Primordial universe with the running cosmological constant

TL;DR

This paper explores the possibility that a running cosmological constant in the early universe could lead to particle creation from vacuum decay, affecting cosmic evolution and observable phenomena like the CMB and matter power spectrum.

Contribution

It develops a systematic framework to study vacuum decay with a running cosmological constant during the early universe, incorporating linear perturbations and observational data fitting.

Findings

Vacuum decay impacts the matter power spectrum and CMB peak.

Best-fit parameters suggest compatibility with observational data.

Model provides a new perspective on early universe dynamics with a running cosmological constant.

Abstract

Theoretically, the running of the cosmological constant in the IR region is not ruled out. On the other hand, from the QFT viewpoint, the energy released due to the variation of the cosmological constant in the late universe cannot go to the matter sector. For this reason, the phenomenological bounds on such a running are not sufficiently restrictive. The situation can be different in the early universe when the gravitational field was sufficiently strong to provide an efficient creation of particles from the vacuum. We develop a framework for systematically exploring this ossibility. It is supposed that the running occurs in the epoch when the Dark Matter already decoupled and is expanding adiabatically, while baryons are approximately massless and can be abundantly created from vacuum due to the decay of vacuum energy. By using the handy model of Reduced Relativistic Gas for describing the Dark Matter, we consider the dynamics of both cosmic background and linear perturbations and evaluate the impact of the vacuum decay on the matter power spectrum and to the first CMB peak. Additionally, using the combined data of CMB+BAO+SNIa we find the best fit values for the free parameters of our model.