2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/128122This Thesis is devoted to the analysis of entanglement in relevant physical systems. Entanglement is the conducting theme of this research, though I do not dedicate to a single topic, but consider a wide scope of physical situations. I have followed mainly three lines of research for this Thesis, with a series of different works each, which are, Entanglement and Relativistic Quantum Theory, Continuous-variable entanglement, and Multipartite entanglement.Ph.D. Thesis, April 2007, Universidad Autonoma de MadridQuantum Physicstext