2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/39509We discuss the possible applications of string theory for the construction of generalizations of the $SU(3)\times SU(2)\times U(1)$ standard model of strong and electroweak interactions. This includes an investigation of effective $d=4$ dimensional supergravity theories that could be derived from higher dimensional string theories ($d=10$) and M-theory ($d=11$).It is shown how the question of unification of gauge and gravitational coupling constants could find a solution within this framework. The mechanism of hidden sector supersymmetry breakdown and its consequences for the pattern for soft supersymmetry breaking terms are discussed in detail.For those that asked for a copy: TASI97 lectures as published in Supersymmetry, Supergravity and Supercolliders, World Scientific, Ed. J. A. BaggerHigh Energy Physics - Phenomenologytext