Particle Production in an expanding universe dominated by dark energy fluid

TL;DR

This paper analyzes how particle production evolves in an expanding universe filled with dark energy, showing that production rates decrease under certain conditions but diverge in phantom scenarios, potentially avoiding singularities.

Contribution

It provides exact calculations of particle production rates for any dark energy equation of state in a flat universe, highlighting conditions that prevent big rip singularities.

Findings

Particle production decreases when the strong energy condition holds.

In phantom cases, particle production diverges in finite time.

Backreaction effects may prevent big rip singularities.

Abstract

We investigate the fate of particle production in an expanding universe dominated by a perfect fluid with equation of state $p = \alpha\rho$. The rate of particle production, using the Bogolioubov coefficients, are determined exactly for any value of $\alpha$ in the case of a flat universe. When the strong energy condition is satisfied, the rate of particle production decreases as time goes on, in agreement to the fact that the four-dimensional curvature decreases with the expansion; the opposite occurs when the strong energy condition is violated. In the phantomic case, the rate of particle production diverges in a finite time. This may lead to a backreaction effect, leading to the avoidance of the big rip singularity, specially if $- 1 > \alpha > - {5/3}$.