Light Scalars at the Cosmological Collider

Understand

We study the self-energies of weakly interacting scalar fields in de Sitter space with one field much lighter than the Hubble scale.

• We argue that self-energies drastically simplify in this light limit.
• We illustrate this in theories with two scalar fields, one heavy and one light, interacting with one another through either cubic or quartic interactions.
• To regulate infrared divergences, we compute these self-energies in Euclidean de Sitter space and then carefully analytically continue to Lorentzian signature.