Supersymmetric gauge theories from D3-branes on singularities

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 167-173).In this thesis we study four-dimensional supersymmetric gauge theories and their string theory realization. After an introduction and a brief review of some basic concepts at the interface of gauge theories and string theory, we begin by examining the duality cascade phenomenon for quiver gauge theories. We give a general formulation for these cascades and use it to identify an example of a duality wall in a theory which can be realized on D3-branes at the apex of the complex cone over the zeroth Hirzebruch surface with the addition of fractional branes. Next, we compute global U(1) charges for the matter fields of the del Pezzo gauge theories and formulate several of their features in the language of exceptional Lie algebras. We suggest the possibility of global symmetry enhancement at infinite coupling for these theories. Finally, we present two contributions to the solution of the geometric engineering problem. We construct the toric phases of the yp,q theories and then identify and study a new infinite family of quiver gauge theories, Xpq, whose dual geometries are known in terms of toric diagrams.by Pavlos Kazakopoulos.Ph.D