Explore the third lecture in a comprehensive series on cosmic inflation delivered by Antonio Riotto at the Galileo Galilei Institute (GGI). This 86-minute presentation continues the exploration of inflationary cosmology, building upon the foundations established in previous lectures. Delve into advanced concepts and mathematical frameworks that explain how the universe underwent rapid expansion in its earliest moments. Gain insights into the theoretical underpinnings of inflation and its implications for understanding the large-scale structure of the cosmos.