Particle creation from non-geodesic trajectories in multifield inflation

TL;DR

This paper investigates particle creation during inflation due to deviations from perfect de Sitter conditions and non-gravitational interactions, providing analytical insights into how these processes influence primordial spectra.

Contribution

It introduces a framework for calculating particle production from non-geodesic trajectories in multifield inflation, extending understanding beyond standard de Sitter scenarios.

Findings

Particle density relates to the primordial power spectrum's spectral index.

In two-field models, particle production reflects non-gravitational couplings and trajectory turning.

Analytical results apply to various non-adiabatic inflation scenarios.

Abstract

Particle production in de Sitter spacetime arises from the exponential expansion of space, rendering the Bunch-Davies vacuum perceived as a particle-containing state by late-time observers. For states defined as eigenstates of both momentum and the Hamiltonian, the Bunch-Davies vacuum exhibits a constant particle density per physical momentum. We explore particle production beyond this baseline, focusing on deviations from exact de Sitter conditions and non-gravitational interactions, such as slow-roll inflation or interactions arising from the coupling of inflation to other fields. Using Bogoliubov transformations, we calculate the number density of energy/momentum eigenstates. In single-field inflation, this density captures the observed spectral index of the primordial power spectrum, while in two-field models, it reflects the non-gravitational coupling driving background trajectory turning. We present analytical results applicable to various scenarios involving particle production from non-adiabatic processes during inflation.