2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/39408In these lectures, I discuss the role of symmetries in particle physics. I begin by discussing global symmetries and show that they can be realized differently in nature, depending on whether or not the vacuum state is left invariant by the symmetry. I introduce next the notion of local symmetries and show how these symmetries can be implemented through the introduction of gauge fields. Using the simple example of a spontaneously broken U(1) symmetry, I discuss the Higgs mechanism showing that it provides a natural way for the gauge fields to acquire mass. Finally, I show how these concepts are used as the basis for the Standard Model of particle physics, ending with a brief description of some of the salient aspects of Quantum Chromodynamics and of the electroweak theory.Lectures given at the fifth Vietnam School of Physics, Hanoi, December 28, 1998- 9 January, 1999. To appear in the Proceedings of the SchoolHigh Energy Physics - Phenomenologytext