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Thesis (Ph. D.)--University of Iowa, 2007. / Supervisor: Sriram Pemmaraju. Includes bibliographical references (leaves 142-147).

The adjacency matrix of a graph is a (0, 1)-matrix indexed by the vertex set of the graph. And the signless Laplacian matrix of a graph is the sum of its adjacency matrix and its diagonal matrix of vertex degrees. The eigenvalues and the signless Laplacian eigenvalues of a graph are the eigenvalues of the adjacency matrix and the signless Laplacian matrix, respectively. These two matrices of a graph have been studied for several decades since they have been applied to many research field, such as computer science, communication network, information science and so on. In this thesis, we study k-connected graphs and focus on their spectral radius and signless Laplacian spectral radius. Firstly, we determine the graphs with maximum spectral radius among all k-connected graphs of fixed order with given diameter. As we know, when a graph is regular, its spectral radius and signless Laplacian spectral radius can easily be found. We obtain an upper bound on the signless Laplacian spectral radius of k-connected irregular graphs. Finally, we give some other results mainly related to the signless Laplacian matrix.

O objetivo deste trabalho é introduzir a noção de grafos familiarizando os alunos com um conceito pouco estudado no ensino fundamental e médio. Para isso, foram estudados algumas situações práticas e a resolução por meio de grafos. A apresentação da teoria de grafos é feita utilizando alguns dos problemas clássicos (Pontes de Königsberg e o Problema do caixeiro-viajante) que originaram a teoria tal como é conhecida nos dias de hoje. / The aim of this work is to introduce the notion of graphs familiarizing students with a little concept studied in elementary and middle schools. For this, some practical situations were studied and the resolution through graphs. The presentation of the theory of graphs is done using some of the classic problems (The Königsberg bridge problem and The travelling salesman problem) that originated the theory as it is known today.