Topics in Supersymmetry Theory: 1. A Superspace Action for Ten-Dimensional Supersymmetric Yang-Mills Theory in Terms of Four-Dimensional Superfields; 2. Gauge Groups for Type-I Superstrings

This thesis is an account or most of the work that I did in Supersymmetry and Supergravity over the last two years. It deals with two major topics. the construction of a new superspace action for ten-dimensional supersymmetric Yang-Mills theory in terms of four-dimensional superfields. and the classification of the gauge groups allowed at the classical level in the type-I superstring theory. In addition, it contains a discussion of work that I did showing the uniqueness of supergravity in eleven dimensions and the uniqueness of the free Rarita-Schwinger action for massless and massive spin-³/₂ fields