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The purpose of this work is to study the initial value problem for coherent pulse propagation (SIT) for zero area pulses. We employ the machinery of the newly developed mathematical technique of the inverse scattering method (ISM) to deduce general rules by which one can predict the kind of output pulses for a given input pulse impinging on a resonant attenuator. This study is relevant since the area theorem cannot provide unambiguous information about zero area pulses. Thus in effect we introduce an equivalent and more general formulation to the theorem in terms of the reflection coefficient, r(ν), of the ISM. The poles of r(ν) correspond to the steady state solitary pulses called solitons. We show that the threshold for soliton generation, including breathers, is for an absolute initial area of about π, a result consistent with the predictions of the area theorem. We solve an example of an input zero area profile. We also show that if the input pulse has an odd profile with respect to time, only breathers can be expected as solitons. We demonstrate that the conservation equations are of limited use when applied to zero area pulses. They give satisfactory results only in a limited region. We compare the predictions of the conservation equations to the predictions of the ISM, and come to the conclusion that for zero area pulses, the ISM is the only known satisfactory approach.

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The energy of a graph is the sum of the absolute values of the eigenvalues of its adjacency matrix. The concept is related to the energy of a class of molecules in chemistry and was first brought to mathematics by Gutman in 1978 ([8]). In this thesis, we do a comprehensive study on the energy of graphs and digraphs. In Chapter 3, we review some existing upper and lower bounds for the energy of a graph. We come up with some new results in this chapter. A graph with n vertices is hyper-energetic if its energy is greater than 2n−2. Some classes of graphs are proved to be hyper-energetic. We find a new class of hyper-energetic graphs which is introduced and proved to be hyper-energetic in Section 3.3. The energy of a digraph is the sum of the absolute values of the real part of the eigenvalues of its adjacency matrix. In Chapter 4, we study the energy of digraphs in a way that Pe˜na and Rada in [19] have defined. Some known upper and lower bounds for the energy of digraphs are reviewed. In Section 4.5, we bring examples of some classes of digraphs in which we find their energy. Keywords. Energy of a graph, hyper-energetic graph, energy of a digraph. / vii, 80 leaves ; 29 cm

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Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 298-303). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [139]-141).