Based on Cohn and Umans’ group-theoretic method, we embed matrix multiplication into several group algebras, including those of cyclic groups, dihedral groups, special linear groups and Frobenius groups. We prove that SL2(Fp) and PSL2(Fp) can realize the matrix tensor ⟨p, p, p⟩, i.e. it is possible to encode p × p matrix multiplication in the group algebra of such a group. We also find the lower bound for the order of an abelian group realizing ⟨n, n, n⟩ is n3. For Frobenius groups of the form Cq Cp, where p and q are primes, we find that the smallest admissible value of q must be in the range p4/3 ≤ q ≤ p2 − 2p + 3. We also develop an algorithm to find the smallest q for a given prime p.

En 2001, Barannikov a montré que la variété de Frobenius provenant de la cohomologie quantique de l'espace projectif complexe est isomorphe à la variété le Frobenius associée à un polynôme de Laurent. <br /> <br /> L'objectif de cette thèse est de généraliser ce résultat. Plus précisément, nous montrons, modulo une conjecture sur la valeur de certains invariants de Gromov-Witten orbifold, que la structure de Frobenius obtenue sur la cohomologie quantique orbifolde de l'espace projectif à poids est isomorphe à celle obtenue à partir d'un certain polynôme de Laurent.

On décrit et on étudie une matrice Q inversible telle que Q F = JQ ou J est la forme normale de Jordan d'une matrice carrée A, et F sa forme de Frobenius. On propose un algorithme efficace pour le calcul de l'inverse de Q et deux algorithmes donnant la forme de Frobenius d'une matrice n x n quelconque. Dans le cas ou les éléments de A sont des nombres rationnels, on montre que la complexité de l'un des algorithmes est polynomiale. On considère aussi le cas des matrices A coefficients dans le corps des nombres algébriques sur Q

Some of the theory of nonnegative matrices is first presented. The Perron-Frobenius theorem is highlighted. Some of the important linear algebraic methods of information retrieval are surveyed. Latent Semantic Indexing (LSI), which uses the singular value de-composition is discussed. The Hyper-Text Induced Topic Search (HITS) algorithm is next considered; here the power method for finding dominant eigenvectors is employed. Through the use of a theorem by Sinkohrn and Knopp, a modified HITS method is developed. Lastly, the PageRank algorithm is discussed. Numerical examples and MATLAB programs are also provided.

There are several reasons to be interested in conformal field theories in two dimensions. Apart from arising in various physical applications, ranging from statistical mechanics to string theory, conformal field theory is a class of quantum field theories that is interesting on its own. First of all there is a large amount of symmetries. In addition, many of the interesting theories satisfy a finiteness condition, that together with the symmetries allows for a fully non-perturbative treatment, and even for a complete solution in a mathematically rigorous manner. One of the crucial tools which make such a treatment possible is provided by category theory. This thesis contains results relevant for two different classes of conformal field theory. We partly treat rational conformal field theory, but also derive results that aim at a better understanding of logarithmic conformal field theory. For rational conformal field theory, we generalize the proof that the construction of correlators, via three-dimensional topological field theory, satisfies the consistency conditions to oriented world sheets with defect lines. We also derive a classifying algebra for defects. This is a semisimple commutative associative algebra over the complex numbers whose one-dimensional representations are in bijection with the topological defect lines of the theory. Then we relax the semisimplicity condition of rational conformal field theory and consider a larger class of categories, containing non-semisimple ones, that is relevant for logarithmic conformal field theory. We obtain, for any finite-dimensional factorizable ribbon Hopf algebra H, a family of symmetric commutative Frobenius algebras in the category of bimodules over H. For any such Frobenius algebra, which can be constructed as a coend, we associate to any Riemann surface a morphism in the bimodule category. We prove that this morphism is invariant under a projective action of the mapping class group ofthe Riemann surface. This suggests to regard these morphisms as candidates for correlators of bulk fields of a full conformal field theories whose chiral data are described by the category of left-modules over H.

Given a random dynamical system T constructed from Jablonski transformations, consider its Perron-Frobenius operator P_T. We prove a weak form of the Lasota-Yorke inequality for P_T and thereby prove the existence of BV- invariant densities for T. Using the Spectral Decomposition Theorem we prove that the support of an invariant density is open a.e. and give conditions such that the invariant density for T is unique. We study the asymptotic behavior of the Markov operator P_T, especially when T has a unique absolutely continuous invariant measure (ACIM). Under the assumption of uniqueness, we obtain spectral stability in the sense of Keller. As an application, we can use Ulam's method to approximate the invariant density of P_T.

Recently there has been growing interest to characterize and reduce uncertainty in stochastic dynamical systems. This drive arises out of need to manage uncertainty in complex, high dimensional physical systems. Traditional techniques of uncertainty quantification (UQ) use local linearization of dynamics and assumes Gaussian probability evolution. But several difficulties arise when these UQ models are applied to real world problems, which, generally are nonlinear in nature. Hence, to improve performance, robust algorithms, which can work efficiently in a nonlinear non-Gaussian setting are desired. The main focus of this dissertation is to develop UQ algorithms for nonlinear systems, where uncertainty evolves in a non-Gaussian manner. The algorithms developed are then applied to state estimation of real-world systems. The first part of the dissertation focuses on using polynomial chaos (PC) for uncertainty propagation, and then achieving the estimation task by the use of higher order moment updates and Bayes rule. The second part mainly deals with Frobenius-Perron (FP) operator theory, how it can be used to propagate uncertainty in dynamical systems, and then using it to estimate states by the use of Bayesian update. Finally, a method to represent the process noise in a stochastic dynamical system using a nite term Karhunen-Loeve (KL) expansion is proposed. The uncertainty in the resulting approximated system is propagated using FP operator. The performance of the PC based estimation algorithms were compared with extended Kalman filter (EKF) and unscented Kalman filter (UKF), and the FP operator based techniques were compared with particle filters, when applied to a duffing oscillator system and hypersonic reentry of a vehicle in the atmosphere of Mars. It was found that the accuracy of the PC based estimators is higher than EKF or UKF and the FP operator based estimators were computationally superior to the particle filtering algorithms.

Orientador: Edmundo Capelas de Oliveira / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-17T14:35:07Z (GMT). No. of bitstreams: 1 Rosa_EsterCristinaFontesdeAquino_M.pdf: 847998 bytes, checksum: d177526572b19cc1fdd5eeccdf511380 (MD5) Previous issue date: 2011 / Resumo: Este trabalho tem por objetivo modelar e resolver, matematicamente, um problema físico conhecido como pêndulo simples. Discutimos, como caso particular, as chamadas oscilações de pequena amplitude, isto é, uma aproximação que nos leva a mostrar que o período de oscilação é proporcional à raiz quadrada do quociente entre o comprimento do pêndulo e a aceleração da gravidade. Como vários outros problemas oriundos da Física, o pêndulo simples é representado através de equações diferenciais parciais. Assim, na busca de sua solução, aplicamos a metodologia de separação de variáveis que nos leva a um conjunto de equações ordinárias passíveis de simples integração. Escolhendo um sistema de coordenadas adequado, é conveniente usar o método de Hamilton-Jacobi, discutindo, antes, o problema do oscilador harmónico, apresentando, em seguida, o problema do pêndulo simples e impondo condições a fim de mostrar que as equações diferenciais associadas a esses dois sistemas são iguais, ou seja, suas soluções são equivalentes. Para tanto, estudamos o método de separação de variáveis associado às equações diferenciais parciais, lineares e de segunda ordem, com coeficientes constantes e três variáveis independentes, bem como a respectiva classificação quanto ao tipo. Posteriormente, estudamos as equações hipergeométricas, cujas soluções, as funções hipergeométricas. podem ser encontradas pelo método de Frobenius. Apresentamos o método de Hamilton-Jacobi, já mencionado, para o enfren-tamento do problema apresentado. Fizemos no capítulo final um apêndice sobre a função gama por sua presente importância no trato de funções hipergeométricas, em especial a integral elíptica completa de primeiro tipo que compõe a solução exata do período do pêndulo simples / Abstract: This work aims to present and solve, mathematically, the physics problem that is called simple pendulum. We reasoned, as an specific case, the so called low amplitude oscillation, that is, a convenient approximation that make us show that the period of oscillation is proportional to the quotient square root between the pendulum length and the gravity acceleration. Like several other problems arising from the physics, we are going to broach it through partial differential equations. Thus, in the search of its solution, we made use of the variable separation methodology that leads us to a body of ordinary equations susceptible of simple integration. Choosing an appropriate coordinate system, it is convenient to use the method Hamilton-Jacobi, arguing, first, the problem of the harmonic oscillator, with, then the problem of sf simple pendulum and imposing conditions to show that the differential equations associated with these two systems are equal, that is, their solutions are equivalent. With the purpose of reaching the objectives, we studied the variable separation method associated with partial differential equations, linear and of second order, with constant coefficient and three independent variables, as well as the respective classification about the type. Afterwards, we studied the hypergeometrical equations whose solutions, the hypergeometrical functions, are found by the Frobenius method. Introducing the Hamilton-Jacobi method, already mentioned, for addressing the problem presented. We made an appendix in the final chapter on the gamma function by its present importance in dealing with hypergeometric functions, in particular the elliptic integral of first kind consists of the exact period of sf simple pendulum / Mestrado / Fisica-Matematica / Mestre em Matemática

Rational Catalan combinatorics connects various Catalan numbers to the representation theory of rational Cherednik algebras for Coxeter and complex reflection groups. Lewis, Reiner, and Stanton seek a theory of rational Catalan combinatorics for the general linear group over a finite field. The finite general linear group is a modular reflection group that behaves like a finite Coxeter group. They conjecture a Hilbert series for a space of invariants under the action of this group using (q,t)-binomial coefficients. They consider the finite general linear group acting on the quotient of a polynomial ring by iterated powers of the irrelevant ideal under the Frobenius map. Often conjectures about reflection groups are solved by considering the local case of a group fixing one hyperplane and then extending via the theory of hyperplane arrangements to the full group. The Lewis, Reiner and Stanton conjecture had not previously been formulated for groups fixing a hyperplane. We formulate and prove their conjecture in this local case.

Cette thèse étudie une classe des problèmes de Riemann-Hilbert Fuchsiens (à coefficients méromorphes dont tous les pôles sont d'ordre un). Les variétés de Frobenius apparaissent comme une formulation géométrique des structures d'équations de Witten-DijkgraafVerlande-Verlande (WDVV). Nous considérons ces variétés sur les espaces de Hurwitz vus, quant à eux, comme variétés réelles motivés par le fait qu'une variété de Frobenius semisimple peut être construite à partir d'une solution fondamentale du problème de Riemann-Hilbert associé. Une solution au problème Fuchsien de Riemann-Hilbert matriciel (problème de monodromie inverse) correspondant aux structures "réelles doubles" de Frobenius de Dubrovin sur les espaces de Hurwitz, a été construite. La solution est donnée en termes de certaines différentielles méromorphes integrées sur une base appropriée d'homologie relative de la surface de Riemann. La relation avec la solution du problème Fuchsien de Riemann-Hilbert pour les structures de Frobenius Hurwitz de Dubrovin est établie. Une solution du problème de Riemann-Hilbert correspondant aux déformations des "réelles doubles" est aussi donnée.