Cruz, Daniel Filipe Pina da2026-01-072026-01-072025http://hdl.handle.net/10400.5/116504Tese de Mestrado, Física e Astrofísica, 2025, Universidade de Lisboa, Faculdade de CiênciasThis thesis investigates open problems in the early Universe, particularly Baryogenesis and Big Bang Nucleosynthesis. The standard cosmological model, based on General Relativity and the Standard Model of Particle Physics, currently provides the most successful description of the evolution of the Universe. However, the newly arising tensions motivate the search for alternative models, either by modifications in the matter-energy content or modifications in the geometric sector. In this work, we will explore an alternative description to the curvature picture of gravity, where spacetime is encoded with torsion (Teleparallel Gravity). Broader extensions of this setting, namely f(T, Lm) theories of gravity, are employed in the search for solutions to the matter-antimatter asymmetry through the Gravitational Baryogenesis mechanism, as well as to the lithium problem. The results obtained suggest that f(T, Lm) gravity models can provide viable alternatives to address both the matter-antimatter asymmetry and the lithium problem.application/pdfengModified GravityTeleparallel GravityGravitational BaryogenesisBig Bang NucleosynthesisLithium Problemmaster thesis204175569