2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/43242Quantum-gravity effects are expected to be suppressed by the Planck mass. For experimental progress it is therefore important to identify potential signatures from Planck-scale physics that are amenable to ultrahigh-precision tests. It is argued that minuscule violations of Lorentz and CPT symmetry are candidate signals. In addition, theoretical and experimental aspects of the Standard-Model Extension, which describes the emergent low-energy effects, are discussed.Invited talk presented at BEYOND 03, Castle Ringberg, Tegernsee, Germany, June 2003High Energy Physics - Phenomenologytext