Resumen en inglés

Throughout history, humans have exhibited an inexhaustible curiosity about their environment, its components, and abstractions. Science is the humankind instrument to convert this curiosity into knowledge. When the acquired knowledge is mastered, it evolves into wisdom. This practice has been the primary force propelling human progress since ancient times. From the earliest advancements in geometry, arithmetic, and mechanics inscribed on stone tablets, laying the groundwork for architectural marvels, to the principles underpinning rela- tivity and quantum mechanics, upon which technologies like the geo-positioning system (GPS) and magnetic resonance imaging (MRI) rely, science has never been the foremost priority of any civilization. However, while only a handful of passionate individuals have genuinely ap- preciated and delved into the sciences and their accomplishments, the fruits of their endeavors have benefited countless others. The contributions of these dedicated scientists have greatly enriched the vast reservoir of knowledge and wisdom that we now possess. Cosmology, the exploration of our Universe as a physical system encompassing its origin, evolution, and ultimate fate, has been a source of fascination for numerous scientists. While we have reached a point where we possess paradigms to construct instruments for observation and theories to interpret much of the observable Universe, several details remain elusive, such as the principles behind the existence of dark matter and dark energy. As a cosmologist in 2024, with aspirations to attain a doctoral degree in Physics, I find myself pondering: "How can I honor the tireless efforts of my predecessors and current colleagues while contributing to the advancement of cosmology?" Regrettably, I have yet to discover a definitive answer to this question. Therefore, during my postgraduate studies, I have resolved to delve deeply into various topics, seeking novel techniques and approaches to unravel the profound mysteries of our Universe. This dissertation comprises five chapters, each covering the topics I explored during my doctoral studies.