The road to no-scale supergravity

Abstract

No-scale supergravity is a leading candidate for an effective theory that describes nature at energies below the Planck scale ( m p≌10 19 GeV). Its virtues, such as an automatically vanishing cosmological constant (at least at the classical level), dynamical determination of all mass scales in terms of a fundamental one ( m p) and acceptable low-energy phenomenology makes no-scale supergravity unique. Furthermore, it may provide the missing link between an effective low-energy theory and the fundamental Theory Of Everything (TOE), as it may be derived as the low-energy limit of the superstring, our best candidate for the TOE. In this report not only do we discuss the structure, physical properties, and implications of no-scale models but we also study in considerable detail all the basic ingredients that come to play in their structure, such as supersymmetry and supergravity. Supersymmetry and minimal supergravity models are discussed, including their weak points that eventually lead us to no-scale models. At the end, we also cover some recent developments in superstring theories and how these are connected with our no-scale structure.