Defects, Decay, and Dissipated States

1. INTRODUCTION Vacuum selection is one of the most important issues in string/M theory. The standard cartoon of string vacua (see figure 1.1) showing all the ten dimensional perturbative string asymptopia together with the eleven-dimensional limit, refers to solutions with a large number of supersymmetries, and flat directions (moduli) in the effective action. 11d I IIB heterotic IIA Figure 1.1 Schematic picture of the space of string vacua with extended supersym-metry. A much richer story arises as more supersymmetries are broken, and such flat directions are lifted or absent altogether. Eventually we will 1