Dimensions --- p.121 / Chapter 5.2 --- The Growth and the Rank of Semigroups --- p.123 / Chapter 5.3 --- Dimensions on Semigroup Algebras --- p.124 / Chapter 5.4 --- Second Layer Condition --- p.128 / Notations and Abbreviations --- p.132 / Bibliography --- p.133

Die Untersuchung beschäftigt sich mit der Entwicklung der Berichterstattung über das Judentum in Seesen. Das Hauptaugenmerk liegt auf auf Israel Jacobson, der einst Begründer des Reformjudentums in Seesen war, in Vergessenheit geriet und seit einigen Jahren wieder von einigen engagierten Seesenern mit Ausstellungen, Büchern und Vorträgen geehrt wird. Zudem stellt sich der Arbeit die Frage, wie es zu dem "Vergessen" dieser berühmten Seesener Persönlichkeit kam und was zu einem Umdenken geführt haben könnte.

Nesta tese caracterizamos completamente ideais primos, primitivos e maximais em certos subanéis graduados de anéis de polinômios, que chamamos de subanéis admissíveis. Obtivemos uma correspondência biunívoca, via contração entre certas subfamílias de ideais primos, primitivos e maximais de R[x] e certas subfamílias de ideais primos, primitivos e maximais de subanéis admissíveis, respectivamente. Também caracterizamos ideais primos e maximais em subanéis admisséveis com várias variáveis. Ainda, estendemos alguns resultados sobre anéis de Jacobson para anéis admissíveis e generalizamos alguns resultados obtidos em subanéis admissíveis para certos subanéis de skew anéis de polinômios. / In this thesis we completely characterize prime, primitive and maximal ideals in certain graded subrings of polynomial rings, that we call of admissible subrings. We obtain via contraction a one-to-one correspondence between certain subfamily of prime, primitive and maximal ideals of R[x] and certain subfamily of prime, primitive and maximal ideals of admissible subrings, respectively. We also characterize prime and maximal ideals in admissible subrings with several variables. We also extend some results about Jacobson rings for admissible rings and we generalize some results obtained in admissible subrings for certain subrings of skew polynomial rings.

Nesta tese caracterizamos completamente ideais primos, primitivos e maximais em certos subanéis graduados de anéis de polinômios, que chamamos de subanéis admissíveis. Obtivemos uma correspondência biunívoca, via contração entre certas subfamílias de ideais primos, primitivos e maximais de R[x] e certas subfamílias de ideais primos, primitivos e maximais de subanéis admissíveis, respectivamente. Também caracterizamos ideais primos e maximais em subanéis admisséveis com várias variáveis. Ainda, estendemos alguns resultados sobre anéis de Jacobson para anéis admissíveis e generalizamos alguns resultados obtidos em subanéis admissíveis para certos subanéis de skew anéis de polinômios. / In this thesis we completely characterize prime, primitive and maximal ideals in certain graded subrings of polynomial rings, that we call of admissible subrings. We obtain via contraction a one-to-one correspondence between certain subfamily of prime, primitive and maximal ideals of R[x] and certain subfamily of prime, primitive and maximal ideals of admissible subrings, respectively. We also characterize prime and maximal ideals in admissible subrings with several variables. We also extend some results about Jacobson rings for admissible rings and we generalize some results obtained in admissible subrings for certain subrings of skew polynomial rings.

Nesta tese caracterizamos completamente ideais primos, primitivos e maximais em certos subanéis graduados de anéis de polinômios, que chamamos de subanéis admissíveis. Obtivemos uma correspondência biunívoca, via contração entre certas subfamílias de ideais primos, primitivos e maximais de R[x] e certas subfamílias de ideais primos, primitivos e maximais de subanéis admissíveis, respectivamente. Também caracterizamos ideais primos e maximais em subanéis admisséveis com várias variáveis. Ainda, estendemos alguns resultados sobre anéis de Jacobson para anéis admissíveis e generalizamos alguns resultados obtidos em subanéis admissíveis para certos subanéis de skew anéis de polinômios. / In this thesis we completely characterize prime, primitive and maximal ideals in certain graded subrings of polynomial rings, that we call of admissible subrings. We obtain via contraction a one-to-one correspondence between certain subfamily of prime, primitive and maximal ideals of R[x] and certain subfamily of prime, primitive and maximal ideals of admissible subrings, respectively. We also characterize prime and maximal ideals in admissible subrings with several variables. We also extend some results about Jacobson rings for admissible rings and we generalize some results obtained in admissible subrings for certain subrings of skew polynomial rings.

Dan Jacobson has written short stories, many non-fiction articles and eight novels: The Trap (1955), A Dance in The Sun (1956), The Price of Diamonds (1957), The Evidence of Love (1959), The Beginners (1966), The Rape of Tamar (1970), The Wonder-Worker (1973), and · The Confessions of Josef Baisz (1977) . The first five are all set in South Africa, though Jacobson has been living in England since 1954, i.e. since before his first novel was published. A distinct break in terms of subject matter and voice occurs after The Beginners , giving Jacobson what he calls "two rounds as a novelist. But critics recognizing this break seem not to have recognized that all eight novels are linked by certain thematic preoccupations, notably the notion of the trapped identity, which this thesis will attempt to demonstrate. On a first reading of Jacobson's work one is drawn to affirm his portrayal of the position of the white English-speaking South African, but a closer reading reveals that he does not speak as vitally to the South African situation as he seems to, or has been taken to do. Why this should be so is the second main concern of this thesis. In the first chapter the expectations underlying English literary activity in South Africa are outlined, as this is a necessary background to the discussion of Jacobson's South African novels. (Introduction, p. 4)

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Cette thèse s'attache à décrire des algorithmes qui répondent à des questions provenant de la théorie des anneaux et des modules. Nous restreindrons essentiellement notre étude à des algorithmes déterministes, en temps polynomial, ainsi qu'aux anneaux et modules finis. Le premier des principaux résultats de cette thèse concerne le problème de l'isomorphisme entre modules : nous décrivons deux algorithmes distincts qui, étant donnée un anneau fini R et deux R-modules M et N finis, déterminent si M et N sont isomorphes. S'ils le sont, les deux algorithmes exhibent un tel isomorphisme. De plus, nous montrons comment calculer un ensemble de générateurs de taille minimale pour un module donné, et comment construire des couvertures projectives et des enveloppes injectives. Nous décrivons ensuite des tests mettant en évidence le caractère simple, projectif ou injectif d'un module, ainsi qu'un test constructif de l'existence d'un homomorphisme demodules surjectif entre deux modules finis, l'un d'entre eux étant projectif. Par contraste, nous montrons le résultat négatif suivant : le problème consistant à tester l'existence d'un homomorphisme de modules injectif entre deux modules, l'un des deux étant projectif, est NP-complet.La dernière partie de cette thèse concerne le problème de l'approximation du radical de Jacobson d'un anneau fini. Il s'agit de déterminer un idéal bilatère nilpotent tel que l'anneau quotient correspondant soit \presque" semi-simple. La notion de \semi-simplicité approchée" que nous utilisons est la séparabilité. / In this thesis we are interested in describing algorithms that answer questions arising in ring and module theory. Our focus is on deterministic polynomial-time algorithms and rings and modules that are finite. The first main result of this thesis concerns the module isomorphism problem: we describe two distinct algorithms that, given a finite ring R and two finite R-modules M and N, determine whether M and N are isomorphic. If they are, the algorithms exhibit such a isomorphism. In addition, we show how to compute a set of generators of minimal cardinality for a given module, and how to construct projective covers and injective hulls. We also describe tests for module simplicity, projectivity, and injectivity, and constructive tests for existence of surjective module homomorphisms between two finite modules, one of which is projective. As a negative result, we show that the problem of testing for existence of injective module homomorphisms between two finite modules, one of which is projective, is NP-complete. The last part of the thesis is concerned with finding a good working approximation of the Jacobson radical of a finite ring, that is, a two-sided nilpotent ideal such that the corresponding quotient ring is \almost" semisimple. The notion we use to approximate semisimplicity is that of separability.