Introduction to Effective Field Theories and Inflation

The lecture notes presented in this chapter provide an introduction to inflationary cosmology with an emphasis on some of the ways effective field theories (EFTs) are used in its analysis. Topics covered in the chapter include introduction to cosmological backgrounds and fluctuations, including a brief discussion of inflationary models; general relativity as an effective theory; new issues raised by cosmology for EFTs, such as time-dependent backgrounds; and power-counting in cosmological EFTs. It also discusses issues surrounding the existence in the universe of both dark matter and dark energy, and the broader controversial question of their existence. It touches on the Hot Big Bang theory of cosmology, and the various types of particles believed to be 'elementary' at the temperatures of interest.