The following is a study of what may be the most puzzling and yet, at the same time, most significant aspect of Kant's system: his theory of schemata. I will argue that Kant's commentators have failed to make sense of this aspect of Kant's philosophy. A host of questions have been left unanswered, and the doctrine remains a puzzle. While this study is not an attempt to construct a complete, satisfying account of the doctrine, it should be seen as a step somewhere on the road of doing so, leaving much work to be done. I will contend that one way that we may shed light on Kant's doctrine of schemata is to reconsider the manner in which Kant employs schemata in his mathematics. His use of the schemata there may provide some inkling into the nature of transcendental schemata and, in doing so, provide some hints at how the transcendental schemata allow our representations of objects to be subsumed under the pure concepts of the understanding. In many ways, then, the aims of the study are modest: instead of a grand-scale interpretation of Kant's philosophy, a detailed textual analysis and interpretation are presented of his doctrine of schemata. Instead of providing definitive answers, I will suggest clues as to how to begin to answer the questions that previous commentators have left unanswered about the doctrine. / Master of Arts

En el marc de l'estudi de la cohomologia de les varietats algebraiques, i en particular en les aplicacions cohomològiques del teorema de resolució de singularitats d'Hironaka, utilitzem la tècnica de les hiperresolucions cúbiques i el criteri d'extensió de functors de Guillén i Navarro per a definir una variant de la teoria K algebraica de les varietats sobre un cos de característica zero, que coincideix amb la teoria K per a les varietats llises. Considerem la teoria K com un functor de varietats algebraiques a espectres. Anomenem teoria K de descens a aquesta extensió, que satisfà descens per a blow-ups abstractes.Per a aplicar el criteri d'extensió hem demostrat que la categoria d'espectres fibrants és una categoria de descens cohomològic, en el sentit de Guillén i Navarro, amb el límit homotòpic com a functor simple. Més generalment hem demostrat que la subcategoria d'objectes fibrants d'una categoria de models simplicial és una categoria de descens cohomològic si i només si se satisfà un criteri d'aciclicitat. En particular les categories de models simplicials estables satisfan el criteri d'aciclicitat i per tant són de descens cohomològic.Hem vist com una teoria obtinguda pel criteri d'extensió hereta moltes de les propietats del functor sobre les varietats llises, de manera que la teoria K de descens satisfà per exemple la propietats de Mayer-Vietoris i d'invariància homotòpica.Hem demostrat també que sota certes hipòtesis l'extensió de Guillén i Navarro d'un functor a espectres coincideix amb l'aproximació fibrant en la categoria de models de prefeixos d'espectres considerant la cd-topologia dels blow-ups abstractes.Utilitzant un resultat de Haesemeyer hem demostrat que la teoria K de descens és equivalent a la teoria K homotòpica introduïda per Weibel. Hem demostrat també que hi ha una filtració pel pes natural en els grups de teoria K homotòpica. / En el marco del estudio de la cohomología de las variedades algebraicas, y en particular de las aplicaciones cohomológicas del teorema de resolución de singularidades de Hironaka, utilizamos la técnica de las hiperresoluciones cúbicas y el criterio de extensión de funtores de Guillén y Navarro para definir una variante de la teoría K algebraica de las variedades sobre un cuerpo de característica cero, que coincide con la teoría K para las variedades lisas. Consideramos la teoría K como un funtor de variedades algebraicas a espectros. Llamamos teoría K de descenso a esta extensión, que satisface descenso para blow-ups abstractos. Para aplicar el criterio de extensión hemos demostrado que la categoría de espectros fibrantes es una categoria de descenso cohomológico, en el sentido de Guillén y Navarro, con el límite homotópico como funtor simple. Más generalmente hemos demostrado que la subcategoría de objectos fibrantesde una categoría de modelos simplicial es una categoría de descenso cohomológico si y sólo si se satisface un criterio de aciclicidad. En particular las categorías de modelos simpliciales estables satisfacen el criterio de aciclicidad y por lo tanto son de descenso cohomológico.Hemos visto como una teoría obtenida por el criterio de extensión hereda muchas de las propiedades del funtor sobre las variedades lisas, de manera que la teoría K de descenso satisface por ejemplo las propiedades de Mayer-Vietoris y de invariancia homotópica.Hemos demostrado también que bajo ciertas hipótesis la extensión de Guillén y Navarro de un funtor a espectros coincide con la aproximación fibrante en la categoría de models de prehaces de espectros considerando la cd topología de los blow-ups abstractos.Usando un resultado de Haesemeyer hemos demostrado que la teoría K de descenso es equivalente a la teoría K homotópica introducida por Weibel. Hemos demostrado también que hay una filtración por el peso natural en los grupos de teoría K homotópica. / In the setting of the study of the cohomology of algebraic varieties, and in particular in the cohomological applications of Hironaka's resolution of singularities theorem, we use the technique of cubical hyperresolutions and the extension criterion of functors of Guillén and Navarro to define a variant of algebraic K-theory of varietes over a field of characteristic zero, which coincides with K-theory for smooth varieties. We consider K- theory as a functor from algebraic varieties to spectra. We call this extension descent algebraic K-theory, which satisfies descent for abstract blow-ups.In order to apply the extension criterion we prove that the category of fibrant spectra is a cohomological descent category, in the sense of Guillén and Navarro, with the homotopy limit as a simple functor. More generally we prove that the subcategory of fibrant objects of a simplicial model category is a descent category if and only if an acyclicity criterion holds. In particular stable simplicial model categories satisfy the aciclicity criterion so they are cohomological descent categories.We see that a theory obtained by extension criterion inherits many properties of the functor over smooth varieties, in a way such that descent algebraic K-theory satisfies for example Mayer-Vietoris and homotopy invariance properties.We prove also that under certain hypotheses the Guillén and Navarro extension of a functor to spectra coincides with the fibrant approximation in the model category of presheaves of spectra considering the abstract blow-up cd-topology.After a result of Haesemeyer we prove that descent K-theory is equivalent to the homotopy algebraic K-theory introduced by Weibel. We prove also that there is a natural weight filtration in the groups of homotopy algebraic K-theory.

Thesis by publication. / Thesis (PhD)--Macquarie University (Division of Information & Communication Sciences, Dept. of Mathematics), 2007. / Bibliography: p. 119-123. / Introduction -- Mackey functors on compact closed categories -- Lax braidings and the lax centre -- On centres and lax centres for promonoidal catagories -- Pullback and finite coproduct preserving functors between categories of permutation representations -- Conclusion. / This thesis studies the theory of Mackey functors as an application of enriched category theory and highlights the notions of lax braiding and lax centre for monoidal categories and more generally promonoidal categories ... The third contribution of this thesis is the study of functors between categories of permutation representations. / x,123 p. ill

The main goal of this thesis is to construct a tensor product on the 2-category BFC-A of braided fusion categories containing a symmetric fusion category A. We achieve this by introducing the new notion of Z(A)-crossed braided categories. These are categories enriched over the Drinfeld centre Z(A) of the symmetric fusion category. We show that Z(A) admits an additional symmetric tensor structure, which makes it into a 2-fold monoidal category. ByTannaka duality, A= Rep(G) (or Rep(G; w)) for a finite group G (or finite super-group (G,w)). Under this identication Z(A) = VectG[G], the category of G-equivariant vector bundles over G, and we show that the symmetric tensor product corresponds to (a super version of) to the brewise tensor product. We use the additional symmetric tensor product on Z(A) to define the composition in Z(A)-crossed braided categories, whereas the usual tensor product is used for the monoidal structure. We further require this monoidal structure to be braided for the switch map that uses the braiding in Z(A). We show that the 2-category Z(A)-XBF is equivalent to both BFC=A and the 2-category of (super)-G-crossed braided categories. Using the former equivalence, the reduced tensor product on BFC-A is dened in terms of the enriched Cartesian product of Z(A)-enriched categories on Z(A)-XBF. The reduced tensor product obtained in this way has as unit Z(A). It induces a pairing between minimal modular extensions of categories having A as their Mueger centre.

Quantum information brings together theories of physics and computer science. This synthesis challenges the basic intuitions of both fields. In this thesis, we show that adopting a unified and general language for process theories advances foundations and practical applications of quantum information. Our first set of results analyze quantum algorithms with a process theoretic structure. We contribute new constructions of the Fourier transform and Pontryagin duality in dagger symmetric monoidal categories. We then use this setting to study generalized unitary oracles and give a new quantum blackbox algorithm for the identification of group homomorphisms, solving the GROUPHOMID problem. In the remaining section, we construct a novel model of quantum blackbox algorithms in non-deterministic classical computation. Our second set of results concerns quantum foundations. We complete work begun by Coecke et al., definitively connecting the Mermin non-locality of a process theory with a simple algebraic condition on that theory's phase groups. This result allows us to offer new experimental tests for Mermin non-locality and new protocols for quantum secret sharing. In our final chapter, we exploit the shared process theoretic structure of quantum information and distributional compositional linguistics. We propose a quantum algorithm adapted from Weibe et al. to classify sentences by meaning. The clarity of the process theoretic setting allows us to recover a speedup that is lost in the naive application of the algorithm. The main mathematical tools used in this thesis are group theory (esp. Fourier theory on finite groups), monoidal category theory, and categorical algebra.

Let (W, S) be an arbitrary Coxeter system, and let J be the asymptotic Hecke algebra associated to (W, S) via Kazhdan-Lusztig polynomials by Lusztig. We study a subalgebra J_C of J corresponding to the subregular cell C of W . We prove a factorization theorem that allows us to compute products in J_C without inputs from Kazhdan-Lusztig theory, then discuss two applications of this result. First, we describe J_C in terms of the Coxeter diagram of (W, S) in the case (W, S) is simply- laced, and deduce more connections between the diagram and J_C in some other cases. Second, we prove that for certain specific Coxeter systems, some subalgebras of J_C are free fusion rings, thereby connecting the algebras to compact quantum groups arising in operator algebra theory.

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Doctor of Philosophy / Department of Mathematics / Yan S. Soibelman / Recall the classical Riemann-Roch theorem for curves: Given a smooth projective complex curve and two holomorphic vector bundles E, F on it, the Euler can be computed in terms of the ranks and the degrees of the vector bundles. Remarkably, there are a number of similarly looking formulas in algebra. The simplest example is the Ringel formula in the theory of quivers. It expresses the Euler form of two finite-dimensional representations of a quiver algebra in terms of a certain pairing of their dimension vectors. The existence of Riemann-Roch type formulas in these two settings is a consequence of a deeper similarity in the structure of the corresponding derived categories - those of sheaves on curves and of modules over quiver algebras. The thesis is devoted to a version of the Riemann-Roch formula for abstract derived categories. By the latter we understand the derived categories of differential graded (DG) categories. More specifically, we work with the categories of perfect modules over DG algebras. These are a simultaneous generalization of the derived categories of modules over associative algebras and the derived categories of schemes. Given an arbitrary DG algebra A, satisfying a certain finiteness condition, we define and explicitly describe a canonical pairing on its Hochschild homology. Then we give an explicit formula for the Euler character of an arbitrary perfect A-module, the character is an element of the Hochschild homology of A. In this setting, our noncommutative Riemann-Roch formula expresses the Euler characteristic of the Hom-complex between any two perfect A-modules in terms of the pairing of their Euler characters. One of the main applications of our results is a theorem that the aforementioned pairing on the Hochschild homology is non-degenerate when the DG algebra satisfies a smoothness condition. This theorem implies a special case of the well-known noncommutative Hodge-to-de Rham degeneration conjecture. Another application is related to mathematical physics: We explicitly construct an open-closed topological field theory from an arbitrary Frobenius algebra and then, following ideas of physicists, interpret the noncommutative Riemann-Roch formula as a special case of the so-called topological Cardy condition.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Some of the diagram lemmas of Homological Algebra, classically known for abelian categories, are not characteristic of the abelian context; this naturally leads to investigations of those non-abelian categories in which these diagram lemmas may hold. In this Thesis we attempt to bring together two different directions of such investigations; in particular, we unify the five lemma from the context of homological categories due to F. Borceux and D. Bourn, and the five lemma from the context of modular semi-exact categories in the sense of M. Grandis. / AFRIKAANSE OPSOMMING: Verskeie diagram lemmata van Homologiese Algebra is aanvanklik ontwikkel in die konteks van abelse kategorieë, maar geld meer algemeen as dit behoorlik geformuleer word. Dit lei op ’n natuurlike wyse na ’n ondersoek van ander kategorieë waar hierdie lemmas ook geld. In hierdie tesis bring ons twee moontlike rigtings van ondersoek saam. Dit maak dit vir ons moontlik om die vyf-lemma in die konteks van homologiese kategoieë, deur F. Borceux en D. Bourn, en vyflemma in die konteks van semi-eksakte kategorieë, in die sin van M. Grandis, te verenig.