The cosmological collider signal in the non-BD initial states

TL;DR

This paper explores how non-Bunch Davies initial states enhance the cosmological collider signal, allowing it to probe energy scales much higher than the Hubble scale during inflation.

Contribution

It analytically computes inflaton correlators with non-BD states and shows these states remove Boltzmann suppression, boosting the CC signal's reach.

Findings

Non-BD initial states eliminate Boltzmann suppression of the CC signal.

The CC can probe energy scales much higher than the Hubble scale.

Analytic solutions to bootstrap equations for correlators are provided.

Abstract

We investigate the cosmological collider (CC) signal arising from the tree-level exchange of a scalar spectator particle with a non-Bunch Davies (BD) initial state. We decompose the inflaton correlators into seed integrals, which we compute analytically by solving the bootstrap equations. We show that the non-BD initial state eliminates the Hubble scale Boltzmann suppression $e^{-\pi m /H}$ that usually affects the CC signal. Consequently, in this scenario, the CC can probe an energy scale much higher than the inflationary Hubble scale $H$.