959 resultados para Canonical matrices
Resumo:
The matrices studied here are positive stable (or briefly stable). These are matrices, real or complex, whose eigenvalues have positive real parts. A theorem of Lyapunov states that A is stable if and only if there exists H ˃ 0 such that AH + HA* = I. Let A be a stable matrix. Three aspects of the Lyapunov transformation LA :H → AH + HA* are discussed.
1. Let C1 (A) = {AH + HA* :H ≥ 0} and C2 (A) = {H: AH+HA* ≥ 0}. The problems of determining the cones C1(A) and C2(A) are still unsolved. Using solvability theory for linear equations over cones it is proved that C1(A) is the polar of C2(A*), and it is also shown that C1 (A) = C1(A-1). The inertia assumed by matrices in C1(A) is characterized.
2. The index of dissipation of A was defined to be the maximum number of equal eigenvalues of H, where H runs through all matrices in the interior of C2(A). Upper and lower bounds, as well as some properties of this index, are given.
3. We consider the minimal eigenvalue of the Lyapunov transform AH+HA*, where H varies over the set of all positive semi-definite matrices whose largest eigenvalue is less than or equal to one. Denote it by ψ(A). It is proved that if A is Hermitian and has eigenvalues μ1 ≥ μ2…≥ μn ˃ 0, then ψ(A) = -(μ1-μn)2/(4(μ1 + μn)). The value of ψ(A) is also determined in case A is a normal, stable matrix. Then ψ(A) can be expressed in terms of at most three of the eigenvalues of A. If A is an arbitrary stable matrix, then upper and lower bounds for ψ(A) are obtained.
Resumo:
El proyecto tiene como objetivo el estudio de las propiedades más importantes de las matrices doblemente estocásticas y algunas aplicaciones. Se comienza analizando algunas propiedades espectrales de las matrices no negativas de las que aquellas son un caso particular y se demuestra, en particular, el Teorema de Perron-Frobenius. Posteriormente se discute en detalle la relación entre las matrices doblemente estocásticas y la mayorización de vectores reales y el importante teorema de Birkhoff. El proyecto finaliza desarrollando algunas aplicaciones de este tipo de matrices.
Resumo:
Quantum Computing is a relatively modern field which simulates quantum computation conditions. Moreover, it can be used to estimate which quasiparticles would endure better in a quantum environment. Topological Quantum Computing (TQC) is an approximation for reducing the quantum decoherence problem1, which is responsible for error appearance in the representation of information. This project tackles specific instances of TQC problems using MOEAs (Multi-objective Optimization Evolutionary Algorithms). A MOEA is a type of algorithm which will optimize two or more objectives of a problem simultaneously, using a population based approach. We have implemented MOEAs that use probabilistic procedures found in EDAs (Estimation of Distribution Algorithms), since in general, EDAs have found better solutions than ordinary EAs (Evolutionary Algorithms), even though they are more costly. Both, EDAs and MOEAs are population-based algorithms. The objective of this project was to use a multi-objective approach in order to find good solutions for several instances of a TQC problem. In particular, the objectives considered in the project were the error approximation and the length of a solution. The tool we used to solve the instances of the problem was the multi-objective framework PISA. Because PISA has not too much documentation available, we had to go through a process of reverse-engineering of the framework to understand its modules and the way they communicate with each other. Once its functioning was understood, we began working on a module dedicated to the braid problem. Finally, we submitted this module to an exhaustive experimentation phase and collected results.
Resumo:
221 p.+ anexos
