Snowmass White Paper: Effective Field Theories in Cosmology

Understand

Small fluctuations around homogeneous and isotropic expanding backgrounds are the main object of study in cosmology.

• Their origin and evolution is sensitive to the physical processes that happen during inflation and in the late Universe.
• As such, they hold the key to answering many of the major open questions in cosmology.
• Given a large separation of relevant scales in many examples of interest, the most natural description of these fluctuations is formulated in terms of effective field theories.