A Kahler category axiomatizes the algebraic geometric theory of Kahler Differentials in an abstract categorical setting. To facilitate this, a Kahler category is equipped with an algebra modality, which endows each object in the image of a specified monad with an associative algebra structure; universal derivations are then required to exist naturally for each of these objects. Moreover, it can be demonstrated that for each T-algebra of said monad there is a natural associative algebra structure. In this paper I will show that under certain conditions on the Kahler category, the universal derivations for the algebras arising from T-algebras exist and arise via a coequalizer. Furthermore, this result is extended to provide an alternative construction for universal derivations for a more general class of algebras, including all algebras in a Kahler category. A prospective categorical formulation of the theory of noncommutative Kahler differentials is then given, and the above said results are shown to apply in this context. Finally, another class of algebras is constructed via a colimit, and the modules of differential forms for these algebras is computed.

Conjugacy classes of nilpotent elements in complex semisimple Lie algebras are classified using the Bala-Carter theory. In this theory, nilpotent orbits in g are parametrized by the conjugacy classes of pairs (l,pl) of Levi subalgebras of g and distinguished parabolic subalgebras of [l,l]. In this thesis we present this theory and use it to give a list of representatives for nilpotent orbits in so(8) and from there we give a partition-type parametrization of them.

Let k be a field of characteristic zero and q ∈ kx not a root of unity. We may obtain non-commutative counterparts of various commutative algebras by twisting the multiplication using the scalar q: one example of this is the quantum plane kq[x; y], which can be viewed informally as the set of polynomials in two variables subject to the relation xy = qyx. We may also consider the full localization of kq[x; y], which we denote by kq(x; y) or D and view as the non-commutative analogue of k(x; y), and also the quantization Oq(Mn) of the coordinate ring of n x n matrices over k. Our aim in this thesis will be to use the language of deformation-quantization to understand the quantized algebras by looking at certain properties of the commutative ones, and conversely to obtain results about the commutative algebras (upon which a Poisson structure is induced) using existing results for the non-commutative ones. The q-division ring kq(x; y) is of particular interest to us, being one of the easiest infinite-dimensional division rings to define over k. Very little is known about such rings: in particular, it is not known whether its fixed ring under a finite group of automorphisms should always be isomorphic to another q-division ring (possibly for a different value of q) nor whether the left and right indexes of a subring E ? D should always coincide. We define an action of SL2(Z) by k-algebra automorphisms on D and show that the fixed ring of D under any finite group of such automorphisms is isomorphic to D. We also show that D is a deformation of the commutative field k(x; y) with respect to the Poisson bracket fy; xg = yx and that for any finite subgroup G of SL2(Z) the xed ring DG is in turn a deformation of k(x; y)G. Finally, we describe the Poisson structure of the fixed rings k(x; y)G, thus answering the Poisson-Noether question in this case. A number of interesting results can be obtained as a consequence of this: in particular, we are able to answer several open questions posed by Artamonov and Cohn concerning the structure of the automorphism group Aut(D). They ask whether it is possible to define a conjugation automorphism by an element z 2 LnD, where L is a certain overring of D, and whether D admits any endomorphisms which are not bijective. We answer both questions in the affirmative, and show that up to a change of variables these endomorphisms can be represented as non-bijective conjugation maps. We also consider Poisson-prime and Poisson-primitive ideals of the coordinate rings O(GL3) and O(SL3), where the Poisson bracket is induced from the non-commutative multiplication on Oq(GL3) and Oq(SL3) via deformation theory. This relates to one case of a conjecture made by Goodearl, who predicted that there should be a homeomorphism between the primitive (resp. prime) ideals of certain quantum algebras and the Poisson-primitive (resp. Poisson-prime) ideals of their semi-classical limits. We prove that there is a natural bijection from the Poisson-primitive ideals of these rings to the primitive ideals of Oq(GL3) and Oq(SL3), thus laying the groundwork for verifying this conjecture in these cases.

M.Sc. (Mathematics) / Please refer to full text to view abstract

Orientadores: Ruy Exel Filho, Jorge Tulio Mujica Ascui / Tese (Doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-04T01:37:00Z (GMT). No. of bitstreams: 1 Royer_Danilo_D.pdf: 374070 bytes, checksum: c3e7702f1d2d2d102d668d4c0f823deb (MD5) Previous issue date: 2004 / Doutorado / Matematica / Doutor em Matemática

Orientadores: Adriano Adrega de Moura, Evgeny Mukhin / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-26T22:56:39Z (GMT). No. of bitstreams: 1 Brito_MatheusBatagini_D.pdf: 1928614 bytes, checksum: bd194d09898859744dc51e0bcccd7fa1 (MD5) Previous issue date: 2015 / Resumo: Estudamos representações de dimensão finita para uma álgebra afim quantizada a partir de dois pontos de vista distintos. Na primeira parte deste trabalho estudamos o limite graduado de uma certa subclasse de representações irredutíveis. Seja V uma representação de dimensão finita para uma álgebra do tipo A e suponha que V é isomorfa ao produto tensorial de uma afinização minimal por partes cujo peso máximo é a soma de distintos pesos fundamentais por módulos de Kirillov--Reshetikhin cujos pesos máximos são o dobro de um peso fundamental. Provamos que V admite limite graduado L e que L é isomorfo a um módulo de Demazure de nível dois bem como ao produto de fusão dos limites graduados de cada um dos supramencionados fatores tensoriais de V. Provamos ainda que, se a álgebra for do tipo clássica (resp. G), o limite graduado das afinizações minimais (regulares) (resp. módulos de Kirillov--Reshetikhin) são isomorfos ao módulos CV para alguma R^+ partição descrita explicitamente. Na segunda parte provamos que um módulo para a álgebra afim quantizada do tipo B e posto n é manso se, e somente se, ele é fino. Em outras palavras, os geradores da subálgebra de Cartan afim são diagonalizáveis se, e somente se, os autoespaços generalizados associados têm dimensão um. Classificamos tais módulos e descrevemos seus respectivos q-caracteres. Em alguns casos, o q-caracter é descrito por super standard Young tableaux do tipo (2n|1) / Abstract: We study finite--dimensional representations for a quantum affine algebra from two different points of view. In the first part of this work we study the graded limit of a certain subclass of irreducible representations. Let V be a finite--dimensional representation for a quantum affine algebra of type A and assume that V is isomorphic to the tensor product of a minimal affinization by parts whose highest weight is a sum of distinct fundamental weights by Kirillov-Reshetkhin modules whose highest weights are twice a fundamental weight. We prove that V admits a graded limit L and that L is isomorphic to a level-two Demazure module as well as to the fusion product of the graded limits of each of the aforementioned tensor factors of V. We also prove that if the quantum affine algebra is of classical type (resp. type G), the graded limit of (regular) minimal affinizations (resp. Kirillov--Reshetkin modules) are isomorphic to CV-modules for some R^+ partition explicitly described. In the second part we show that a module for the quantum affine algebra of type B and rank n is tame if and only if it is thin. In other words, the Cartan currents are diagonalizable if and only if all joint generalized eigenspaces have dimension one. We classify all such modules and describe their q-characters. In some cases, the q-characters are described by super standard Young tableaux of type (2n|1) / Doutorado / Matematica / Doutor em Matemática

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This dissertation is divided into two parts. The first part addresses the following problem: Suppose 𝑣 is a finitely additive probability measure defined on the power set 𝒜 of the integer Z so that each singleton set gets measure zero. Let X be a product space Π/β∈B * Zᵦ where each Zₐ is a copy of the integers. Let 𝒜ᴮ be the algebra of subsets of X generated by the subproducts Π/β∈B * Cᵦ where for all but finitely many β, Cᵦ = Zᵦ. Let 𝑣_B denote the product measure on 𝒜ᴮ which has each factor measure a copy of 𝑣. A subset E of X is said to be 𝑣_B -measurable iff [sic] there is only one finitely additive probability on the algebra generated by 𝒜ᴮ ∪ [E] which extends 𝑣_B. The set E ⊆ X is said to be universally product measurable (u.p.m.) iff [sic] for each finitely additive probability measure μ on 𝒜 which gives each singleton measure zero,E is μ_B -measurable. Two theorems are proved along with generalizations. The second part of this dissertation gives a proof of the following theorem and some generalizations: There are 2ᶜ nonisomorphic subalgebras of the power set algebra of the integers (where c = power of the continuum).