Cosmological collider signals of modular spontaneous CP breaking

TL;DR

This paper explores how a modular-invariant extension of the Standard Model with the modulus as the inflaton can produce detectable cosmological collider signals influenced by CP violation and chemical potentials during inflation.

Contribution

It introduces a novel framework linking modular invariance, CP violation, and cosmological collider signals, with precise calculations for fermions in de Sitter space.

Findings

Next-generation experiments can probe sub-Planckian modulus decay constants.

The model predicts enhanced collider signals due to chemical potentials during inflation.

Provides exact formulas for Dirac fermions with chemical potentials in de Sitter space.

Abstract

We consider a modular-invariant extension of the Standard Model. Assuming that the modulus is the inflaton, the CP-violating phases of the Yukawa couplings evolve during inflation. This dynamics favours a Higgs condensate, so that Standard Model fermions mediate a one-loop cosmological collider signal enhanced by chemical potentials. Next-generation experiments can probe sub-Planckian values of the modulus decay constant. We provide precise expressions for Dirac fermions with chemical potentials in de Sitter.