ETD

• bouncing cosmology
• constant roll inflation
• inflation
• modified gravity
• Trans-Planckian problem

Starting from a review of cosmological perturbations in the inflationary paradigm, the recently proposed Trans-Planckian Censorship Conjecture (TCC) is analyzed; furthermore, I study and formally develop the constraints that the TCC poses on some commonly used viable models of inflation (e.g. single-field, f(R) models, constant-roll), concluding that a different approach to early universe cosmology may be the natural consequence of the conjecture. In light of this consideration, I then move on to alternative scenarios, namely bouncing cosmologies: specifically, after reviewing the Teleparallel Gravity framework, bouncing solutions in the f(T) modified gravity scenario are analyzed.