| In this two-part thesis, we study various non-supersymmetric aspects of field theory and string theory.; In part I, we focus on N = 1 supersymmetric gauge theories. Nonperturbative effects in these theories can spontaneously break supersymmetry, a phenomenon known as dynamical supersymmetry breaking (DSB). Motivated by the search for simpler models of DSB, we explore the (phenomenologically viable) possibility that the non-supersymmetric vacuum is only meta-stable. We find that meta-stable DSB occurs in a surprisingly simple class of models: N = 1 supersymmetric QCD, with massive flavors. We also discuss how various model building challenges, such as large flavor symmetries and the absence of an R-symmetry, can be easily accommodated in these theories.; In part II, we switch gears to study a class of non-supersymmetric string theories known (p, q) minimal string theories. These models describe strings propagating in a d < 2 dimensional target space. Although they are exactly solvable, they nevertheless provide a rich source of stringy phenomena, including D-branes, open/closed duality, and holography. In chapter 5, we analyze the D-branes of the minimal string. We show how an auxiliary Riemann surface emerges from the D-branes and provides a unified geometric description of all of these theories. In chapter 6, we compute the annulus amplitudes between different types of branes and show how they fit into the geometrical framework. Finally, in chapter 7 we study the target space of the minimal string, using the D-branes as probes. We find that target space is drastically modified by nonperturbative quantum effects, and we discuss the possible implications of this for topological strings and black holes. |
