2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/188063Violations of spacetime symmetries have recently been identified as promising signatures for physics underlying the Standard Model. The present talk gives an overview over various topics in this field: The motivations for spacetime-symmetry research, including some mechanisms for Lorentz breaking, are reviewed. An effective field theory called the Standard-Model Extension (SME) for the description of the resulting low-energy effects is introduced, and some experimental tests of Lorentz and CPT invariance are listed.8 pages, 2 figures, Plenary talk at 12th Mexican School on Particles and Fields and 6th Latin American Symposium on High Energy Physics (VI-Silafae/XII-MSPF), Puerto Vallarta, Mexico, 1-8 Nov 2006General Relativity and Quantum Cosmologytext