The Early Universe Seen through Gravitational Waves | Colóquio do DFMA

Abstract: Studying the early universe requires identifying which signals were able to traverse cosmic history and reach us today. The cosmic microwave background provides a clear example: light that has traveled almost freely since the recombination of electrons and protons about 13 billion years ago, offering us a snapshot of the universe at that epoch. However, probing even earlier times demands more subtle observables. Primordial gravitational waves, generated in the very early universe, provide a unique window into these epochs. Although extremely challenging to detect directly, they can leave distinctive imprints on the polarization of the cosmic microwave background. Interpreting such signals requires a precise description of the primordial plasma, including out-of-equilibrium effects and non-ideal phenomena that become increasingly relevant in the era of precision cosmology. In this talk, we will explore, through a concrete example, how primordial gravitational waves encode information about the earliest moments of the universe, its composition, and its interactions, as well as how we can contribute to their observation.

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