Probing P and CP Violations on the Cosmological Collider

TL;DR

This paper explores how primordial fluctuations' 4-point correlation functions can reveal P and CP violations, proposing a model with axion-like couplings that predicts observable signals in future surveys, thus opening new high-energy physics avenues.

Contribution

It introduces a model with axion-like couplings that produces observable P and CP-violating signals in the primordial trispectrum, linking cosmological observations to high-energy physics.

Findings

Large CP-violating trispectrum predicted for future surveys

On-shell particle production is crucial for observing P and CP violations

Local 4-scalar EFT operators respecting dS isometries cannot produce these signals

Abstract

In direct analogy to the 4-body decay of a heavy scalar particle, the 4-point correlation function of primordial fluctuations carries P and CP information. The CP violation appears as a P-odd angular dependence in the imaginary part of the trispectrum in momentum space. We construct a model with axion-like couplings which leads to observably large CP-violating trispectrum for future surveys. Furthermore, we show the importance of on-shell particle production in observing P- and CP-violating signals. It is impossible to observe these signals from local 4-scalar EFT operators that respect dS isometries, and thus any such observation can rule out single-field EFT with sufficiently small slow-roll parameters. This calculation opens a new frontier of studying P and CP at very high energy scales.