A First-Quantized Formalism for Cosmological Particle Production

TL;DR

This paper introduces a first-quantized formalism for calculating cosmological particle production that relies solely on late-time modes and the Feynman propagator, potentially enabling string theory extensions.

Contribution

It presents a novel first-quantized approach to determine particle production without early-time mode reference or Bogolubov transformations.

Findings

Particle production can be derived from late-time modes alone.

The Feynman propagator in an auxiliary spacetime encodes particle production.

The method may extend to string-theoretic frameworks.

Abstract

We show that the amount of particle production in an arbitrary cosmological background can be determined using only the late-time positive-frequency modes. We don't refer to modes at early times, so there is no need for a Bogolubov transformation. We also show that particle production can be extracted from the Feynman propagator in an auxiliary spacetime. This provides a first-quantized formalism for computing particle production which, unlike conventional Bogolubov transformations, may be amenable to a string-theoretic generalization.